Operation Manual OM AGS

Group: Chiller

Part Number:

Date: March 2002Supersedes: New

GeneSys Air-Cooled Screw Compressor Chiller

AGS 230A through AGS 475ASoftware Version AGSU30101A60 Hertz

OM AGS 2

Table Of Contents

Features of the Control Panel ................................................ 4

General Description............................................................... 5General Description ............................................................................. 5Control Architecture ............................................................................ 5

Component Description......................................................... 6Unit/Circuit Controller Description ..................................................... 6

Control Operation.................................................................. 7

Circuit Controller .................................................................. 7

Unit Controller ...................................................................... 18

Using the Controller .............................................................. 25Unit Controller Menus ......................................................................... 27SET Screen Definitions ....................................................................... 30Circuit Controller Menus ..................................................................... 33Screen Definitions ............................................................................... 33

Sequence of Operation .......................................................... 38

Start-up and Shutdown .......................................................... 41Seasonal Start-up ................................................................................. 41Temporary Shutdown........................................................................... 41Start-up After Temporary Shutdown.................................................... 42Extended (Seasonal) Shutdown ........................................................... 42Start-up After Extended (Seasonal) Shutdown .................................... 43

Our facility is ISO CertifiedInitial Issue February 2002

"McQuay" is a registered trademark of McQuay International

2002 McQuay International"Information covers the McQuay International products at the time of publication and we reserve the right to make changes in

design and construction at anytime without notice"

OM AGS 3

This manual provides setup, operating, and troubleshooting information for the McQuayMicroTech ΙΙ controller for Model AGS air-cooled rotary screw compressor chillers.Please refer to the current version of IMM AGS for information relating to the unit itself.

NOTE: This manual covers units with Software Version AGSU30101A. The softwareversion can be viewed by pressing the MENU and ENTER keys (the two right keys)simultaneously. Then pressing the MENU key will return to the Menu screen.

WARNINGElectric shock hazard. Can cause personal injury or equipment damage. This

equipment must be properly grounded. Connections to and service of the MicroTechcontrol panel must be performed only by personnel that are knowledgeable

in the operation of the equipment being controlled.

CAUTIONStatic sensitive components. A static discharge while handling electronic circuit

boards can cause damage to the components. Discharge any static electrical chargeby touching the bare metal inside the control panel before performing any service

work. Never unplug any cables, circuit board terminal blocks, or power plugs whilepower is applied to the panel.

NOTICEThis equipment generates, uses and can radiate radio frequency energy and, if not

installed and used in accordance with this instruction manual, may causeinterference to radio communications. Operation of this equipment in a residential

area is likely to cause harmful interference in which case the user will be required tocorrect the interference at his own expense.

McQuay International Corporation disclaims any liability resulting from anyinterference or for the correction thereof.

Temperature and Humidity ConsiderationsThe MicroTech ΙΙ controller is designed to operate within an ambient temperature range of -20°F to +149°F (-29°C to +65.1°C) with a maximum relative humidity of 95% (non-condensing).

OM AGS 4

Features of the Control Panel

• Control of leaving chilled water within a ±0.2°F (±0.1°C) tolerance.• Readout of the following temperature and pressure readings:

• Entering and leaving chilled water temperature• Saturated evaporator refrigerant temperature and pressure• Saturated condenser temperature and pressure• Outside air temperature• Suction line, liquid line and discharge line temperatures - calculated superheat for discharge

and suction lines – calculated subcooling for liquid line

• Automatic control of primary and standby evaporator pumps.• History trend feature will constantly log chiller functions and set points. The controller will store

and display all accumulated data for recall.• Three levels of security protection against unauthorized changing of setpoints and other control

parameters.• Warning and fault diagnostics to inform operators of warning and fault conditions in plain

language. Al1 warnings, problems and faults are time and date stamped so there is no guessing ofwhen the fault condition occurred. In addition, the operating conditions that existed just prior toshutdown can be recalled to aid in isolating the cause of the problem.

• Twenty-five previous faults and related operating conditions are available.• Remote input signals for chilled water reset, demand limiting and unit enable.• Manual control mode allows the service technician to command the unit to different operating

states. Useful for system checkout.• BAS communication capability via LONMARK or BACnet standard protocols for all BAS

manufacturers.• Service Test mode for troubleshooting controller hardware.• Pressure transducers for direct reading of system pressures. Preemptive control of low evaporator

pressure conditions and high discharge temperature to take corrective action prior to a fault trip.

OM AGS

General DescriptionGeneral DescriptionThe AGS MicroTech ΙΙ control system consists of microprocessor-based controllers thatprovide all monitoring and control functions required for the controlled, efficient operationof the chiller. The system consists of the following components:

• Unit Controller, one per chiller-controls unit functions and communicates with all othercontrollers. It is located in the control panel for circuit #1.

• Circuit Controller for each compressor/circuit on the chiller (two or three)-controlscompressor functions and can operate a compressor without the unit controller. Thecontrollers are located in their circuit's control panel that is mounted between condensercoil sections.

In addition to providing all normal operating controls, the MicroTech II control systemmonitors equipment protection devices on the unit and will take corrective action if thechiller is operating outside of it’s normal design conditions. If a fault condition develops,the controller will shut the compressor down and activate an alarm output. Importantoperating conditions at the time an alarm condition occurs are retained in the controller’smemory to aid in troubleshooting and fault analysis.

The system is protected by a password scheme that only allows access by authorizedpersonnel. The operator must enter the operator password into the controller's keypadbefore any setpoints can be altered.

Control ArchitectureFigure 1, Major Control Components

Chiller AACnet MS/TP

B

5

UnitController

Circuit #1Controller4x20 LCD

SolidState

Starter

pLAN

BACnet IPLonTalk

Circuit #2 (#3)Controller

RS485/LON/Ethernet

RS485

(future)

4x20 LCD

Digital/Analog I/O

(future)

EXV

OM AGS 6

Component DescriptionUnit and Circuit Controller Description

Hardware StructureThe controllers are fitted with a 16-bit microprocessor for running the control program.There are terminals for connection to the controlled devices (for example: solenoid valves,expansion valves, chilled water pumps). The program and settings are saved permanently inFLASH memory, preventing data loss in the event of power failure without requiring aback-up battery. It also has remote communication access capability for BAS interface.

Each chiller has one unit controller and a circuit controller for each compressor circuit (twoor three depending on unit size). The controllers are connected and communicate via apLAN. The circuit controllers communicate with, and control the operation of, thecompressor's solid state starter and the circuit electronic expansion valve (EXV).

KeypadA 4 line by 20 character/line liquid crystal display and 6-button keypad is mounted on theunit and compressor controllers. Its layout is shown below.

Air Conditioning

ALARMVIEW

SET

<<<

The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.• Scroll between data screens in the direction indicated by the arrows (default mode).• Select a specific data screen in the menu matrix using dynamic labels on the right side

of the display such as ALARM, VIEW, etc (this mode is entered by pressing the MENUkey). For ease of use, a pathway connects the appropriate button to its respective labelon the screen.

• Change field values in setpoint programming mode according to the following table:LEFT key = Default RIGHT key = CancelUP key = Increase (+) DOWN key = Decrease (-)

These four programming functions are indicated by one-character abbreviation on theright side of the display. This programming mode is entered by pressing the ENTERkey.

ENTER Key

MENU Key

ARROW Keys

Key-to-Screen Pathway

OM AGS 7

Control OperationThis section on MicroTech II control is divided into five subsections:

• Circuit Controller, explains the functions of the circuit controller, see page 7.

• Unit Controller, explains the functions of the unit controller, see page 14.

• Using the Controller, explains how to navigate through the menus and how to makeentries, see page 25.

• Screen Description, details the content on the menu screens and how to use them, seepage 28

• Quick Reference Guide, brief description on how to perform commonly used tasks

Circuit Controller

Inputs/OutputsTable 1, Analog Inputs

# Description Signal Source Range1 Evaporator Pressure 0.1 to 0.9 VDC 0 to 132 psi2 Condenser Pressure 0.1 to 0.9 VDC 3.6to 410 psi3 Liquid Pressure 0.1 to 0.9 VDC 3.6to 410 psi4 Suction Temperature NTC Thermistor (10k@25°C) -58 to 212°F5 Discharge Temperature NTC Thermistor (10k@25°C) -58 to 212°F6 Liquid Temperature NTC Thermistor (10k@25°C) -58 to 212°F7 Slide Load Indicator 4 to 20 mA 0 to 100%8 Open

These parameters are analog inputs to this controller. They are used internally as neededand are sent to the correct pLAN addresses for use by other controllers or displays.

Table 2, Analog Outputs# Description Output Signal Range1 Fan 1&2 VFD 0 to 10 VDC 20 to 60 Hz2 Open3 EXV Driver 0 to 10 VDC 0 to 1000 steps4 Open

These parameters are analog outputs from this controller. The values are sent to the correctpLAN addresses for use by other controllers or displays.

