McQuay AGS 230A, AGS 206A, AGS 206B, AGS 411A, AGS 411B Operation Manual

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Operation Manual

OM AGSB-5

GeneSys

™

Air-Cooled Screw Compressor Chiller

AGS 230A/B through AGS 475A/B, 60 Hertz AGS 206A/B through AGS 411A/B, 50 Hertz

Software Version AGSU30101H

Group: Chiller Part Number: 331373201 Date: June 2005

Supersedes: OM AGSB-4

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............................................26

Unit Mode Selection..............................27

Evaporator Pump State Control.............30

Evaporator Heater Control ....................30

Leaving Water Temperature (LWT) Reset

...............................................................30

Manufactured in an ISO Certified facility

ALARMS AND EVENTS ................33

Alarm and Event Logging.....................35

USING THE CONTROLLER.........37

Security..................................................39

Entering Passwords ...............................39

Editing Setpoints ...................................39

Clearing Alarms.....................................39

Unit Controller Menus...........................40

Screen Definitions.................................41

SET Screen Definitions.........................43

Circuit Controller Menus.......................47

Screen Definitions.................................47

SEQUENCE OF OPERATION.......52

START-UP AND SHUTDOWN......54

Expansion Valve Operation...................55

Extended (Seasonal) Shutdown.............57

Evaporator Freeze Protection................58

Operating Limits: ..................................59

REFRIGERANT CHARGING........60

BAS INTERFACE............................63

FIELD WIRING DIAGRAM ..........64

Unit controllers are LONMARK

certified with the optional

communications module.

LONWORKS

"McQuay" is a registered trademark of McQuay International, Information covers the McQuay International products at the time of

publication and we reserve the rig ht to m ak e changes in desi gn an d const ruction at anytime without notice.

®™ The following are trademarks or registered trademarks of their respective companies: BACnet from ASHRAE; L

Corporation; GeneS ys, McQu ay and MicroTech II from McQuay International.

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ONMARK and LONWORKS from Echelon

This manual provides setup, operating, and troubleshooting information for the McQuay MicroTech ΙΙ™ controller for Model AGS-B vintage, air-cooled rotary screw compressor chillers. Please refer to the current version of IMM AGSB (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 AGSU30101H. 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 3.56

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 be performed only 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% (noncondensing).

OM AGSB-5 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 − calcula ted subco oling for liqu id 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 protocols for all BAS manufacturers-simplified with McQuay’s Protocol Selectability™ 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.

4 OM AGSB-5

General Description

The AGS MicroTech ΙΙ distributed control system consists of multiple microprocessorbased 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 contro l pan el th at 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

BACnet MS/TP BACnet IP BACnet Ethernet LonTalk

Chiller A

RS485/LON/Ethernet

Solid State

Starter

EXV

OM AGSB-5 5

Unit

Controller

4x20 LCD

RS485

pLAN

(future)

Circuit #1

Controller

4x20 LCD

Other Circuit Controllers

(future)

Component Description

Unit and Circuit Controller Descri ption

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 min imum an d maxi mum set point s. 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

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EvapRecTimer

The evaporator recirculation timer establishes the length of time the chilled water pump will run after the controller receives an enable signal and the Wait for Flow timer time out. This period 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 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 unloading 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.

OM AGSB-5 7

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.

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.

8 OM AGSB-5

Each chiller has one unit controller and a cir cuit 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

Key-to-Screen Pathway

Red Alarm Light

MENU Key

Air Conditioni ng

ALARM

VIEW

< <

ARROW Keys (4)

SET

ENTER Key & Green Ru n Li ght

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.

OM AGSB-5 9

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 37.

• Screen Content, details the menu screen content and how to use them, see page 41.

Circuit Controller

Inputs/Outputs

Table 1, Analog Inputs

# Description Signal Source Range

1 Evaporator Pressure 0.5 - 4.5 VDC (NOTE) 2 Condenser Pressure 0.5 - 4.5 VDC (NOTE) 3 Liquid Pressure 0.5 - 4.5 VDC (NOTE) 4 Suction Temperature Thermistor (10k@25°C) 5 Discharge Temperature Thermistor (10k@25°C) 6 Liquid Temperature Thermistor (10k@25°C) -58 to 212°F 7 Slide Load Indicator 4 to 20 mA 8 Open

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

0 to 132 psi

3.6 to 410 psi

-58°F to 212°F

-58° to 212°F

0 to 100%

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)

Oil Differential

Pressure Switch 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

0 VAC (Fault) 24 VAC (No Fault)

10 OM AGSB-5

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 3 M2 Contactor (fan 2) Contactor Coil Fans off Fans on 120 4 M3 Contactor (fan 3) Contactor Coil Fans off Fans on 120 5 M4 Contactor (fan 4) Contactor Coil Fans off Fans on 120 6 M5 Contactor (fan 5 & 6) Contactor Coil Fans off Fans on 120 7 Load/Unload Pulse S ol enoi d Hold l oad sl i de 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

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.

