Air-Cooled Screw Compressor Chiller - Daikin...

Operation Manual OM AGSDP-3

Group: Chiller

Part Number: 331375901

Date: January 2009

Supersedes: OM AGSDP-2

Air-Cooled Screw Compressor Chiller

Models AGS 226DP to AGS 501DP

230 to 475 Tons, 805 to 1662 kW

R-134a

60 Hz

Software Version AGSU30101K

2 OM AGSDP-3

Table of Contents MICROTECH II FEATURES .......4

GENERAL DESCRIPTION..............5

COMPONENT DESCRIPTION .......6 Unit and Circuit Controller Description.. 8

CONTROL OPERATION ...............10

CIRCUIT CONTROLLER..............10 Inputs/Outputs....................................... 10 Setpoints................................................ 11 Compressor Control .............................. 15 Condenser Fan Control ......................... 19 EXV Control ......................................... 21 Evaporator Oil Return Line Control...... 23 Oil Heater Control................................. 23 Interstage Injection................................ 23

UNIT CONTROLLER .....................24 Inputs/Outputs....................................... 24 Setpoints................................................ 24 Unit Enable ........................................... 27 Unit Mode Selection ............................. 28 Evaporator Pump Control ..................... 30 Evaporator Heater Control .................... 31 Leaving Water Temperature (LWT) Reset

.............................................................. 31

ALARMS AND EVENTS ................ 34 Alarm and Event Logging..................... 37

USING THE CONTROLLER......... 38 Security ................................................. 40 Entering Passwords ............................... 40 Editing Setpoints ................................... 40 Clearing Alarms .................................... 40 Unit Controller Menus .......................... 41 Screen Definitions................................. 42 SET Screen Definitions......................... 44 Circuit Controller Menus ...................... 48 Screen Definitions................................. 48

SEQUENCE OF OPERATION ...... 53

START-UP AND SHUTDOWN...... 55 Expansion Valve Operation................... 56 Extended (Seasonal) Shutdown............. 58 Evaporator Freeze Protection................ 59 Operating Limits: .................................. 60

REFRIGERANT CHARGING ....... 61

BAS INTERFACE............................ 64

FIELD WIRING DIAGRAM.......... 65

Manufactured in an ISO Certified facility

2007 McQuay International. "McQuay" is a registered trademark of 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.

The following are trademarks or registered trademarks of their respective companies: BACnet from ASHRAE; LONMARK and LONWORKS Logo are

managed, granted and used by LONMARK International under a license granted by Echelon Corporation; McQuay and MicroTech II, Open Choices, FanTrol from McQuay International.

OM AGSDP-3 3

This manual provides setup, operating, and troubleshooting information for the McQuay

MicroTech ΙΙ controller for Model AGSDP, air-cooled, rotary screw compressor chillers.

Please refer to the current version of IMM AGSDP (available from the local McQuay sales

office or on www.mcquay.com) for information relating to the solid state starters and to the

unit itself.

NOTE: This manual covers units with Software Version AGSU30101K. The unit’s

software version number 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.

BOOT version 3.0F

BIOS version 3.86

! WARNING

Electric shock hazard. Can cause personal injury or equipment damage. This equipment must be properly grounded. Connections to, and service of the MicroTech II control panel must only be performed by personnel who are knowledgeable in the operation of the equipment being controlled.

! CAUTION

Static sensitive components. A static discharge while handling electronic circuit boards can cause damage to the components. Discharge any static electrical charge by touching the bare metal inside the control panel before performing any service work. Never unplug any cables, circuit board terminal blocks, or power plugs while power is applied to the panel.

NOTICE This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with this instruction manual, can cause interference 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 to correct the interference at the user’s expense. McQuay International Corporation disclaims any liability resulting from any interference or for the correction thereof.

Temperature and Humidity Limitations

The 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).

4 OM AGSDP-3

MicroTech II Features

• 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 chilled water pumps. The control will start one

of the pumps (based on lowest run-hours) when the unit is enabled to run (not necessarily

running on a call for cooling) and when the ambient temperature reaches a point of freeze

possibility.

• Two 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. All events, alarms, and faults are time- and date-stamped, for identification of

when the fault condition occurred. In addition, the operating conditions that existed just

prior to shutdown can be recalled to aid in isolating the cause of the problem.

• Twenty-five previous alarms 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. This function can be useful for system checkout.

• Building Automation System (BAS) communication capability via LONWORKS,

Modbus, or BACnet standard open protocols for all BAS manufacturers-simplified

with McQuay’s Open Choices feature.

• 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 and pressure to take

corrective action prior to a fault trip.

• Quiet Night function that reduces the unit sound level during a selected night-time period.

OM AGSDP-3 5

General Description

General Description

The Model AGS MicroTech ΙΙ distributed control system consists of multiple

microprocessor-based controllers that provide monitoring and control functions required for

the controlled, efficient operation of the chiller. The system consists of the following

components:

• Unit Controller, one per chiller − controls functions and settings that apply to the unit

and communicates with all other controllers. It is located in the control panel for circuit

#1 and is labeled “UNIT CONTROL”.

• Circuit Controller for each compressor/circuit (two or three depending on model size)

that control compressor functions and settings specific to the circuit. The controllers are

located in their circuit's control panel that is mounted between the condenser coil

sections and are labeled “CIRCUIT CONROL”.

In addition to providing all normal operating controls, the MicroTech II control system

monitors equipment protection devices on the unit and will take corrective action if the

chiller is operating outside of its normal design envelope. If an alarm condition develops,

the controller will shut the compressor down and activate an alarm output. Important

operating conditions at the time an alarm condition occurs are retained in the controller’s

memory to aid in troubleshooting and fault analysis.

The system is protected by a password scheme that allows access only by authorized

personnel. The operator must enter the operator password into the controller's keypad

before any setpoints can be altered.

Control Architecture

Figure 1, Major Control Components

Chiller A

Unit Controller

Circuit #1

Controller

4x20 LCD

Solid State

Starter

pLAN

BACnet MS/TP

BACnet IP

BACnet Ethernet

LonTalk

ModBus

RS485/LON/Ethernet

RS485

( Future)

4x20 LCD

( Future)

EXV

Other Circuit

Controllers

6 OM AGSDP-3

Component Description

Unit and Circuit Controller Description

Terminology and Definitions

Accumulator The accumulator is an electronic “bank” that stores information relative to fan operation and

fan capacity required. It is the heart of the controller’s fuzzy logic feature. Various events

such as cooling load changes and ambient air temperature changes, add or subtract points in

the bank. When a certain number of points are accumulated, a fan will be started.

Active Setpoint The active setpoint is the setting in effect at any given moment. This occurs on setpoints

that can be altered during normal operation. Resetting the chilled water leaving temperature

setpoint by one of several methods, such as return water temperature, is an example.

Condenser Saturated Temperature Target The saturated condenser temperature target is calculated by first using the following

equation:

Sat condenser temp target raw = 0.833(evaporator sat temp) + 68.34

The “raw” value is the initial calculated value. This value is then limited to a range defined

by the Condenser Saturated Temperature Target minimum and maximum setpoints. These

setpoints simply cut off the value to a working range, and this range can be limited to a

single value if the two setpoints are set to the same value.

CPU Error These are problems caused by a malfunction of the central processing unit.

Dead Band The dead band is a set of values associated with a setpoint such that a change in the variable

occurring within the dead band causes no action from the controller. For example, if a

temperature setpoint is 44°F and it has a dead band of ± 2 degrees, nothing will happen until

the measured temperature is less than 42°F or more than 46°F.

Delta-T Delta-T is a range of degrees of temperature. For example, a Start Up Delta-T of 5 degrees

means that the water temperature must be 5 degrees above the LWT setpoint before the start

signal is given.

Discharge Superheat Discharge superheat shall be calculated for each circuit using the following equation:

Discharge Superheat = Discharge Temperature – Condenser Saturated Temperature

Error In the context of this manual, “Error” is the difference between the actual value of a variable

and the target setting or setpoint.

Evaporator Approach The evaporator approach is calculated for each circuit. The equation is as follows:

Evaporator Approach = LWT – Evaporator Saturated Temperature

OM AGSDP-3 7

EvapRecTimer The evaporator recirculation timer establishes the time the chilled water pump will run after

the controller receives an enable signal and the Wait for Flow timer time out. This allows

time for the chilled water to circulate sufficiently to determine if there is a need for cooling.

EXV Electronic expansion valve, used to control the flow of refrigerant to the evaporator,

controlled by the circuit microprocessor.

High Saturated Condenser – Hold Value High Cond Hold Value = Max Saturated Condenser Value – 5°F

This function prevents the compressor from loading whenever the pressures approach

within 5 degrees of the maximum discharge pressure. The purpose is to keep the

compressor online during periods of possibly temporary elevated pressures.

Low Ambient Lockout Prevents compressors from starting when ambient air temperature is below the setpoint

(55°F default). Clears when ambient rises 5-degrees above the setpoint.

Low OAT Start Allows start attempts at low ambient temperatures.

High Saturated Condenser – Unload Value High Cond Unload Value = Max Saturated Condenser Value – 3°F.

This function unloads the compressor whenever the pressures approach within 3 degrees of

the maximum discharge pressure. The purpose is to keep the compressor online during

periods of possibly temporary elevated pressures.

Low Pressure Hold Setpoint The psi evaporator pressure setting at which the controller will not allow further compressor

loading.

Low/High Superheat Error The difference between actual evaporator superheat and the superheat target.

LWT Leaving water temperature. The “water” is any fluid used in the chiller circuit.

LWT Error Error in the controller context is the difference between the value of a variable and the

setpoint. For example, if the LWT setpoint is 44°F and the actual temperature of the water

at a given moment is 46°F, the LWT error is +2 degrees.

LWT Slope The LWT slope is an indication of the trend of the water temperature. It is calculated by

taking readings of the temperature every few seconds and subtracting them from the

previous value, over a rolling one minute interval.

Maximum Saturated Condenser Temperature The maximum saturated condenser temperature allowed is calculated based on the

compressor operational envelope.

Mode There are three possible operating modes for the unit: Some can be combined and then

selected by an external signal or from the keypad.

1. Cool, the compressors are under normal loading and staging control and the minimum

LWT setpoint is 40°F. Cool with Glycol merely reduces the minimum LWT to 30°F.

2. ICE, primarily controls the compressor at full load until the LWT setpoint is reached,

then shuts unit off.

3. Test, allows outputs to be actuated manually.

8 OM AGSDP-3

ms Milli-second

OAT Outside ambient air temperature

pLAN Peco Local Area Network is the proprietary name of the network connecting the control

elements.

Refrigerant Saturated Temperature Refrigerant saturated temperature is calculated from the pressure sensor readings for each

circuit. The pressure is fitted to an R-134a temperature/pressure curve to determine the

saturated temperature.

Slide Slide is an abbreviation for the compressor slide valve, which determines the compressor

capacity. It is positioned by the controller such that to unload, it moves toward the main

rotor suction end and discharge gas is bypassed from the rotor discharge back to suction.

Slide Target, Slide Position See page 14 for explanation of these terms.

SP Setpoint

SSS Solid state starter as used on McQuay screw compressors

Suction Superheat Suction superheat is calculated for each circuit using the following equation:

Suction Superheat = Suction Temperature – Evaporator Saturated Temperature

Stageon/Stageup Stage On or Stage Up is the act of starting a compressor or fan when another is still

operating. The two phrases are interchangeable and either one can be used depending on

the date of issue of the software. “Start” is the act of starting the first compressor or fan on

a unit.

Stageoff/Stagedown Stage Off or Stage Down is the act of stopping a compressor or fan when another is still

operating. The two phrases are interchangeable and either one can be used depending on

the date of issue of the software. “Stop” is the act of stopping the last compressor or fan on

a unit.

VDC Volts, Direct current, sometimes noted as vdc

VFD Variable Frequency Drive, a device used to vary an electric motor’s speed.

Unit and Circuit Controller Description Hardware Structure The 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 in

FLASH memory, preventing data loss in the event of power failure without requiring a

back-up battery. It also has optional remote communication access capability for a BAS

interface.

OM AGSDP-3 9

Each chiller has one unit controller and a circuit controller for each compressor circuit (two

or three depending on unit size). The controllers are connected and communicate via a

pLAN (local area network). The circuit controllers communicate with, and control the

operation of, the compressor's solid state starter and the circuit electronic expansion valve

(EXV).

Keypad A 4-line by 20-character liquid crystal display and 6-button keypad is mounted on the unit

and compressor controllers.

Figure 2, Keypad

Air Conditioning

ALARMVIEW

SET

<<<

The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.

1. Scroll between data screens in the direction indicated by the arrows (default mode).

2. 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

MENU key). For ease of use, a pathway connects the appropriate button to its

respective label on the screen.

3. Change field values in setpoint programming mode as follows:

LEFT key = Default RIGHT key = Cancel

UP key = Increase (+) DOWN key = Decrease (-)

These four programming functions are indicated by one-character abbreviation on the right

side of the display. This programming mode is entered by pressing the ENTER key.

ENTER Key & Green Run Light

MENU Key

ARROW Keys (4)

Key-to-Screen Pathway

Red Alarm Light

10 OM AGSDP-3

Control Operation

This section on MicroTech II control is divided into four subsections:

• Circuit Controller, explains the functions of the circuit controller, see page 10.

• Unit Controller, explains the functions of the unit controller, see page 24.

• Using the Controller, explains how to navigate through the menus and how to make

entries, see page 38.

• Screen Definitions, details the menu screen content and how to use them, see page 42.

Circuit Controller

Inputs/Outputs

Table 1, Analog Inputs

# Description Signal Source Range

1 Evaporator Pressure 0.5 - 4.5 VDC (NOTE)

0 to 132 psi

2 Condenser Pressure 0.5 - 4.5 VDC (NOTE)

3.6 to 410 psi

3 Liquid Pressure 0.5 - 4.5 VDC (NOTE)

3.6 to 410 psi

4 Suction Temperature Thermistor (10k@25°C) -58°F to 212°F

5 Discharge Temperature Thermistor (10k@25°C) -58° to 212°F

6 Liquid Temperature Thermistor (10k@25°C) -58 to 212°F

7 Slide Load Indicator 4 to 20 mA

0 to 100%

8 Open

NOTE: Value at the converter board input. Value at the converter board output is 0.1 VDC – 0.9 VDC.

These parameters are analog inputs to the circuit controller. They are used internally as

needed and are sent to the correct pLAN addresses for use by other controllers or displays.

Table 2, Analog Outputs

# Description Output Signal Range

1 Fan 1&2 VFD 0 to 10 VDC 20 to 60 Hz

2 Open

3 EXV Driver 0 to 10 VDC 0 to 6386 steps

4 Open

These parameters are analog outputs from this controller. The values are sent to the correct

pLAN addresses for use by other controllers or displays.