Table 3, Digital Inputs# Description Signal Signal1 Circuit Switch 0 VAC (Off) 24 VAC (Auto)2 Open3 Starter Fault 0 VAC (Fault) 24 VAC (No Fault)4 VFD Fault 0 VAC (Fault) 24 VAC (No Fault)

5 Oil DifferentialPressure Switch 0 VAC (Fault) 24 VAC (No Fault)

6 Mech High Pressure 0 VAC (Fault) 24 VAC (No Fault)7 Open8 Open9 Oil Level Sensor 0 VAC (Fault) 24 VAC (No Fault)

10 Open11 Open

OM AGS 8

Table 4, Digital Outputs# Description Load Output OFF Output ON Voltage1 Compressor SSS Contact Relay Compressor off Compressor on 1202 M1 Contactor (fan 1) Contactor Coil Fans off Fans on 1203 M2 Contactor (fan 2) Contactor Coil Fans off Fans on 1204 M3 Contactor (fan 3) Contactor Coil Fans off Fans on 1205 M4 Contactor (fan 4) Contactor Coil Fans off Fans on 1206 M5 Contactor (fan 5 & 6) Contactor Coil Fans off Fans on 1207 Load/Unload Pulse Solenoid Hold load slide Move load slide 248 Load/Unload Select Relay Unload Load 249 M7 Contactor (fan 7 & 8) Contactor Coil Fans off Fans on 120

10 Oil Return Line Solenoid Closed Open11 Open12 Open13 Open

These parameters are digital outputs from this controller. Their values are sent to the correctpLAN addresses for use by other controllers or displays.

Set PointsThe following parameters are remembered during power off, are factory set to theDefault value, and can be adjusted to any value in the Range column.

The “Type" column defines whether the set point is part of a coordinated set ofduplicate set points in different controllers. The possibilities are given below:

• N = Normal set point - Not copied from, or copied to, any other controller.

• D = Duplicate set point. Set point is duplicated (same value) in all compressorcontrollers on the same chiller.

• G = Group set point. Set point is duplicated (same value) in all compressorcontrollers on all chillers in a group.

• M = Master set point - Set point is copied to all controllers.

• S = Slave set point - Set point is a copy of the master set point (in the Unitcontroller).

The PW (password) column indicates the password that must be active in order tochange the set point. Codes are as follows:

O = Operator,

M = Manager,

F = Factory setpoints not available for field adjustment

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Table 5, Circuit Controller Set PointsDescription Default Range PWCompressorCircuit mode enable Disable, enable, test MSlide control auto Auto, manual MSlide position N/a 0-100 MCompressor Size 205 205,220,235 MCapacity change interval 5 2-10 sec FLWT error multiplier 1 1-10 FLWT slope multiplier 2 1-10 FTotal error multiplier 1 1-10 FMax slide change 1.0 0-10.0% FSlide deadband 3.0 0-10.0% FSlide pulse length 200 100-500 ms FSlide pulse delay 3 0-10 sec F

EXVEXV control auto Auto, manual MEXV position N/a 0-1000 MMinimum EXV position 250 100-500 steps FMax EXV position at min load 1400 1000-2000 steps FMinimum discharge superheat 20.0 15.0 – 25.0 oF FPressure control proportional band 5.0 1.0 – 30.0 oF FSubcool control proportional band 10.0 1.0 – 50.0 oF FPressure control integral time 60 30-9999 sec FSubcool control integral time 200 30-9999 sec F

FansFan VFD enable No No, Yes MNumber of fans 6 6,8 MSaturated Condenser Temp Target 110.0 90.0 – 130.0 oF FStage 1 Up Deadband 5.0 1.0-20.0 oF FStage 2 Up Deadband 8.0 1.0-20.0 oF FStage 3 Up Deadband 11.0 1.0-20.0 oF FStage 4 Up Deadband 14.0 1.0-20.0 oF FStage 1 Down Deadband 6.0 1.0-20.0 oF FStage 2 Down Deadband 5.0 1.0-20.0 oF FStage 3 Down Deadband 4.0 1.0-20.0 oF FStage 4 Down Deadband 3.0 1.0-20.0 oF FStage Up Error Set 200 10-999 FStage Down Error Set 50 10-200 FStage Up Delay Time 5 1-30 sec FStage Down Delay Time 5 1-50 sec FVFD Proportional Band 5.0 5.0-20.0 oF FVFD Integration Time 50 0-99 sec FVFD Max Speed 100% 90 to 110% MVFD Min Speed 25% 25 to 100% M

SensorsEvap pressure offset 0 -20.0 to 20.0 psi MCond pressure offset 0 -20.0 to 20.0 psi MLiquid pressure offset 0 -20.0 to 20.0 psi MSuction temp offset 0 -5.0 to 5.0 deg MDischarge temp offset 0 -5.0 to 5.0 deg MLiquid temp offset 0 -5.0 to 5.0 deg M

Note: A setting of 0° F for the Low Subcooling alarm disables the alarm.

OM AGS 10

Circuit Operating ModeThe circuits on the chiller can each be individually enable or disabled. Test mode on eachcircuit can also be entered independent of the all other circuits. With the circuit switch on,the circuit mode set point offers settings of either enable or disable. This simply allows thecircuit to be disabled through a keypad setting.

Slide PositionEach compressor will estimate its slide load percentage from the present value of the slideload indicator. The percentage is based on the 4-20mA signal from the slide load indicator.A percentage value of 0 corresponds to approximately a 4mA signal, a percentage value of100 corresponds to approximately a 20mA signal.

Table 6, Automatically Adjusted LimitsThe following set point ranges will be adjusted based on selected options.

Low Evaporator PressureMode Range

Unit Mode = Cool 27 to 45 PsigUnit Mode = Cool w/Glycol, Ice w/ Glycol 10 to 45 Psig

Low Evaporator Pressure Hold and UnloadMode Range

Unit Mode = Cool 30 to 45 PsigUnit Mode = Cool w/Glycol, Ice w/ Glycol 20 to 45 Psig

Stop AlarmsStop Alarms (also known as "Faults" or "Equipment Protection Alarms") result in rapidcompressor shutdown, bypassing sequences such as pumpdown.

The following table identifies each shutdown alarm, gives the condition that causes thealarm to occur, and states the action taken because of the alarm. All stop alarms requiremanual reset.

NOTE: SP = Set Point

Table 7, Circuit Controller Stop AlarmsDescription Occurs When: Action Taken

Low Evaporator Pressure[Evaporator Press < Low Evap Pressure SP for time > Low

Evap Press Delay OR Evaporator Press < 5 psi ] ANDCompressor State = Run

Rapid Stop

High Condenser Pressure Cond Press > High Condenser Pressure Value (Note 1) Rapid StopMechanical High Pressure Digital Input 6 = Open Rapid Stop

Below Minimum Lift Pressure Cond Press < Min Sat Cond Value for time > Min Lift Delay SP(Note 2) Rapid Stop

High Discharge Temperature Temp > High Discharge Temperature SP Rapid StopLow Subcooling Calculated Subcooling < Low Subcooling SP for 300 seconds Rapid StopLow Oil Level DI 9 = Open for Time greater than Low Oil Level Delay AND

the Low Oil Level Event has occured in the past hour Rapid Stop

High Oil Pressure Difference Digital Input 5 = Open for time greater thanHighPressDiffDelay Rapid Stop

VFD Fault VFD option enabled and Digital Input 4 = Open PumpdownStarter Fault Digital Input 3 = Open Rapid StopEvaporator Pressure SensorFault Sensor shorted or open Rapid Stop

Condenser Pressure SensorFault Sensor shorted or open Rapid Stop

Liquid Line Pressure SensorFault Sensor shorted or open Rapid Stop

Suction Temperature SensorFault Sensor shorted or open Rapid Stop

Discharge TemperatureSensor Fault Sensor shorted or open Rapid Stop

Liquid Line TemperatureSensor Fault Sensor shorted or open Rapid Stop

OM AGS 11

NOTES:1. High Condenser Pressure Value

• If Sat Evap Temp < 32 thenShutdown value = 155 + 1.588(Sat Evap Temp – 32)

• If Sat Evap Temp >= 32 AND Sat Evap Temp < 40 thenShutdown value = 155

• If Sat Evap Temp >= 40 AND Sat Evap Temp < 55 thenShutdown value = 155 – 0.667(Sat Evap Temp – 40)

• If Sat Evap Temp >=55 thenShutdown value = 145

2. Minimum Saturated Condenser Value• If Sat Evap Temp < 35, then

Min Lift Value = 73• If Sat Evap Temp >= 35 and < 55, then

Min Lift Value = (6/5)(Sat Evap Temp – 35) + 73;• If Sat Evap Temp >= 55 then

Min Lift Value = 97

EventsAlso know as "Limit Alarms" or "Problems", these alarms do not cause compressorshutdown but instead limit operation of the chiller in some way as described in the ActionTaken column.

Table 8, Circuit Controller Event AlarmsDescription Occurs When: Action Reset

Low Evaporator Pressure -Hold

Pressure < Low Evap Pressure -Hold SP

Inhibitloading

Evap Press rises above(SP + 3psi)

Low Evaporator Pressure -Unload

Pressure < Low Evap Pressure -Unload SP Unload Evap Press rises above

(SP + 5psi)High Condenser Pressure -Hold

Pressure > High Cond Pressure -Hold Value

Inhibitloading

Cond Press drops below(Hold Value – 10psi)

High Condenser Pressure -Unload

Pressure > High Cond Pressure -Unload Value Unload Cond Press drops below

(Unload Value – 10psi)

Subcooling Low Subcool < Low Subcool SP forlonger than 5 minutes None Subcool > set point or

Comp state = off

Discharge Superheat LowAt Startup

EXV Control = Pressure ControlAND Disc SH < Min SH Set Point

for 10 minutes

Pumpdownand stop Comp state = off

Low Oil LevelDI9 = Open for Time greater than

Low Oil Level Delay AND more thanone hour since last occurance

Rapid stop Comp state = off

NOTES:

1. High Condenser Pressure – Hold Value• High Cond Hold Value = High Cond Pressure Value – 4oF

2. High Condenser Pressure – Unload Value• High Cond Unload Value = High Cond Pressure Value – 2oF

Circuit Operating ModeThe circuits on the chiller can each be individually enabled or disabled. Test mode on each circuitcan also be entered independent of the all other circuits. With the circuit switch on, the circuit modeset point offers settings of either enable or disable. This simply allows the circuit to be disabledthrough a keypad setting.

