CB SERIES
Condensing Units
Installation Operation
amp Maintenance
FOR YOUR SAFETY
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance
WARNING
If the information in this manual is not followed exactly a fire or explosion may result causing property damage personal injury or loss of life
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
2
Table of Contents AAON
reg CB Series Features and Options Introduction 5
Safety 6 CB Base Model and Features Description 10 General Description 11
Codes and Ordinances 11
Receiving Unit 11 Storage 12 Direct Expansion (DX) Condensing Units 12 Wiring Diagrams 13 General Maintenance 13
Installation 14 Lifting the Unit 14
Locating Unit 14 Mounting Isolation 15
Access Panel 15 Electrical 16
Thermostat 17 Refrigerant Piping 18
General 18
Determining Refrigerant Line Size 18
Liquid Line Sizing 19
Suction Line Sizing 20
Hot Gas Bypass Line 22
Hot Gas Reheat 22
Predetermined Line Sizes 23
Startup 26
Compressors 26 Charging Refrigerant amp Adjusting Refrigerant Charge 27
Before Charging 27
Checking Liquid Sub-cooling 27
Checking Evaporator Superheat 28
Adjusting Sub-cooling and Superheat Temperatures 28
Air Flow 29 Operation 31
Thermostat Operation 31 Compressor 31 Variable Capacity Compressor Controller 31 Low Ambient Operation 34 LAC Valve 35 Condenser Flooding 36
3
Compressor Lockouts 36
Maintenance 37 Coils 37 E-Coated Coil Cleaning 37
DX Cooling 39 Condenser Fan Motor 39 Replacement Parts 39 Warranty Service and Parts Department 39
Refrigerant Piping Diagrams 40
CB Series Startup Form 52 Literature Change History 55
4
Index of Tables and Figures
Tables Table 1 - Recommended Elevation Minimums 15 Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A 25 Table 3 - Acceptable Refrigeration Circuit Values 28
Table 4 - Performance Testing Air Flow Setpoints 29 Table 5 - R-410A Refrigerant Temperature-Pressure Chart 30 Table 6 - Demand Signal vs Compressor Capacity Modulation 32 Table 7 - Thermistor Temperature vs Resistance Values 33 Table 8 - Condenser Flooding 36
Figures Figure 1 ndash Forklift Channels amp Access Panel 14 Figure 2 ndash Condensing Unit Clearances 15 Figure 3 ndash Utility Entry 16 Figure 4 ndash Heat Pump Piping Schematic of Suction Vapor Flow Down in Double Riser 21
Figure 5 ndash Heat Pump Piping Schematic of Discharge Vapor Flow Up in Double Riser 21 Figure 6 - Riser height versus total equivalent line length 25 Figure 7 - Variable Capacity Compressor Controller 32
Figure 8 - Compressor Controller Flash Code Details 33 Figure 9 - Adjustable Fan Cycling Switch 34
Figure 10 - Piping Schematic of Example System using the LAC Valve 35 Figure 11 - Adjustable compressor lockout 36 Figure 12ndash AC only piping AHU above CU 40
Figure 13 ndash AC only piping AHU below CU 41
Figure 14 ndash Modulating hot gas reheat piping AHU above CU 42 Figure 15 ndash Modulating hot gas reheat piping AHU below CU 43 Figure 16 ndash Hot gas bypass piping AHU above CU 44
Figure 17 ndash Hot gas bypass piping AHU below CU 45 Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU 46
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU 47 Figure 20 ndash Heat pump piping AHU above CU 48 Figure 21 ndash Heat pump piping AHU below CU 49 Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU 50
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU 51
R57611 Rev A 161221
(ACP J00187)
5
AAONreg CB Series Features and Options Introduction
Energy Efficiency
Two Step or Variable Capacity Scroll
Compressor
Air-Source Heat Pump
Variable Speed Condenser Fans for Head
Pressure Control
Humidity Control
Modulating Hot Gas Reheat
Safety
Suction Pressure Transducer
Heavy Duty Wire Guards or Louvered
Panels for Condenser Coils
Automatic Low Pressure and Manual
reset High Pressure Safety Cut-outs
Suction and Liquid Line Schrader Valves
Installation and Maintenance Easily Removable Panel Access to
Service Compartment
Run Test Report and Installation Manuals
Included in Controls Compartment
Color Coded Wiring and Wiring
Diagrams
24V Control Circuit Transformer Option
System Integration
Split System Matching
Modulating Head Pressure Control
Single Point Power
High Density Foam Compressor Sound
Suppression Blanket
Environmentally Friendly
R-410A Refrigerant
Extended Life
2500 Hour Salt Spray Tested Exterior
Corrosion Paint
Optional 5 Year Non-Prorated
Compressor Warranty
Polymer E-Coated Condenser Coils
6
ELECTRIC SHOCK Electric shock hazard Before servicing shut off all electrical power to the unit including remote disconnects to avoid shock hazard or injury from rotating parts Follow proper Lockout-Tagout procedures
WARNING
Safety
Attention should be paid to the following statements
NOTE - Notes are intended to clarify the unit installation operation and maintenance
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage property damage or personal injury
WARNING - Warning statements are given to prevent actions that could result in
equipment damage property damage personal injury or death
DANGER - Danger statements are given to prevent actions that will result in equipment
damage property damage severe personal injury or death
ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing controls label all
wires prior to disconnecting Reconnect wires correctly
Verify proper operation after servicing Secure all doors with key-lock or nut and bolt
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
2
Table of Contents AAON
reg CB Series Features and Options Introduction 5
Safety 6 CB Base Model and Features Description 10 General Description 11
Codes and Ordinances 11
Receiving Unit 11 Storage 12 Direct Expansion (DX) Condensing Units 12 Wiring Diagrams 13 General Maintenance 13
Installation 14 Lifting the Unit 14
Locating Unit 14 Mounting Isolation 15
Access Panel 15 Electrical 16
Thermostat 17 Refrigerant Piping 18
General 18
Determining Refrigerant Line Size 18
Liquid Line Sizing 19
Suction Line Sizing 20
Hot Gas Bypass Line 22
Hot Gas Reheat 22
Predetermined Line Sizes 23
Startup 26
Compressors 26 Charging Refrigerant amp Adjusting Refrigerant Charge 27
Before Charging 27
Checking Liquid Sub-cooling 27
Checking Evaporator Superheat 28
Adjusting Sub-cooling and Superheat Temperatures 28
Air Flow 29 Operation 31
Thermostat Operation 31 Compressor 31 Variable Capacity Compressor Controller 31 Low Ambient Operation 34 LAC Valve 35 Condenser Flooding 36
3
Compressor Lockouts 36
Maintenance 37 Coils 37 E-Coated Coil Cleaning 37
DX Cooling 39 Condenser Fan Motor 39 Replacement Parts 39 Warranty Service and Parts Department 39
Refrigerant Piping Diagrams 40
CB Series Startup Form 52 Literature Change History 55
4
Index of Tables and Figures
Tables Table 1 - Recommended Elevation Minimums 15 Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A 25 Table 3 - Acceptable Refrigeration Circuit Values 28
Table 4 - Performance Testing Air Flow Setpoints 29 Table 5 - R-410A Refrigerant Temperature-Pressure Chart 30 Table 6 - Demand Signal vs Compressor Capacity Modulation 32 Table 7 - Thermistor Temperature vs Resistance Values 33 Table 8 - Condenser Flooding 36
Figures Figure 1 ndash Forklift Channels amp Access Panel 14 Figure 2 ndash Condensing Unit Clearances 15 Figure 3 ndash Utility Entry 16 Figure 4 ndash Heat Pump Piping Schematic of Suction Vapor Flow Down in Double Riser 21
Figure 5 ndash Heat Pump Piping Schematic of Discharge Vapor Flow Up in Double Riser 21 Figure 6 - Riser height versus total equivalent line length 25 Figure 7 - Variable Capacity Compressor Controller 32
Figure 8 - Compressor Controller Flash Code Details 33 Figure 9 - Adjustable Fan Cycling Switch 34
Figure 10 - Piping Schematic of Example System using the LAC Valve 35 Figure 11 - Adjustable compressor lockout 36 Figure 12ndash AC only piping AHU above CU 40
Figure 13 ndash AC only piping AHU below CU 41
Figure 14 ndash Modulating hot gas reheat piping AHU above CU 42 Figure 15 ndash Modulating hot gas reheat piping AHU below CU 43 Figure 16 ndash Hot gas bypass piping AHU above CU 44
Figure 17 ndash Hot gas bypass piping AHU below CU 45 Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU 46
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU 47 Figure 20 ndash Heat pump piping AHU above CU 48 Figure 21 ndash Heat pump piping AHU below CU 49 Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU 50
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU 51
R57611 Rev A 161221
(ACP J00187)
5
AAONreg CB Series Features and Options Introduction
Energy Efficiency
Two Step or Variable Capacity Scroll
Compressor
Air-Source Heat Pump
Variable Speed Condenser Fans for Head
Pressure Control
Humidity Control
Modulating Hot Gas Reheat
Safety
Suction Pressure Transducer
Heavy Duty Wire Guards or Louvered
Panels for Condenser Coils
Automatic Low Pressure and Manual
reset High Pressure Safety Cut-outs
Suction and Liquid Line Schrader Valves
Installation and Maintenance Easily Removable Panel Access to
Service Compartment
Run Test Report and Installation Manuals
Included in Controls Compartment
Color Coded Wiring and Wiring
Diagrams
24V Control Circuit Transformer Option
System Integration
Split System Matching
Modulating Head Pressure Control
Single Point Power
High Density Foam Compressor Sound
Suppression Blanket
Environmentally Friendly
R-410A Refrigerant
Extended Life
2500 Hour Salt Spray Tested Exterior
Corrosion Paint
Optional 5 Year Non-Prorated
Compressor Warranty
Polymer E-Coated Condenser Coils
6
ELECTRIC SHOCK Electric shock hazard Before servicing shut off all electrical power to the unit including remote disconnects to avoid shock hazard or injury from rotating parts Follow proper Lockout-Tagout procedures
WARNING
Safety
Attention should be paid to the following statements
NOTE - Notes are intended to clarify the unit installation operation and maintenance
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage property damage or personal injury
WARNING - Warning statements are given to prevent actions that could result in
equipment damage property damage personal injury or death
DANGER - Danger statements are given to prevent actions that will result in equipment
damage property damage severe personal injury or death
ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing controls label all
wires prior to disconnecting Reconnect wires correctly
Verify proper operation after servicing Secure all doors with key-lock or nut and bolt
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
3
Compressor Lockouts 36
Maintenance 37 Coils 37 E-Coated Coil Cleaning 37
DX Cooling 39 Condenser Fan Motor 39 Replacement Parts 39 Warranty Service and Parts Department 39
Refrigerant Piping Diagrams 40
CB Series Startup Form 52 Literature Change History 55
4
Index of Tables and Figures
Tables Table 1 - Recommended Elevation Minimums 15 Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A 25 Table 3 - Acceptable Refrigeration Circuit Values 28
Table 4 - Performance Testing Air Flow Setpoints 29 Table 5 - R-410A Refrigerant Temperature-Pressure Chart 30 Table 6 - Demand Signal vs Compressor Capacity Modulation 32 Table 7 - Thermistor Temperature vs Resistance Values 33 Table 8 - Condenser Flooding 36