Table 3, Digital Inputs

# Description Signal Signal

1 Circuit Switch 0 VAC (Off) 24 VAC (Auto)

2 Open

3 Starter Fault 0 VAC (Fault) 24 VAC (No Fault)

4 VFD Fault 0 VAC (Fault) 24 VAC (No Fault)

5 Oil Differential Pressure Switch

0 VAC (Fault) 24 VAC (No Fault)

6 Mech High Pressure 0 VAC (Fault) 24 VAC (No Fault)

7 Low Pressure Switch 0 VAC (Fault) 24 VAC (No Fault)

8 Open

9 Oil Level Sensor 0 VAC (Fault) 24 VAC (No Fault)

10 Open

11 Open

OM AGSDP-3 11

Table 4, Digital Outputs

# Description Load Output OFF Output ON Voltage

1 Compressor Starter Contact Relay Compressor off Compressor on 120

2 M1 Contactor (fan 1) Contactor Coil Fans off Fans on 120




6 M5 Contactor (fan 5 & 6) Contactor Coil Fans off Fans on 120

7 Load/Unload Pulse Solenoid Hold load slide Move load slide 24

8 Load/Unload Select Relay Unload Load 24

9 M7 Contactor (fan 7 & 8) Contactor Coil Fans off Fans on 120

10 Oil Return Line Solenoid Closed Open

11 Open

12 Open

13 EXV Close Signal Contact EXV Follows 0 – 10 VDC

EXV Closed, Ignores 0 – 10

VDC 10

These parameters are digital outputs from this controller. Their values are sent to the correct

pLAN addresses for use by other controllers or displays.

Setpoints The following parameters are remembered during power off, are factory set to the

Default value, and can be adjusted to any value in the Range column.

The PW (password) column indicates the password that must be active in order to

change the setpoint. Codes are as follows:

O = Operator, password is 100

M = Manager

Entering a Password

The password is located in the unit controller only and can be found at SET, UNIT SPS on

the last menu conveniently located so that you can scroll up one menu to access the

Password Enter Screen.

12 OM AGSDP-3

Table 5, Circuit Controller Setpoints

Description Default Range PW

Compressor

Circuit mode Enable Disable, Enable, Test M

Slide control Auto Auto, Manual M

Slide position 0 0-100% M

Compressor Size 205 205,220,235 M

Clear Cycle Timers N o No, Yes M

Maximum Slide Target 100.0 0-100.0% M

EXV

EXV control Auto Auto, Manual M

Manual EXV position 0 0-6386 M Pre-open timer 60 20-120 sec M

Service Pumpdown No No, Yes M

Fans

Fan VFD enable Yes No, Yes M

Number of fans 6 6,8 M

Saturated Condenser Temp Target 110.0 90.0 – 130.0 oF M

Stage 1 Up Deadband 5.0 1.0-20.0 oF M




Stage 1 Down Deadband 8.0 1.0-20.0 oF M




VFD Max Speed 100% 90 to 110% M

VFD Min Speed 25% 20 to 60% M

Forced FanTrol 1 1 1-8 M



Sensors

Evap pressure offset 0 -10.0 to 10.0 psi M

Cond pressure offset 0 -10.0 to 10.0 psi M

Liquid pressure offset 0 -10.0 to 10.0 psi M

Suction temp offset 0 -5.0 to 5.0 deg M

Discharge temp offset 0 -5.0 to 5.0 deg M

Liquid temp offset 0 -5.0 to 5.0 deg M

Slide Minimum Position 0 -15 to 15% M

Slide Maximum Position 0 -15 to 15% M

OM AGSDP-3 13

Circuit Operating Mode The circuits on the chiller can each be individually enable or disabled. Test mode on each

circuit can also be entered independent of the all other circuits. With the circuit switch on,

the circuit mode setpoint offers settings of either Enable or Disable. This simply allows the

circuit to be disabled through a keypad setting.

Cool Mode

When the chiller is in COOL mode, capacity of the compressor is adjusted to maintain

leaving water temperature at the Active LWT setpoint while balancing the load between

running circuits. Load balance offset, LWT error, and LWT slope are used to calculate a

change in slide position.

ICE Mode

Ice mode is designed to have the compressors run at full load until the LWT setpoint is

reached, then shut off until the next ice making cycle starts. ICE settings are made in the

unit controller.

In ICE mode, the compressor capacity is increased at the maximum rate continuously until

reaching the maximum slide position. Load balancing, LWT error, and LWT slope are

ignored. Low and high pressure events are disabled.

An adjustable Start-to-Start Ice Delay Timer will limit the frequency with which the chiller

may start in ICE mode. The timer starts when the first compressor starts while the unit is in

ICE mode. While this timer is active, the chiller cannot restart in ICE mode. The time

delay is user adjustable.

The Ice Delay Timer may be manually cleared to force a restart in ICE mode. A set point

specifically for clearing the ICE mode delay is available. In addition, cycling the power to

the controller will clear the Ice Delay Timer.

Circuit Test Mode

The circuit test mode allows manual testing of all controller outputs. Entering this mode

requires the following conditions.

• Circuit Switch = OFF

• Technician password active

• Circuit Mode setpoint = TEST

A test menu can then be selected to allow activation of the outputs. It is possible to switch

each digital output ON or OFF and set the analog outputs to any value. Upon entering the

test mode, all outputs will always default to the OFF state. Upon leaving the test mode, all

outputs will automatically reset to the OFF state.

Compressors cannot be started in TEST mode.

Slide Position Each compressor will estimate its slide load percentage from the present value of the slide

load indicator. The percentage is based on the 4-20mA signal from the slide load indicator

and varies somewhat by compressor size. A load percentage value of 0 corresponds to mA

Low signal; a percentage value of 100 corresponds to the mA High signal shown in Table 6.

This information is located on the View Cir Status (1) menu. It shows slide position and

slide target.

Table 6, Slide Valve Position

Compressor Size

mA Low mA High

205 4.94 14.6

220 4.62 17.0

235 4.32 19.4

NOTE: See the Physical Data tables in the current version of IMM AGSDP for unit compressor sizes.

14 OM AGSDP-3

Slide Calibration Procedure

The slide is calibrated in the factory before shipment but may have to be recalibrated in the

field, especially if relevant slide parts have been replaced.

Slide Position is a relative capacity adjustment from 0.0%(Min load) to 100.0%(Max Load).

There are two MicroTech II controller readings that apply to the indicator, Slide Target and

Slide Position. It is important to understand the difference between these. The Slide Target

is the value in which the controller uses to display the calculated prediction of slide

position. This value represents the destination or goal of pulsing the load and unload

solenoids. The slide target is used for direction of control for all load and unload operations,

including alarm limit events. When putting a circuit in Manual mode, the slide target is the

value that you will be adjusting and the controller will load or unload the chiller to match,

with in about 3%, the target entered with the current slide position value. The second value

is the Slide Position (Pos) this is the slide position value which is the 4-20mA reading

received from the position indicator. These values can be viewed at the circuit controller on

screen “VIEW CIR STATUS (1)”.

A slide target of 0.0% is fully unloaded and the unload solenoid will be constantly

energized. A slide target of 100.0% means that the chiller is at full load and the load

solenoid is continually energized. The chiller will regulate the slide position to infinite steps

between 0% and 100% by pulsing the appropriate solenoid. Facing the front of the

compressor the solenoid on the left is for load (oil vent) and the solenoid on the right is for

unload (oil feed). In Circuit Enable mode (normal operation) the controller makes decisions

to move the Slide target, the calculated value, and pulses the proper solenoid in order to

keep the actual and the target position with in a few percent.

1. It is recommended that the circuit to be calibrated is near normal operating

temperatures, although a preliminary calibration before first starting the compressor is

acceptable, as long as the value is verified soon after compressor shuts down. Note that

it requires sufficient oil pressure to unload the compressor while it is running, and may

load up due to lack of oil pressure. When the compressor is not running there is a large

spring that forces the compressor unloaded, therefore in the off state you have the best

opportunity for verifying an accurate calibration at minimum slide position.

2. On the Circuit controller first verify what your current slide target is at screen “View

Circ Status (1)” and then go to screen “SET COMP SPs (2)” to switch circuit into

manual slide control. Note: Some inhibit limits will be ignored but all alarm limits are

still active.

3. Slowly take the circuit either to 0% or 100% load. When the slide target is at either 0%

or 100%, you may want to verify that the corresponding coil is energized.

4. On the circuit controller scroll all the way to the right, then the calibration and offsets

menu. Scroll down until you see “SET SENSOR OFFSET (3)”. You will see an

adjustment for Min Load and Max Load and on the bottom line you will see the value of

the actual slide position indicator. Add offset until value is within +/-.5%.

5. Repeat until all circuits have both positions calibrated with in +/-.5%.

Note: The Slide Indicator Transducers may vary a considerable amount with temperature

change, and therefore they need to be calibrated at typical running temperatures.

OM AGSDP-3 15

Compressor Control

Multiple Compressor Staging

This section defines which compressor is the next one to start or stop. The next section

defines when the start, or stop, is to occur.

Functions

1. Can start/stop compressors according to an operator-defined sequence.

2. Can start compressors based on the least number of starts (run hours if starts are equal)

and stop on most run hours.

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 any in the

second group, etc. Conversely, all compressors in a group are stopped (based on run hours)

before any in the preceding group, etc.

Required Parameters

1. Sequence number setpoint for all compressors. Possible settings = (1-3). Compressors

will start in the specified order. Default operation sequence is 1 for all compressors

(meaning they will start based on number of starts). That is, if all are 1s, the controller

will look at number of starts and run-hours

2. Maximum Number of compressors ON setpoint. Possible settings = (1-3).

3. Number of starts for all compressors.

4. Number of run hours for all compressors.

5. Status of all compressors (Available/Unavailable, Pumping down, Running, etc.).

Multiple Compressor Start/Stop Timing

This section defines when a compressor is to start, or stop, and the scenario for doing so.

Starting

Staging up, no compressors on the unit are running:

The first compressor can start when the LWT is more than the sum of the active LWT

setpoint and the Startup Delta-T. For example, with default settings, the active setpoint

would be 44°F and the startup delta would be 10 degrees F. In this case, the LWT must be

greater than 54°F. This is a necessary, but may not be a sufficient, condition for starting the

first compressor. The Startup Delta-T is adjustable from 10 degrees down to 0 degrees F.

Staging up, at least one compressor is already running:

Additional compressors can start when the LWT is more than the sum of the active LWT

setpoint and the Stage Delta-T. With the default settings, the active setpoint is 44°F, and the

Stage Delta would be 2 degrees F. So, one necessary condition for staging an additional

compressor on is that the LWT must be higher than 46°F.

If in Cool Mode, an additional requirement is that all running compressors are running at

their maximum capacity, or at least 75% slide position and the Stage Up Delay Timer (5

minute default) has timed out. Also, a compressor is considered to be at its maximum

capacity if it is in an inhibit or unload situation due to low evaporator pressure, high

condenser pressure, or low discharge superheat. If a compressor is set for manual slide

control, or the slide target has reached the maximum allowed by the Max Slide setpoint, it

will also be flagged as being at maximum capacity.

16 OM AGSDP-3

Stopping

Staging down, at least two compressors running:

For staging off compressors, the LWT must be less than the active LWT setpoint minus the

Stage Delta-T. Based on default settings, the active setpoint would be 44°F, and stage delta

of 2 degrees F. So the LWT must be less than 42°F to stage off a compressor. This is a

sufficient condition to trigger a stage down.

For 3 compressor units, the Stage Down Delay Timer must time out before the second lag

compressor will stage down, unless LWT minus Stage Down Delta-T is exceeded, or the

LWT rises above the setpoint.

Staging down, one compressor running:

With one compressor left running, the stage off requires that the LWT be less than the active

LWT setpoint minus the Stop Delta-T. With default settings, the active setpoint is 44°F, and

the Stop Delta is 3 degrees F, so the LWT must be less than 41°F to stage off the last

compressor. This is a sufficient condition to trigger a stage down.

History Storage The number of starts and total compressor run hours is maintained in non-volatile memory

and can be viewed on the Unit Controller or corresponding Circuit Controller.

Compressor Capacity Control

Compressor capacity is determined by calculating a slide position target. Adjustment to the

slide target for normal running conditions occurs every 10 seconds. For loading, a

maximum change of 1% is allowed, and for unloading, a maximum change of 2% is

allowed. During alarm conditions, the slide target may be reduced to satisfy alarm limits.

The change to the target is calculated as follows.

Capacity Overrides – Limits of Operation

The following conditions override the automatic slide control when the chiller is in COOL

mode or ICE mode. These overrides keep the circuit from entering a condition in which it

is not designed to run. As previously noted, any compressor that is running with capacity

limits because of these conditions will be considered to be at full load in the compressor

staging logic. An important point to realize is that a particular chiller’s components are

designed for a specific range of capacity and chilled water flow. Varied conditions such as

high water temperature or low condenser pressure can cause higher refrigerant flow than the

chiller is designed to handle, therefore the chiller control may limit unit operation to

maintain system integrity at the highest compressor load possible.

Low Evaporator Pressure

If the compressor is running and the evaporator pressure drops below the Low Evaporator

Pressure-Hold setpoint, the compressor will not be allowed to increase capacity. The slide

position target will be limited to a maximum value equal to the target at the time the hold

condition was triggered. This limit will be active until the evaporator pressure reaches the

hold setpoint plus 2-psi.

If the compressor is running above minimum load capacity and the evaporator pressure

drops below the Low Evaporator Pressure-Unload setpoint, the compressor will begin

reducing capacity. The maximum allowed slide target will be adjusted down 5% every 5

seconds until the evaporator pressure rises above the Low Evaporator Pressure-Unload

setpoint. The slide target will then be limited to the current value until the evaporator

pressure rises to the unload setpoint plus 2-psi. If the pressure drops to the Unload Setpoint,

the EXV will switch to pressure control.

OM AGSDP-3 17

For low evaporator pressure at start, logic will disable the low-pressure cutout if the outside

ambient temperature is below 35°F and the evaporator saturated temperature is at least 10

degrees below the evaporator LWT. This logic is disabled when the evaporator pressure

rises above the unload setpoint and 45 seconds has elapsed.

High Condenser Pressure

If the compressor is running and the condenser pressure rises above the High Lift Pressure

Hold setpoint, the compressor will not be allowed to increase capacity. The slide position

target will be limited to a maximum value equal to the target at the time the hold condition

was triggered. This limit shall be active until the condenser pressure drops 10 psi below the

hold setpoint.

If the compressor is running above minimum load capacity and the condenser pressure rises

above the High Condenser Pressure Unload setpoint, the compressor will begin reducing

capacity. The maximum allowed slide target will be adjusted down 5% every 5 seconds

until the condenser pressure drops below the High Condenser Pressure-Unload setpoint.

The slide target will then be limited to the current value until the condenser pressure drops

to 10 psi below the unload setpoint.

High Leaving Water Temperature

If the LWT is above 50°F, then the Max Slide is limited to 80% to avoid overloading.

Low Discharge Superheat

If the compressor is running, and the discharge superheat is less than 22oF, the compressor

will not be allowed to increase capacity. This limit will be active until the superheat is more

than 22oF.

If the compressor is running above minimum load capacity, and the discharge superheat is

less than 20oF, then the compressor will begin reducing capacity. The slide target will be

adjusted down 2% every 5 seconds, as long as the superheat remains below 20oF.