OM AGS 12

Compressor StagingSlide Load IndicatorEach compressor shall estimate its slide load percentage from the present value of the slide loadindicator. The percentage is based on the 4-20mA signal from the slide load indicator. A percentagevalue of 0 corresponds to approximately a 4mA signal, a percentage value of 100 corresponds toapproximately a 20mA signal.

Multiple Compressor StagingThis section defines which compressor is the next one to start or stop.1. Can start/stop compressors according to an operator defined sequence.2. Can start compressors based on the number of starts (run hours if starts are equal) and

stop on run hours3. The above two modes can be combined so that there are two or more groups where all

compressors in the first group are started (based on number of starts/hours) before anyin the second group, etc. Conversely, all compressors in a group are stopped (based onrun hours) before any in the preceding group, etc.

Compressor Capacity ControlLeaving Water Control ModeWhen the Compressor Slide Control Set Point is set to AUTO, compressor loading andunloading will be under software control as defined below.

Chiller Mode = COOLWhen the chiller is in COOL mode, an automatic algorithm shall adjust capacity of thecompressor to maintain leaving water temperature at the Active LWT set point whilebalancing the load between running circuits. Load balance offset, lwt error, and lwt slopeare used to calculate a change in slide position as described below.

Load Balance Offset:Balance Offset = [Present slide load % – Average slide load %] (more than one compressorrunning)

where: Present slide load % = The present slide target value of this compressor.

Average slide load % = Average slide target of all other runningcompressors on the same chiller.

LWT Error = (Leaving Evaporator Water Temp) – (Active LWT set point).LWT Slope:Slope (deg/minute) = sum of last five LWT changes as calculated every 12 seconds

Chiller Mode = ICEWhen the chiller is in the ICE mode, each compressor is loaded continuously when it is inthe RUN state. Each running compressor is considered a stage, and compressors are stagedon sequentially using the interstage timers. When the LWT goes below the ice set point, thechiller will stage down compressors sequentially using the interstage timers. Eachcompressor that shuts down will perform a normal shutdown sequence.

Capacity OverridesThe following conditions shall override the AUTO capacity control mode when the chiller isin the COOL mode. These overrides shall not be in effect when the Slide Control Mode isset to MANUAL.

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Low Evaporator Pressure OverrideIf the compressor is running and the evaporator pressure drops below the Low EvaporatorPressure-Hold set point, the unit will not be allowed to increase capacity. This conditionwill inhibit the unit from loading until the evaporator pressure reaches the hold set pointplus 3-psi.

If the unit is running above minimum load capacity and the evaporator pressure drops belowthe Low Evaporator Pressure-Unload set point, the compressor will begin reducing capacity.The maximum allowed slide position will be adjusted down 5% every 10 seconds until theevaporator pressure rises above the Low Evaporator Pressure-Unload set point. Then slideposition shall be limited to this value until the evaporator pressure rises to 3 psi above theunload set point.

High Condenser Pressure OverrideIf the discharge pressure rises above the High Condenser Pressure Hold set point, thecontroller will inhibit loading of the compressor. This condition will remain in effect untilthe condenser pressure drops 10-psi below the hold set point.

If the unit is running above minimum load capacity and the condenser pressure rises abovethe High Condenser Pressure Unload set point, the compressor will begin reducing capacity.The maximum allowed slide position will be adjusted down 5% every 10 seconds until thecondenser pressure drops below the High Condenser Pressure-Unload set point. Then slideposition shall be limited to this value until the condenser pressure drops to 10 psi below theunload set point.

Maximum LWT Pulldown RateThe maximum rate at which the leaving water temperature can drop (chiller mode = COOL)is limited at all times by the Maximum Rate set point. If the rate exceeds this set point,capacity increases are inhibited.

Soft LoadSoft Loading is a configurable function used on compressor startup to limit the maximumcurrent draw on the compressor in a ramp-up type manner. It is only active on the firstcompressor to start. The set points that control this function are:

• Soft Load – (ON/OFF)

• Begin Slide Load Limit – (Slide Load %)

• Max Slide Load Limit – (Slide Load %)

• Soft Load Ramp – (seconds)

The active soft load limit value (in Slide Load %) increases linearly from the Begin SlideLoad Limit set-point to the Max Slide Load Limit set-point over the amount of timespecified by the Soft Load Ramp set-point.

Demand LimitThe maximum slide position of the compressor can be limited by a 4 to 20 mA signal on theDemand Limit analog input. This function is only enabled if the Demand Limit set point isset to ON. The slide position decreases linearly from the Maximum Slide % set point (at 4mA) to the Minimum Slide % set point (at 20mA). Maximum slide position is limited to theslide % corresponding to the demand limit signal.

OM AGS 14

Network LimitThe maximum slide load percentage of the compressor can be limited by a value sentthrough a BAS network connection and stored in the Network Limit variable. Thisfunction will be enabled if the Network Limit set point is set to ON.

Low Ambient StartThe following start method shall be used when a condenser fan VFD is present.

The low ambient start method will bypass the “Low Evaporator Pressure” alarm until LowAmbient Start is completed. The steps below are in effect when there is a call for Cooling.

Table 9, Low Ambient Starting StepsDescription Occurs When: Action Taken

Check #1 After 15 Seconds after starting Lead Compressor, If the EvapPress is < (.48*Low Evap Press SP) take Action else continue

Rapid Stop – See LowAmbient Re-Start below CT

Check #2 After 15 Seconds after Check #1, If the Evap Press is <(.66*Low Evap Press SP) take Action else continue

Rapid Stop – See LowAmbient Re-Start below CT

Check #3 After 15 Seconds after Check #2, If the Evap Press is <(.83*Low Evap Press SP) take Action else continue

Rapid Stop – See LowAmbient Re-Start below CT

Check #4After 15 Seconds after Check #3, If the Evap Press is < Low

Evap Pressure SP take Action else continue in normaloperation

Rapid Stop – See LowAmbient Re-Start below CT

NOTE: CT = Rapid Stop for that Circuit Only

Low Ambient Re-StartIf the Evap Pressure fails during the low ambient start, the controller will wait until the anti-cycle timers expire then try to re-start. It will allow a circuit to attempt a start 3 times, andthen reset counter if unit continues in normal operation. If it fails on the third attempt, itwill initiate the Low Ambient Re-Start Alarm Fault (Manual Reset).

Digital Output ControlEach digital output is controlled according to the following rules/algorithms and inaccordance with whether the Compressor Mode set point is set to AUTO or MANUAL(normal operation) or TEST (test mode). All outputs shall be initialized to OFF at poweron.

Compressor SSS Contact• Normal Operation, This output is ON when the compressor is running or pumping

down. It is OFF for all other cases.

• Test Mode, This output cannot be turned on when in test mode.

Load and Unload Pulse• Normal Operation (AUTO), This output controls the compressor slide position in

order to reach the desired compressor capacity. Whenever a change in capacity isneeded, this output will pulse for 200 ms every 3 seconds until the slide position iswithin the deadband around the target.

• Test Mode, These outputs are set ON or OFF manually when Unit Mode = Test.

Load/Unload Select• Normal Operation (AUTO), The load/unload selector determines which solenoid will

be pulsed for a change in capacity. When unloading is required, this output should beoff. When loading of the compressor is required, the output should be on.

• Test Mode, These outputs are set ON or OFF manually when Unit Mode = Test.

OM AGS 15

FanTrol Standard Fan StagingThere are 8 stages of FanTrol available with 8 fan circuits, and 6 stages available on 6 fancircuits. Although fans 5/6 and 7/8 are controlled by one contactor each, more stages arecreated by using virtual stages. See the following table:

Table 10, FanTrol Fan SequencingFantrol Stage Fans On

1 12 1,23 1,2,34 1,2,3,45 1,2,4,5,66 1,2,3,4,5,67 1,2,3,5,6,7,88 1,2,3,4,5,6,7,8

Optional Low Ambient VFD Condenser FansIn the optional Low Ambient Control, the first two fans are controlled by the fan VFD andthe balance are staged on and off. (VFD operation is described on page 17.) There are 6stages of Fantrol available with 8 fan circuits, and 4 stages available on 6 fan circuits.Although fans 5/6 and 7/8 are controlled by one contactor each, more stages are created byusing virtual stages. See the following table:

Table 11, Optional VFD Fan SequencingFantrol Stage Fans On

1 1,2,32 1,2,3,43 1,2,4,5,64 1,2,3,4,5,65 1,2,3,5,6,7,86 1,2,3,4,5,6,7,8

Normal Operation - Staging UpThere are four Stage Up dead bands that apply to the six stages of Fantrol. Stages onethrough three use their respective dead bands. Stage four to six share the fourth Stage Updead band.

When the saturated condenser temperature is above the Target + the active deadband, aStage Up error is accumulated.

Stage Up Error Step = Saturated Condenser Refrigerant temperature – (Target + Stage Updead band)

The Stage Up Error Step is added to Stage Up Accumulator once every Stage Up ErrorDelay seconds. When Stage Up Error Accumulator is greater than the Stage Up Error SetPoint another stage is started.