Figures Figure 1 ndash Forklift Channels amp Access Panel 14 Figure 2 ndash Condensing Unit Clearances 15 Figure 3 ndash Utility Entry 16 Figure 4 ndash Heat Pump Piping Schematic of Suction Vapor Flow Down in Double Riser 21
Figure 5 ndash Heat Pump Piping Schematic of Discharge Vapor Flow Up in Double Riser 21 Figure 6 - Riser height versus total equivalent line length 25 Figure 7 - Variable Capacity Compressor Controller 32
Figure 8 - Compressor Controller Flash Code Details 33 Figure 9 - Adjustable Fan Cycling Switch 34
Figure 10 - Piping Schematic of Example System using the LAC Valve 35 Figure 11 - Adjustable compressor lockout 36 Figure 12ndash AC only piping AHU above CU 40
Figure 13 ndash AC only piping AHU below CU 41
Figure 14 ndash Modulating hot gas reheat piping AHU above CU 42 Figure 15 ndash Modulating hot gas reheat piping AHU below CU 43 Figure 16 ndash Hot gas bypass piping AHU above CU 44
Figure 17 ndash Hot gas bypass piping AHU below CU 45 Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU 46
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU 47 Figure 20 ndash Heat pump piping AHU above CU 48 Figure 21 ndash Heat pump piping AHU below CU 49 Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU 50
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU 51
R57611 Rev A 161221
(ACP J00187)
5
AAONreg CB Series Features and Options Introduction
Energy Efficiency
Two Step or Variable Capacity Scroll
Compressor
Air-Source Heat Pump
Variable Speed Condenser Fans for Head
Pressure Control
Humidity Control
Modulating Hot Gas Reheat
Safety
Suction Pressure Transducer
Heavy Duty Wire Guards or Louvered
Panels for Condenser Coils
Automatic Low Pressure and Manual
reset High Pressure Safety Cut-outs
Suction and Liquid Line Schrader Valves
Installation and Maintenance Easily Removable Panel Access to
Service Compartment
Run Test Report and Installation Manuals
Included in Controls Compartment
Color Coded Wiring and Wiring
Diagrams
24V Control Circuit Transformer Option
System Integration
Split System Matching
Modulating Head Pressure Control
Single Point Power
High Density Foam Compressor Sound
Suppression Blanket
Environmentally Friendly
R-410A Refrigerant
Extended Life
2500 Hour Salt Spray Tested Exterior
Corrosion Paint
Optional 5 Year Non-Prorated
Compressor Warranty
Polymer E-Coated Condenser Coils
6
ELECTRIC SHOCK Electric shock hazard Before servicing shut off all electrical power to the unit including remote disconnects to avoid shock hazard or injury from rotating parts Follow proper Lockout-Tagout procedures
WARNING
Safety
Attention should be paid to the following statements
NOTE - Notes are intended to clarify the unit installation operation and maintenance
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage property damage or personal injury
WARNING - Warning statements are given to prevent actions that could result in
equipment damage property damage personal injury or death
DANGER - Danger statements are given to prevent actions that will result in equipment
damage property damage severe personal injury or death
ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing controls label all
wires prior to disconnecting Reconnect wires correctly
Verify proper operation after servicing Secure all doors with key-lock or nut and bolt
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
4
Index of Tables and Figures
Tables Table 1 - Recommended Elevation Minimums 15 Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A 25 Table 3 - Acceptable Refrigeration Circuit Values 28
Table 4 - Performance Testing Air Flow Setpoints 29 Table 5 - R-410A Refrigerant Temperature-Pressure Chart 30 Table 6 - Demand Signal vs Compressor Capacity Modulation 32 Table 7 - Thermistor Temperature vs Resistance Values 33 Table 8 - Condenser Flooding 36
Figures Figure 1 ndash Forklift Channels amp Access Panel 14 Figure 2 ndash Condensing Unit Clearances 15 Figure 3 ndash Utility Entry 16 Figure 4 ndash Heat Pump Piping Schematic of Suction Vapor Flow Down in Double Riser 21
Figure 5 ndash Heat Pump Piping Schematic of Discharge Vapor Flow Up in Double Riser 21 Figure 6 - Riser height versus total equivalent line length 25 Figure 7 - Variable Capacity Compressor Controller 32
Figure 8 - Compressor Controller Flash Code Details 33 Figure 9 - Adjustable Fan Cycling Switch 34
Figure 10 - Piping Schematic of Example System using the LAC Valve 35 Figure 11 - Adjustable compressor lockout 36 Figure 12ndash AC only piping AHU above CU 40
Figure 13 ndash AC only piping AHU below CU 41
Figure 14 ndash Modulating hot gas reheat piping AHU above CU 42 Figure 15 ndash Modulating hot gas reheat piping AHU below CU 43 Figure 16 ndash Hot gas bypass piping AHU above CU 44
Figure 17 ndash Hot gas bypass piping AHU below CU 45 Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU 46
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU 47 Figure 20 ndash Heat pump piping AHU above CU 48 Figure 21 ndash Heat pump piping AHU below CU 49 Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU 50
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU 51
R57611 Rev A 161221
(ACP J00187)
5
AAONreg CB Series Features and Options Introduction
Energy Efficiency
Two Step or Variable Capacity Scroll
Compressor
Air-Source Heat Pump
Variable Speed Condenser Fans for Head
Pressure Control
Humidity Control
Modulating Hot Gas Reheat
Safety
Suction Pressure Transducer
Heavy Duty Wire Guards or Louvered
Panels for Condenser Coils
Automatic Low Pressure and Manual
reset High Pressure Safety Cut-outs
Suction and Liquid Line Schrader Valves
Installation and Maintenance Easily Removable Panel Access to
Service Compartment
Run Test Report and Installation Manuals
Included in Controls Compartment
Color Coded Wiring and Wiring
Diagrams
24V Control Circuit Transformer Option
System Integration
Split System Matching
Modulating Head Pressure Control
Single Point Power
High Density Foam Compressor Sound
Suppression Blanket
Environmentally Friendly
R-410A Refrigerant
Extended Life
2500 Hour Salt Spray Tested Exterior
Corrosion Paint
Optional 5 Year Non-Prorated
Compressor Warranty
Polymer E-Coated Condenser Coils
6
ELECTRIC SHOCK Electric shock hazard Before servicing shut off all electrical power to the unit including remote disconnects to avoid shock hazard or injury from rotating parts Follow proper Lockout-Tagout procedures
WARNING
Safety
Attention should be paid to the following statements
NOTE - Notes are intended to clarify the unit installation operation and maintenance
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage property damage or personal injury
WARNING - Warning statements are given to prevent actions that could result in
equipment damage property damage personal injury or death
DANGER - Danger statements are given to prevent actions that will result in equipment
damage property damage severe personal injury or death
ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing controls label all
wires prior to disconnecting Reconnect wires correctly
Verify proper operation after servicing Secure all doors with key-lock or nut and bolt
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
5
AAONreg CB Series Features and Options Introduction
Energy Efficiency
Two Step or Variable Capacity Scroll
Compressor
Air-Source Heat Pump
Variable Speed Condenser Fans for Head
Pressure Control
Humidity Control
Modulating Hot Gas Reheat
Safety
Suction Pressure Transducer
Heavy Duty Wire Guards or Louvered
Panels for Condenser Coils
Automatic Low Pressure and Manual
reset High Pressure Safety Cut-outs
Suction and Liquid Line Schrader Valves
Installation and Maintenance Easily Removable Panel Access to
Service Compartment
Run Test Report and Installation Manuals
Included in Controls Compartment
Color Coded Wiring and Wiring
Diagrams
24V Control Circuit Transformer Option
System Integration
Split System Matching
Modulating Head Pressure Control
Single Point Power
High Density Foam Compressor Sound
Suppression Blanket
Environmentally Friendly
R-410A Refrigerant
Extended Life
2500 Hour Salt Spray Tested Exterior
Corrosion Paint
Optional 5 Year Non-Prorated
Compressor Warranty
Polymer E-Coated Condenser Coils
6
ELECTRIC SHOCK Electric shock hazard Before servicing shut off all electrical power to the unit including remote disconnects to avoid shock hazard or injury from rotating parts Follow proper Lockout-Tagout procedures
WARNING
Safety
Attention should be paid to the following statements
NOTE - Notes are intended to clarify the unit installation operation and maintenance
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage property damage or personal injury
WARNING - Warning statements are given to prevent actions that could result in
equipment damage property damage personal injury or death
DANGER - Danger statements are given to prevent actions that will result in equipment
damage property damage severe personal injury or death
ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing controls label all
wires prior to disconnecting Reconnect wires correctly
Verify proper operation after servicing Secure all doors with key-lock or nut and bolt
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
6
ELECTRIC SHOCK Electric shock hazard Before servicing shut off all electrical power to the unit including remote disconnects to avoid shock hazard or injury from rotating parts Follow proper Lockout-Tagout procedures
WARNING
Safety
Attention should be paid to the following statements
NOTE - Notes are intended to clarify the unit installation operation and maintenance
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage property damage or personal injury
WARNING - Warning statements are given to prevent actions that could result in
equipment damage property damage personal injury or death
DANGER - Danger statements are given to prevent actions that will result in equipment
damage property damage severe personal injury or death
ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing controls label all
wires prior to disconnecting Reconnect wires correctly
Verify proper operation after servicing Secure all doors with key-lock or nut and bolt
WARNING
QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with the unit
WARNING
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
7
FIRE EXPLOSION OR CARBON MONOXIDE POISONING HAZARD Failure to replace proper controls could result in fire explosion or carbon monoxide poisoning Failure to follow safety warnings exactly could result in serious injury death or property damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this appliance
WARNING
LIVE ELECTRICAL During installation testing servicing and troubleshooting of the equipment it may be necessary to work with live electrical components Only a qualified licensed electrician or individual properly trained in handling live electrical components shall perform these tasks Standard NFPA-70E an OSHA regulation requiring an Arc Flash Boundary to be field established and marked for identification of where appropriate Personal Protective Equipment (PPE) be worn should be followed