Maximum LWT Pulldown Rate

The maximum rate at which the leaving water temperature can drop is limited by the

Maximum Rate setpoint. A slope unload factor is used to reduce the slide target if the

pulldown rate exceeds the Maximum Rate setpoint.

Slope Unload Factor: Maximum Rate + LWT slope

If the pulldown rate is too fast, the slide adjustment will be made equal to the slope unload

factor.

Unit Capacity Overrides

Unit capacity limits can be used to limit total unit capacity in COOL and COOL w/

GLYCOL modes only. Multiple limits may be active at any time, and the lowest limit is

always used in the compressor capacity control.

These limits represent a limit on the unit capacity as a whole. Therefore, an estimate of the

current unit capacity is needed. Any circuit that is off is considered to be running at 0% of

its capacity. A running circuit is assumed to be running at a minimum of 20% capacity, and

the assumed capacity will very linearly from 20% to 100% as the slide position varies from

0% to 100%. The unit capacity is calculated using the following formula:

Unit Capacity = (Cir1 Capacity + Cir2 Capacity + Cir3 Capacity) / Number of Circuits

The estimated unit capacity and the active capacity limit are sent to all circuits for use in

compressor capacity control.

The active capacity limit values can be viewed at View Unit Status (2) and consist of the

following:

18 OM AGSDP-3

Soft Load

Soft Loading is a configurable function used to ramp up the unit capacity over a given time.

The set points that control this function are:

• Soft Load – (ON/OFF)

• Begin Capacity Limit – (Unit %)

• Soft Load Ramp – (seconds)

The Soft Load Unit Limit increases linearly from the Begin Capacity Limit set-point to

100%, over the amount of time specified by the Soft Load Ramp set-point. If the option is

turned off, the soft load limit is set to 100%.

Demand Limit

The maximum unit capacity can be limited by a 4 to 20 mA signal on the Demand Limit

analog input. This function is only enabled if the Demand Limit setpoint is set to ON. The

maximum unit capacity changes linearly from 0% (at 20 mA) to the 100% (at 0 mA).

Network Limit

The maximum slide load percentage of the compressor can be limited by a value sent

through a BAS network connection and stored in the Network Limit variable. This function

will be enabled if the control source is set to BAS.

ICE Mode Start Delay

In ICE mode there is a 12 hour delay from the time the unit shuts off until it may start again.

If the chiller is in ICE mode and the delay is active, the unit state will be Off and the unit

status will indicate this condition. The time left will also be displayed. While this delay is

active, the chiller may still start in cool mode.

If needed, the ice delay can be cleared using a setting found in the unit set points menu.

Pumpdown When a circuit reaches a condition where the compressor needs to shut down normally, a

pumpdown will be performed. The slide target will automatically go to 0 while pumping

down, and the compressor will run until the pumpdown pressure has been reached, or the

pumpdown time has been exceeded. The Pumpdown Setpoint may need to be reduced if the

unit is running in the COOL w/ GLYCOL mode.

Service Pumpdown

If the option for a service pumpdown is enabled, then on the next pumpdown the pressure

setpoint will be 15 psi. The circuit will pump down to this pressure and shut off. When the

compressor has completed the service pumpdown, the setpoint is reset to No.

Manual Slide Control Mode The slide position on each circuit can be controlled manually. A setting on the compressor

setpoints screen in each circuit controller allows the operator to select manual slide control.

On the same screen, a slide target can be selected from 0% to 100%.

Anytime a circuit is in manual slide control, it is considered to be at full load in the staging

logic. It also will not be considered a running compressor for load balancing purposes.

None of the capacity limits outlined above will apply in manual slide control, but all stop

alarms are still applicable.

Slide Positioning

Slide Load Indicator

Each compressor will estimate its slide load percentage from the present value of the slide

load indicator. The percentage is based on the 4-20mA signal from the slide load indicator.

See Table 6 on page 13 for the mA signal corresponding to slide position.

OM AGSDP-3 19

Load/Unload Select

The load/unload selector determines which solenoid will be pulsed for a change in capacity.

When unloading is required, the load/unload select output should be off. When loading of

the compressor is required, the output should be on.

Slide Pulse

The slide pulse output moves the compressor slide in order to reach the capacity reflected

by the slide position target. The output will pulse for 200 ms every 3 seconds until the slide

position is within a 3% deadband around the target.

Condenser Fan Control The compressor must be running in order to stage its fans on.

VFD (Standard) Condenser pressure trim control is accomplished using a variable frequency drive (VFD) on

the first two fans that turn on. This VFD control uses a proportional integral function to

drive the saturated condenser temperature to a target value by changing the fan speed. The

target value is normally the same as the saturated condenser temperature target setpoint.

The VFD will start the fans when the saturated condenser temperature goes above the

temperature target. Once the VFD fans are on, they will not shut off until the saturated

condenser temperature is less than the minimum saturated temperature plus 5 degrees F.

Stage up Compensation

In order to create a smoother transition when another fan is staged on, the VFD compensates

by slowing down initially. This is accomplished by adding the new fan stage up deadband

to the VFD target. The higher target causes the VFD logic to decrease fan speed. Then,

every 10 seconds, 0.5oF is subtracted from the VFD target until it is equal to the saturated

condenser temperature target setpoint. This will allow the VFD to slowly bring the

saturated condenser temperature back down.

Condenser Target

This logic is only used with VFD = Yes. Most applications will benefit from using the

default values. In the software versions previous to AGSU30101F, there was only one

setting for condenser target setpoint, with a default of 110°. Beginning with AGSU30101F

software there are two setpoints used to set a minimum (Min) and a maximum (Max) range

for the saturated condenser target. This can be found on the circuit controller at Set Fan

Sps(5). This will allow for a floating condenser target based on saturated evaporator

temperature. The default values of the minimum and maximum are both set to 110°

saturated condensing temperature. This will allow for the most stable unit operation.

Adjusting the Min or Max setpoint at each circuit controller will vary the condenser target

along a line determined by two points which are, 85° saturated condenser at 20° saturated

suction and 110° saturated condenser at 50° saturated suction. Note that the chiller system

is designed for specific refrigerant flow capacities, which may be exceeded by decreasing

the condenser target. The result will be at lower ambient temperatures, the chiller may

attain the maximum unit tonnage capacities while compressor loading will be limited on

low discharge superheat.

Fan Stages with VFD Option

The VFD option must always be enabled. The first two fans are controlled by the fan VFD.

This leaves 6 stages 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 by using virtual stages. See the table below:

20 OM AGSDP-3

Table 7, Staging with VFD

Stage Fans On

1 1,2,3

2 1,2,3,4

3 1,2,4,5,6

4 1,2,3,4,5,6

5 1,2,3,5,6,7,8

6 1,2,3,4,5,6,7,8

Staging Up

There are four stage-up deadbands that apply to the FanTrol stages. Stages one through

three use their respective deadbands. Stage four to eight share the fourth stage-up

deadband.

When the saturated condenser temperature is above the Target + the active deadband, a

Stage Up error is accumulated.

The saturated condenser temperature must not be falling for a Stage Up accumulation to

occur.

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

Up Deadband)

The Stage Up Error Step is added to Stage Up Accumulator once every Stage Up Error

Delay seconds. When Stage Up Error Accumulator is greater than the Stage Up Error

Setpoint, another stage is added.

When a stage up occurs, or the saturated condenser temperature falls back within the Stage

Up deadband, the Stage Up Accumulator is reset to zero.

Forced Fan Stage At Start

Fans may be started simultaneously with the compressor based on outdoor ambient

temperature. When the compressor starts, a FanTrol stage is forced, based on the following

table.

Table 8, Forced Staging

Outside Air Temperature

FanTrol Stage At Start

> 75oF Forced FanTrol 1 SP



Staging Down

There are four Stage Down deadbands. Stages one through three use their respective

deadbands. Stages four to eight share the fourth Stage Down deadband.

When the condenser saturated refrigerant temperature is below the Target – the active

deadband, a Stage Down error is accumulated.

Stage Down Error Step = (Target - Stage Down deadband) - Saturated Condenser

Refrigerant temperature

The Stage Down Error Step is added to Stage Down Accumulator once every Stage Down

Error Delay seconds. When the Stage Down Error Accumulator is greater than the Stage

Down Error Setpoint, another stage of condenser fans turned off.

When a stage down occurs, or the saturated temperature rises back within the Stage Down

deadband, the Stage Down Error Accumulator is reset to zero. The accumulator is also held

at zero after startup until either the outside ambient temperature is less than or equal to 75°F,

or the saturated condenser temperature is greater than the condenser target less the active

stage down deadband.

OM AGSDP-3 21

EXV Control Three different expansion valve (EXV) control modes are used. Any time the EXV is not in

one of these control modes, it will be closed. For any of the control modes, the EXV

position is limited to a range based on the slide position target. The minimum setting

provides sufficient flow for motor cooling, the maximum flow limit helps prevent flood

back to the compressor. The table below shows the EXV range for each size compressor, at

minimum and maximum capacity. The minimum and maximum values vary linearly with

slide position, defining a new EXV control range for every change in slide position.

Table 9, EXV Range

Compressor Size EXV Slide %

205mm 220mm 235mm

Min 0 250 250 250

Max 0 3000 3000 3000

Min 100 870 1080 1300

Max 100 3400 4200 5000

Based on the values in the above table, the EXV control range varies as shown in the figure

below. The shaded area is the control range.

Figure 3, EXV Control Range

Max EXV@ 100%

100

Max EXV

@ 0%

Min EXV@ 0%

EXV Control Range

0 Slide Position (%)

EXV

StepsMin EXV

@ 100%

1. Pre-Open At the time of a start request, the EXV will perform a pre-open function. This is to provide

sufficient liquid refrigerant in the evaporator to avoid low pressure situations at startup.

During pre-open, the EXV will open to 3000 steps, while the saturated evaporator

temperature is less than the LWT. The EXV will move to 250 steps when the saturated

evaporator temperature is equal to, or greater than, the LWT.

The EXV must be in the pre-open state for a time equal to the pre-open timer setpoint

before the compressor will start. This state may be skipped if the start request occurs, and

the evaporator saturated temperature is greater than LWT + 5°F. In this case, the

compressor would start and the EXV would go straight to pressure control.

2. Pressure Control The EXV will be in pressure control mode after startup, and always when in the ICE mode.

In this mode, the EXV controls discharge superheat with adjustments to the evaporator

pressure target. A proportional integral function is used to keep the evaporator pressure at

the target.

22 OM AGSDP-3

The base pressure target is calculated using the following formula:

Base target = 2/3LWT – 8

The base target is limited to a range from the low pressure inhibit setpoint, plus 2 psi, up to

52 psi.

The pressure control target may be adjusted if the discharge superheat is not within an

acceptable range. If the superheat is less than 22°F, the base pressure target will be reduced

by a value equal to the low superheat error. If the superheat is more than 40°F, the base

pressure target will be increased by a value equal to the high superheat error. At any time,

the adjusted target pressure cannot go below the low pressure inhibit setpoint plus 2 psi, or

above 52 psi.

The EXV will transition from pressure control to subcool control when all of the following

are true:

• Discharge Superheat > 22°F for at least 3 minutes while in pressure control

• LWT <= 60°F

• Subcool > current base subcool value

• Unit mode = Cool (includes Available Modes: Cool w/ Glycol. Subcool control is not

used in ICE Mode)

The pressure target will ramp down when transition to pressure control occurs. The

pressure target will decrement 0.2 psi every second until it reaches the normal target. The

starting target is the current pressure at transition to pressure control, but is limited to a

maximum of 52 psi.

The EXV may transition from subcool control back to pressure control. This occurs when

the LWT is greater than 63°F , the unit mode is switched from Cool to Ice, or in F code, a

low evaporator pressure unload occurs. Starting with F code, when suction pressure drops

below the low evaporator pressure unload setpoint, the controller will switch from subcool

control to pressure control, until sufficient subcooling is established.

3. Subcool Control

After completing pressure control, the EXV transitions to the primary mode of operation,

subcool control. In this mode, subcooling is controlled by the EXV, with adjustments to the

subcool target based on discharge superheat. The base subcool target varies linearly from 5

degrees F to 20 degrees F as slide position changes from 0 to 100%.

The base subcool target value is adjusted when the discharge superheat is less than 22

degrees F, or greater than 40 degrees F. For every degree below the minimum, the subcool

target is adjusted up one degree. Similarly, for every degree above the maximum, the

subcool target is adjusted down one degree. The maximum offset to the base subcool value

is 15 degrees F, and the adjusted subcool target is limited to a minimum of 2 degrees F.

When the circuit initially enters subcool control, the subcool target is set to the current

subcool value less 2 degrees. This value may be above the normal 5 to 20 degree range.

The target subcool value is then reduced 0.1 degree every two seconds until it reaches the

calculated target value.


the LWT is greater than 63°F or if the pressure drops to the LPUnload SP, while in subcool

control.

The EXV will transition from subcool control to pressure control if a low pressure unload

occurs. The normal rules to transition back to subcool control will apply.

OM AGSDP-3 23

Closed

Any time the EXV is not in pre-open, pressure control, or subcool control, it will be in a

closed state. At this time, the EXV position is 0 steps and the EXV close signal is active.

Manual EXV Control

The EXV position can be set manually. Manual control can only be selected when the

compressor is in the run state. At any other time, the EXV control setpoint is forced to auto.

When EXV control is set to manual, the EXV position is equal to the manual EXV position

setting. If set to manual when the compressor state transitions from run to another state, the

control setting is automatically set back to auto.

To verify EXV operation in an off state, see Unit Test Mode on page 29.

Evaporator Oil Return Line Control The oil return solenoid shall be on any time the compressor is running and any of the

following occurs:

Slide position target < 60 AND Discharge superheat > 35

Slide position target >= 60 AND Discharge superheat > 50

Oil Level input = open AND Discharge superheat > 35

Oil Heater Control The oil heater shall be on when the compressor is not running AND the oil level input is

closed.

Interstage Injection The purpose is to control the discharge temperature at low LWT conditions when the

dischare temperature is high. The interstage injection is activated when the compressor is

running AND the discharge temperature rises above 185°F. The output shall be turned off

when either the compressor is no longer running, OR the discharge temperature drops below

170°F.

24 OM AGSDP-3

Unit Controller

Inputs/Outputs

The following parameters are analog inputs to this controller. They are used internally as


Table 10, Unit Analog Inputs

# Description Signal Source Range

1 Outdoor Ambient Temperature Thermistor (10k@25°C) -58°F to 212°F

2 Demand Limit 4-20 mA Current 25-100 %RLA

3 Chilled Water Reset 4-20 mA Current 0 to10 degrees

60°F max inlet

4 Leaving Evaporator Water Temperature Thermistor (10k@25°C) -58°F to 212°F

5 Entering Evaporator Water Temperature Thermistor (10k@25°C) -58°F to 212°F

The following parameters are digital inputs to this controller. They are used internally as


The status of digital inputs can be viewed on Unit Status screen #4, on the unit controller

only.