When a stage up occurs or the saturated condenser temperature falls back within the StageUp dead band the Stage Up Accumulator is reset to zero.

OM AGS

Normal Operation - Staging DownThere are four Stage Down dead bands. Stages one through three use their respective deadbands. Stages four to six share the fourth Stage Down dead band.

When the saturated condenser refrigerant temperature is below the Target – the activedeadband, a Stage Down error is accumulated.

Stage Down Error Step = (Target - Stage Down dead band) - Saturated CondenserRefrigerant temperature

The Stage Down Error Step is added to Stage Down Accumulator once every Stage DownError Delay seconds. When the Stage Down Error Accumulator is greater than the StageDown Error Set Point another stage of condenser fans turned off.

When a stage down occurs or if the saturated temperature rises back within the Stage Downdead band the Stage Down Error Accumulator is reset to zero.

Test ModeThese outputs shall be set ON or OFF manually when Unit Mode = Test.

Oil Return SolenoidNormal OperationThe oil return solenoid shall be on any time the slide position target is less than 60%. Theoutput will also be on if the discharge superheat is more than 20 degree F, and the oil levelsensor shows no oil.

Test ModeThis output shall be set ON or OFF manually when Unit Mode = Test.

Analog Output ControlEach analog output is controlled according to the following rules/algorithms. All outputsshall be initialized to 0 at power on.

EXVTwo different EXV control modes are used. With either control mode, the EXV position isdetermined by a proportional integral function and the operating range is limited based onthe slide position target. As the compressor capacity is increased, the minimum andmaximum EXV position increase.

Pressure ControlInitially, the EXV will be in pressure control mode after startup. In this mode, the EXVonly controls the evaporator pressure. If the evaporator LWT is less than or equal to 60°F,the control pressure will be the low evaporator pressure inhibit set point (INH SP). If theevaporator LWT is more than 60°F, the EXV will control the evaporator to a higher pressurevalue. This pressure value varies as shown by the following graph:

Low INH

Pressure(psi)

52

EvapSP

90°F

60°F

16

LWT

OM AGS 17

This mode of EXV control will transition to Subcool Control when two conditions are met.

• The evaporator LWT must be less than or equal to 60°F and

• The discharge superheat must be more than the minimum discharge superheat set point.

If the discharge superheat reaches the minimum superheat set point and the LWT is stillhigher than 60°F, the compressor will begin increasing capacity. If the superheat reaches theminimum set point while the LWT is less than 60 deg F, then the EXV will begin subcoolcontrol and the compressor will begin increasing capacity.

Subcooling ControlAfter completing pressure control, the EXV transitions to the primary mode of operationwhich is subcooling control. In this mode, a Subcool Target is calculated and EXV positionis adjusted to drive the Subcool value to the target. The base Subcool Target varies from 9to 20 degrees F as slide position changes from 0 to 100%. This value is adjusted when thedischarge superheat is less than the minimum superheat set point or greater than themaximum superheat value. The maximum superheat value varies from 80 to 50 degrees Fas the slide position changes from 0 to 100%. For every degree below the minimum, theSubcool Target is adjusted up two degrees. Similarly, for every degree above the maximum,the Subcool Target is adjusted down two degrees.

Fan VFDCondenser pressure trim control is accomplished using a VFD on the first two fans that turnon. This VFD control uses a proportional integral function to drive the saturated condensertemperature to a target value. The target value is normally the same as the saturatedcondenser temperature target set point.

In order to create a smoother transition when another fan is staged on, the VFD compensatesby slowing down initially. This is accomplished by adding the new fan stage up deadbandto the VFD target. The higher target causes the VFD logic to decrease fan speed. Then,every 10 seconds, 0.5 degree F is subtracted from the VFD target until it is equal to thesaturated condenser temperature target set point. This will allow the VFD to slowly bringthe saturated condenser temperature back down.

History StorageThe number of starts and total compressor run hours is maintained in non-volatile memoryand placed on the pLAN.

OM AGS 18

Unit Controller

Inputs/OutputsTable 12, Analog InputsThe following parameters are analog inputs to this controller. They are used internally asneeded and are sent to the correct pLAN addresses for use by other controllers or displays.

# Description Signal Source Range1 Outdoor Ambient Temperature NTC Thermistor (10k@25°C) -58 to 212°F2 Leaving Evaporator Water Temperature NTC Thermistor (10k@25°C) -58 to 212°F3 Entering Evaporator Water Temperature NTC Thermistor (10k@25°C) -58 to 212°F4 Demand Limit 4-20 mA Current 25-100 %RLA5 Chilled Water Reset 4-20 mA Current 0 to max reset

Table 13, Analog OutputsThere are no analog outputs from this controller.

Table 14, Digital InputsThe following parameters are digital inputs to this controller. They are used internally asneeded and are sent to the correct pLAN addresses for use by other controllers or displays.

# Description Signal Signal1 Unit Switch 0 VAC (Stop) 24 VAC (On)2 Remote Switch 0 VAC (Stop) 24 VAC (Start)3 Evaporator Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)4 Mode Switch 0 VAC (Cool) 24 VAC (Ice)5 Open6 Open

Table 15, Digital OutputsThese parameters are digital outputs from this controller. Their values are sent to the correctpLAN addresses for use by other controllers or displays.

# Description Load Output OFF Output ON1 Alarm Remote Alarm No alarm Safety alarm2 Evaporator Water Pump 1 Pump Contactor Pump OFF Pump ON3 Evaporator Water Pump 2 Pump Contactor Pump OFF Pump ON4 Evap Heaters Heater relay Heater OFF Heater ON5 Open6 Open

Set PointsThe “Type: column defines whether the set point is part of a coordinated set of duplicate setpoints in different controllers. There are three possibilities as given below:

• N = Normal set point - Not copied from, or copied to, any other controller

• M = Master set point - Set point is copied to all controllers in the “Sent To” column

• S = Slave set point - Set point is a copy of the master set point (in the Unit controller)

At power-up the slave node checks if the master node is operational and if so, it sets its copyof the set point equal to the master’s. Otherwise, the set point remains unchanged. Duringnormal operation, any time the master set point changes the slave is updated as well.

The PW (password) column indicates the password that must be active in order to changethe set point. Codes are as follows:

• O = Operator

• M = Manager

OM AGS 19

Table 16, Unit Controller Set PointsDescription Default Range Type PWUnitUnit Enable OFF OFF, ON N OUnit Mode COOL COOL, TEST (other options to be added) M OAvailable Modes COOL COOL, TEST (other options to be added) N MControl source SWITCHES SWITCHES, KEYPAD, NETWORK N ODisplay UnitsLanguage

BAS Protocol NONE NONE, BACnet, LonWorks,CAREL, MODBUS, N2 N M

Ident numberBaud RateCool LWT 44. 0°F 20.0 to 60.0 °F M OStartup Delta T 3.0°F 0.0 to 10.0 °F M OStop Delta T 3.0°F 0.0 to 3.0 °F M OStage Delta T 2.0°F 0.0 to 3.0 °F M OMax Pulldown 0.5 0.1-5.0 deg/min M MEvap pump control #1 Only #1 Only, #2 Only N MEvap Recirculate 30 sec 15 sec to 5 min N MLWT Reset Type NONE NONE, RETURN, 4-20mA, OAT N MMax Reset 0.0°F 0.0 to 20.0 °F N MStart Reset 10. 0°F 0.0 to 20.0 °F N MSoft Load no No,yes N MBegin Capacity Limit 20 20-100% N MSoft Load Ramp 5 1-60 minutes N MDemand Limit no No,yes N M

CompressorsSequence # Cir 1 1 1-3 M MSequence # Cir 2 1 1-3 M MSequence # Cir 3 1 1-3 M MMax Compressors On 3 1-3 M MStart-start timer 20 15-60 minutes M MStop-start timer 5 3-20 minutes M MPumpdown pressure 25.0 10.0-30.0 psi M MPumpdown time limit 120 0-180 sec M M

Alarms & DelaysLow Evap Pressure 15 psi 12 to 45 psi or 10 to 45 psi M MLow Evap Pressure-Unload 28 psi 25 to 45 psi or 10 to 45 psi M MLow Evap Pressure-Hold 30 psi 25 to 45 psi or 10 to 45 psi M MLow Evap Press delay 30 15-60 sec M MLow Oil Level Delay 120 10-180 sec M MHigh Oil Press Diff Delay 15 0-60 sec M MMin Lift Delay 30 10-120 sec M MHigh Discharge Temperature 200 F 150 to 250 F M MLow Subcooling 5 F 0 to 10 F M MEvap Flow Proof 3 sec 3 sec to 120 sec N MLow Ambient Lockout 35.0 °F 35 to 60 °F N MEvaporator Water Freeze 34.0 °F 15 to 42 °F N M

SensorsOAT sensor offset 0 -5.0 to 5.0 deg N MLWT sensor offset 0 -5.0 to 5.0 deg N MEWT sensor offset 0 -5.0 to 5.0 deg N M

These parameters are remembered during power off, are factory set to the Default value, and canbe adjusted to any value in the Range column.

OM AGS 20

Automatic Adjusted LimitsThe following set point ranges will be adjusted based on selected options.