WARNING
GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NECCEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements
WARNING
ROTATING COMPONENTS Unit contains fans with moving parts that can cause serious injury Do not remove grill containing fans until the power to the unit has been disconnected and fan has stopped rotating
WARNING
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of 3 phase units at startup by a qualified service technician Scroll compressors are directional and can be damaged if rotated in the wrong direction Compressor rotation must be checked using suction and discharge gauges Fan motor rotation should be checked for proper operation Alterations should only be made at the unit power connection
CAUTION
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
8
Compartments containing hazardous voltage or rotating parts are equipped with a panel requiring tooled access Always re-install screws on the panel after installation or service is completed
CAUTION
UNIT HANDLING To prevent injury or death lifting equipment capacity shall exceed unit weight by an adequate safety factor Always test-lift unit not more than 24 inches high to verify proper center of gravity lift point to avoid unit damage injury or death
WARNING
LEAK TESTING
Do not use oxygen acetylene or air in place of refrigerant and dry nitrogen for leak testing A violent explosion may result causing injury or death
WARNING
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
COIL CLEANERS
To prevent damage to the unit do not use acidic chemical coil cleaners Do not use alkaline chemical coil cleaners with a pH value greater than 85 after mixing without first using an aluminum corrosion inhibitor in the cleaning solution
CAUTION
COIL CLEANERS
Some chemical coil cleaning compounds are caustic or toxic Use these substances only in accordance with the manufacturerrsquos usage instructions Failure to follow instructions may result in equipment damage injury or death
WARNING
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
9
1 Startup and service must be performed
by a Factory Trained Service
Technician
2 The unit is for outdoor use only See
General Information section for more
unit information
3 Every unit has a unique equipment
nameplate with electrical operational
and unit clearance specifications
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased
4 READ THE ENTIRE INSTALLATION
OPERATION AND MAINTENANCE
MANUAL OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL
5 Keep this manual and all literature
safeguarded near or on the unit
COIL CLEANING
Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil
CAUTION
ENCLOSED AREA
Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present and cause
injury or death
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
CB Series Feature String Nomenclature
Model Options Unit Feature Options
GE
N
MJ
RE
V
UN
IT
SIZ
E
VL
T
CO
MP
CK
TS
1
2
3
4
5
6
7
CB - B - 060 - 3 - B - 1 B D 0 0 D A 0
10
CB Base Model and Features Description
BASE MODEL SERIES AND GENERATION
CB
REVISION
B = Design Sequence
UNIT SIZE
024 = 24 MBH - 2 Ton - Vertical Discharge
036 = 36 MBH - 3 Ton - Vertical Discharge
048 = 48 MBH - 4 Ton - Vertical Discharge
060 = 60 MBH - 5 Ton - Vertical Discharge
VOLTAGE
1 = 230V1Φ60Hz
2 = 230V3Φ60Hz
3 = 460V3Φ60Hz
4 = 575V3Φ60Hz
8 = 208V3Φ60Hz
9 = 208V1Φ60Hz
COMPRESSOR TYPE
B = R-410A Two Step Scroll Compressor
D = R-410A Variable Capacity Scroll Compressor
F = R-410A Two Step Scroll Compressor with Sound
Blanket
H = R-410A Variable Capacity Scroll Compressor
with Sound Blanket
NUMBER OF CIRCUITS
1 = One Circuit
FEATURE 1 AMBIENT CONTROL 0 = Standard (55degF Ambient)
B = Adjustable Fan Cycling (35degF Ambient)
D = Modulating Fan Pressure Control (35degF
Ambient)
F = Flooded Condenser Ambient Controls (0degF) +
Option B
G = Flooded Condenser Ambient Controls (0degF) +
Option D
FEATURE 2 REFRIGERATION
OPTIONS 0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
FEATURE 3 CONTROLS
0 = Standard - Terminal Block
A = Suction Pressure Transducer (F1- Wattmaster
Reheat)
H = Control Circuit Transformer
S = Suction Pressure Transducer (Not F1 -
Wattmaster Controls)
T = Control Circuit Transformer w Suction Pressure
Transducer
FEATURE 4 COIL PROTECTION
0 = Standard
A = Polymer E-Coated Coil
FEATURE 5 CABINET OPTIONS D = Standard ndash Louvered Panels + 2500 Hour Salt-
Spray Tested Exterior Paint
G = Wire Grille + 2500 Hour Salt-Spray Tested
Exterior Paint
FEATURE 6 WARRANTY 0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
FEATURE 7 TYPE 0 = Standard
X = Special Pricing Authorization
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
11
General Description
AAON CB Series condensing units have
been designed for outdoor installation only
Startup and service must be performed by a
Factory Trained Service Technician
Codes and Ordinances
CB Series units have been tested and
certified by ETL in accordance with UL
Safety Standard 1995CSA C222 No 236
System should be sized in accordance with
the American Society of Heating
Refrigeration and Air Conditioning
Engineers Handbook
Installation of CB Series units must conform
to the ICC standards of the International
Mechanical Code the International Building
Code and local building plumbing and
waste water codes All appliances must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Receiving Unit
When received the unit should be checked
for damage that might have occurred in
transit If damage is found it should be noted
on the carrierrsquos Freight Bill A request for
inspection by carrierrsquos agent should be made
in writing at once
Nameplate should be checked to ensure the
correct model sizes and voltages have been
received to match the job requirements
If repairs must be made to damaged goods
then the factory should be notified before
any repair action is taken in order to protect
the warranty Certain equipment alteration
repair and manipulation of equipment
without the manufacturerrsquos consent may
void the product warranty Contact AAON
Warranty Department for assistance with
handling damaged goods repairs and
freight claims (903) 236-4403
NOTE Upon receipt check shipment for
items that ship loose Consult order and
shipment documentation to identify potential
loose-shipped items Loose-shipped items
The Clean Air Act of 1990 bans the intentional venting of refrigerant as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed
CAUTION
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a Factory Trained Service Technician
WARNING
SHARP EDGES
Coils and sheet metal surfaces present sharp edges and care must be taken when working with equipment
WARNING
Failure to observe the following instructions will result in premature failure of your system and possible voiding of the warranty
WARNING
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
12
may have been placed inside the unit cabinet
for security Installers and owners should
secure all doors with locks or nuts and bolts
to prevent unauthorized access
The warranty card must be completed in full
and returned to AAON not more than 3
months after the unit is delivered
Storage
If installation will not occur immediately
following delivery store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place Secure all loose-shipped
items
Direct Expansion (DX) Condensing Units
CB Series condensing units are factory
assembled and wired including a full charge
of R-410A refrigerant for up to 25 feet of
line set Systems with the modulating hot
gas reheat option will require refrigerant to
be field added because of the additional
refrigerant components and piping
associated with the system
Failure to observe the following instructions
may result in premature failure of your
system and possible voiding of the
warranty
Never cut off the main power supply to the
unit except for servicing emergency or
complete shutdown of the unit When power
is cut off from the unit compressors using
crankcase heaters cannot prevent refrigerant
migration This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor Since the
compressor is designed to pump refrigerant
gas damage may occur when power is
restored
If power to the unit must be off for more
than an hour turn the thermostat system
switch to ldquoOffrdquo or turn the unit off at the
control panel and then cut off the main
power supply Leave the unit off until the
main power supply has been turned on again
for at least 24 hours This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run
Always control the system from the
thermostat or control panel never at the
main power supply except for servicing
emergency or complete shutdown of the
unit
The standard compressors must be on a
minimum of 5 minutes and off for a
minimum of 5 minutes The cycle rate must
be no more than 6 starts per hour
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes The cycle rate must
be no more than 10 starts per hour
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and liquid refrigerant
CRANKCASE HEATER OPERATION
Units are equipped with compressor crankcase heaters which should be energized at least 24 hours prior to cooling operation to clear any liquid refrigerant from the compressors
CAUTION
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
13
Note Low Ambient Operation
Units without a low ambient option such as
condenser fan cycling or the 0degF low
ambient option will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55degF Low
ambient andor air handling unit economizer
options are recommended if cooling
operation below 55degF is expected
Note Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode cooling mode or off Do not
leave part of the systems switched to the
opposite mode Cooling only systems should
be switched off at the thermostat during the
heating season
Wiring Diagrams
Unit specific wiring diagram is laminated in
plastic and located inside the controls
compartment door
General Maintenance
When the initial startup is made and on a
periodic schedule during operation it is
necessary to perform routine service checks
on the performance of the condensing unit
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
14
Installation
AAON equipment has been designed for
quick and easy installation
Lifting the Unit
CB Series condensing units have channels
underneath the base which provide lifting
access to the underside of the equipment and
allow moving and placement without
physical damage
Figure 1 ndash Forklift Channels amp Access Panel
Dollies andor carts are recommended to lift
and place the unit to prevent damage to the
equipment and injury to the installer
Care should be taken if using spreader bars
blocking or other lifting devices to prevent
any damage to the cabinet coil or
condensing fans
Before lifting unit be sure that all shipping
material has been removed from unit
Hoist unit to a point directly above the
condenser pad and lower unit into the
proper place Unit may also be positioned
with a dolly When the unit is in place
remove the dolly or lifting device Make