Table 11, Unit Digital Inputs

# Description Signal Signal

1 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 Open

6 Open

The following parameters are digital outputs from this controller. Their values are sent to

the correct pLAN addresses for use by other controllers or displays. The status of digital

outputs can be viewed on Unit Status screen #4, on the unit controller only.

Table 12, Unit Digital Outputs

# Description Load Output OFF Output ON

1 Open

2 Evaporator Water Pump 1 Pump Contactor Pump OFF Pump ON

3 Evaporator Water Pump 2 Pump Contactor Pump OFF Pump ON

4 Evap Heaters Heater relay Heater OFF Heater ON

5 Open

6 Open

7 Open

8 Alarm Remote Alarm No Alarm Stop Alarm

Setpoints At power-up, the slave node checks if the master node is operational and if so, it sets its

copy of the setpoint equal to the master’s. Otherwise, the setpoint remains unchanged.

During normal operation, any time the master setpoint changes, the slave is updated as well.

The PW (password) column indicates the password that must be active in order to change

the setpoint. Codes are as follows:

O = Operator, M = Manager

OM AGSDP-3 25

Table 13, Unit Controller Setpoints

Description Default Range Type PW

Unit

Unit Enable Off Off,On N O

Unit Mode Cool Cool, Ice, Test M O

Available Modes Cool Cool, Cool w/Glycol, Cool/Ice w/Glycol, Ice w/Glycol, Test

N M

Control source Switches Switches, Keypad, Network N O

BAS Protocol Modbus BACnet, LonWorks, Modbus N M

Ident number 1 0-200 N M Baud Rate 19200 1200,2400,4800,9600,19200 N M

Cool LWT 44. 0 °F See page 26 N O

Ice LWT 25.0 °F 20.0 to 38.0°F N O

Startup Delta T 10.0 °F 0.0 to 10.0 °F M O

Stop Delta T 3.0 °F 0.0 to 3.0 °F M O

Stage Delta T 2.0 °F 0.0 to 3.0 °F M O

Max Pulldown 0.5 °F/min 0.1-5.0 °F /min M M

Evap pump control #1 Only #1 Only, #2 Only, Auto N M Evap Recirculate Timer 30 sec 0 to 300 sec N M

LWT Reset Type None None, Return, 4-20mA, OAT N M

Max Reset 10.0 °F 0.0 to 20.0 °F N M

Start Reset Delta T 10. 0 °F 0.0 to 20.0 °F N M

Soft Load no No,yes N M

Begin Capacity Limit 40% 20-100% N M Soft Load Ramp 20 min 1-60 minutes N M

Demand Limit Off Off, On N M

Low Ambient Lockout 55 °F See 26 N M

Ice Time Delay 12 1 to 23 hours N M

Clear Ice Timer No No,Yes N M

Quiet Night Disabled Disabled, Enabled N M Quiet Night Start Time 21:00 18:00 – 23:59 N M

Quiet Night End Time 6:00 5:00 – 9:59 N M

Quiet Night Condenser Offset 10.0 °F 0.0 to 25.0 °F N M

Compressors

Sequence # Cir 1 1 1-3 M M

Sequence # Cir 2 1 1-3 M M Sequence # Cir 3 1 1-3 M M

Max Compressors On 3 1-3 M M

Start-start timer 20 min 15-60 minutes M M

Stop-start timer 5 min 3-20 minutes M M

Number of Compressors 2 2-3 N M Pumpdown pressure 25.0 psi 10.0-30.0 psi M M

Pumpdown time limit 120 sec 0-180 sec M M

Light Load Stage Down Point 25% 20 to 50% M M

Light Load Stage Down Delay 3 min 3 to 30 min M M

Stage Up Delay 5 min 0 to 60 min M M

Discharge Temperature Sensor Type

PT1000 NTC, PT1000 M M

Alarms

Low Evap Pressure-Unload 28 psi See page 26 M M

Low Evap Pressure-Hold 30 psi See page 26 M M

Low Oil Level Delay 120 sec 10-180 sec M M

High Oil Press Diff Delay 15 sec 0-90 sec M M

Min Lift Delay 30 sec 10-120 sec M M

High Discharge Temperature See page 26 See page 26 M M

Low Subcooling 5 °F 0 to 10 F M M

High Lift Delay 5 sec 0 to 30 sec M M

Continued next page.

26 OM AGSDP-3

Table 13, Unit Controller Setpoints, Continued

Description Default Range Type PW

Evap Flow Proof 15 sec 5 to 15 sec N M

Evaporator Water Freeze 36 °F See section Error! Reference source

not found. N M

Sensors

OAT sensor offset 0 -5.0 to 5.0 deg N M

LWT sensor offset 0 -5.0 to 5.0 deg N M EWT sensor offset 0 -5.0 to 5.0 deg N M

These parameters are remembered during power off, and are factory set to the Default value.

Automatic Adjusted Limits The following setpoint ranges will be adjusted based on selected options.

Table 14, Evaporator Leaving Water Temperature Range

Mode Range

Unit Mode = Cool 40 to 60°F

Unit Mode = Cool w/Glycol, Ice, Ice w/ Glycol 20 to 60°F

Table 15, Evaporator Freeze Temperature Range

Mode Range

Unit Mode = Cool 34 to 42°F

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

Table 16, Low Evaporator Pressure Inhibit

Mode Range

Unit Mode = Cool 30 to 45 Psig Unit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 45 Psig

Table 17, Low Evaporator Pressure Unload

Mode Range

Unit Mode = Cool 28 to 45 Psig

Unit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 45 Psig

Table 18, Low Ambient Lockout Temperature Range

Fan VFD Range

Fan VFD = N 35– 60°F

Fan VFD = Y 0 – 60°F

Table 19, High Discharge Temperature

Discharge Temp Sensor Type Range

NTC 150 to 200 oF

PT1000 150 to 230 oF

OM AGSDP-3 27

Unit Enable Enabling and disabling the chiller is controlled by the Unit Enable Setpoint with options of

OFF and ON. The Unit OFF input (unit On/Off switch), field installed Remote stop switch,

keypad entry, or BAS request can alter this setpoint providing the correct control source

setpoint is selected. The Control Source Setpoint determines which sources can change the

Unit Enable Setpoint with options of SWITCHES, KEYPAD, or NETWORK.

Changing the Unit Enable Setpoint can be accomplished according to Table 20 on page 27.

NOTE: An “x” indicates that the value is ignored.

Set Unit Setpoints Screen #1 (shown below) shows three fields “Enable”, “Mode” and

“Source.”

Unit Setpoints

SET UNIT SPs (1)

Enable=On

Mode= COOL

Source = KEYPAD

The Enable field is for use with Source = Keypad only, to enable and disable the chiller

through the key pad, ignoring any other control inputs including unit and pumpdown

switches and BAS controls.

1. The Mode field is an informational display, showing the active control mode of the

chiller. It is used as an input only when the source is set to keypad, only then can this

field be changed manually.

2. The Source field has three options, “SWITCHES” (default), “KEYPAD”, and “BAS

NETWORK”.

a. Switches source is used when there is no BAS interface used. This allows the unit

switches to function as pumpdown and shut down switches for the circuit. This

option is used with applications using the remote start/stop input and not using a

BAS interface.

b. Keypad source is used to override BAS or remote start/stop commands. This would

be used for servicing only.

c. BAS Network source would be used for those applications using “MODBUS”,

“BACNET”, or “LON” communications through a building automation system.

BAS Protocol is set at Set Unit Setpoints item #11.

Table 20, Unit Enable Settings

Unit On/Off Switch

Control Source Setpoint

Remote Stop Switch

Key-pad Entry

BAS Request

Unit Enable

OFF x x x x OFF

x SWITCHES OFF x x OFF

ON SWITCHES ON x x ON

ON KEYPAD x OFF x OFF

ON KEYPAD x ON x ON

ON NETWORK x x OFF OFF

ON NETWORK OFF x x OFF

ON NETWORK ON x ON ON

28 OM AGSDP-3

All methods of disabling the chiller, except for the unit switch, will cause a normal

shutdown of any running circuits. Any time the unit switch is used to disable the chiller, all

running circuits will shut down immediately, without pumping down.

Shutdown by the unit switch without going through the pumpdown cycle is undesirable and

should only be used for an emergency shutdown or for disabling the unit after both circuits

have gone through a normal shutdown.

Unit Mode Selection The overall operating mode of the chiller is set by the Unit Mode Setpoint with options of

COOL, COOL w/Glycol, ICE w/Glycol, and TEST. The system switch must be off (unit

not running) to change the mode of operation.

Available Modes setpoint: usually set during initial setup and determines the operational

modes available at any time with options of:

• COOL, cooling only operation, with setpoints available for normal water temperatures.

• COOL w/Glycol, cooling only operation, allows lower setpoints than COOL.

• COOL/ICE w/Glycol, allows cooling and ice mode operation, switchable by a remote

digital signal, by the network or through the keypad.

• ICE w/Glycol, ice mode only, i.e., full load operation until LWT setpoint is reached.

• TEST

SET UNIT SPs (2)

Available Modes = COOL

Select w/Unit Swt Off

The setpoint can be altered by the keypad, BAS, and Mode input. Changes to the Unit

Mode Setpoint are controlled by two additional setpoints.

• Control Source Setpoint: Determines the source that can change the Unit Mode

Setpoint with options of KEYPAD (pCO2), NETWORK, or SWITCHES.

When the Control source is set to KEYPAD, the Unit Mode stays at its previous setting until

changed by the operator. When the Control source is set to BAS, the most recent BAS

mode request goes into effect even if it changed while the Control source was set to

KEYPAD or DIGITAL INPUTS.

Changing the Unit Mode Setpoint can be accomplished according to the following table.

NOTE: An “x” indicates that the value is ignored.

Table 21, Unit Mode Settings

Control Source Setpoint

Remote ICE Mode

Switch Keypad Entry

BAS Request

Available Modes Setpoint

Resultant Unit Mode

x x x x COOL COOL

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

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

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

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

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

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

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

x x x x ICE w/Glycol ICE w/Glycol

x x x x TEST TEST

OM AGSDP-3 29

The Remote ICE Mode Switch (usually a time clock) is a field installed option and is used

to switch from ice mode operation at night to cooling mode operation during the day. This

requires that the Control Source be set to SWITCHES, which in this case refers to the

Remote ICE Mode Switch.

There are really only three operational modes for the unit, although they can be used in

combination:

1. COOL, the unit unloading and compressor staging is controlled by the Active LWT

Setpoint. COOL w/ Glycol is a special case of this mode, providing for lower setpoint

ranges.

2. ICE, the unit runs with all compressors fully loaded until the LWT (set for making ice)

is reached, and the unit shuts off. The Ice Delay Timer can be set to prevent restarting

until the next ice making cycle.

3. TEST, manually energize outputs.

Unit Test Mode

Before beginning you must have the Manager password active. Note: To put each circuit

controller in test mode, you do not have to put the unit controller into test mode, therefore

you may allow one or more circuits to operate while in test mode on another circuit.

Circuit Controllers:

Be sure the pumpdown switch is in the off position. Press the Menu button (the top far right

button with three horizontal lines on it) on the circuit controller. Press the button that

corresponds to “SET”, then press “COMPRESSOR SPs”. Now press the down arrow

button once. Now that you are on the proper screen (SET COMP SPs (2)) you may push the

enter button to go into Change Values Mode for that screen.

You will now see the cursor blinking on the first line, also there will be a “D”, “C”, “+” and

“-” down the right side of the screen. Press the corresponding “+” or “-” button to scroll

through the menu options. You will see “Enable”, “Disable” and “Test”. To select “Test”,

press the enter button. Press the enter button until the cursor scrolls to the top left corner of

the screen on to the Menu title. Now scroll to the right to the last menu, this menu is the

“Test Circuit” menu. This menu was added when you entered “Test” in the Circuit Mode

field.

“Test Circuit” item #1 is for digital outputs for the fan contactor outputs. The unit is

equipped with fan VFD and fan outputs 1 and 2 will not function. The VFD fans will be

tested later. Press the enter button to go into change values mode. Continue to press enter

until you reach the output you would like to turn on, then press the “+” or “-” turn the

output on or off. Check that each fan is rotating in the proper direction, and does not have

excessive vibration.

“Test Circuit” item #2 is for digital outputs for Slide indicator. You will see a selection to

choose the slide pulse direction, with the options of “Load” (left coil) or “Unload”(right

coil). Then there is a selection to turn the pulse on or off. Choose “on” for the “Pulse” field

and then you can toggle between Load or Unload, checking the corresponding coil to see if

it energizes.

“Test Circuit” item #3 is for digital outputs for the Evaporator oil return line solenoid and

for the EXV close output. Turn the “Oil Return” on and check that the evaporator oil return

line solenoid is energizing. It is located on the base rail behind the suction line connection

to the compressor.

30 OM AGSDP-3

“TEST CIRCUIT” item #4 is for analog outputs for the fan VFD and the EXV. Here you

can ramp up the VFD by adjusting the frequency in the VFD field or manually open and

close the EXV. The EXV operation may be verified by observing operation through the

sight glass on the side of the valve body. Note: Unlike the digital outputs, you must hit

enter for the analog outputs to react to your change.

Unit Controller: At the main menu select “SET”, then select “UNIT SPs”, scroll down 1 screen to screen #2

on the “SET UNIT SPs” screen. You will see “Available Modes”. Change the mode to

“TEST”. (Note: this will disable all running circuits.) Now scroll all the way to the right on

the unit test screen, there is only one screen. Verify the “Alarm Out” output at J15-NO8.

Verify the evap heaters are on by checking the amps on the appropriate wires. Verify the

evaporator pump outputs and wiring by turning the pump outputs on and off.

Note: When the service test is completed, remember to take both the unit and each of the

circuit controllers out of “Test” Mode and back into “Enable.”

Evaporator Pump Control Operation of the evaporator pump is controlled by the state-transition diagram shown below.

Power ON OFF

RUN START

T1

T4

T2

T3

Evaporator PumpStates

T5

Transitions:

T1 – Transition from Off to Start, Requires any of the following

• Unit state = Auto AND If Low OAT Lockout is active then LWT <= 40 °F

• LWT < Freeze set point – 1 °F

T2 – Transition from Start to Run

• Flow ok for time > evaporator recirculate time

T3 – Transition from Run to Off, Requires any of the following

• Unit state = Off AND LWT > Freeze set point

• Low OAT Lockout is active AND No compressors running AND LWT > 70°F

T4 – Transition from Start to Off, Requires any of the following

• Unit state = Off AND LWT > Freeze set point

• Low OAT Lockout is active AND No compressors running AND LWT > 70°F

T5 – Transition from Run to Start

• Evaporator flow input low AND Evaporator state = Run for time greater than Flow

Proof set point

OM AGSDP-3 31

Pump Selection

The pump output used will be determined by the Evap Pump Control set point. This setting

allows the following configurations:

#1 only – Pump 1 will always be used

#2 only – Pump 2 will always be used

Auto – The primary pump is the one with the least run hours, the other is used as a backup

#1 Primary – Pump 1 is used normally, with pump 2 as a backup

#2 Primary – Pump 2 is used normally, with pump 1 as a backup

Primary/Standby Pump Staging

The pump designated as primary will start first. If the evaporator state is Start for a time

greater than the recirculate timeout set point and there is no flow, then the primary pump

will shut off and the standby pump will start. When the evaporator is in the Run state, if

flow is lost for more than half of the flow proof set point, the primary pump will shut off

and the standby pump will start. Once the standby pump is started, the flow loss alarm logic

will apply if flow cannot be established in the evaporator Start state, or if flow is lost in the

evaporator Run state. Auto Control

If auto pump control is selected, the primary/standby logic above is still used. When the

evaporator is not in the Run state, the run hours of the pumps will be compared. The pump

with the least hours will be designated as the primary at this time.