OM AGSB-5 11

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 2 Up Deadband 8.0 1.0-20.0 oF M Stage 3 Up Deadband 10.0 1.0-20.0 oF M Stage 4 Up Deadband 12.0 1.0-20.0 oF M Stage 1 Down Deadband 8.0 1.0-20.0 oF M Stage 2 Down Deadband 7.0 1.0-20.0 oF M Stage 3 Down Deadband 6.0 1.0-20.0 oF M Stage 4 Down Deadband 5.0 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 Forced FanTrol™ 2 Forced FanTrol™ 3

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

1 1-8 M 2 1-8 M 3 1-8 M

12 OM AGSB-5

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 I ce 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

205 220

235

NOTE: See the Physical Data tables in IMM AGSB-60 for unit compressor sizes.

mA Low mA High

4.94 14.6

4.62 17.0

4.32 19.4

OM AGSB-5 13

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.

14 OM AGSB-5

Compressor Control

Multiple Compressor Staging

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

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.

the start, or stop, is to occur.

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.

OM AGSB-5 15

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 tr ig ger 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.

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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 22

If the compressor is running above minimum load capacity, and the discharge superheat is less than 20 adjusted down 2% every 5 seconds, as long as the superheat remains below 20

F, then the compressor will begin reducing capacity. The slide target will be

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

following:

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:

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• 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 pumpdown to this pressure and shut off. When the compressor has completed the service pumpdown, the setpo int is re set 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

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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, 0.5 condenser temperature target setpoint. This will allow the VFD to slowly bring the saturated condenser temperature back down.

F is subtracted from the VFD target until it is equal to the saturated

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:

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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

> 75oF Forced FanTrol 1 SP > 90oF Forced FanTrol 2 SP

> 105oF Forced FanTrol 3 SP

Staging Down

FanTrol Stage At Start

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.

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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 mini mum and maximu m capa city. The mini mum and maximu m value s vary l inear ly wit h slide position, defining a new EXV control range for every change in slide position.

Table 9, EXV Range

EXV Slide %

Min 0 250 250 250

Max 0 3000 3000 3000

Min 100 870 1080 1300

Max 100 3400 4200 5000

205mm 220mm 235mm

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%

Compressor Size

EXV Control Range

EXV

Steps

Max EXV

@ 0%

Min EXV @ 100%

Min EXV

@ 0%

Slide Position (%)

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 e qual to, or grea ter tha n, 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.

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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, th e ba s e 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 EXV may transition from subcool control back to pressure control. This occurs when 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.

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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 28.

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.

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Unit Controller

Inputs/Outputs

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

Table 10, Unit Analog Inputs

# Description Signal Source Range

1 Outdoor Ambient Temperature Thermistor (10k@25°C) 2 Demand Limit 4-20 mA Current 25-100 %RLA

3 Chilled Water Reset 4-20 mA Current 4 Leaving Evaporator Water Temperature Thermistor (10k@25°C)

5 Entering Evaporator Water Temperature Thermistor (10k@25°C)

The following parameters are digital inputs to this controller. They are used internally as needed and are sent to the correct pLAN addresses for use by other controllers or displays. 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

-58°F to 212°F

0 to10 degrees 60°F max inlet

-58°F to 212°F

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 Evaporat or Water Pump 1 Pump Contactor Pump OFF Pump ON 3 Evaporat or Water Pump 2 Pump Contactor Pump OFF Pump ON 4 E vap Heat ers 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

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Table 13, Unit Controller Setpoints

Description Default Range PW Unit

Unit Enable OFF OFF, ON O Unit Mode COOL Control source SWITCHES SWITCHES, KEYPAD, NETWORK O Available Modes COOL Cool LWT