sure the unit is properly seated and level
Locating Unit
CB Series condensing units are designed for
outdoor application and placement at ground
level or on a rooftop Units must be placed
on a level and solid foundation that can
support the unitrsquos weight
When rooftop mounted a steel frame must
be provided that will support the unit above
the roof itself for load distribution
When installed at ground level a one-piece
concrete slab or composite condenser pad
should be used with footings that extend
below the frost line (a substantial base that
will not settle) Slab should be surrounded
by a graveled area for proper drainage and
should not adjoin the building as sound and
vibration may be transmitted to the
structure Care must also be taken to protect
the coils and fins from damage due to
vandalism or other hazards
Airflow to and from the condensing unit
must not be restricted Coils and fans must
be free of any obstructions and debris in
order to start and operate properly with a
correct amount of airflow Obstruction to air
flow will result in decreased performance
and efficiency
The installation position must provide at
least one foot of clearance from the wall for
proper air flow to the coils When multiple
units are mounted adjacent to each other the
clearance required between them is three
feet
Service compartment must be accessible for
periodic servicing of controls safety
devices and refrigerant serviceshutoff
valves At least two feet of clearance on this
Incorrect lifting can cause damage to the unit
CAUTION
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
15
corner of the unit is recommended for
service
Figure 2 ndash Condensing Unit Clearances
Condensing units should not be installed in
an enclosure or pit that is deeper than the
height of the unit When recessed
installation is necessary the clearance to
maintain proper airflow is at least three feet
CB Series condensing units are single
circuited with vertical air discharge There
must be no obstruction above the equipment
Do not place the unit under an overhang
Placement relative to the building air intakes
and other structures must be carefully
selected Consider the effects of outdoor fan
noise on conditioned space and any adjacent
occupied space It is recommended that the
unit be placed so that discharge does not
blow toward windows less than 25 feet
away
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and in areas with prolonged continuous
subfreezing temperatures Heat pump unit
bases are cutout under the outdoor coil to
permit drainage of frost accumulation The
unit must be situated to permit free
unobstructed drainage of the defrost water
and ice A minimum 3 inches clearance
under the outdoor coil is required in the
milder climates In more severe weather
locations it is recommended that the unit be
elevated to allow unobstructed drainage and
airflow
Table 1 - Recommended Elevation
Minimums
Design
Temperature
Suggest Minimum
Elevation
+15 F and above 3rdquo
-5 F to +17 F 8rdquo
Below -5 F 12rdquo
Mounting Isolation
For roof mounted applications or anytime
vibration transmission is a factor vibration
isolators may be used
Access Panel
Access panel is provided to electrical
compartment To remove the panel
unscrew the four screws
PVC PIPING
PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride) are vulnerable to attack by certain chemicals Polyolester (POE) oils used with R-410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fittings and complete piping system failure
CAUTION
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
16
Electrical
Verify the unit nameplate agrees with the
power supply Connect power and control
field wiring as shown on the unit wiring
diagram provided with the unit
Route power and control wiring separately
through the utility entry right above the
service valves Do not run power and signal
wires in the same conduit
Figure 3 ndash Utility Entry
Size supply conductors based on the unit
MCA rating Supply conductors must be
rated a minimum of 75degC
Protect the branch circuit in accordance with
code requirements The unit must be
electrically grounded in accordance with
local codes or in the absence of local codes
the current National Electric Code
ANSINFPA 70 or the current Canadian
Electrical Code CSA C221
Note Units are factory wired for 208V
230V 460V or 575V In some units the
208V and 230V options may also be
provided in single or three phase
configurations The transformer
configuration must be checked by a
qualified technician prior to startup
Wire power leads to the unit terminal block
All wiring beyond this point has been done
by the manufacturer and cannot be modified
without affecting the units agencysafety
certification
All units require field supplied electrical
overcurrent and short circuit protection
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate
Codes may require a disconnect switch be
within sight of the unit
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Before attempting to perform any installation service or maintenance shut off all electrical power to the unit at the disconnect switches Unit may have multiple power supplies Failure to disconnect power could result in dangerous operation serious injury death or property damage
WARNING
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
17
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit
Supply voltage must be within the minmax
range shown on the unit nameplate
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate
Three phase voltage imbalance will cause
motor overheating and premature failure
The maximum allowable imbalance is 20
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage
Example
(221V+230V+227V)3 = 226V then
100(226V-221V)226V = 22 which
exceeds the allowable imbalance
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal Contact your local power company
for line voltage corrections
Installing contractor must check for proper
motor rotation and check blower motor
amperage listed on the motor nameplate is
not exceeded
Wire control signals to the unitrsquos low
voltage terminal block located in the
controls compartment
If any factory installed wiring must be
replaced use a minimum 105degC type AWM
insulated conductors
Thermostat
If a thermostat is used for unit control
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts sun exposure or
heat from electrical fixtures or appliances
Follow thermostat manufacturerrsquos
instructions for general installation
procedure
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation
All external devices must be powered via a
separate external power supply
Units with the modulating hot gas reheat
dehumidification feature must use a
humidistat or a thermostat with a normally
closed (NC) dehumidification option The
following thermostats have been approved
for usage with the dehumidification feature
Robertshawreg 9825i2 Thermostat
Honeywell VisionPROreg IAQ Thermostat
AAON Mini Controller
Three phase voltage imbalance will cause motor overheating and premature failure
CAUTION
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
18
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor
Use only clean type ldquoACRrdquo copper tubing
that has been joined with high temperature
brazing alloy
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler
All CB Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines These should remain
closed until the system is ready for start-up
after installation
Piping should conform to generally accepted
practices and codes
Upon completion of piping connection the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less
leak checked and charged with refrigerant
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure
1 Minimum pressure drop and
2 Continuous oil return and
3 Prevention of liquid refrigerant slugging
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective
reducing installation costs and reducing the
potential for leakage However as pipe
diameters narrow pressure-reducing
frictional forces increase
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash resulting in faulty Thermal Expansion
Valve (TXV) operation and improper
system performance In order to operate
efficiently and cost effectively while
avoiding malfunction refrigeration systems
must be designed to minimize both cost and
pressure loss
REFRIGERANT PIPING
This section is for information only and is not intended to provide all details required by the designer or installer of the refrigerant piping between the condenser or condensing unit and the air handling unit AAON Inc is not responsible for interconnecting refrigerant piping Consult ASHRAE Handbook ndash Refrigeration and ASME Standards
CAUTION
REFRIGERANT PIPING
Line sizes must be selected to meet actual installation conditions not simply based on the connection sizes at the condensing unit or air handling unit
CAUTION
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
19
Equivalent Line Length
All line lengths discussed in this manual
unless specifically stated otherwise are
Equivalent Line Lengths The frictional
pressure drop through valves fittings and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter Always use equivalent line
lengths when calculating pressure drop
Special piping provisions must be taken
when lines are run underground up vertical
risers or in excessively long line runs
Liquid Line Sizing
When sizing the liquid line it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability This can be achieved by
minimizing the liquid line diameter
However reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line and causes other
undesirable effects such as noise
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature avoiding flashing upstream of
the TXV and maintaining system
efficiency Pressure losses through the
liquid line due to frictional contact installed
accessories and vertical risers are
inevitable Maintaining adequate sub-
cooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV
Liquid refrigerant traveling upwards in a
riser loses head pressure If the evaporator is
below the condenser and the liquid line
does not include risers the gravitational
force will increase the pressure of the liquid
refrigerant This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line The sight glass should
not be used to determine if the system is
properly charged Use temperature and
pressure measurements to determine
liquid sub-cooling not the sight glass
Liquid Line Routing
Care should be taken with vertical risers
When the system is shut down gravity will
pull liquid down the vertical column and
back to the condenser when it is below the
evaporator This could potentially result in
compressor flooding A check valve can be
installed in the liquid line where the liquid
column rises above the condenser to prevent
this The liquid line is typically pitched
along with the suction line or hot gas line
to minimize the complexity of the
configuration
Liquid Line Insulation
When the liquid line is routed through
regions where temperature losses are