Evaporator Heater Control Evaporator heaters are controlled by the unit controller. This output is turned on when the

evaporator LWT is less than the water freeze setpoint + 2 degrees F. The output is turned off

when the LWT is more than the freeze setpoint + 4 degrees F.

Leaving Water Temperature (LWT) Reset The Active Leaving Water setpoint is set to the current Leaving Water Temperature (LWT)

setpoint, unless the unit is in COOL mode, and any of the reset methods below are selected.

The type of reset in effect is determined by the LWT Reset Type setpoint. The Active

Leaving Water variable is sent to all circuits for capacity control after the applicable reset is

applied.

Reset Type – NONE The Active Leaving Water setpoint is set equal to the current LWT setpoint.

Reset Type – RETURN The return water temperature adjusts the Active Leaving Water setpoint. When the chiller

mode = COOL, the Active Leaving Water setpoint is reset using the following parameters:

1. Cool LWT setpoint

2. Max Reset Delta-T setpoint

3. Start Reset Delta-T setpoint

4. Evap Delta-T

Reset is accomplished by changing the Active Leaving Water setpoint from the Cool LWT

setpoint to the Cool LWT setpoint + Max Reset setpoint as the EWT – LWT (Evap Delta-T)

varies from the Start Reset Delta-T setpoint to 0.

32 OM AGSDP-3

Figure 4, Return Water Reset Conditions

Start Reset Delta T

Cool LWT+Max Reset

(54)

Cool LWT Set-Point

(44)

Return Reset

0

Max Reset

(10)

Evap Delta T (oF)

ActiveLWT

(oF)

Reset Type – 4-20 mA Input Signal The Active Leaving Water setpoint is adjusted by the 4 to 20 mA reset analog input.

Parameters used:


2. Max Reset setpoint

3. LWT Reset signal

Reset is 0 if the reset signal is less than or equal to 4 mA. Reset is equal to the Max Reset

Delta-T setpoint if the reset signal equals or exceeds 20 mA. The amount of reset will vary

linearly between these extremes if the reset signal is between 4 mA and 20 mA.

Figure 5, External Reset Conditions

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 setpoint is reset based on the outdoor ambient temperature.

Parameters used:


2. Max Reset setpoint

3. OAT

OM AGSDP-3 33

Reset is 0 if the outdoor ambient temperature is greater than 75°F. From 75 down to 60°F

the reset varies linearly from no reset to the max reset at 60°F. At ambient temperatures less

than 60°F, reset is equal to the Max Reset setpoint.

Figure 6, Outside Air Reset

75

Cool LWT+Max Reset

(54)

Cool LWT Set-Point

(44)

OAT Reset

60

Max Reset

(10)

OAT (oF)

ActiveLWT(oF)

34 OM AGSDP-3

Alarms and Events

Situations may arise that 1) require some action from the chiller, or that 2) should be logged

for future reference. A condition that causes a shutdown and requires manual reset is known

as a stop alarm. Other conditions can trigger what is known as an event, which may or may

not require an action in response. All stop alarms and events are logged. The Unit

Controller and the Circuit Controller have different Alarms and Events.

Unit Stop (Shutdown) Alarms

This table identifies each unit stop alarm, gives the condition that causes the alarm to occur,

and states the action taken as a result of the alarm. (See the “Stop Alarms” section under the

Circuit Controller for a description of these alarms.)

The alarm output and red button LED are turned ON when any stop alarm occurs. They are

turned OFF when all alarms have been cleared.

Table 22, Unit Stop Alarms

Description Occurs When: Action Taken

No Evaporator Water Flow (NOTE)

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

Rapid Stop

Evaporator Freeze Protect Evap LWT goes below evap freeze protect setpoint Rapid Stop

Leaving Evaporator Water Temperature Sensor Fault

Sensor shorted or open Rapid Stop

Outside Air Temperature Sensor Fault

Sensor shorted or open Normal Shutdown

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

NOTE: Beginning with this software version, two automatic resets per day (beginning at 12:00 am)

are allowed on the flow loss alarm. The Unit State remains on Auto and the evaporator will go back

to Start, waiting for flow.

Unit Events

The following events only generate a warning message to the operator. Chiller operation is

not affected. They are logged in the Event Log with a time stamp.

Table 23, Unit Events

Description Occurs When: Action Taken Reset

Entering Evaporator Temperature Sensor Fault

Sensor is open or shorted

Cannot use return water temperature control

Automatic

Circuit Stop (Shutdown) Alarms

The following table identifies each circuit stop alarm, gives the condition that causes the

alarm to occur, and states the action taken because of the alarm. All stop alarms require

manual reset. Rapid stop alarms do not initiate a pumpdown before shutting off. All other

alarms will initiate a pumpdown. The occurrence of a circuit stop alarm only affects the

circuit on which it occurred.

Table 24, Circuit Stop Alarms


No Pressure at Start Evap or Cond pressure< 5 psi when Compressor Start

Requested

Start Aborted, Circuit Locked Out on Manual Reset

Low Evaporator Pressure [Freezestat trip OR Evaporator Press < 0 psi OR Low

Pressure Sw Open] AND Compressor State = Run Rapid Stop

High Lift Pressure Cond Sat Temp > Max Sat Cond Value for a period

exceeding the setting of the High lift Delay timer Rapid Stop

Continued on next page.

OM AGSDP-3 35


Mechanical High Pressure Digital Input 6 = Open Rapid Stop

Below Minimum Lift Pressure Cond Press < Min Sat Cond Value for time > Min Lift

Delay SP Pumpdown

High Discharge Temperature Temp > High Discharge Temperature SP Rapid Stop

Low Oil Level DI9 = Open for Time greater than Low Oil Level Delay

+ the Low Oil Level Event has occurred in the past hour

Rapid Stop

High Oil Pressure Difference Digital Input 5 = Open for time greater than High

Press Diff Delay SP Rapid Stop

Starter Fault (Note) Digital Input 3 = Open Rapid Stop

Evaporator Press. Sensor Fault Sensor shorted or open Rapid Stop

Condenser Press. Sensor Fault Sensor shorted or open Rapid Stop

Liquid Line Pressure Sensor Fault Sensor shorted or open Pumpdown

Discharge Temp. Sensor Fault Sensor shorted or open Pumpdown

Liquid Line Temp. Sensor Fault Sensor shorted or open Pumpdown

Slide Position Sensor Fault Sensor shorted or open Pumpdown

NOTE: As long as starter communication is functioning, power data will be displayed and starter

faults will be indicated. Some starter faults are self-clearing in the starter itself. Alarms triggered by

these faults will be allowed to self-clear twice per day. The third will trigger a manual reset in the

controller requiring it to be cleared via the active alarm screens on the unit controller. Alarms using

this logic are:

Current Imbalance Current low Phase Loss Phase Reversal

Voltage High Voltage Low No Starter Transition Other Starter Faults

Some starter faults never auto-clear in the starter. They can be cleared via the Active Alarm screens

on the unit controller or on the starter itself. Alarms using this logic are:

High Current Trip Ground Fault High Motor Temperature

Evaporator Flow Loss Alarm description (as shown on screen): Evap Water Flow Loss

Trigger: [Evaporator Pump State = Run AND Evaporator Flow Digital Input = No Flow

for time > Flow Proof Set Point AND at least one compressor running] OR [Evaporator

Pump State = Start for time > Recirculate Timeout set point AND Evaporator Flow Input =

No Flow AND No other pump to try]

Action Taken: Rapid stop all circuits

Reset: This alarm can be cleared at any time manually via the keypad or via the BAS clear

alarm signal. It will also auto reset the first two occurrences each day that are triggered due

to the first condition listed above, with the third occurrence being manual reset. Any time

the second condition triggers the alarm, it is a manual reset alarm.

For the auto reset occurrences, the alarm will reset automatically when the evaporator state

is Run again. This means the alarm stays active while the unit waits for flow, then it goes

through the recirculation process after flow is detected. Once the recirculation is complete,

the evaporator goes to the Run state which will clear the alarm.

Evaporator Freezestat Freezestat logic allows the circuit to run for varying times at low pressures. The lower the

pressure, the shorter the time the compressor can run. This time is calculated as follows:

Freeze error = Low Evaporator Pressure Unload – Evaporator Pressure

Freeze time = 60 – 6.25 x (Freeze error), limited to a range of 10-60 seconds

When the evaporator pressure goes below the Low Evaporator Pressure Unload setpoint, a

timer starts. If this timer exceeds the freeze time, then a freezestat trip occurs. If the

evaporator pressure rises to the unload setpoint or higher, and the freeze time has not been

exceeded, the timer will reset.

The following two values are designed to keep the compessor in its design operating

envelope.

36 OM AGSDP-3

Mechanical Low Pressure Alarm description (as shown on screen): Mech Low Pressure N

Trigger: Mechanical Low Pressure switch input is low AND Circuit State = Run for longer

than 20 seconds

Action Taken: Rapid stop circuit

Reset: This alarm can be cleared manually via the Unit Controller keypad.

Maximum Saturated Condenser Value If Sat Evap Temp < 32 then

Max sat cond value = 155 + 1.588(Sat Evap Temp – 32)

If [Sat Evap Temp >= 32 AND Sat Evap Temp < 40] OR Circuit State = Pumpdown then

Max sat cond value = 155

If Sat Evap Temp >= 40 AND Sat Evap Temp < 55 then

Max sat cond value = 155 – 0.667(Sat Evap Temp – 40)

If Sat Evap Temp >=55 then

Max sat cond value = 145

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

Min sat cond value = 73

If Sat Evap Temp >= 35 and < 55, then

Min sat cond value = (6/5)(Sat Evap Temp – 35) + 73

If Sat Evap Temp >= 55 then

Min sat cond value = 97

Circuit Events

The following events do not cause compressor shutdown but limit operation of the circuit in

some way as described in the Action Taken column.

Table 25, Circuit Events

Description Occurs When: Action Reset

Low Evaporator Pressure - Hold

Pressure < Low Evap Pressure - Hold SP Inhibit loading

Evap Press rises above (SP + 2 psi)

Low Evaporator Pressure - Unload

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

(Hold SP + 2 psi)

High Lift Pressure - Hold

Pressure > High Sat Cond - Hold Value Inhibit loading

Cond Press drops below (Hold Value – 10

oF)

High Lift Pressure - Unload

Pressure > High Sat Cond - Unload Value Unload Cond Press drops below (Unload Value – 10

oF)

Subcooling Low

EXV = Pressure Control AND Subcool < Low Subcool SP OR EXV = Subcool Control AND Subcool < (the lowest of the Low Subcool SP and SC target – 0.5

oF) for longer than 5 min.

None Subcool > setpoint or

Comp state = off

Discharge Superheat Low

EXV Control = Pressure Control AND Disc SH < Min SH Setpoint for 10 minutes

Pumpdown and stop

Comp state = off

Oil Level Low DI9 = Open for Time greater than Low Oil Level

Delay AND more than one hour since last occurrence

Rapid stop Comp state = off

Failed Pumpdown Circuit state = pumpdown for more than the

Pumpdown Time SP Stop N/A

Suction Temp. Sensor Fault

Sensor shorted or open None Sensor Problem

corrected

VFD Fault VFD option enabled and Digital Input 4 = Open Pumpdown Automatic

Power Loss While Running

Circuit controller is powered up after losing power while compressor was running

Delay start of compressor

N/A

OM AGSDP-3 37

High Saturated Condenser – Hold Value

High Cond Hold Value = Max Saturated Condenser Value – 5oF

High Saturated Condenser – Unload Value

High Cond Unload Value = Max Saturated Condenser Value – 3oF

Alarm and Event Logging Alarm Logging When an alarm occurs, the alarm type, date, and time are stored in the active alarm buffer

corresponding to that alarm (viewed on the Alarm Active screens) and also in the alarm

history buffer (viewed on the Alarm Log screens). The active alarm buffers hold a record of

all current alarms. The active alarms can be cleared by pressing the Enter key when the end

of the list has been reached by scrolling. Active alarms may be cleared only if a password is

active.

Beginning with this version, the BAS can clear the flow loss alarm, evaporator water freeze

alarm and pLAN failure, regardless of what other alarms are active.

A separate alarm log stores the last 25 alarms to occur. When an alarm occurs, it is put into

the first slot in the alarm log and all others are moved down one, dropping the last alarm. In

the alarm log, the date and time the alarm occurred are stored, as well as a list of other

parameters. These parameters include unit state, OAT, LWT, and EWT for all alarms. If the

alarm is a circuit alarm, then the circuit state, refrigerant pressures and temperatures, EXV

control state, EXV position, slide position, and number of fans on are also stored.

To view alarms, activate the manager password, press Menu on the unit controller, then

select Alarm (left arrow), then select Active or Log.

A compressor run time and slide valve target are in the alarm log.

Event Logging

An event log similar to the alarm log holds the last 25 events to occur. When an event

occurs, it is put into the first slot in the event log and all other entries are moved down one,

dropping the last event. Each entry in the event log includes an event description, as well as

the time and date of the occurrence. No additional parameters are logged for events.

To view events, press Menu on the unit controller, then select Alarm (left arrow), then scroll

left to Event Log. See menu matrix on page 41.

38 OM AGSDP-3

Using the Controller

4x20 Display & Keypad

Layout

The 4-line by 20-character/line liquid crystal display and 6-key keypad for both the circuit

controller and unit controller is shown below.

Figure 7, Display (in MENU mode) and Keypad Layout

Air Conditioning

ALARMVIEW

SET

<<<

Note that each ARROW key (except the down arrow) has a pathway to a line in the display.

Pressing an ARROW key will activate the associated line when in the MENU mode.

Arrow Keys

The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.

1. Scroll between data screens as indicated by the arrows (default mode).

2. Select a specific data screen in a hierarchical fashion using dynamic labels on the right

side of the display (this mode is entered by pressing the MENU key).

3. Change field values in edit mode according to the following table:

LEFT Default (D)

RIGHT Cancel (C)

UP Increment (+)

DOWN Decrement (-)

These four edit functions are indicated by one-character abbreviations on the right side of

the display (this mode is entered by pressing the ENTER key).

Getting Started, Navigating-Press the MENU key to get started. The navigating

procedures are the same for both the unit controller and the circuit controller.

MENU Key

The MENU key is used to switch between the MENU mode as shown in Figure 7 and the

SCROLL mode as shown in Figure 8. The MENU mode is basically a shortcut to specific

groups of menus used for checking ALARMS, for VIEWING information, or to SET

setpoint values. The SCROLL mode allows the user to move about the matrix (from one

menu to another, one at a time) by using the four ARROW keys.