Table 17, Evaporator Leaving Water Temperature RangeMode Range

Unit Mode = Cool 38 to 60°FUnit Mode = Cool w/Glycol 20 to 60°F

Table 18, Evaporator Freeze Temperature RangeMode Range

Unit Mode = Cool 38 to 42°FUnit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 42°F

Table 19, Low Ambient Lockout Temperature RangeFan VFD Range

Fan VFD = N 35– 60°FFan VFD = Y 0 – 60°F

Stop (Shutdown) AlarmsThis table identifies each shutdown alarm, gives the condition that causes the alarm tooccur, and states the action taken as a result of the alarm. (See the “Stop Alarms” sectionunder the Circuit Controller for a description of these alarms.)

Table 20, Unit Stop AlarmsDescription Occurs When: Action Taken

No Evaporator Water Flow Evap Pump State = RUN AND Evap Flow Digital Input =No Flow for time > Flow Proof SP

Start standbypump/Rapid

StopEvaporator Freeze Protect Evap LWT goes below evap freeze protect set point Rapid StopLeaving Evaporator WaterTemperature Sensor Fault Sensor shorted or open Rapid Stop

Outside Air Temperature Sensor Fault Sensor shorted or open NormalShutdown

PLAN Failure No other controller found on the pLAN for 60 seconds Rapid Stop

EventsThe following “alarms” only generate a warning message to the operator. Chiller operationis not affected. They are logged in the Event Log with a time stamp.

Table 21, Unit Event AlarmsDescription Occurs When: Action Taken Reset

Entering Evaporator TemperatureSensor Fault

Sensor is open orshorted

Cannot use return watertemperature control Automatic

Unit Mode SelectionThe overall operating mode of the chiller is set by the Unit Mode Set Point with options ofCOOL, COOL w/Glycol, ICE w/Glycol, and TEST. This set point can be altered by thekeypad, BAS, and Mode input. Changes to the Unit Mode Set Point are controlled by twoadditional set points.

OM AGS 21

• Available Modes Set Point: Determines the operational modes available at any timewith options of COOL, COOL w/Glycol, COOL/ICE w/Glycol, and TEST

• Control Source Set Point: Determines the source that can change the Unit Mode SetPoint with options of KEYPAD (pCO2 or Touchscreen), NETWORK, or SWITCHES.

When the Control source is set to KEYPAD, the Unit Mode stays at its previous setting untilchanged by the operator. When the Control source is set to BAS, the most recent BASmode request goes into effect even if it changed while the Control source was set toKEYPAD or DIGITAL INPUTS.

Changing the Unit Mode Set Point can be accomplished according to the following table.NOTE: An “x” indicates that the value is not applicable.

Control SourceSet Point

ModeInput Keypad Entry BAS

RequestAvailable Modes

Set Point Unit Mode

x x x x COOL COOLx x x x COOL w/Glycol COOL w/Glycol

SWITCHES OFF x x COOL/ICE w/Glycol COOL w/GlycolSWITCHES ON x x COOL/ICE w/Glycol ICE w/Glycol

KEYPAD x COOL w/Glycol x COOL/ICE w/Glycol COOL w/GlycolKEYPAD x ICE w/Glycol x COOL/ICE w/Glycol ICE w/Glycol

NETWORK x x COOL COOL/ICE w/Glycol COOL w/GlycolNETWORK x x ICE COOL/ICE w/Glycol ICE w/Glycol

x x x x TEST TEST

Unit Test ModeThe unit test mode allows manual testing of all controller outputs. Entering this moderequires the following conditions.

• Unit OFF input = OFF (i.e. entire chiller is shut down).• Manager password active.• Available Unit Mode set point = TESTA test menu can then be selected to allow activation of the outputs. It is possible to switcheach digital output ON or OFF and set the analog outputs to any value.

Unit EnableEnabling and disabling the chiller is controlled by the Unit Enable Set Point with options ofOFF and ON. This set point can be altered by the Unit OFF input, Remote input, keypadentry, and BAS request. The Control Source Set Point determines which sources can changethe Unit Enable Set Point with options of SWITCHES, KEYPAD or NETWORK.

Changing the Unit Enable Set Point can be accomplished according to the following table.NOTE: An “x” indicates that the value is ignored.

Unit OffInput

Control SourceSetPoint

RemoteInput

KeypadEntry

BASRequest

UnitEnable

OFF x x x x OFFx SWITCHES OFF x x OFF

ON SWITCHES ON x x ONON KEYPAD x OFF x OFFON KEYPAD x ON x ONON NETWORK x x OFF OFFON NETWORK OFF x x OFFON NETWORK ON x ON ON

OM AGS 22

Evaporator Pump State ControlOperation of the evaporator pump is controlled by the state-transition diagram shown below.A state variable (Evap State) is used to maintain the current state (OFF, START, or RUN).The Evap Flow Timer starts when flow is first indicated by the Evaporator Water FlowSwitch digital input. This timer is considered expired when it equals the Evap RecirculateSet Point. Tests involving compressor state must be checked for all compressors on thechiller.

Leaving Water Temperature (LWT) ResetThe Active Leaving Water variable is set to the current Leaving Water Temperature (LWT)set point unless modified by one of the reset methods below. (The current LWT set point isCool LWT or Ice LWT as determined by the chiller mode.) The type of reset in effect isdetermined by the LWT Reset Type set point.

Reset Type – NONEThe Active Leaving Water variable is set equal to the current LWT set point.

Reset Type – RETURNThe return water temperature adjusts the Active Leaving Water variable. When the chillermode = COOL, the Active Leaving Water variable is reset using the following parameters:

1. Cool LWT set-point2. Max Reset Delta T set-point3. Start Reset Delta T set-pointReset is accomplished by changing the Active Leaving Water variable from the (Cool LWTset-point) to the (Cool LWT set-point + Max Reset Delta T set-point) when the evaporatorwater temperature Delta-T varies from the (Start Reset Delta T set-point) to 0.

OFF

RUN STARTTEST: Flow OK & Evap Recirc Timer Expired

TEST: Unit State=OFF & Comp State=OFF &

TEST: Unit State = AUTO ANDAt least one circuit is enabled for start

TEST: Unit State=OFF & Comp State=OFF

Power ON

OM AGS 23

Reset Type – 4-20 mAThe Active Leaving Water variable is adjusted by the 4 to 20 mA reset analog input.

20 ma

(54.0°F)

Cool LWT Set-Point(44.0°F)

4 ma

LWT Reset (Cool mode)(temperatures are examples only)

0 ma

Max Reset Delta T(10.0°F)

Reset Type – Outside Air Temperature (OAT)The Active Leaving Water variable is adjusted by the outdoor ambient temperature. TheActive Leaving Water variable is set equal to the Cool LWT set point if the outdoor ambienttemperature is greater than 75 F. From 75 down to 60 F the reset varies linearly from noreset to the max reset at 60 F. At ambient temperatures less than 60 F, the max reset shall beapplied to the active set point.

Normal OperationThe Evaporator Water Pump outputs will be controlled in one of two ways depending on theStandby Pump set-point which may be set to YES or NO.

• If NO standby pump is selected, only pump #1 will be started even in event of a failure.

• If Standby Pump=YES, pump #1 will always be started first. Pump #2 will only bestarted if there is a failure indicated on pump #1.

One Evaporator Water Pump output will be ON if the Evap State is set to START or RUN.Both outputs will be OFF if the Evap State is set to OFF. It shall not be possible to activateboth pump outputs simultaneously at any time.

Building Automation System (BAS) Interface

Protocols SupportedThe following building automation system (BAS) protocols are supported. It shall bepossible to change the building automation interface without loading different software.

Table 22, Standard Protocol DataProtocol Physical Layer Data Rate Controller Other

BACnet/IP Ethernet 10 Base-T 10 Megabits/sec Color graphics SBC Conformance Class 3BACnet MSTP RS485 (TBD) pCO2 Unit Controller Conformance Class 2

LONworks FTT-10A 78kbits/sec pCO2 Unit Controller Chiller Profile

MODBUS RTU RS-485 (TBD) pCO2 Unit Controller

OM AGS 24

The following functions are available through the BAS where possible. Exact capabilitiesmay vary depending on the protocol in use.

• Enable/Disable chiller operation by setting the Unit Enable set point.

• Select the operating mode by setting the Unit Mode set point.

• Set the Cool LWT and Ice LWT set points.

• Set the Network Limit variable.

• Read all digital and analog I/O values.

• Read Enable status of chiller

• Read current operating mode and status (state) of chiller.

• Send a description of each alarm when it occurs.

NOTE: Detailed installation and operating manuals for the specific protocol ordered will beincluded with the unit.

OM AGS 25

Using the Controller

4x20 Display & KeypadLayoutThe 4-line by 20-character/line liquid crystal display and 6-key keypad for both the circuitcontroller and unit controller is shown below.

Figure 2, Display (in MENU mode) and Keypad Layout

Air Conditioning

ALARMVIEW

SET

<<<

Note that each ARROW key has a pathway to a line in the display. Pressing an ARROWkey will activate the associated line when in the MENU mode.

Getting Started-Press the MENU key to get started The navigating procedures are thesame for both the unit controller and the circuit controller.

MENU KeyThe MENU key is used to switch between the MENU mode as shown in Figure 2 and theSCROLL mode as shown in Figure 3. The MENU mode is basically a shortcut to specificgroups of menus used for checking ALARMS, for VIEWING information, or to SETsetpoint values. The SCROLL mode allows the user to move about the matrix (from onemenu to another, one at a time) by using the four ARROW keys.