expected no insulation is required as this
may provide additional sub-cooling to the
refrigerant When routing the liquid line
through high temperature areas insulation of
the line is appropriate to avoid loss of sub-
cooling through heat gain
Liquid Line Guidelines
In order to ensure liquid at the TXV the
sum of frictional losses and pressure loss
due to vertical rise must not exceed
available sub-cooling A commonly used
guideline to consider is a system design with
pressure losses due to friction through the
line not to exceed a corresponding 1-2degF
change in saturation temperature An
additional recommendation is that the sum
of frictional losses and pressure loss due to
vertical rise should not exceed 5degF
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
20
If the velocity of refrigerant in the liquid line
is too great it could cause excessive noise or
piping erosion The recommended
maximum velocities for liquid lines are 100
fpm from the condenser to a receiver tank to
discourage fluid backup and 300 fpm from
receiver tank to the evaporator to minimize
valve induced liquid hammer
Liquid Line Accessories
Liquid line shut off valves and filter driers
are factory provided Filter driers must be
field installed The total length equivalent of
pressure losses through valves elbows and
fittings must be considered when adding
additional components in the field It is a
good practice to utilize the fewest elbows
that will allow the mating units to be
successfully joined
A solenoid valve is recommended on lines
over 100ft in length to prevent liquid
migration when the compressors are off
The solenoid needs to be wired so that it is
open when the compressors turn on and
closed when the compressors turn off
Suction Line Sizing
The suction line is more critical than the
liquid line from a design and construction
standpoint More care must be taken to
ensure that adequate velocity is achieved to
return oil to the compressor at minimum
loading conditions However reducing the
piping diameter to increase the velocity at
minimal load can result in excessive
pressure losses capacity reduction and
noise at full load
Suction Line Routing
Pitch the suction line in the direction of flow
(about 1 foot per 120 feet of length) to
maintain oil flow towards the compressor
and keep it from flooding back into the
evaporator Crankcase heaters are provided
to keep any condensed refrigerant that
collects in the compressor from causing
damage or wear Make sure to provide
support to maintain suction line positioning
and insulate completely between the
evaporator and condensing unit
It is important to consider part load
operation when sizing suction lines At
minimum capacity refrigerant velocity may
not be adequate to return oil up the vertical
riser Decreasing the diameter of the vertical
riser will increase the velocity but also the
frictional loss
For difficult line routing applications a
double suction riser can be applied to the
situation of part load operation with a
suction riser A double suction riser is
designed to return oil at minimum load
while not incurring excessive frictional
losses at full load A double suction riser
consists of a small diameter riser in parallel
with a larger diameter riser and a trap at the
base of the large riser At minimum
capacity refrigerant velocity is not sufficient
to carry oil up both risers and it collects in
the trap effectively closing off the larger
diameter riser and diverting refrigerant up
the small riser where velocity of the
refrigerant is sufficient to maintain oil flow
At full load the mass flow clears the trap of
oil and refrigerant is carried through both
risers The smaller diameter pipe should be
sized to return oil at minimum load while
the larger diameter pipe should be sized so
that flow through both pipes provides
acceptable pressure drop at full load
SUCTION LINE SIZING
Suction line must be sized in accordance to the minimum capacity of the variable speed compressor
CAUTION
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
21
A double riser used for heat pump operation
works differently than that described above
The specific volume (ft3lb) of refrigerant at
the discharge temperature (heating mode
line conditions) is significantly lower than
the specific volume at the suction
temperature (cooling mode line conditions)
To compound the issue the capacity in
heating mode is lower than the capacity in
cooling mode The discharge velocity in the
riser during heating mode is much lower
than the suction velocity during cooling
mode Often a double riser is necessary to
get acceptable velocities for the discharge
mode and acceptable velocities for the
suction mode A solenoid valve must be
added to the second riser The solenoid
valve must be wired to the reversing valve
so that the solenoid valve opens in cooling
mode and closes in heating mode See the
diagrams below
Figure 4 ndash Heat Pump Piping Schematic of
Suction Vapor Flow Down in Double Riser
Figure 5 ndash Heat Pump Piping Schematic of
Discharge Vapor Flow Up in Double Riser
Suction Line Insulation
The entire suction line should be insulated
with a minimum 1 inch thick Armaflex
insulation This prevents condensation from
forming on the line and reduces any
potential loss in capacity associated with
heat gain placing additional load on the
system
Suction Line Guidelines
For proper performance suction line
velocities less than a 4000 fpm maximum
are recommended The minimum velocity
required to return oil is dependent on the
pipe diameter however a general guideline
of 1000 fpm minimum may be applied
When suction flow is up variable capacity
compressors require a minimum velocity of
2000 fpm
Heat pump vapor lines must be checked for
suction flow (cooling mode operation) and
discharge flow (heating mode operation)
The same line must be used for both modes
of operation
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
22
In a fashion similar to the liquid line a
common guideline to consider is a system
design with pressure losses due to friction
through the line not to exceed a
corresponding 1-2degF change in saturation
temperature
At points where small pipe size can be used
to provide sufficient velocity to return oil in
vertical risers at part loads greater pressure
losses are incurred at full loads This can be
compensated for by over sizing the
horizontal runs and vertical drop sections
This will however require additional
refrigerant charge
Circuits with variable capacity scroll
compressors require suction riser traps every
10 feet
Suction Line Accessories
If the job requirements specify suction
accumulators they must be separately
purchased and field installed
Hot Gas Bypass Line
Hot Gas Bypass (HGB) is available for use
with DX systems that may experience low
suction pressure during the operating cycle
This may be due to varying load conditions
associated with VAV applications or units
supplying a large percentage of outside air
The system is designed to divert refrigerant
from the compressor discharge to the low
pressure side of the system in order to keep
the evaporator from freezing and to maintain
adequate refrigerant velocity for oil return at
minimum load
Hot discharge gas is redirected to the
evaporator inlet via an auxiliary side
connector (ASC) to false load the evaporator
when reduced suction pressure is sensed
Field piping between the condensing unit
and the evaporator is required
Hot Gas Bypass Piping Considerations for
Evaporator above Condensing Unit
Pitch the hot gas bypass line downward in
the direction of refrigerant flow toward the
evaporator
When installing hot gas bypass risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Install a sight glass in the oil drip
line for observation Run an oil return line
using 18 inch capillary tube 10 feet in
length from the oil drip line to the suction
line Connect the oil return line below the
sight glass and 1 inch above the bottom of
the oil drip line
HGB valves are adjustable Factory HGB
valve settings will be sufficient for most
applications but may require slight
adjustments for some applications including
some make up air applications
Insulate the entire length of the HGB line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Bypass Piping Considerations for
Evaporator Below Condensing Unit
The line must slope downward from the
HGB valve toward the evaporator
Hot Gas Bypass Line Guidelines
Choose a small size line to ensure oil return
and minimize refrigerant charge
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline to use is approximately 900 fpm
Hot Gas Reheat
The AAON modulating hot gas reheat
system diverts hot discharge gas from the
condenser to the air handling unit through
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
23
the hot gas line Field piping between the
condensing unit and the air handler is
required
The line delivers the hot discharge gas to the
reheat coil andor the hot gas bypass valve
so it is sized as a discharge line
Discharge lines should be sized to ensure
adequate velocity of refrigerant to ensure oil
return avoid excessive noise associated with
velocities that are too high and to minimize
efficiency losses associated with friction
Pitch the hot gas line in the direction of flow
for oil return
When installing hot gas reheat risers an oil
drip line must be provided at the lowest
point in the system The oil drip line must be
vertical its diameter should be the same as
the diameter of the riser and it should be 1
foot long Run a drip line using 18 inch
capillary tube 10 feet in length from the oil
drip line to the suction line Connect the oil
return line below the sight glass and 1 inch
above the bottom of the oil drip line
Insulate the entire length of the hot gas line
with a minimum 1 inch thick Armaflex
insulation
Hot Gas Reheat Guidelines
Maintain velocities below a maximum of
4000 fpm A general minimum velocity
guideline is 900 fpm
Predetermined Line Sizes
To aid in line sizing and selection AAON
has predetermined line sizes for the liquid
suction and hot gas lines in comfort cooling
applications
In order to generate this information the
following cycle assumptions are made
Saturated suction temperature = 50degF
Saturated condensing temperature = 125degF
Sub-cooling = 10degF Superheat = 15degF
The liquid lines have been chosen to
maintain velocities between 100 and 350
fpm The suction line diameters are selected
to limit velocities to a 4000 fpm maximum
while a minimum velocity restriction is
imposed by the ability to entrain oil up
vertical suction risers (ASHRAE Handbook
- Refrigeration)
Acceptable pressure loss criteria are applied
to each of the lines The total equivalent
length of the liquid line available is
determined such that 3degF of liquid sub-
cooling remain at the TXV This includes
the pressure losses in horizontal and vertical
sections accessories elbows etc
Recall that the available sub-cooling for the
cycle is assumed as 10degF To maintain at
least 3degF sub-cooling as a factor of safety to
avoid flashing at the TXV we consider a
maximum pressure loss equivalent to a 7degF
change in saturation temperature Pressure