Ice LWT Startup Delta-T 10.0 degF 0.0 to 10.0 degF O Stop Delta-T 3.0 degF 0.0 to 3.0 degF O Stage Delta-T 2.0 degF 0.0 to 3.0 degF O Max Pulldown 0.5 degF/min 0.1-5.0 degF/min M Evap Recirculate 30 sec 0 to 300 sec M Evap pump control #1 Only #1 Only, #2 Only, Auto M LWT Reset Type NONE NONE, RETURN, 4-20mA, OAT M Max Reset 0.0 degF 0.0 to 20.0 degF M Start Reset Delta-T 10. 0 degF 0.0 to 20.0 degF M Soft Load On On, Off M Begin Capacity Limit 40% 20-100% M Soft Load Ramp 20 min. 1-60 min. M Demand Limit no No,yes M Low Ambient Lock Ice Time Dlay 12 hrs. 1-23 hrs. M Clear ice Timer No No, Yes M Display Units Language English English M

BAS Protocol NONE Ident number 1 0=200 M

Baud Rate 19200 1200, 2400, 4800, 9600, 19200 M

Compressors

Sequence # Cir 1 1 1-3 M Sequence # Cir 2 1 1-3 M Sequence # Cir 3 1 1-3 M Max Compressors On 3 1-3 M Start-start timer 20 min 15-60 minutes M Stop-start timer 5 min 3-20 minutes M Number of Compressors 2 2-3 M Pumpdown pressure 25.0 psi 10.0-30.0 psi M Pumpdown time limit 120 sec 0-180 sec M Light Load Stage Down Point 255 20-50% Slide M Light Load Stage Down Delay 3 min. 3-30 min. M Stage Up Delay 5 min. 0-60 min. M

Alarms

Low Evap Pressure-Unload 28 psi 0 to 45 psi M Low Evap Pressure-Hold 30 psi 0 to 45 psi M Low Oil Level Delay 120 s ec 10-180 sec M High Oil Press Diff Delay 15 sec 0-60 sec M Min Lift Delay 30 s ec 10-120 sec M Low Subcooling 5 degF 0 to 10 degF M High Discharge Temperature Evaporator Water Freeze Evap Flow Proof 3 sec 3 to 120 sec M High Lift Delay 5 sec. 0-30 sec. M

Sensors

OAT sensor offset 0 degF -5.0 to 5.0 degF M LWT sensor offset 0 degF -5.0 to 5.0 degF M EWT sensor offset 0 degF -5. 0 t o 5.0 degF M

44. 0°F 25.0(40.0) to 60.0 °F

25.0°F 20.0 to 38.0°F

55°F

°F, psi °F, psi

200° F

36 °F 15(34) to 42 °F

COOL, COOL w/Glycol,

ICE w/Glycol, TEST

COOL, COOL w/Glycol, COOL/ICE

w/Glycol, ICE w/Glycol, TEST

35-70 degF M

NONE, BACnet, LonWorks,

CAREL, MODBUS, N2

150 to 200 F M

M O

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

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Automatic Adjust ed Limits

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

Table 14, Evaporator Leaving Water Temperature Range

Mode Range

Unit Mode = Cool Unit Mode = Cool w/Glycol, Ice, Ice w/ Glycol

Table 15, Evaporator Freeze Temperature Range

Mode Range

Unit Mode = Cool Unit Mode = Cool w/Glycol, Ice, Ice w/ Glycol

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

40 to 60°F 20 to 60°F

34 to 42°F 15 to 42°F

Table 18, Low Ambient Lockout Temperature Range

Fan VFD Range

Fan VFD = N Fan VFD = Y

35– 60°F

0 – 60°F

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. T he 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 19 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.

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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 19, Unit Enable Settings

Unit On/Off

Switch

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

Control Source

Setpoint

Remote

Stop Switch

Key-pad

Entry

BAS

Request

Unit

Enable

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

OM AGSB-5 27

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 (pCO

), 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 20, Unit Mode Settings

Control Source

Setpoint

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

Remote

ICE Mode

Switch

Keypad Entry

BAS

Request

Available Modes

Setpoint

Resultant Unit

Mode

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.

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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.

“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.”

OM AGSB-5 29

Evaporator Pump State Control

The state-transition diagram shown below controls operation of the evaporator pump.