When in the MENU mode (as shown in Figure 2), pressing the LEFT ARROW key willselect the ALARM menus, the RIGHT ARROW key will select the VIEW menus and theUP key the SET menus. The controller will go the next lower menu in the hierarchy, andthen other menus can be accessed by using the ARROW keys. Pressing the MENU keyfrom any menu screen will automatically return to the MENU mode as shown in Figure 2.

Another way to navigate through the menus is to press the MENU key when in the MENUmode (as above). This will switch the controller to the SCROLL mode. The controller willautomatically go to the first screen as shown below (the upper-left menu on the menu matrixshown in Table 23 on page 27. From there the four ARROW keys can be used to scroll up,down, or across to any other menu.

ENTER Key

MENU Key

ARROW Keys (4)

Key to Screen

OM AGS 26

Figure 3, Display (in SCROLL Mode) and Keypad Layout

Air Conditioning

VIEW UNIT STATUSUnit = COOLCompr. #1/#2=OFF/OFFEvap Pump = RUN

ENTER KeyPressing the ENTER key changes the function of the ARROW keys to the editing functionas shown below:

LEFT key, Default, changes a value to the factory-set default value.

RIGHT key, Cancel, cancels any change made to a value and returns to the originalsetting.

UP key, Increment, increases the value of the setting

DOWN key, Decrement decreases the value of a setting.

These four edit functions are indicated by one-character abbreviation on the right side of thedisplay (this mode is entered by pressing the ENTER key).

Most menus containing setpoint values have several different setpoints shown on one menu.When in a setpoint menu, the ENTER key is used to proceed from the top line to the secondline and on downward. The cursor will blink at the entry point for making a change. TheARROW keys (now in the edit mode) are used to change the setpoint as described above.When the change has been made, press the ENTER key to enter it. Nothing is changed untilthe ENTER key is pressed.

For example, to change the chilled water setpoint:

1. Press MENU key to go to the MENU mode (see Figure 2).

2. Press SET (the UP Key) to go to the setpoint menus.

3. Press UNIT SPs (the Right key) to go to setpoints associated with unit operation.

4. Press the DOWN key to scroll down through the setpoint menus to the third menu whichcontains Evap LWT=XX.X°F

5. Press the ENTER key to move the cursor down from the top line to the second line inorder to make the change.

6. Use the ARROW keys (now in the edit mode as shown above) to change the setting.

7. When the desired value is achieved, press ENTER to enter it and also move the cursordown.

At this point, the following actions can be taken:

1. Change another setpoint in this menu by scrolling to it with the ENTER key

2. Using the ENTER key, scroll to the first line in the menu. From there the ARROW keyscan be used to scroll to different menus.

MENU Key

ENTER KeyARROW Keys (4)

OM AGS 27

Unit Controller MenusVarious menus are shown in the controller display. Each menu screen shows specificinformation. In some cases menus are used only to view status of the unit, in some casesthey are used for checking alarms, and in some case they are used to set the setpoint valuesthat can be changed.

The menus are arranged in a matrix of screens across a top horizontal row. Some of thesetop-level screens have sub-screens located under them. The content of each screen and itslocation in the matrix are shown in Table 23. A description of each menu begins on page28.

The ARROW keys on the controller are used to navigate through the menus. The keys arealso used to change numerical setpoint values contained in certain menus.

As an alternate to selecting screens with the menu function, it is possible to scroll throughall of them with the 4 arrow keys. For this use, the screens shall be arranged logically in amatrix as shown below.

Table 23, Unit Controller Menu StructureVIEW MENUS

VIEWUNIT

STATUS(1)

VIEWUNITTEMP

(2)

VIEWCOMP

#1(1)

VIEWCOMP

#2(1)

VIEWCOMP

#3(1)

VIEWREFRGCIR 1

(1)

VIEWREFRGCIR 2

(1)

VIEWREFRGCIR 3

(1)

VIEWFANSCIR 1

(1)

VIEWFANSCIR 2

(1)

VIEWFANSCIR 3

(1)VIEWUNIT

STATUS(2)

VIEWUNITTEMP

(2)

VIEWCOMP

#1(2)

VIEWCOMP

#2(2)

VIEWCOMP

#3(2)

VIEWREFRGCIR 1

(2)

VIEWREFRGCIR 2

(2)

VIEWREFRGCIR 3

(2)

VIEWFANSCIR 1

(2)

VIEWFANSCIR 2

(2)

VIEWFANSCIR 3

(2)VIEWUNIT

STATUS(3)

� � �

VIEWREFRGCIR 1

(5)

VIEWREFRGCIR 2

(5)

VIEWREFRGCIR 3

(5)

Right half oftable

continuedbelow

ALARM MENUS SET MENUSEVENT

LOG(1)

ALARMLOG(1)

ALARMACTIVE

(1)

SET UNITSPs (1)

SETCOMP SP

(1)

SETALARM

LMTS (1)

SETSENSOROFFSET

� � �SET UNIT

SPs(2)

SETCOMP SP

(2)

SETALARMLMTS

(2)

EVENTLOG(25)

ALARMLOG(25)

ALARMACTIVE

(n)

SET UNITSPs(3)

SETCOMP SP

(3)

SETALARMLMTS

(3)

SET UNITSPs(4)

SETALARMLMTS

(4)

Left half oftable

continuedfrom above

SET UNITSPs(5)

SET UNITSPs(6)

�SET UNIT

SPs(to 12)ENTERPASS-WORD

Continued

OM AGS 28

Selection can then be made by using the LEFT/RIGHT keys to move between columns andthe UP/DOWN keys to move between rows. The memory allows the return to the lastscreen viewed in each column. (This feature also applies to navigation using the functionkeys.) As an example:

If the VIEW COMP#2 (3) screen is being viewed and the RIGHT arrow key ispressed, the display will show VIEW EVAP. If the LEFT arrow key is then pressed,the display will show VIEW COMP#2 (3) again (not VIEW COMP (1)).

Attempts to scroll past the limits of the matrix are ignored.

Screen DefinitionsThe following section illustrates all the "unit" screens. The screens are listed in the order ofthe matrix, starting from the upper-left. Unit "view" screens are used to view the operationof a circuit's compressor, refrigerant condition, EXV position, and fan operation. Nosettings are made to these screens.

View Unit StatusVIEW UNIT STATUS (1)Auto

Evap Pump= run

VIEW UNIT STATUS (2)Softload Limit=100.0Demand Limit=100.0Network Limit=100.0

VIEW UNIT STATUS (3)1 2 3 4

D.O. 0 1 0 0D.I. 1 1 1 0

VIEW UNIT TEMP (1)Evap LWT= XXX.X FEvap EWT= XXX.X FActive SP= XXX.X F

VIEW UNIT TEMP (2)LWT Pulldn= 0.0 F/mEvap Delta T=XX.X FOutdoor Air=XXX.X F

NOTE: In the following VIEW CIRCUIT screens, the N field indicates which compressor(#1, #2, etc.) is being viewed.

VIEW CIR N STATUS(1)Off:ReadySlide Position=000.0

OM AGS 29

VIEW CIR N STATUS(2)Hours = XXXXXStarts = XXXXX

VIEW REFR CIR N (1)Evap Press=XXX.X psiCond Press=XXX.X psiLiq Press= XXX.X psi

VIEW REFRG CIR N (2)Sat Evap= XXX.X °°°°FSat Cond= XXX.X °°°°FSat LiqLine= XXX.X°°°°F

VIEW REFRG CIR N (3)Suct Temp = XXX.X °°°°FDisc Temp = XXX.X °°°°FLiq Temp = XXX.X °°°°F

VIEW REFRG CIR N (4)Suct SH = XXX.X °°°°FDisc SH= XXX.X °°°°FLiquid SC= XXX.X °°°°F

VIEW REFRG CIR N (5)Evap Approach=XX.X°°°°FCond Approach=XX.X°°°°FEXV position = XXXX

VIEW FANS (1)Fans On, Cir 1= 0Fans On, Cir 2= 0

VIEW FANS (2)VFD Cir 1= 000.0 %VFD Cir 2= 000.0 %

OM AGS 30

ALARM Screen DefinitionsThe following screens are shown in °F/psi. When the Display Units set point is set to °C/kPa, theunits and values shall change accordingly.

ALARM LOG: (1)High Condenser Presshh:mm:ss dd/mmm/yyyyUnit State= Auto

ALARM ACTIVE (1)hh:mm:ss dd/mmm/yyyyMech High Press

SET Screen DefinitionsThe following screens are shown in °F/psi. When the Display Units set point is set to °C/kPa, theunits and values shall change accordingly.