losses in the suction line are not to exceed
2degF
When to Use Predetermined Line Sizing
The line sizes presented are not the only
acceptable pipe diameters they are however
appropriate for general comfort cooling
applications and satisfy common job
requirements Examine the conditions
assumptions and constraints used in the
generation of the predetermined pipe
diameters to ensure that this method is
applicable to a particular case Do not
assume that these line sizes are appropriate
for every case Consult ASHRAE
Handbook ndash Refrigeration for generally
accepted system piping practices
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
24
How to Use Predetermined Line Sizing
First read the previous section When to Use
Predetermined Line Sizing to decide if this
method is applicable Next consult Table 2
below for pipe diameters
Examine Figure 6 below to determine the
acceptable line dimensions associated with
the pipe diameters determined in Table 2
below The figure is shown as total available
riser height versus total equivalent line
length for the liquid line The curve
identifies a region of acceptable piping
configuration when the predetermined line
sizes are selected for any model in the table
A piping configuration above the curve falls
outside the assumptions used to determine
the line size and will result in a loss of sub-
cooling and additional pressure losses in the
suction and hot gas lines
The total equivalent line length definition
includes the height of vertical rise pressure
drop through elbows and accessories and
horizontal line length so elbows
accessories and vertical rise must be
considered when determining horizontal
length available from the total equivalent
line length
The figure below is presented in terms of the
liquid line but it assumes that the suction
line length is similar as these lines are
commonly routed together to minimize the
space and cost required for split system
installation
Before using this table read the When to Use Predetermined Line Sizes section Do not assume that these line sizes are appropriate for every case Consult ASHRAE Handbook ndash Refrigeration for generally accepted system piping practices The AAON Refrigerant Piping Calculator in Ecat32 can be used for job specific line sizing
CAUTION
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
25
Table 2 - Predetermined Line sizes for CB units with two step compressors and R-410A
Model Connection Sizes Predetermined Line Size
Liquid Suction Hot Gas Liquid Suction HGBP HGRH
CB-024 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 38rdquo
CB-036 38rdquo 34rdquo 38rdquo 38rdquo 34rdquo 38rdquo 12rdquo
CB-048 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
CB-060 38rdquo 78rdquo 12rdquo 12rdquo 78rdquo 12rdquo 12rdquo
Hot Gas Bypass line
Hot Gas Reheat line
Figure 6 - Riser height versus total equivalent line length
Note Figure 6 is for R-410A split system applications with two step compressor CB-024
through CB-060 units The region of acceptable riser height is the lighter area Select the
corresponding predetermined line size from Table 2 above
Total Equivalent Line Length in this figure is limited to 160 equivalent feet
CAUTION
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
26
Startup (See back of the manual for startup form)
Before startup of the condenser or
condensing unit make sure that the
following items have been checked
1 Verify that electrical power is available
to the unit
2 Verify that any remote stopstart device
connected to the unit controller is
requesting the unit to start
Confirm the compressor is operating within
tolerance
While performing the check use the startup
form to record observations of amps and
refrigerant pressures
When all is running properly place the
controller in the Run mode and observe the
system until it reaches a steady state of
operation
Compressors
All compressors are equipped with
crankcase heaters which should be
energized at least 24 hours prior to cooling
operation of the compressor
3-PHASE ROTATION
Rotation must be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection
CAUTION
COMPRESSOR ROTATION
Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconnected after factory testing Rotation should be checked by a qualified service technician at startup using suction and discharge pressure gauges and any wiring alteration should only be made at the unit power connection
CAUTION
ELECTRIC SHOCK
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
QUALIFIED INSTALLER
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician
WARNING
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
27
Charging Refrigerant amp Adjusting
Refrigerant Charge
The unit comes with full charge based on a
25 foot line set Charging a system in the
field must be based on determination of
liquid sub-cooling and evaporator superheat
On a system with a TXV liquid sub-cooling
is more representative of the charge than
evaporator superheat but both measurements
must be taken
Before Charging
Refer to the Unit Nameplate to determine
which refrigerant must be used to charge the
system
Unit being charged must be at or near full
load conditions before adjusting the charge
Units equipped with hot gas bypass must
have the hot gas bypass valve closed to get
the proper charge
Units equipped with hot gas reheat must be
charged with the hot gas valves closed while
the unit is in cooling mode After charging
unit should be operated in reheat
(dehumidification) mode to check for
correct operation
Units equipped with heat pump options
should be charged in heating mode to get the
proper charge After charging unit should
be operated in cooling mode to check for
correct charge Charge may need to be
adjusted for cooling mode If adjustments
are made in the cooling mode heating mode
must be rerun to verify proper operation
After adding or removing charge the system
must be allowed to stabilize typically 10-15
minutes before making any other
adjustments
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat Refer to the table of acceptable
refrigerant circuit values when determining
the proper sub-cooling
Checking Liquid Sub-cooling
Measure the temperature of the liquid line as
it leaves the condenser coil
Read the gauge pressure reading of the
liquid line close to the point where the
temperature was taken You must use liquid
line pressure as it will vary from discharge
pressure due to condenser coil pressure
drop
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart or Table 5 below
CLEAN AIR ACT
The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCrsquos and HCFCrsquos) as of July 1 1992 Approved methods of recovery recycling or reclaiming must be followed Fines andor incarceration may be levied for non-compliance
CAUTION
COMPRESSOR LUBRICANT
Polyolester (POE) and Polyvinylether (PVE) oils are two types of lubricants used in hydrofluorocarbon (HFC) refrigeration systems Refer to the compressor label for the proper compressor lubricant type
CAUTION
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
28
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling
Compare calculated sub-cooling to Table 3
below for the appropriate unit type and
options
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor
Read gauge pressure at the suction line close
to the compressor
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat
Compare calculated superheat to Table 3
below for the appropriate unit type and
options
Table 3 - Acceptable Refrigeration Circuit
Values
Air-Cooled CondAir-Source Heat Pump
Sub-Cooling
12-18degF 2-4degF (HP)
Sub-Cooling with
Hot Gas Reheat 15-22degF 2-6degF (HP)
Superheat
8-15degF
In cooling mode operation
Sub-cooling must be increased by 2degF per
20 feet of vertical liquid line rise for R-410A
Superheat will increase with long
suction line runs
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
temperature range as shown in Table 3 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling
The system is undercharged if the superheat
is too high and the sub-cooling is too low
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling
If the sub-cooling is correct and the
superheat is too high the TXV may need
adjustment to correct the superheat
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient control
(LAC) refrigerant flood back option being
charged when the ambient temperature is
warm
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added Add approximately 80 of
the receiver tank volume to the charge to
help fill the receiver tank The additional
charge is required for the system when
running in cold ambient conditions
DO NOT OVERCHARGE Refrigerant overcharging leads to excess refrigerant in the condenser coils resulting in elevated compressor discharge pressure
CAUTION
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
29
For units equipped with low ambient
refrigerant flood back option being charged
when the ambient temperature is cold
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added If the ambient
temperature is 0degF no more charge is
required If the ambient temperature is
around 40degF add approximately 40 of the
receiver tank volume
The unit will have to be checked for proper
operation once the ambient temperature is
above 80degF
Air Flow
Table 4 - Performance Testing Air Flow Setpoints
Model Cooling Stage 2
(cfm)
Cooling Stage 1
(cfm)
Heating Stage 2
(cfm)
Heating Stage 1
(cfm)
CB-B-024---1 885 66375 885 7965
CB-B-036---1 1250 9375 1250 1125
CB-B-048---1 1500 1125 1500 1350
CB-B-060---1 1545 115875 1545 13905
Before completing startup and leaving the unit a complete operating cycle should be observed to verify that all components are functioning properly
CAUTION
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
30
Table 5 - R-410A Refrigerant Temperature-Pressure Chart
degF PSIG degF PSIG degF PSIG degF PSIG degF PSIG
20 783 47 1347 74 2137 101 3210 128 4632
21 800 48 1372 75 2171 102 3256 129 4693
22 818 49 1397 76 2206 103 3302 130 4754
23 836 50 1422 77 2241 104 3349 131 4816
24 854 51 1448 78 2277 105 3396 132 4878
25 872 52 1474 79 2313 106 3444 133 4941
26 891 53 1501 80 2349 107 3493 134 5005
27 910 54 1528 81 2386 108 3542 135 5069
28 929 55 1555 82 2423 109 3591 136 5134
29 949 56 1582 83 2460 110 3641 137 5200
30 968 57 1610 84 2498 111 3691 138 5266
31 988 58 1638 85 2537 112 3742 139 5333
32 1009 59 1667 86 2575 113 3794 140 5401
33 1029 60 1696 87 2614 114 3846 141 5470
34 1050 61 1725 88 2654 115 3899 142 5539
35 1071 62 1754 89 2694 116 3952 143 5609
36 1092 63 1784 90 2735 117 4005 144 5679
37 1114 64 1815 91 2776 118 4059 145 5751
38 1136 65 1845 92 2817 119 4114 146 5823
39 1158 66 1876 93 2859 120 4169 147 5896
40 1181 67 1907 94 2901 121 4225 148 5969
41 1203 68 1939 95 2944 122 4282 149 6044
42 1227 69 1971 96 2987 123 4339 150 6119
43 1250 70 2004 97 3030 124 4396
44 1274 71 2036 98 3075 125 4454
45 1298 72 2070 99 3119 126 4513
46 1322 73 2103 100 3164 127 4573
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
31
Operation
Unit operations should be controlled with
thermostat or unit controller never at the