ENTER Key and

Green Comp.

Run Light

MENU Key

ARROW Keys (4) Key to Screen Pathway

Left Arrow Key and

Red Alarm Light

OM AGSDP-3 39

When in the MENU mode (as shown in Figure 7), pressing the LEFT ARROW key will

select the ALARM menus, the RIGHT ARROW key will select the VIEW menus and the

UP key the SET menus. The controller will go the next lower menu in the hierarchy, and

then other menus can be accessed by using the ARROW keys. Pressing the MENU key

from any menu screen will automatically return to the MENU mode as shown in Figure 7.

Another way to navigate through the menus is to press the MENU key when in the MENU

mode (as above). This will switch the controller to the SCROLL mode. The controller will

automatically go to the first screen as shown below (the upper-left menu on the menu matrix

shown in Table 26 on page 41). From there, the four ARROW keys can be used to scroll

up, down, or across to any other menu.

Figure 8, Display (in SCROLL Mode) and Keypad Layout

Air Conditioning

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

ENTER Key

Pressing the ENTER key changes the function of the ARROW keys to the editing function

as 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 original

setting.

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 the

display (this mode is entered by pressing the ENTER key).

Most menus containing setpoint values have several different setpoints shown on one menu

screen. When in a setpoint menu, the ENTER key is used to proceed from the top line to

the second line and on downward. The cursor will blink at the entry point for making a

change. The ARROW 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 until the ENTER key is pressed.

For example, to change the chilled water setpoint:

1. Press MENU key to go to the MENU mode (see Figure 7).

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 which

contains Evap LWT=XX.X°F.

MENU Key

ENTER Key ARROW Keys (4)

40 OM AGSDP-3

5. Press the ENTER key to move the cursor down from the top line to the second line in

order 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 cursor

down.

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 keys

can be used to scroll to different menus.

Security All setpoints on the unit controller, as well as the circuit controllers, are protected using

passwords that provide OPERATOR and MANAGER levels of access to changeable

parameters. The operator password is 100.

Entering Passwords Passwords can be entered using the ENTER PASSWORD screen on the unit controller,

which is the last screen in the Unit SPs column. The password is entered by pressing the

ENTER key, scrolling to the correct value with the UP and DOWN arrow keys, and pressing

ENTER again. The longer a key is held down, the faster it will increment. The entered

password is not shown after the enter key is pressed. The operator password is 100.

Once the correct password has been entered, the ENTER PASSWORD screen indicates

which password is active (none, operator, or manager). If the wrong password is entered, a

temporary message will appear so stating. If no valid password is active, the active

password level displays “none”.

Entering an incorrect password while a password is active will render that password

inactive. Entering a valid password that is not the same as the active password will result in

the active password level being changed to reflect the new password level.

Editing Setpoints After a valid password has been entered at the unit controller, setpoints on the circuit

controllers and the unit controller can be changed. If the operator attempts to edit a setpoint

for which the necessary password level is not active, no action will be taken.

Once a password has been entered, it remains valid for 60 minutes after the last key-press

on the unit controller.

Clearing Alarms Alarms are cleared at the unit controller as long as any password level is active. If the user

attempts to clear an alarm while no password is active, then the controller will automatically

go to the ENTER PASSWORD screen. The user can then enter a password normally, and

scroll back to the active alarm column to clear the active alarm(s). Clear alarms by pressing

and holding ENTER for 5 seconds.

To clear an alarm, go to the unit controller Alarm, Active Menu. Scroll down to the last

alarm listed. The screen will note “No More Alarms”. Press and hold Enter for five

seconds to clear alarms. If there are no active alarms, the red Alarm light will be off and

alarms status will clear from the unit and circuit controllers.

OM AGSDP-3 41

Unit Controller Menus Various menus are shown in the controller display. Each menu screen shows specific

information. In some cases menus are used only to view status of the unit, in some cases

they are used for checking alarms, and in some case they are used to set the setpoint values

that can be changed.

The menus are arranged in a matrix of screens across a top horizontal row. Some of these

top-level screens have sub-screens located under them. The content of each screen and its

location in the matrix are shown in Table 26. A description of each menu begins on page 42.

The ARROW keys on the controller are used to navigate through the menus. The keys are

also 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 through

all of them with the 4 arrow keys. For this use, the screens are arranged logically in a

matrix as shown below.

Table 26, Unit Controller Menu Structure

VIEW MENUS

VIEW UNIT

STATUS(1)

VIEW UNIT TEMP

(2)

VIEW CIR #1

(1)

VIEW CIR #2

(1)

VIEW CIR #3

(1)

VIEW REFRG CIR #1

(1)

VIEW REFRG CIR #2

(1)

VIEW REFRG CIR #3

(1)

VIEW FANS On-Off

(1)

VIEW UNIT

STATUS(2)

VIEW UNIT TEMP

(2)

VIEW CIR #1

(2)

VIEW CIR #2

(2)

VIEW CIR #3

(2)

VIEW REFRG CIR #1

(2)

VIEW REFRG CIR #2

(2)

VIEW REFRG CIR #3

(2)

VIEW FANS VFD (2)

⇓ ⇓ ⇓ ⇓ VIEW UNIT

STATUS(5)

VIEW REFRG CIR #1

(5)

VIEW REFRG CIR #2

(5)

VIEW REFRG CIR #3

(5)

Right half of matrix

continued below

ALARM MENUS SET MENUS

EVENT

LOG (1)

ALARM LOG (1)

ALARM ACTIVE

(1)

SET UNIT SPs (1)

SET COMP SP

(1)

SET ALARM

LMTS (1)

SET SENSOR OFFSET

TEST UNIT

⇓ ⇓ ⇓ SET UNIT

SPs (2)

SET COMP SP

(2)

SET ALARM LMTS

(2)

EVENT

LOG (25)

ALARM LOG (25)

ALARM ACTIVE

(n)

SET UNIT SPs (3)

SET COMP SP

(3)

SET ALARM LMTS

(3)

SET UNIT

SPs (4)

SET ALARM LMTS

(4)

Right half of matrix

continued from above

SET UNIT SPs (5)

SET ALARM LMTS

(5)

SET UNIT

SPs (6)

⇓

SET UNIT

SPs (to 13)

Continued

42 OM AGSDP-3

Selection can then be made by using the LEFT/RIGHT keys to move between columns and

the UP/DOWN keys to move between rows. The menu structure allows the return to the

last screen viewed in each column. (This feature also applies to navigation using the

function keys.) As an example:

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

Screen Definitions The following section illustrates all the unit screens. The screens are listed in the order of

the matrix, starting from the upper-left.

View Unit Status

View screens are used to view the operation or status of the entire unit or individual circuit.

No settings are entered to these screens.

VIEW UNIT STATUS (1)

{Unit Status}

{Unit Mode}

Evap Pump= run

Unit Status will display one of the following:

Auto Off:Keypad Disable Off:Test Mode Auto:Wait for flow

Off:Ice Mode Timer Off:Remote Switch Auto:Wait for load Auto:Pumpdown

Off:All Cir Disabled Off:BAS Disable Auto:OAT Low

Off:Unit Alarm Off:Unit Switch Auto:Evap Recirc


Softload Limit=100.0

Demand Limit=100.0

Network Limit=100.0

The unit will limit loading to the lowest of the three limit values that are active.


Unit Capacity=xxx.x%

Ice Delay= XXh XXm

Ice delay will be visible only when unit mode is Ice.


1 2 3 4

D.O. 0 1 0 0

D.I. 1 1 1 0

This screen gives the status of Digital Outputs 1 through 4 (D.O.) and Digital Inputs

1 through 4 (D.I.) as defined in Table 3 and Table 4.

0=Off, 1=On.


Analog Inputs (mA)

Demand Limit= XX.X

LWT Reset= XX.X

OM AGSDP-3 43

VIEW UNIT TEMP (1)

Evap LWT= XXX.X F

Evap EWT= XXX.X F

Active SP= XXX.X F

VIEW UNIT TEMP (2)

LWT Pulldn= 0.0 F/m

Evap Delta T=XX.X F

Outdoor 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:Ready

Slide Position=000.0%

Slide Target=000.0%

Slide position and slide target are explained on page 18.


Hours = XXXXX

Starts = XXXXX

VIEW REFR CIR N (1)

Evap Press=XXX.X psi

Cond Press=XXX.X psi

Liq Press= XXX.X psi

VIEW REFRG CIR N (2)

Sat Evap= XXX.X °°°°F

Sat Cond= XXX.X °°°°F

Sat LiqLine= XXX.X°°°°F


Suct Temp = XXX.X °°°°F

Disc Temp = XXX.X °°°°F

Liq Temp = XXX.X °°°°F


Suct SH = XXX.X °°°°F

Disc SH= XXX.X °°°°F

Liquid SC= XXX.X °°°°F

44 OM AGSDP-3


Evap Approach=XX.X°°°°F

Cond Approach=XX.X°°°°F

EXV position = XXXX

VIEW FANS (1)

Fans On, Cir 1= 0

Fans On, Cir 2= 0

Fans On, Cir 3= 0

VIEW FANS (2)

VFD Cir 1= 000.0 %

VFD Cir 2= 000.0 %

VFD Cir 3= 000.0%

ALARM and EVENT Screen Definitions

The alarms and events shown are examples only. Any possible alarm or event could be

shown. The alarm log and event log can show up to the 25 most recent occurrences.

EVENT LOG (1-25)

Event Description

hh:mm mm/dd/yy

ALARM LOG: (1-25)

Alarm Description

hh:mm:ss dd/mmm/yyyy

Parameters

ALARM ACTIVE

hh:mm mmm/dd/yy

Alarm Description

SET Screen Definitions Setpoints shown are typical. Entries can be selected by scrolling through the available

possibilities. Setpoint ranges and choices are show in Table 13 on page 25.

Unit Setpoints

SET UNIT SPs (1)

Enable=On

Mode= COOL

Source = KEYPAD

OM AGSDP-3 45

SET UNIT SPs (2)

Available Modes = COOL

Select w/Unit Swt. Off

SET UNIT SPs (3)

Cool LWT = XX.X°°°°F

Ice LWT – XX.X°°°°F

The unit will only use the setpoint for the Mode selected.

SET UNIT SPs (4)

StartDelta= XX.X°°°°F

StopDelta= XX.X°°°°F

StageDelta= XX.X°°°°F

The StartDelta is the number of degrees above the chilled water setpoint the water

temperature must rise for a compressor to start when no compressors are running. The

default is 10 degrees. F., the range is 0 to 10 degrees. F. Settings below 10 degrees will

have the undesirable effect of increasing compressor cycling.

The StopDelta is the number of degrees below the chilled water setpoint the water

temperature must fall for the last compressor to stop.

The StageDelta is the number of degrees change in the chilled water to initiate a change in

staging.

SET UNIT SPs (5)

Max Pulldn=X.X°°°°F/min

EvapRecTimer=XXX sec

Evap Pump= #1,#2, Auto

The controller can start either of two chilled water pumps or in the Auto mode will

automatically select the pump with the least run hours.

SET UNIT SPs (6)

Reset Type =none

MaxResetDT =XX.X°°°°F

StrtResetDT=XX.X°°°°F

See page 31 for reset options.

SET UNIT SPs (7)

Soft Load = Off

Begin Capacity= XXX%

SoftLoadRamp= XXmin

See page 18 for soft load and demand limit options.

46 OM AGSDP-3

SET UNIT SPs (8)

Demand Limit= Off

Low Amb Lock = XX.X°°°°F

SET UNIT SPs (9)

Ice Time Delay=xxhrs

Clear Ice Timer=No

SET UNIT SPs (10)

Quiet Night= Disable

Start @ XX:XX

End @ XX:XX

SET UNIT SPs (11)

Quiet Night

Cond Offset= XX.X°°°°F

SET UNIT SPs (12)

CLOCK

dd/mmm/yyyy

hh:mm:ss

SET UNIT SPs (13)

Units = °°°°F/psi

Lang = ENGLISH

Inch-Pound units of measure and English language are the only options available in this

software version.

SET UNIT SPs (14)

Protocol=

Ident Number=

Baud Rate=

SET UNIT SPs (15)

Enter Password:0000

Active Password

Level:none

Compressor (Circuit) Setpoints

SET COMP SPs (1)

Seq # Comp 1=

Seq # Comp 2=

Seq # Comp 3=

OM AGSDP-3 47

SET COMP SPs (2)

Max Comprs On = X

Start-Start = XXmin

Stop-Start = XXmin

SET COMP SPs (3)

# of Compressors=X

Pumpdn press=XX.X psi

Pumpdn time= XXX sec

SET COMP SPs (4)

Light Load Stage

Down Point=XX% slide

Stage Dn Delay=XXmin

SET COMP SPs (5)

Stg Up Delay= XXXsec

SET ALARM LMTS (1)

Low Evap Pressure

Hold=59.0 psi

Unload=58.0 psi

SET ALARM LIMITS (2)

LowOilDelay= XXX sec

HighOilDpDel=XXX sec

Low Subcool= XX.X°°°° F


MinLiftDel= XXX sec

Highlift Delay=XXsec

High Disc Temp=XXX°°°°F


Evap Freeze= XX.X°°°°F

Evap Flow Proof=XXX Recirc Timeout=XXmin

SET SENSOR OFFSET

OAT= XX.X°°°°F

Evap LWT= XX.X°°°°F

Evap EWT= XX.X°°°°F

48 OM AGSDP-3

TEST Screen Definitions TEST UNIT

Alarm Out=Off

Evap Heaters=Off

Pump1=Off Pump 2=Off

Circuit Controller Menus See "Using the Controller" on page 38 for information on how to navigate and use the menu

screens, as well as changing setpoints. As an alternate to selecting screens with the menu

function, it is possible to scroll through all of them with the 4 arrow keys. For this use, the

circuit controllers' screens are arranged logically in a matrix as shown below.