Figure 4, Evaporator Pump Control

Power ON

[Unit State=OFF LWT > Freeze sp]

[OAT low All Comp State=OFF LWT>70 F]

AND

RUN

AND

OFF

[Unit LWT > Freeze sp]

[OAT low All CompState=OFF LWT>70 F]

Flow OK for Evap Recirc Time

State=

OFF

AND

[Unit State = AUTO NOT [OAT low AND LWT > 40 F

LWT < Freeze

AND

sp – 1.0 F

START

One of two pumps can be automatically selected based on run hours. The run-hour counters are not visible. When in Auto, the pump with the least hours will start. The options are # 1 only, #2 only, Auto.

The pump output used will be determined by the Evap Pump Control setpoint. This setting allows the operator to select either pump #1 or pump #2. The selected output will be ON if the Evap State is set to START or RUN. Both outputs will be OFF if the Evap State is set to OFF.

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

degrees F. The output is turned off

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

30 OM AGSB-5

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 – LW T (Evap Delta-T) varies from the Start Reset Delta-T setpoint to 0.

Figure 5, Return Water Reset Conditions

Return Reset

Cool LWT+Max Reset

(54)

Active

LWT

(

Max Reset

(10)

Cool LWT Set-Point

(44)

Start Reset Delta T

Evap Delta T (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:

1. Cool LWT setpoint

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 6, External Reset Conditions

LWT Reset (Cool mode)

(temperatures are examples only)

(54.0°F)

Max Reset Delta T

(10.0°F)

Cool LWT Set-Point

(44.0°F)

OM AGSB-5 31

0 ma

4 ma

20 ma

Reset Type – Outside Air Temperature (OAT)

The Active Leaving Water setpoint is reset based on the outdoor ambient temperature. Parameters used:

1. Cool LWT setpoint

2. Max Reset setpoint

3. OAT

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 7, Outside Air Reset

T Reset

Cool LWT+Max Reset

(54)

ctive

LWT

(

Max Reset

(10)

Cool LWT Set-Point

(44)

OAT (oF)

32 OM AGSB-5

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 21, Unit Stop Alarms

Description Occurs When: Action Taken

No Evaporator Water Flow (NOTE) Evaporator Freeze Protect Evap LWT goes below evap freeze protect setpoint Rapid Stop Leaving Evaporator Water Temperature Sensor Fault Outside Air Temperature Sensor Fault

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.

Evap Pump State = RUN AND Evap Flow Digital Input

= No Flow for time > Flow Proof SP

Sensor shorted or open Rapid Stop Sensor shorted or open Normal Shutdown

Rapid Stop

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 22, 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.

OM AGSB-5 33

Table 23, Circuit Stop Alarms

Description Occurs When: Action Taken

No Pressure at Start

Low Evaporator Pressure

High Lift Pressure

Mechanical High Pressure Digital Input 6 = Open Rapid Stop Below Minimum Lift Pressure High Discharge Temperature Temp > High Discharge Temperature SP Rapid St op

Low Oil Level

High Oil Pressure Difference

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 Pum pdown

Liquid Line Temp. Sensor Fault Sensor shorted or open Pumpdown

Slide Position Sensor Fault Sensor shorted or open Pumpdow n

Evap or Cond pressure< 7 psi when Compressor Start

Requested

[Freezestat trip OR Evaporator Press < 0 psi OR Low

Pressure Sw Open] AND Compressor State = Run

Cond Sat Temp > Max Sat Cond Value for a period

exceeding the setting of the High lift Delay timer

Cond Press < Min Sat Cond Value for time > Min Lift

Delay SP

DI9 = Open for Time greater than Low Oil Level Delay

+ the Low Oil Level Event has occurred in the past

hour

Digital Input 5 = Open for time greater than High

Press Diff Delay SP

Start Aborted,

Circuit Locked Out

on Manual Reset

Rapid Stop Rapid Stop

Pumpdown

Rapid Stop

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 Cu rrent 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 clearedvia 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 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.

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

34 OM AGSB-5

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 24, Circuit Events

Description Occurs When: Action Reset

Low Evaporator Pressure - Hold Low Evaporator Pressure - Unload High Lift Pressure

- Hold High Lift Pressure

- Unload

Subcooling Low

Discharge Superheat Low

Oil Level Low

Failed Pumpdown Suction Temp.