SET UNIT SPs (1)Enable=OnMode= COOLSource = KEYPAD

SET UNIT SPs (2)Available Modes = COOL

Select w/Unit Off

SET UNIT SPs (3)Cool LWT = XX.X°°°°F

SET UNIT SPs (4)StartDelta= XX.X°°°°FStopDelta= XX.X°°°°FStageDeltaT= XX.X°°°°F

SET UNIT SPs (5)Max Pulldn=X.X°°°°F/minEvapRecTimer=XXX secEvap Pump= #1 only

SET UNIT SPs (6)Reset Type =noneMaxResetDT =XX.X°°°°FStrtResetDT=XX.X°°°°F

OM AGS 31

SET UNIT SPs (7)Soft Load = OffBegin Capacity= XXX%SoftLoadRamp= XXmin

SET UNIT SPs (8)Demand Limit= Off

SET UNIT SPs (9)CLOCK

dd/mmm/yyyyhh:mm:ss

SET UNIT SPs (10)Units = °°°°F/psiLang = ENGLISH

SET UNIT SPs (11)Protocol=Ident Number=Baud Rate=

SET UNIT SPs (12)Enter Password:0000Active PasswordLevel:none

SET COMP SPs (1)Seq # Comp 1=Seq # Comp 2=Seq # Comp 3=

SET COMP SPs (2)Max Comprs On = XStart-Start = XXminStop-Start = XXmin

SET COMP SPs (3)Pumpdn press=25.0psiPumpdn time= 120 sec

OM AGS 32

SET ALARM LMTS (1)LowEvPrHold=XXXpsiLowEvPrUnld=XXXpsiLowEvPrStop=XXXpsi

SET ALARM LIMITS (2)LowEvPrDel= XXX secLowOilDelay= XXX secHighOilDpDel=XXX sec

SET ALARM LIMITS (3)MinLiftDel= XXX secLow Subcool= XX.X°°°°FHigh Disc Temp=XXX°°°°F

SET ALARM LIMTIS (4)Evap Freeze= XX.X°°°°FLow Amb Lock= XX.X°°°°FEvap Flow Proof=XXX

SET SENSOR OFFSETOAT= XX.X°°°°FEvap LWT= XX.X°°°°FEvap EWT= XX.X°°°°F

TEST Screen Definitions

TEST UNITAlarm Out=OffEvap Heaters=OffPump1=Off Pump 2=Off

OM AGS 33

Circuit Controller MenusSee "Using the Controller" on page 25 for information on how to navigate and use the menuscreens as well as changing setpoints. As an alternate to selecting screens with the menufunction, it is possible to scroll through all of them with the 4 arrow keys. For this use, thecircuit controllers' screens are arranged logically in a matrix as shown below.

Table 24, Circuit Controller Screen Matrix

"VIEW" SCREENS "SET" SCREENS "TEST"SCREENS

VIEWUNIT

VIEWCOMP

(1)

VIEWREFRG

(1)

VIEWFANS

(1)

SETCOMP

SPsSET

EXV SPsSET

FANS(1)

SETSENSOROFFSETS

(1)

TESTCOMP

(1)

VIEWCOMP

(2)

VIEWREFRG

(2)

VIEWFANS

(2)

SETCOMPSPs (2)

SETFANS

(2)

SETSENSOROFFSETS

(2)

TESTCOMP

(2)

VIEWCOMP

(3)

VIEWREFRG

(3)

SETCOMPSPs (3)

SETFANS(3)

TESTCOMP

(3)VIEWCOMP

(4)

VIEWREFRG

(4)

SETCOMPSPs (4)

SETFANS

(4)VIEWCOMP

(5)�

SETCOMPSPs (5)

�

VIEWREFRG

(7

SETFANS

(7)

Screen DefinitionsVIEW ScreensCircuit "VIEW" screens are used to view the operation of a circuit's compressor, refrigerantcondition, EXV position, and fan operation. No settings are made on these screens.

VIEW UNIT (1)Auto

Evap pump = Run

VIEW UNIT (2)Evap LWT= XXX.X°°°°FActive SP= XX.X°°°°FLWT pulldn= XX.X°°°°F/m

VIEW CIR STATUS (1)Off:ReadySlide Pos= XXX.X%Slide Target= XXX.X%

View screens #1 and #2 to theleft are actually Unit screens thatare repeated here for operatorconvenience.

OM AGS 34

VIEW CIR STATUS (2)Slide AIN= XXXXHours = XXXXXStarts = XXXXX

VIEW CIR STATUS (3)Digital Outputs

1 2 3 4 5 6 7 8 9 100 0 0 0 0 0 0 0 0 0

VIEW CIR STATUS (4)Analog Outputs(volts X 100)

1=XXXX 3=XXXX

VIEW REFRIGERANT (1)Evap Press=XXX.X psiCond Press=XXX.X psiLiq Press= XXX.X psi

VIEW REFRIGERANT (2)Sat Evap = XXX.X °°°°FSat Cond = XXX.X °°°°FSat LiqLine= XXX.X °°°°F

VIEW REFRIGERANT (3)Suct Temp = XXX.X °°°°FDisc Temp = XXX.X °°°°FLiq Temp = XXX.X °°°°F

VIEW REFRIGERANT (4)Suct SH = XXX.X °°°°FDisc SH= XXX.X °°°°FLiquid SC= XXX.X °°°°F

VIEW REFRIGERANT (5)Evap Approach=XX.X °°°°FCond Approach=XX.X °°°°F

VIEW REFRIGERANT (6)EXV control=Pressure

Press target= XX.X°°°°FMax Disc SH= XX.X°°°°F

OM AGS 35

VIEW REFRIGERANT (7)EXV Steps= XXXXEXV ctrl range:XXXX – XXXX steps

VIEW FANS (1)VFD Speed= XXX.X%Fans Running= XVFD Target=XXX.X °°°°F

VIEW FANS (2)Target Sat T=XXX.X °°°°FStage Up Err= XXXStage Dn Err= XXX

SET Screen Definitions

SET COMP SPs (1)Circuit Mode=EnableSlide Control=autoSlide Pos= XXX.X%

SET COMP SPs (2)Comp Size= XXXClear Cycle Tmr= no

SET COMP SPs (3)LWT Error Mult=XXLWT Slope Mult=XXTotal Error Mult=XX

SET COMP SPs (4)Cap Change Int =XXsecMaxSlideChange =XX.X%

SET COMP SPs (5)Slide Deadband=XX.X%Slide Pulse On=XXXmsPulse Delay= XX sec

SET EXV SPs (1)EXV Control=autoEXV Pos= XXXX steps

OM AGS 36

SET EXV SPs (2)@Minimum LoadMin EXV Steps= XXXMax EXV Steps=XXXX

SET EXV SPs (3)Pressure ControlPropo Band= XX.XIntegral Time= XXXX

SET EXV SPs (4)Subcool ControlPropo Band= XX.XIntegral Time= XXXX

SET EXV SPs (5)Min Disc SH=XXX.X °°°°F

SET FAN SPs (1)Fan VFD = noNumber of fans = X

SET FAN SPs (2)Stg Up Deadband(°°°°F)Stg1=XXX Stg3=XXXStg2=XXX Stg4=XXX

SET FAN SPs (3)Stg Down Deadband(°°°°F)Stg1=XXX Stg3=XXXStg2=XXX Stg4=XXX

SET FAN SPs (4)Delay Error

StgUp XXsec XXXStgDn XXsec XXX

OM AGS 37

SET FAN SPs (5)VFD Min speed= XXX%VFD Max speed= XXX%

SET FAN SPs (6)VFD Speed Control

Propo Band= XX.X °°°°FIntegral Time=XX sec

SET FAN SPs (7)Cond Sat Temp Target

Set Point= XXX.X °°°°F

SET SENSOR OFFSET (1)Evap Press= XX.X psiCond Press= XX.X psiLiq Press= XX.X psi

SET SENSOR OFFSET (2)Suct Temp= X.X FDisch Temp= X.X FLiq Temp= X.X F

TEST CIRCUIT (1)Fans:1=Off 2=Off

3=Off 4=Off5/6=Off 7/8=Off

TEST CIRCUIT (2)Slide Dir= UnloadSlide Pulse= OffOil Return Sol=Off

TEST CIRCUIT (3)Fan VFD Spd%= XXX.XEXV Position=XXXX

OM AGS 38

Sequence of Operation

The following sequence of operation is typical for McQuay models AGS chillers. Thesequence may vary depending on the software revision or various options that may beinstalled on the chiller.

Off ConditionsPower is supplied to each power panel located between condenser sections. Optionally, thepower may be supplied to a single power connection in a terminal box located on the base ofthe unit.

With power supplied to the unit, 115 VAC power is applied through the control fuse F1 tothe compressor heaters (HTR1, HTR2, (and HTR3), and evaporator heater and the primaryof the 24V control circuit transformer.

Note:Compressor heaters must be on for at least 12 hours prior to start-up to

avoid compressor damage.The 24V transformer provides power to the MicroTech II controller and related components.With 24V power applied, the controller will check the position of the front panel systemswitch. If the switch is in the "stop" position the chiller will remain off and the display willindicate the operating mode to be OFF: System Sw. The controller will then check thepumpdown switches. If any of the switches are in the "stop" position, that circuit’soperating mode will be displayed as OFF: PumpDwnSw. If the switches for both circuitsare in the "Stop" position the unit status will display OFF: PumpdownSw’s. If the remotestart/stop switch is open the chiller will be OFF: RemoteSw. The chiller may also becommanded off via communications from a separate communicating panel such a BASprotocol interface. The display will show OFF: RemoteComm if this operating mode is ineffect. If an alarm condition exists which prevents normal operation of both refrigerantcircuits, the chiller will be disabled and the display will indicate OFF: Alarm. If thecontrol mode on the keypad is set to "Manual Unit Off," the chiller will be disabled and theunit status will display OFF: ManualMode. Assuming none of the above stop conditionsare true, the controller will examine the internal time schedule to determine whether thechiller should be permitted to start. The operating mode will be OFF: TimeClock if thetime schedule indicates time remaining in an "off" time period.

AlarmThe alarm light in back of the left arrow button on the controller will be illuminated whenone or more of the cooling circuits has an active alarm condition which results in the circuitbeing locked out. Unless the alarm condition affects all circuits the remaining circuits willoperate as required.