Table 27, Circuit Controller Screen Matrix

"VIEW" SCREENS "SET" SCREENS "TEST"

SCREENS

VIEW UNIT (1)

VIEW CIR (1)

VIEW REFRG

(1)

VIEW FANS

(1)

SET COMP

SPs

SET EXV SPs

(1)

SET FANS

(1)

SET SENSOR OFFSETS

(1)

TEST COMP

(1)

VIEW UNIT (2)

VIEW CIR (2)

VIEW REFRG

(2)

VIEW FANS

(2)

SET COMP SPs (2)

SET EXV SPs

(2)

SET FANS

(2)

SET SENSOR OFFSETS

(2)

TEST COMP

(2)

VIEW CIR (3)

VIEW REFRG

(3)

SET COMP SPs (3)

SET

FANS(3)

SET SENSOR OFFSETS

(3)

TEST COMP

(3)

VIEW CIR (4)

VIEW REFRG

(4)

SET FANS

(4)

VIEW CIR (5)

⇓ ⇓

VIEW CIR (6)

VIEW REFRG

(7

SET FANS

(6)

Screen Definitions

VIEW Screens

Circuit VIEW screens are used to view the operation of a circuit's compressor, refrigerant

condition, 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°°°°F

Active SP= XX.X°°°°F

LWT pulldn= XX.X°°°°F/m

OM AGSDP-3 49

View Circuit Status

VIEW CIR STATUS (1)

Off:Ready

Slide Pos= XXX.X%

Slide Target= XXX.X%

VIEW CIR STATUS (2)

Hours = XXXXX

Starts = XXXXX


Current (amps)

L1 L2 L3 Avg

XXX XXX XXX XXX


Voltage

L1-2 L2-3 L3-1 Avg

XXX XXX XXX XXX


PF= 0.XX %RLA=XXX.X

KW= XXX

View Refrigerant

VIEW REFRIGERANT (1)

Evap Press=XXX.X psi

Cond Press=XXX.X psi

Liq Press= XXX.X psi


Sat Evap = XXX.X °°°°F

Sat Cond = XXX.X °°°°F

Sat LiqLine= XXX.X °°°°F


Suct Temp = XXX.X °°°°F

Disc Temp = XXX.X °°°°F

Liq Temp = XXX.X °°°°F


Suct SH = XXX.X °°°°F

Disc SH= XXX.X °°°°F

Liquid SC= XXX.X °°°°F

50 OM AGSDP-3


Evap Approach=XX.X °°°°F

Cond Approach=XX.X °°°°F


MaxCondSatT=XXX.X°°°°F

EXV Control=Pressure


EXV Steps= XXXX

EXV ctrl range:

XXXX – XXXX steps

VIEW FANS (1)

VFD Speed= XXX.X%

Fans Running= X

VFD Target=XXX.X °°°°F

VIEW FANS (2)

Target Sat T=XXX.X °°°°F

Stage Up Err= XXX

Stage Dn Err= XXX

SET Screen Definitions

Compressor Setpoints

SET COMP SPs (1)

Clear Cycle Tmr=no

Comp Size=XXX

Max Slide= XXX.X%

Clearing the anti-recycle timer is a one-time event. If “yes” is selected, the timer will go to

zero but will then revert back to the original setting for any future occurrences.

SET COMP SPs (2)

Circuit Mode=Enable

Slide Control=auto

Slide Target= XXX.X%

SET COMP SPs (3)

Oil return

Max slide= XX.X%

Min Disch SH=XX.X oF

OM AGSDP-3 51

SET COMP SPs (4)

Motor FLA = NNNN amps

Mptpr RLA = NNNN amps

EXV Setpoints

SET EXV SPs (1)

EXV Control=auto

Manual EXV Pos=XXXX

Pre-open time=XXX sec

SET EXV SPs (2)

Min EXV= XXX steps

Service pumpdown=No

Fan Setpoints

SET FAN SPs (1)

Fan VFD = no

Number of fans = X

SET FAN SPs (2)

Stg Up Deadband(°°°°F)

Stg1=XXX Stg3=XXX

Stg2=XXX Stg4=XXX

SET FAN SPs (3)

Stg Down Deadband(°°°°F)

Stg1=XXX Stg3=XXX

Stg2=XXX Stg4=XXX

SET FAN SPs (4)

VFD Min speed= XXX%

VFD Max speed= XXX%

52 OM AGSDP-3

SET FAN SPs (5)

Cond Sat Temp Target

Setpoint= XXX.X °°°°F

SET FAN SPs (6)

# Fans On At Startup

>75°°°°F >90°°°°F >105°°°°F

X X X

Sensor Offsets

SET SENSOR OFFSET (1)

Evap Press= XX.X psi

Cond Press= XX.X psi

Liq Press= XX.X psi


Suct Temp= X.X F

Disch Temp= X.X F

Liq Temp= X.X F


Slide min pos=XX%

Slide max pos=XX%

Slide Pos=XXX.X%

Test

TEST CIRCUIT (1)

Fans:1=Off 2=Off

3=Off 4=Off

5/6=Off 7/8=Off

TEST CIRCUIT (2)

Slide Dir= Unload

Slide Pulse= Off

TEST CIRCUIT (3)

Oil Return= Off

EXV Closed= Off

TEST CIRCUIT (4)

Fan VFD Spd%= XXX.X

EXV Position=XXXX

OM AGSDP-3 53

Sequence of Operation

The following sequence of operation is typical for McQuay models AGS chillers. The

sequence may vary depending on the software revision or various options that may be

installed on the chiller.

Off Conditions Power is supplied to each power panel located between condenser sections. Optionally, the

power may be supplied to a single power connection located in a terminal box on the base

of the unit.

With power supplied to the unit, 115 VAC power is applied through the control fuse F1 to

the compressor heaters (HTR1, HTR2, (and HTR3), evaporator heater, and the primary of

the 24V control circuit transformer.

! CAUTION

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 system

switch. If the switch is in the "stop" position, the chiller will remain off, and the display

will indicate the operating mode to be OFF: System Sw. The controller will then check the

pumpdown switches. If any of the switches are in the "stop" position, that circuit’s

operating mode will be displayed as OFF: PumpDwnSw. If the switches for both circuits

are in the "Stop" position, the unit status will display OFF: PumpdownSw’s. If the remote

start/stop switch is open the chiller will be OFF: RemoteSw. The chiller may also be

commanded off via communications from a separate communicating panel such a BAS

protocol interface. The display will show OFF: RemoteComm if this operating mode is in

effect. If an alarm condition exists which prevents normal operation of both refrigerant

circuits, the chiller will be disabled and the display will indicate OFF: Alarm. If the

control mode on the keypad is set to "Manual Unit Off," the chiller will be disabled and the

unit status will display OFF: ManualMode. Assuming none of the above stop conditions

are true, the controller will examine the internal time schedule to determine whether the

chiller should be permitted to start.

Alarm The red alarm light in back of the left arrow key on the controller will be illuminated when

one or more of the cooling circuits has an active alarm condition which results in the circuit

being locked out and manual reset is required. Unless the alarm condition affects all

circuits, the remaining circuits will operate as required. Events will not cause the key to

light.

Start-up If none of the above "off" conditions are true, the MicroTech II controller will initiate a start

sequence and energize the chilled water pump output relay. The chiller will remain in the

WaitForFlow mode until the field installed flow switch indicates the presence of chilled

water flow. If flow is not proven within 30 seconds, the alarm output will be turned on, the

keypad display will be WaitForFlow, and the chiller will continue to wait for proof of

chilled water flow. Once flow is established, the controller will sample the chilled water

temperature and compare it against the Leaving Chilled Water Setpoint, the Control Band,

and the Start-up Delta-Temperature, which have been programmed into the controller’s

memory.

54 OM AGSDP-3

If the leaving chilled water temperature is above the Leaving Chilled Water Setpoint plus

one-half of the Control Band plus the adjustable Start-up Delta-T, the controller will select

the refrigerant circuit with the lowest number of starts as the lead circuit and initiate a start

request. The controller will perform a PreOpen function, opening the EXV and initiating

the pre-open timer. After the pre-open timer times out, the controller will start the

compressor and energize the evaporator oil return solenoid and the display will show

Opened EXV. A green light under the Enter key will illuminate.

If additional cooling capacity is required, the controller will energize the additional cooling

capacity by activating the first compressor’s capacity control solenoids. As the system load

increases, the controller will start the lag refrigerant circuit when the lead circuit reaches

75%, some other capacity limit is reached, and the interstage timers are satisfied. The

compressors and capacity control solenoids will automatically be controlled as required to

meet the cooling needs of the system. The electronic expansion valves are operated by the

MicroTech II controller to maintain precise refrigerant control to the evaporator at all

conditions.

Standard VFD Condenser Fan Control

The first condenser fan stage will be started along with the first compressor to provide

initial condenser head pressure control. The first stage consists of two fans with VFDs,

which are controlled by the MicroTech II controller to maintain a discharge temperature

target. An increase in temperature will stage the remaining constant speed condenser fans

on and off as needed to maintain proper condensing pressure. The number of condenser

fans operating will vary with outdoor temperature and system load. The condenser fans are

matched to the operating compressors so that when a compressor is off, all fans for that

circuit will also be off.

Pumpdown

As the system chilled water load requirements diminish, the compressors will unload. As

the system load continues to drop, the electronic expansion valves will be stepped closed

and the refrigerant circuits will go through a pumpdown sequence. As the evaporator

pressure falls below the pumpdown pressure setpoint while pumping down, the

compressor(s) and condenser fans will stop. The unit has a one-time pumpdown control

logic; therefore, if the evaporator pressure rises while the refrigerant circuit is in a

pumpdown mode, the controller will not initiate another pumpdown sequence. The

controller will keep the unit off until the next 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 stop

position, or a separate communications panel such as the Remote Monitoring and

Sequencing Panel or an Open Protocol interface deactivates the chilled water pump output.

Liquid injection

Liquid injection is turned on automatically at 185°F or discharge superheat above 60

degrees F. It is turned off at 170°F or discharge superheat below 40 degrees F.

OM AGSDP-3 55

Figure 9, AGS Piping Schematic

DISCHARGE

TUBING

SIGHTGLASS

AIR

FLOW

WATER OUT

WATER IN

LIQUID

TUBING

EXPANSION

VALVE

SCHRADER

VALVE

CHARGING

VALVE

SIGHT

GLASS

CONDENSER

ASSEMBLY

AIR

FLOW

AIR

FLOW

AIR

FLOW

CONDENSER

ASSEMBLY

CHARGING VALVE

LIQUID SHUT-OFF VALVE

SCHRADER VALVE

FILTER DRIER

OIL

SEPARATOR

OIL

RETURN

DISCHARGE

TUBINGSCHRADER(EACH DISCHHEADER)

TO REAR OF

COMPRESSORSUCTION

BUTTERFLY VALVE(OPTION)

RELIEF VALVE(EVAP SHELL)

RELIEFVALVE

CHECK

VALVE

ANGLE

VALVE

BALL

VALVE

SOLENOID

VALVE

SIGHT

GLASS

STRAINER

CHARGING

VALVE

SCHRADER

Start-up and Shutdown

NOTICE

McQuay Factory Service personnel or factory authorized service agency must perform initial start-up in order to activate warranty.

! CAUTION

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

Seasonal Start-up

1. 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. Check the leaving chilled water temperature setpoint on the MicroTech II controller to

be sure it is set at the desired chilled water temperature.

4. Start the auxiliary equipment for the installation by turning on the time clock, and/or

remote on/off switch, and chilled water pump.

56 OM AGSDP-3

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. Repeat steps 8 and 9 for PS2.

Expansion Valve Operation

Pre-open:

At the time of a start request, the EXV will perform a pre-open function. This process

insures that sufficient liquid refrigerant resides in the evaporator to avoid low pressure

situations at startup. During pre-open, the EXV will open to 3000 steps while the saturated

evaporator temperature is less than the LWT. The EXV will move to 250 steps when the

saturated evaporator temperature is equal to or greater than the LWT. The EXV must be in

the pre-open state for a time equal to the pre-open timer set point before the compressor will

start. The timer is adjustable from 20 to 120 seconds, and has a default setting of 60

seconds.

Pressure Control:

The EXV will be in pressure control mode after startup. The EXV controls the evaporator

pressure to a calculated pressure target. The base pressure target is calculated using the

following formula:

Base target = 2/3LWT – 8

The base target is limited to a range from the low pressure inhibit set point plus 2 psi, up to

52 psi.

The base pressure target value is adjusted when the discharge superheat is less than 22°F or

greater than 40°F. For every degree below the minimum, the pressure target is adjusted

down one psi. Similarly, for every degree above the maximum, the pressure target is

adjusted up one psi. At any time, the adjusted target pressure cannot go below the low

pressure inhibit set point plus 2 psi, or above 52 psi.

EXV will transition from pressure control to subcool control when all of the following are

true:

Discharge Superheat > 22°F for at least 3 minutes while in pressure control

LWT <= 60°F

Subcool > current base subcool value OR EXV steps > (max EXV steps – 100)

Unit mode = Cool (includes Available Modes: Cool w/ Glycol. Subcool control is not

used in Ice Mode)

The EXV may transition from subcool control back to pressure control. This occurs when:

The LWT is greater than 63°F,

The unit mode is switched from Cool to Ice,

A low evaporator pressure unload occurs.

The suction pressure drops below the low evaporator pressure unload setpoint, the

controller will switch from subcool control to pressure control, until sufficient

subcooling is established.

OM AGSDP-3 57

Subcool Control:

After completing pressure control, the EXV transitions to subcool control, which is used

only when the unit mode is Cool. In this mode, subcooling is controlled by the EXV, with

adjustments to the subcool target based on discharge superheat. The base subcool target

varies linearly from 9 to 20oF as slide position changes from 0 to 100%. The subcool target

will vary from 5 to 20, if 20°< DSH < 40°.

The base subcool target value is adjusted when the discharge superheat is less than 22°F, or

greater than 40°F. For every degree below the minimum, the subcool target is adjusted up

one degree. Similarly, for every degree above the maximum, the subcool target is adjusted

down one degree. The maximum offset to the base subcool value is 15 °F, and the adjusted

subcool target is limited to a minimum of 2°F.


the LWT is greater than 63°F, the unit mode is switched from Cool to Ice, or a low

evaporator pressure unload occurs.

Temporary Shutdown

Move pumpdown switches PS1 and PS2 to the "Pumpdown and Stop" position. After the

compressors 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 a proper shutdown/pumpdown sequence.

! CAUTION

The unit has a one-time pumpdown operation. When PS1 and PS2 are in the "Pumpdown and Stop" position the unit will pumpdown once and not run again until the PS1 and PS2 switches are moved to the auto position. If PS1 and PS2 are in the auto position and the load has been satisfied, the unit will go into one-time pumpdown and will remain off until the MicroTech II control senses a call for cooling and starts the unit. Under no circumstance use the compressors for pumpdown of the system with the liquid line valves closed.

! CAUTION

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

! CAUTION

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

58 OM AGSDP-3

Start-up After Temporary Shutdown

1. 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.

! CAUTION

If the unit is shutdown during periods below freezing ambient temperatures, protect the chiller vessel from freezing. See Freeze-Up Protection in this manual for more information.

Extended (Seasonal) Shutdown 1. 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. If fluid is left in the evaporator, confirm that the evaporator immersion heaters are

operational.

5. Move the emergency stop switch S1 to the "off" position.

6. Close the optional compressor suction valve (if so equipped) as well as the liquid line

shutoff valves.

7. Tag all opened compressor disconnect switches to warn against start-up before opening

the compressor suction valve and liquid line shutoff valves.

8. 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 the atmosphere over the shutdown period.

9. Do not apply power to the evaporator immersion heaters if the system is drained of

fluids as this can cause the heaters to burn out.

Start-up After Extended (Seasonal) Shutdown

1. With all electrical disconnects locked and tagged 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 the crankcase heaters. Wait a minimum of 12

hours before starting up unit. Turn compressor 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.

OM AGSDP-3 59

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 in the system. Verify the correct flow rate by taking the pressure drop

across the evaporator and checking the pressure drop curves in the installation manual,

IMM AGS.

Evaporator Freeze Protection Flooded evaporators are popular with chiller manufacturers because of their inherent high

efficiency. Care must be exercised in the equipment design and in the operation of these

evaporators to prevent freezing between 32°F and -20°F.