main power supply except for emergency
servicing or complete shutdown of the unit
Thermostat Operation
Heating
Thermostat system switch - Heat
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Cooling
Thermostat system switch - Cool
Thermostat fan switch - Auto or On
Thermostat temperature set to desired point
Air Circulation
Thermostat system switch - Off
Thermostat fan switch - Auto or On
No change of the thermostat temperature
With these settings the air handlerrsquos supply
fan will run continuously but the supply air
will not be heated cooled or dehumidified
System Off
Thermostat system switch - Off
Thermostat fan switch - Auto
No change of the thermostat temperature
With these settings the system is shut down
with the exception of the control system
power (24 VAC) and the crankcase heaters
(about 60 wattscompressor)
Night and Weekend Unoccupied Operation
To reduce the operating time of the unit
when the space is unoccupied such as nights
and weekends it is recommended that the
temperature setting be raised about 5degF
while unoccupied during the cooling season
and lowered about 10degF during the heating
season
Compressor
The compressors must be off for a minimum
of 5 minutes and on for a minimum of 5
minutes Short cycling of the compressors
can causes undue stress and wear
Variable Capacity Compressor
Controller
Units with variable capacity scroll
compressors may include variable capacity
compressor controller The following is an
explanation of the terminals and
troubleshooting of the alert flash codes on
the controller For more information on the
compressor controller see Emerson Climate
Bulletin AE8-1328
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME To prevent motor overheating compressors must cycle off for a minimum of 5 minutes
5 MINUTE MINIMUM ON TIME To maintain the proper oil level compressors must cycle on for a minimum of 5 minutes The cycle rate must not exceed 6 starts per hour
WARNING
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
32
Figure 7 - Variable Capacity Compressor
Controller
Low Voltage Terminals
24COM Module Common
24VAC Module Power
C1 amp C2 Demand Input
P1 Pressure Common
P2 Pressure Input
P3 Pressure Power 5VDC
P4 Pressure Shield
P5 amp P6 Pressure Output
T1 amp T2 Discharge Temperature Sensor
High Voltage Terminals
A1 amp A2 Alarm Relay Out
M1 amp M2 Contactor
L1 Control Voltage N
L2 Control Voltage L
U1 amp U2 Digital Unloader Solenoid
V1 amp V2 Vapor Injection Solenoid
The compressor controller modulates the
compressor unloader solenoid in an onoff
pattern according the capacity demand
signal of the system The following table
shows the linear relationship between the
demand signal and compressor capacity
modulation The compressor controller also
protects the compressor against high
discharge temperature Refer to Table 7 for
the relationship between thermistor
temperature readings and resistance values
Table 6 - Demand Signal vs Compressor Capacity Modulation
Demand
Signal (VDC) Loaded Unloaded Time Loaded
Time
Unloaded
Compressor
Capacity
100 Off Off Off Off 0
144 10 90 15 sec 135 sec 10
300 50 50 75 sec 75 sec 50
420 80 20 12 sec 3 sec 80
500 100 0 15 sec 0 sec 100
To avoid damaging the compressor controller DO NOT connect wires to terminals C3 C4 T3 T4 T5 or T6
WARNING
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
33
Figure 8 - Compressor Controller Flash Code Details
Table 7 - Thermistor Temperature vs Resistance Values
degC degF kΩ degC degF kΩ
-40 -40 288960 75 167 1273
-35 -31 208722 80 176 1079
-30 -22 152220 85 185 920
-25 -13 112144 90 194 787
-20 -4 83472 95 203 677
-15 5 62728 100 212 585
-10 14 47574 105 221 509
-5 23 36399 110 230 445
0 32 28082 115 239 387
5 41 21841 120 248 335
10 50 17117 125 257 292
15 59 13514 130 266 258
20 68 10744 135 275 228
25 77 8600 140 284 202
30 86 6928 145 293 180
35 95 5616 150 302 159
40 104 4581 155 311 139
45 113 3758 160 320 125
50 122 3099 165 329 112
55 131 2568 170 338 101
60 140 2140 175 347 092
65 149 1791 180 356 083
70 158 1507
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
34
Low Ambient Operation
During low ambient temperatures the vapor
refrigerant will migrate to the cold part of
the system (condenser) and condense into
liquid All CB Series compressors are
provided with factory installed crankcase
heaters to help prevent liquid refrigerant
from slugging the compressors during
startup in low ambient conditions The
condenser or condensing unit must have
continuous power 24 hours prior to startup
This ensures the compressor will receive
sufficient refrigerant vapor at startup
Standard units can operate down to 55degF
ambient temperature
AAON head pressure control units can
operate down to 35degF ambient temperature
Two different head pressure control options
available are adjustable fan cycling or ECM
condenser fan See detailed information
following
The AAON low ambient (condenser flood-
back) system is used to operate a refrigerant
system down to 0degF outside air temperature
See detailed information below
Fan Cycling Low Ambient
Adjustable fan cycling is a low ambient
head pressure control option that cycles the
condenser fans to maintain refrigerant
circuit head pressures at acceptable levels
during cooling operation The head pressure
set point (100-470 psi) and pressure
differential (35-200 psi) can be field
adjusted using a flathead screwdriver For
example if the head pressure is set to
300psi and the differential is set to 100psi
then fans will cut in at 300psi and cut out at
200psi Fan cycling and variable speed
condenser fan head pressure control options
allow mechanical cooling with ambient
temperatures down to 35degF
Figure 9 - Adjustable Fan Cycling Switch
Variable Speed Low Ambient
Variable speed condenser fan head pressure
control is a low ambient head pressure
control option that sends to an electronically
commutated motor a variable signal in
relation to the refrigerant circuit head
pressure of the system The motor either
speeds up or slows down air flow
accordingly in order to maintain constant
head pressure Fan cycling and variable
speed condenser fan head pressure control
options allow mechanical cooling with
ambient temperatures down to 35degF
Flooded Condenser Low Ambient
Flooded Condenser low ambient control
maintains normal head pressure during
periods of low ambient When the ambient
temperature drops the condensing
temperature and therefore pressure drops
Without ambient control the system would
shut down on low discharge pressure The
flooded condenser method of low ambient
control fills the condenser with liquid
refrigerant decreasing the heat transfer
capacity of the coil which allows the coil to
operate at an acceptable discharge pressure
The condenser coil will not be flooded
during summer ambient temperatures so a
receiver is included to store the additional
liquid refrigerant required to flood the
condenser in low ambient
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
35
The low ambient system maintains normal
head pressure during periods of low ambient
by restricting liquid flow from the condenser
to the receiver and at the same time
bypassing hot gas around the condenser to
the inlet of the receiver This reduces liquid
refrigerant flow from the condenser
reducing its effective surface area which in
turn increases the condensing pressure At
the same time the bypassed hot gas raises
liquid pressure in the receiver allowing the
system to operate properly CF Series
condensers and condensing units use an
LAC valve for low ambient operation
LAC Valve
The Low Ambient Control (LAC) valve is a
non-adjustable three way valve that
modulates to maintain receiver pressure As
the receiver pressure drops below the valve
setting (295 psig for R-410A) the valve
modulates to bypass discharge gas around
the condenser The discharge gas warms the
liquid in the receiver and raises the pressure
to the valve setting The following
schematic shows an example system using
the LAC valve
Figure 10 - Piping Schematic of Example System using the LAC Valve
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
36
Condenser Flooding
In order to maintain head pressure in the
refrigeration system liquid refrigerant is
kept in the condenser to reduce condenser
surface The following chart shows the
percentage that a condenser must be flooded
in order to function properly at the given
ambient temperature
During higher ambient temperatures the
entire condenser is required to condense
refrigerant During these higher ambient
temperatures a receiver tank is used to
contain the refrigerant that was required to
flood the condenser during low ambient
operation The receiver is factory-sized to
contain all of the flooded volume Without a
receiver there would be high head pressures
during higher ambient conditions
Table 8 - Condenser Flooding PERCENTAGE OF CONDENSER TO BE
FLOODED
Ambient
Temperature
(degF)
Evaporating Temperature (degF)
0deg 10deg 20deg 30deg 35deg 40deg 45deg 50deg
70deg 40 24 0 0 0 0 0 0
0deg 60 47 33 17 26 20 10 4
50deg 70 60 50 38 45 40 33 28
40deg 76 68 60 50 56 52 46 42
30deg 80 73 66 59 64 60 55 51
20deg 86 77 72 65 69 66 62 59
0deg 87 83 78 73 76 73 70 68
Compressor Lockouts
Some units include adjustable compressor
lockouts The compressor lockout in the
picture below can be set to any temperature
between -10degF and 70degF The ambient
temperature sensor hangs right outside the
unit with a cover
Figure 11 - Adjustable compressor lockout
Heat pump units include a non-adjustable
compressor lockout for the cooling mode set
to 55degF and an adjustable compressor
lockout for the heating mode that can be set
between 20degF to 95degF If a heat pump is
selected with the compressor lockout
feature the adjustable compressor lockout
will change to the -10degF to 70degF range
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
37
Maintenance (See back of the manual for maintenance
log)
At least once each year a qualified service
technician should check out the unit This
includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat
Only trained and qualified service
technicians experienced in both condensing
units and air conditioning are permitted to
service the CB Series units to keep
warranties in effect
Coils
The condenser coils should be inspected
yearly to ensure unrestricted airflow If the
coils contain a large amount of airborne dust
or other material they should be cleaned
Care must be taken to prevent bending of the
aluminum fins on the coils
Before attempting to clean the coils set
thermostat to the OFF position turn the
electrical power to the unit to the OFF
position at the disconnect switch The
condenser coil can be cleaned by washing
from the inside out with water and a coil
cleaner If coil is extremely dirty with
clogged fins a service professional
specializing in coil cleaning should be
called
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow If unable to back wash
the side of the coil opposite of the coils
entering air side then surface loaded fibers
or dirt should be removed with a vacuum
cleaner If a vacuum cleaner is not available