Start-upIf none of the above "off" conditions are true, the MicroTech II controller will initiate a startsequence and energize the chiller water pump output relay. The chiller will remain in theWaitForFlow mode until the field installed flow switch indicates the presence of chilledwater flow. If flow is not proven within 30 seconds, the alarm output will be turned on, thekeypad display will be WaitForFlow and the chiller will continue to wait for proof ofchilled water flow. Once flow is established, the controller will sample the chilled watertemperature and compare it against the Leaving Chilled Water Set Point, the Control Band,and the Start-up Delta Temperature, which have been programmed into the controller’smemory.

OM AGS 39

If the leaving chilled water temperature is above the Leaving Chilled Water Set Point plus ½the Control Band plus the adjustable Start-up Delta Temperature, the controller will selectthe refrigerant circuit with the lowest number of starts as the lead circuit and energize thefirst stage of the Cool Staging mode. The controller will start the compressor and energizethe evaporator oil return solenoid. The controller will delay the opening of the electronicexpansion valve until the evaporator pressure decreases to a preset value. This is theevaporator prepurge mode and the display will show Pre-Purge. The valve will then openallowing refrigerant to flow through the expansion valve and into the evaporator and thedisplay will show Opened EXV. If additional cooling capacity is required, the controllerwill energize the additional cooling capacity by activating the first compressor’s capacitycontrol solenoids. As the system load increases, the controller will start the lag refrigerantcircuit in the same manner after interstage timers are satisfied. The compressors andcapacity control solenoids will automatically be controlled as required to meet the coolingneeds of the system. The electronic expansion valves are operated by the MicroTech IIcontroller to maintain precise refrigerant control to the evaporator at all conditions.

Standard FanTrol Condenser Fan ControlThe first condenser fan stage will be started along with the first compressor to provide initialcondenser head pressure control. The MicroTech II controller will activate the remainingcondenser fans as needed to maintain proper condenser pressure. The MicroTech IIcontroller continuously monitors the condenser minus evaporator lift pressure and willadjust the number of operating condenser fans as required. The number of condenser fansoperating will vary with outdoor temperature and system load. The condenser fans arematched to the operating compressors so that when a compressor is off all fans for thatcircuit will also be off.

Optional VFD Condenser Fan Control

PumpdownAs the system chilled water requirements diminish. The compressors will be unloaded. Asthe system load continues to drop, the electronic expansion valves will be stepped closedand the refrigerant circuits will go through a pumpdown sequence. As the evaporatorpressure falls below the pumpdown pressure set point while pumping down, thecompressor(s) and condenser fans will stop. The unit has a one-time pumpdown controllogic; therefore, if the evaporator pressure rises while the refrigerant circuit is in apumpdown mode, the controller will not initiate another pumpdown sequence. Thecontroller will keep the unit off until a call for cooling occurs.

The chilled water pump output relay will remain energized until the time schedule’s "on"time expires, the remote stop switch is opened, the system switch is moved to the stopposition, or a separate communications panel such as the Remote Monitoring andSequencing Panel or an Open Protocol interface deactivates the chilled water pump output.

CAUTION

The screw compressor must not be used as a pump out compressor for service work involvingremoval of refrigerant from the compressor or evaporator. That is, the compressor must not berun with the liquid line valve (king valve) closed. Portable recovery equipment must be used toremove the refrigerant. Serious damage to the compressor could result.

OM AGS 40

Figure 4, AGS Piping Schematic

DISCHARGETUBING

SIGHTGLASS

AIRFLOW

WATER OUT

WATER IN

LIQUIDTUBING

EXPANSIONVALVE

SCHRADERVALVE

CHARGINGVALVE

SIGHTGLASS

CONDENSERASSEMBLY

AIRFLOW

AIRFLOWAIR

FLOW

CONDENSERASSEMBLY

CHARGING VALVE

LIQUID SHUT-OFF VALVE

SCHRADER VALVEFILTER DRIER

OIL FILTER

OILSEPARATOR

OILRETURN

DISCHARGETUBING SCHRADER

(EACH DISCHHEADER)

TO REAR OFCOMPRESSOR

SUCTION

BUTTERFLY VALVE(OPTION)

SIGHTGLASS

RELIEF VALVE(EVAP SHELL)

RELIEFVALVE

CHECKVALVE

ANGLEVALVE

S

OM AGS 41

Start-up and Shutdown

NOTICE

McQuayService personnel or factory authorized service agencymust perform initial start-up.

CAUTION

Most relays and terminals in the unit control center are powered when S1 is closed and thecontrol circuit disconnect is on. Therefore do not close S1 until ready for start-up.

Seasonal Start-up1. Double check that the optional compressor suction butterfly valve is open. There is a check

valve between the oil separator and condenser..2. Check that the manual liquid-line shutoff valves at the outlet of the subcooler coils on each side

of the unit are open.3. Adjust the leaving chilled water temperature set point on the MicroTech II controller to the

desired chilled water temperature. The control band is preset for 10 degrees Delta-T between theentering and leaving evaporator water temperature at full load. If the Delta-T is outside an 8°-12°F range, at full load, reset the control band as per the instructions found in the Control sectionof this manual.

4. Start the auxiliary equipment for the installation by turning on the time clock, and/or remoteon/off switch, and chilled water pump.

5. Check to see that pumpdown switches PS1 and PS2 are in the "Pumpdown and Stop" (open)position. Throw the S1 switch to the "auto" position.

6. Under the "Control Mode" menu of the keypad place the unit into the automatic cool mode.7. Start the system by moving pumpdown switch PS1 to the "auto" position.8. After running circuit #1 for a short time, check for flashing in the refrigerant sightglass under

stable conditions.9. Repeat steps 8 and 9 for PS2.10. Superheat is factory adjusted to maintain between 0° and 3°F.

CAUTIONThe superheat should be between 0°F and 3°F, with the liquid line sightglass full, once thesystem temperatures have stabilized at the MicroTech II set point temperatures.

Temporary ShutdownMove pumpdown switches PS1 and PS2 to the "Pumpdown and Stop" position. After thecompressors have pumped down, turn off the chilled water pump.

Caution:Do not turn the unit off using the "S1" switch, without first moving PS1 and PS2 to the"Stop" position, unless it is an emergency as this will prevent the unit from going through aproper shutdown sequence.

OM AGS 42

CAUTIONThe unit has one time pumpdown operation. When PS1 and PS2 are in the "Pumpdown andStop" position the unit will pumpdown once and not run again until the PS1 and PS2switches are moved to the auto position. If PS1 and PS2 are in the auto position and theload has been satisfied the unit will go into one time pumpdown and will remain off untilMicroTech II senses a call for cooling and starts the unit. Under no circumstance use thecompressors for pumpdown with the liquid line valves closed.

It is important that the water flow to the unit is not interrupted before the compressorspumpdown to avoid freeze-up in the evaporator.

If all power is turned off to the unit the compressor heaters will become inoperable. Oncepower is resumed to the unit it is important that the compressor and oil separator heaters areenergized a minimum of 12 hours before attempting to start the unit. Failure to do so coulddamage the compressors due to excessive accumulation of liquid in the compressor.

Start-up After Temporary Shutdown1. Insure that the compressor heaters have been energized for at least 12 hours prior to starting the

unit.2. Start the chilled water pump.3. With System switch S1 in the "on" position, move pumpdown switches PS1 and PS2 to the

"auto" position.4. Observe the unit operation until the system has stabilized.

WARNINGIf shutdown occurs or will continue through periods below freezing ambient temperatures,protect the chiller vessel from freezing. See Freeze Up Protection in this manual for moreinformation.

Extended (Seasonal) Shutdown1. Move the PS1 and PS2 switches to the manual pumpdown position.2. After the compressors have pumped down, turn off the chilled water pump.3. Turn off all power to the unit and to the chilled water pump.4. Move the emergency stop switch S1 to the "off" position.5. Close the optional compressor suction valve (if so equipped) as well as the liquid line shutoff

valves.6. Tag all opened compressor disconnect switches to warn against start-up before opening the

compressor suction valve and liquid line shutoff valves.7. If glycol is not used in the system, drain all water from the unit evaporator and chilled water

piping if the unit is to be shutdown during winter. Do not leave the vessels or piping open to theatmosphere over the shutdown period.

8. Leave power applied to the evaporator heaters if a separate disconnect is used.

OM AGS 43

Start-up After Extended (Seasonal) Shutdown1. With all electrical disconnects open, check all screw or lug type electrical connections to be sure

they are tight for good electrical contact.2. Check the voltage of the unit power supply and see that it is within the ±10% tolerance that is

allowed. Voltage unbalance between phases must be within ±3%.3. See that all auxiliary control equipment is operative and that an adequate cooling load is

available for start-up.4. Check all compressor flange connections for tightness to avoid refrigerant loss. Always replace

valve seal caps.5. Make sure system switch S1 is in the "Stop" position and pumpdown switches PS1 and PS2 are

set to "Pumpdown and Stop," throw the main power and control disconnect switches to "on."This will energize crankcase heaters. Wait a minimum of 12 hours before starting up unit. Turncompressor circuit breakers to "off" position until ready to start unit.

6. Open the optional compressor suction butterfly as well as the liquid line shutoff valves.7. Vent the air from the evaporator water side as well as from the system piping. Open all water

flow valves and start the chilled water pump. Check all piping for leaks and recheck for air inthe system.

Post Office Box 2510, Staunton, Virginia 24402 USA • (800) 432-1342 • www.mcquay.com