For protection down to 0°F (-18°C), the AGS chillers are equipped with thermostatically

controlled evaporator heaters that help protect against freeze-up provided the chiller goes

through its normal pumpdown cycle. Several occurrences can prevent this normal

pumpdown from happening:

1. A power failure will prevent pumpdown and there is a potential for freezing outdoor

equipment in systems using 100 percent water as the chilled fluid.

2. Unit shutdown due to a fault will cause immediate compressor shutdown without the

pumpdown cycle. This situation can be remedied by correcting the fault, restarting the

unit, and allowing it to go through its normal shutdown pumpdown.

! CAUTION

The heaters come from the factory connected to the control power circuit. The control power can be rewired to a separate 115V supply (do not wire directly to the heater). If this is done, the disconnect switch should be clearly marked to avoid accidental deactivation of the heater during freezing temperatures. Exposed chilled water piping also requires freeze protection.

! DANGER

If more than one power source connects to the unit, each must be clearly marked that there are additional power sources to the unit, and the unit must have a notice that there are multiple power sources to it.

It is required that the chilled water pump’s starter be wired to, and controlled by, the chiller's

microprocessor. The controller will energize the pump whenever at least one circuit on the

chiller is enabled to run, whether there is a call for cooling or not. The pump will also be

energized when the controller senses a near-freezing temperature at the chiller outlet sensor

to assist in cold weather freeze protection. Connection points are shown in Figure 11 on

page 65.

For additional protection to -20°F (-29°C) and to protect against the consequences described

above, it is recommended that at least one of the following procedures be used during

periods of sub-freezing temperatures:

1. Addition of a concentration of a glycol anti-freeze with a freeze point 15 degrees below

the lowest expected temperature. This will result in decreased capacity and increased

pressure drop.

Note: Do not use automotive grade antifreezes as they contain inhibitors harmful to

chilled water systems. Only use glycols specifically designated for use in building

cooling systems.

2. Draining the water from outdoor equipment and piping and blowing the chiller tubes

dry. Do not energize the evaporator immersion heaters when fluid is drained from the

vessel.

60 OM AGSDP-3

! CAUTION

If fluid is absent from the evaporator, the evaporator heater must be de-energized to avoid burning out the heater and causing damage from the high temperatures.

3. Providing operation of the chilled water pump, circulating water through the chilled

water system and through the evaporator. The chiller microprocessor will automatically

start up the pump if so wired.

Table 28, Freeze Protection Percent Volume Glycol Concentration Required

For Freeze Protection For Burst Protection Temperature

°F (°C) Ethylene Glycol Propylene Glycol Ethylene Glycol Propylene Glycol

20 (6.7) 16 18 11 12

10 (-12.2) 25 29 17 20

0 (-17.8) 33 36 22 24

-10 (-23.3) 39 42 26 28

-20 (-28.9) 44 46 30 30

-30 (-34.4) 48 50 30 33

-40 (-40.0) 52 54 30 35

-50 (-45.6) 56 57 30 35

-60 (-51.1) 60 60 30 35

Notes: 1. These figures are examples only and cannot be appropriate to every situation. Generally, for an extended margin of

protection, select a temperature at least 10°F lower than the expected lowest ambient temperature. Inhibitor levels should be adjusted for solutions less than 25% glycol.

2. Glycol of less than 25% concentration is not recommended because of the potential for bacterial growth and loss of heat transfer efficiency.

Operating Limits: Maximum standby ambient temperature, 130°F (55°C)

Maximum operating ambient temperature, 115°F (46°C), or 125°F (52°C) with optional

high ambient package

Minimum operating ambient temperature (standard), 35°F (2°C)

Minimum operating ambient temperature (optional low-ambient control), 0°F (-18°C)

Leaving chilled water range, 38°F to 50°F (3°C to 10°C)

Leaving chilled fluid range (with anti-freeze), 20°F to 50°F (7°C to 10°C)

Operating Delta-T range, 6 degrees F to 16 degrees F (10.8 C to 28.8 C)

Maximum operating inlet fluid temperature, 66°F (19°C)

Maximum startup inlet fluid temperature, 90°F (32°C)

Maximum non-operating inlet fluid temperature, 100°F (38°C)

NOTE: Contact the local McQuay sales office for operation outside of these limits.

OM AGSDP-3 61

Refrigerant Charging

Why does the AGS flooded evaporator use subcooling control?

Subcool control maintains proper evaporator level for efficiency and is the most stable value with

which to control the flooded evaporator chiller. Discharge superheat control is affected by many

variables such as motor heat, refrigerant flow, number of fans operating, amount of refrigerant in the

oil, etc,. Additionally the chiller cannot be controlled by the traditional suction superheat control

due to the saturated refrigerant entering the suction cooled motor. Often this is a heavily saturated

vapor which helps cool the motor and is not a useful value to control to.

Do not use the evaporator sight glasses to charge the unit.

Use these sight glasses for reference only. On some of the first evaporators the sight glasses are not

in the correct location for charge level indication. The expansion valve control varies with operating

conditions and may cause a higher or lower level based on control decisions. You can use the sight

glasses to give you some relative decision making information. If there is a considerable amount of

oil out in the system, you may see oil floating on the evaporator liquid level and/or oil smearing on

the sight glass as the liquid level rises and falls.

Discharge Superheat

The most important value to monitor while setting the charge on a flooded evaporator AGS chiller is

the discharge superheat, and especially at full load. Between 20° and 22° DSH the compressor will

hold its slide target and will not load up. If the DSH drops below 20° then it will unload. Excessive

refrigerant charge, excessive oil, a large amount of oil in circulation and a leaking or over feeding

evaporator solenoid valve will all cause low discharge superheat.

Approaches:

When oil gets out into the system it will affect the condenser and evaporator approaches. The

design approach on the condenser at full load is approximately 35°. The Evaporator approach

should be 3-10°, depending on conditions and percent of glycol.

Oil In Evaporator:

If there is oil in the evaporator, it will float on the liquid level and get pulled out with suction gas,

carrying liquid refrigerant with it and reducing you discharge superheat. The goal is to keep the

discharge superheat above 22° and ideally 35°, while trying to get the compressor loaded up. The

higher the refrigerant flow, the quicker the oil will be recovered.

Evaporator Oil Return Line:

In some applications we have seen that the evaporator oil return line causes low discharge superheat

and some oil loss in to the system. It may be necessary to reduce the flow through the evaporator oil

return line by closing down the ball valve some. This may help maintain oil in the oil separator and

keep higher DSH, if it is overfeeding and dropping the DSH too much. In F code, the minimum

superheat the circuit will allow the solenoid to energize is moved from 22° to 35° DSH to help

ensure that it does not cause issues with limiting the compressor with low discharge superheat or

cause oil loss. One thing to keep in mind is that most of your oil recovery is done through carry

over through the suction line. The evaporator oil return line is used more effectively for discharge

temperature control, and a by product is we will recover some small percentage of oil.

62 OM AGSDP-3

Basic Charging Information: Determine the following:

1. What control mode is the EXV in?

2. What is the circuit status?

3. What is the compressor slide position?

4. What is the DSH at 100%?

5. What is the suction pressure at 100%?

6. Is the EORL solenoid on, is it overfeeding liquid?

7. What is the OAT and how many fans are on?

8. How does the discharge superheat compare to Figure 10 on page 63.

Details to Consider: 1. The unit must be in subcool control before being able to fine-tune the charge. If the unit

does not have sufficient subcooling, it will not convert to subcool control. At 100%

load there must be a minimum of 20° of liquid line subcooling before the circuit will

allow subcooling control, therefore you may need to add charge to get to this point in

the case of severely undercharged units.

2. Verify that the circuit is not limited on a capacity limit or inhibit event. If the chiller is

inhibited on low DSH, high lift, low evaporator pressure, etc. these things may be clues

to help determine a refrigerant or oil charging issue.

3. It is hard to determine proper charge amounts while at part loads. For best charging

results the slide target should be at 100%. If there is a significant over or under charge

you may have to make adjustments to get the compressor to full load.

4. In order to maintain oil integrity, the discharge superheat needs to be greater than 20° at

a minimum. Below 20° DSH the compressor will unload. Between 20 and 22° DSH

the compressor will not load up and will be in an low discharge superheat inhibit event.

The higher the refrigerant flow, the more liquid carry over we will get from the flooded

evaporator and therefore, the lower DSH. This means to set up the refrigerant charge

correctly the compressor will need to be at l00%.

5. Typically the suction pressure will be near the low pressure hold setpoint while at full

load. You may need to sacrifice some suction pressure by removing some refrigerant to

get the discharge superheat up.

6. See note above on Evaporator Oil Return Line.

7. The lower the OAT, and the lower the saturated condensing temperature is, the more

refrigerant flow there will be and the possibility of more liquid carry over from the

evaporator.

8. Use the Discharge Superheat vs, Lift pressure chart on the following page to verify

charge. For a given lift, superheat above the curve indicates low charge, below

indicates high charge.

Summary: At 100% slide position, in subcool control, the DSH should be as high as possible with

suction pressure at a operable value based on water/glycol mixture. At 100% load, in

subcool control, the DSH and suction pressure need to be balanced.

Example: Running circuit 1 at 100% slide target, with water only in the loop, set the low

evaporator pressure unload to 28psi (32°sat.) and the low evaporator pressure hold to 30psi.

Run the suction pressure at approximately 32psi at full load. This should allow room for

25-30° DSH. As a rule of thumb, as outdoor air temperature drops, it becomes more

difficult to maintain minimum DSH with a given charge amount, due to higher refrigerant

flows.

OM AGSDP-3 63

Figure 10, Discharge Superheat vs. Pressure Lift

Discharge superheat is directly related to the amount of liquid carried from the evaporator and amount

of motor heat rejected into the refrigerant.

Higher pressure ratios will result in higher discharge superheats.

More liquid carry over will result in lower discharge superheats, less liquid carry over will result in

higher discharge superheats.

More liquid carry over will occur when:

1. The refrigerant circuit is overcharged.

2. Excessive oil is in the evaporator.

3. Mass flow rate of compressor is increased.

4. Oil return solenoid is energized or leaking (more liquid inj than oil return).

5. Evaporator tubes fouled or are plugged.

Discharge Superheat vs. Pressure Lift

15

20

25

30

35

40

45

50

50.0 70.0 90.0 110.0 130.0 150.0 170.0 190.0 210.0 230.0 250.0

Pressure Lift(Discharge Pressure - Suction Pressure)

Dis

ch

arg

e S

up

erh

ea

t (F

)

34/44

44/54

54/64

64/74

64 OM AGSDP-3

BAS Interface

Connection to Chiller

Connection to the chiller for all Building Automatic Systems (BAS) protocols will be at the

unit controller. An interface card, depending on the protocol being used, will have been

factory installed in the unit controller if so ordered, or it can be field installed.

Protocols Supported

Table 29, Standard Protocol Data

Protocol Physical Layer Data Rate Controller Other

BACnet/IP Ethernet 10 Base-T 10 Megabits/sec Color graphics SBC Reference ED 15057:

BACnet PICS

BACnet MSTP RS485 (TBD) pCO2 Unit Controller

Reference ED 15057: BACnet PICS

LonTalk FTT-10A 78kbits/sec pCO2 Unit Controller

LONMARK Chiller Functional Profile

Modbus RTU RS-485 (TBD) pCO2 Unit Controller

Unit Controller Setting

Set Unit Setpoint, menu 1 is set to Network, menu 12 is set to the protocol being used.

Modbus - When selected, the ident number and baud can also be changed to suit the

application.

LONWORKS – When selected, the ident number and baud rate setpoints are not available.

Baud rate is locked at 4800.

BACnet – When selected, the ident number and baud rate setpoints are not available. Baud

rate is locked at 19200.

The factory-installed kits on the MicroTech II controller are as follows:

• BACnet Kit P/N 350147404: BACnet/IP, BACnet MS/TP, or BACnet Ethernet

• LONWORKS Kit P/N 350147401: LonTalk (FTT-10A)

• Modbus RTU

The following functions are available through the BAS where possible. Exact capabilities

may vary depending on the protocol in use.

• Enable/Disable chiller operation by setting the Unit Enable setpoint.

• Select the operating mode by setting the Unit Mode setpoint.

• Set the Cool LWT and Ice LWT setpoints.

• 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.

Reference McQuay documents ED 15057 and ED 15062 may be obtained from the local

McQuay sales office, from the local McQuay Factory Serevice office, or from the McQuay

Technical Response Center, located in Staunton, Virginia (540-248-0711).

OM AGSDP-3 65

Field Wiring Diagram

Figure 11, Typical Field Wiring Diagram

LABEL DWG. 330803901 REV. 0D

TO COMPRESSOR(S)

AND FAN MOTORS

DISCONNECT(BY OTHERS)

3 PHASE

POWER

SUPPLY

GND LUG

UNIT MAINTERMINAL BLOCK

FUSED CONTROL

CIRCUIT TRANSFORMER

120 VAC

NOTE: ALL FIELD WIRING TO BE

INSTALLED AS NEC CLASS 1

WIRING SYSTEM WITH CONDUCTOR

RATED 600 VOLTS

TB1(115 VAC)

TB1-2

1

82

2CHW PUMP RELAY #1

(BY OTHERS)120 VAC 1.0 AMP MAX

N

120 VAC

85

2CHW PUMP RELAY #2

(BY OTHERS)120 VAC 1.0 AMP MAX

N

120 VAC

81

75

24 VAC

ALARM BELL RELAY

FACTORY SUPPLIED ALARMFIELD WIRED

ALARM BELL

OPTION

TB1(24 VAC OR 30 VDC)

71

72

69

60

67

NOR. OPEN PUMP AUX.

CONTACTS (OPTIONAL)

CHW FLOW SWITCH---MANDATORY–-

(BY OTHERS)

PE

PE

IF REMOTE STOP CONTROLIS USED, REMOVE LEAD 897FROM TERM. 40 TO 53.

89760

66

AUTO

ON

OFF

MANUAL

60

68

AUTO

ON

OFF

MANUAL

REMOTE STOPSWITCH

(BY OTHERS)

ICE MODESWITCH

(BY OTHERS)

TIMECLOCK

70

4-20MA FOR

CHW RESET

(BY OTHERS)

4-20MA FOR

DEMAND LIMIT

(BY OTHERS)

-

+

-

+

GND

*COMMUNICATION

PORT

J11Rx-/Tx-

Rx-/Tx-

GND

CONTROLLER

BLACK

WHITE

GREEN

24 VAC

24 VAC

(800) 432-1342 • www.mcquay.com OM AGSDP-3 (1/09)

This document contains the most current product information as of this printing. For the most up-to-date product information, please go to www.mcquay.com. All McQuay equipment is sold pursuant to McQuay's Standard Terms and Conditions of Sale and Limited Product Warranty.

All McQuay equipment is sold pursuant to McQuay’s Standard Terms and Conditions of Sale and Limited Product Warranty. Consult your local McQuay Representative for warranty details. Refer to form 933-430285Y-00-A (09/08). To find your local representative, go to www.mcquay.com

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