a soft non-metallic bristle brush may be
used In either case the tool should be
applied in the direction of the fins Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins
Use of a water stream such as a garden
hose against a surface loaded coil will drive
the fibers and dirt into the coil This will
make cleaning efforts more difficult Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse
A monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides dirt and debris It is very
important when rinsing that water
temperature is less than 130degF and pressure
is than 100 psig to avoid damaging the fin
edges An elevated water temperature (not to
exceed 130degF) will reduce surface tension
increasing the ability to remove chlorides
and dirt
Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Installation and service must be performed by a trained qualified installer
WARNING
Electric shock hazard Shut off all electrical power to the unit to avoid shock hazard or injury from rotating parts
WARNING
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
38
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage Coil cleaning shall be part of the unitrsquos
regularly scheduled maintenance
procedures Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability
For routine quarterly cleaning first clean the
coil with the below approved coil
cleaner After cleaning the coils with the
approved cleaning agent use the approved
chloride remover to remove soluble salts and
revitalize the unit
Recommended Coil Cleaner The following cleaning agent assuming it is
used in accordance with the manufacturerrsquos
directions on the container for proper mixing
and cleaning has been approved for use on
e-coated coils to remove mold mildew
dust soot greasy residue lint and other
particulate
Enviro-Coil Concentrate Part Number H-
EC01
Recommended Chloride Remover CHLORRID DTStrade should be used to
remove soluble salts from the e-coated coil
but the directions must be followed closely
This product is not intended for use as a
degreaser Any grease or oil film should first
be removed with the approved cleaning
agent
Remove Barrier - Soluble salts adhere
themselves to the substrate For the effective
use of this product the product must be able
to come in contact with the salts These salts
may be beneath any soils grease or dirt
therefore these barriers must be removed
prior to application of this product As in all
surface preparation the best work yields the
best results
Apply CHLORRID DTS - Apply directly
onto the substrate Sufficient product must
be applied uniformly across the substrate to
thoroughly wet out surface with no areas
missed This may be accomplished by use of
a pump-up sprayer or conventional spray
gun The method does not matter as long as
the entire area to be cleaned is wetted After
the substrate has been thoroughly wetted
the salts will be soluble and is now only
necessary to rinse them off
Rinse - It is highly recommended that a hose
be used as a pressure washer will damage
the fins The water to be used for the rinse is
recommended to be of potable quality
though a lesser quality of water may be used
if a small amount of CHLORRID DTS is
added Check with CHLORRID
High velocity water from a pressure washer or compressed air should only be used at a very low pressure to prevent fin andor coil damages The force of the water or air jet may bend the fin edges and increase airside pressure drop Reduced unit performance or nuisance unit shutdowns may occur
CAUTION
Harsh chemicals household bleach or acid cleaners should not be used to clean outdoor or indoor e-coated coils These cleaners can be very difficult to rinse out of the coil and can accelerate corrosion and attack the e-coating If there is dirt below the surface of the coil use the recommended coil cleaners
CAUTION
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
39
International Inc for recommendations on
lesser quality rinse water
DX Cooling
Set unit controls to cooling mode of
operation with supply fans on Check
compressor operation rotation amperage
and voltage to the unit nameplate (check the
amperage on the load side of the compressor
contactor)
The scroll compressors are fully hermetic
and require no maintenance except for
keeping the shell clean
Refrigerant circuit includes factory provided
and field installed line filter drier The unit
does not include a liquid line solenoid valve
This must be field furnished and installed if
required by job conditions
Condenser Fan Motor
All original motors and bearings are
furnished with factory lubrication They
require no lubrication
The electrically commutated condenser fan
motor (ECM) is factory preprogrammed and
requires no maintenance
Replacement Parts
Parts for AAON equipment may be obtained
from your local AAON representative
Reference the unit serial number and part
number when ordering parts
AAON ndash Longview
Warranty Service and Parts Department
203 Gum Springs Rd
Longview TX 75602
Ph 903-236-4403
Fax 903-247-9219
wwwaaoncom
Note Before calling technician should have
model and serial number of the unit
available for the service department to help
answer questions regarding the unit
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
40
Refrigerant Piping Diagrams
Figure 12ndash AC only piping AHU above CU
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
41
Figure 13 ndash AC only piping AHU below CU
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
42
Figure 14 ndash Modulating hot gas reheat piping AHU above CU
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
43
Figure 15 ndash Modulating hot gas reheat piping AHU below CU
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
44
Figure 16 ndash Hot gas bypass piping AHU above CU
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
45
Figure 17 ndash Hot gas bypass piping AHU below CU
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
46
Figure 18 ndash Modulating hot gas reheat with hot gas bypass piping AHU above CU
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
47
Figure 19 ndash Modulating hot gas reheat with hot gas bypass piping AHU below CU
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
48
Figure 20 ndash Heat pump piping AHU above CU
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
49
Figure 21 ndash Heat pump piping AHU below CU
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
50
Figure 22 ndash Heat pump with modulating hot gas reheat piping AHU above CU
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
51
Figure 23 ndash Heat pump with modulating hot gas reheat AHU below CU
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
CB Series Startup Form
Date______________
Job Name_____________________________________________________________________
Address______________________________________________________________________
Model Number_________________________________________________________________
______________________________________________________________________________
Serial Number_____________________________________________ Tag_______________
Startup Contractor______________________________________________________________
Address__________________________________________________
_________________________________________________________ Phone_____________
Pre Startup Checklist
Installing contractor should verify the following items
1 Is there any visible shipping damage Yes No
2 Is the unit level Yes No
3 Are the unit clearances adequate for service and operation Yes No
4 Do all access doors open freely and are the handles operational Yes No
5 Have all shipping braces been removed Yes No
6 Have all electrical connections been tested for tightness Yes No
7 Does the electrical service correspond to the unit nameplate Yes No
8 On 208230V units has transformer tap been checked Yes No
9 Has overcurrent protection been installed to match the unit nameplate
requirement Yes No
10 Have all set screws on the fans been tightened Yes No
11 Do all fans and pumps rotate freely Yes No
12 Is all copper tubing isolated so that it does not rub Yes No
Ambient Temperature
Ambient Dry Bulb Temperature ________degF Ambient Wet Bulb Temperature ________degF
Refrigeration System 1 - Cooling Mode
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
Refrigeration System 1 - Heating Mode (Heat Pump Only)
Pressure Saturated
Temperature
Line
Temperature Sub-cooling Superheat
Discharge
Suction
Liquid
Air-Cooled Condenser Fan
Alignment_____
Check Rotation_____
Nameplate Amps________
Number hp L1 L2 L3
1
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
Maintenance Log
This log must be kept with the unit It is the responsibility of the owner andor
maintenanceservice contractor to document any service repair or adjustments AAON Service
and Warranty Departments are available to advise and provide phone help for proper operation
and replacement parts The responsibility for proper start-up maintenance and servicing of the
equipment falls to the owner and qualified licensed technician
Entry Date Action Taken NameTel
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
Literature Change History
November 2009
Update of manual formatting to match with other IOMs and adding variable capacity scroll
compressor information
April 2012
Added oil drip note below piping diagrams Updated the Startup Form
May 2012
Updated the Table of Contents
March 2013
Update of the manual revising Table S1 - Sub-Cooling and Superheat adding Table S2 -
Performance Testing Air Flow Setpoints adding information about compressor cycling
June 2013
Updated piping diagrams to show internal modulating hot gas reheat and hot gas bypass valves
New part number assigned
July 2014 Updated service clearance drawing
February 2015
Updated Feature 5 options to reflect standard exterior corrosion protection
July 2015
Updated Replacement Parts instructions Added Features and Options section
August 2016
Added Storage information Added guidelines for variable capacity compressors in the line
sizing section Added double riser schematics and discussion for heat pump operation Added a
section about oil level under the refrigerant line sizing section Added a section on compressor
lockouts Included heat pump charging guidelines in the Acceptable Refrigeration Circuit
Values Table Added Special Low Ambient Option Charging Instructions Changed e-coated
coil cleaning to100 psi water pressure
December 2016
Fixed a reference error
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
AAON
203 Gum Springs Rd
Longview TX 75602-1721
Phone 903-236-4403
Fax 903-236-4463
wwwaaoncom
CB Series
Installation Operation amp
Maintenance
R57611 Rev A 161221
(ACP J00187)
It is the intent of AAON to provide accurate and current product information However in the
interest of product improvement AAON reserves the right to change pricing specifications
andor design of its product without notice obligation or liability
Copyright copy AAON all rights reserved throughout the world
AAONreg and AAONAIRE
reg are registered trademarks of AAON Inc Tulsa OK
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