Sensor Fault VFD Fault VFD option enabled and Digital Input 4 = Open Pumpdown Automatic Power Loss While Running

Pressure < Low Evap Pressure - Hold SP

Pressure < Low Evap Pressure -Unload SP Unload

Pressure > High Sat Cond - Hold Value

Pressure > High Sat Cond - Unload Value Unload

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

EXV Control = Pressure Control AND Disc SH

< Min SH Setpoint for 10 minutes

DI9 = Open for Time greater than Low Oil Level

Delay AND more than one hour since last

Circuit state = pumpdown for more than the

Sensor shorted or open None

Circuit controller is powered up after losing

power while compressor was running

F) for longer than 5 min.

occurrence

Pumpdown Time SP

Inhibit

None

Pumpdown

and stop

Rapid stop Comp state = off

Stop N/A

Delay start of

compressor

Evap Press rises above

(SP + 2 psi)

Evap Press rises above

(Hold SP + 2 psi)

Cond Press drops below

(Hold Value – 10

Cond Press drops below

(Unload Value – 10

Subcool > setpoint or

Comp state = off

Sensor Problem

corrected

N/A

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.

OM AGSB-5 35

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.

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 40.

36 OM AGSB-5

Using the Controller

ght

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 8, Display (in MENU mode) and Keypad Layout

Air Conditioni ng

Key to Screen Pathway

Left Arrow Key and

Red Alarm Light

ALARM

VIEW

< <

SET

ARROW Keys (4)

MENU Key

ENTER Key an

Green Comp.

Run Li

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 8 and the SCROLL mode as shown in Figure 9. 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.

OM AGSB-5 37

When in the MENU mode (as shown in Figure 8), 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 8.

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 25 on page 40). From there, the four ARROW keys can be used to scroll up, down, or across to any other menu.

Figure 9, Display (in SCROLL Mode) and Keypad Layout

Air Conditioni ng

MENU Key

VIEW UNIT ST ATUS Unit = COOL Compr. #1/#2=OFF/OFF Evap Pump = RUN

ARROW Keys (4)

ENTER Key

Pressi ng the E NTER key c hange s the functi on of t he ARROW keys to t he edit ing fun ction as shown below:

LEFT key, Default RIGHT key, Cancel

, changes a value to the factory-set default value.

, cancels any change made to a value and returns to the original

setting. UP key, Increment DOWN key, Decrement

, increases the value of the setting.

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 8).

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.

38 OM AGSB-5

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 AGSB-5 39

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 25. A description of each menu begins on page 41.

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 25, Unit Controller Menu S tructure

VIEW MENUS

VIEW UNIT

STATUS

(1) VIEW UNIT

STATUS

(2) VIEW UNIT

STATUS

(3) VIEW UNIT

STATUS

(4)

Right half of

table

continued

from above

VIEW

UNIT

TEMP

(2)

VIEW

UNIT

TEMP

(2)

VIEW

CIR #1

(1)

VIEW

CIR #1

(2)

ALARM MENUS SET MENUS

EVENT

LOG

(1)



EVENT

LOG

(25)

VIEW

CIR #2

(1)

VIEW

CIR #2

(2)

ALARM

LOG

(1)

ALARM

ACTIVE

(1)

 

ALARM

LOG

(25)

ALARM

ACTIVE

(n)

VIEW

CIR #3

(1)

VIEW

CIR #3

(2)

VIEW

REFRG

CIR #1

(1)

VIEW

REFRG

CIR #1

(2)

  

VIEW

REFRG

CIR #1

(5)

Continued

SET UNIT

SPs (1)

SET UNIT

SPs

(2)

SET UNIT

SPs

(3)

SET UNIT

SPs

(4)

SET UNIT

SPs

(5)

SET UNIT

SPs

(6)

COMP SP



SET UNIT

SPs

(to 13)

VIEW

REFRG

CIR #2

(1)

VIEW

REFRG

CIR #2

(2)

VIEW

REFRG

CIR #3

(1)

VIEW

REFRG

CIR #3

(2)

VIEW

FANS

On-Off

(1)

VIEW

FANS

VFD

(2)

Right half of

table

VIEW

REFRG

CIR #2

(5)

SET

(1)

SET

(2)

SET

(3)

VIEW

REFRG

CIR #3

(5)

SET

ALARM

LMTS (1)

SET

ALARM

LMTS

(2)

SET

ALARM

LMTS

(3)

SET

ALARM

LMTS

(4)

SET

ALARM

LMTS

(5)

continued

SET

SENSOR

OFFSET

below

TEST

UNIT

40 OM AGSB-5

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

VIEW UNIT STATUS (2) 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.

VIEW UNIT STATUS (3) Unit Capacity=xxx.x% Ice Delay= XXh XXm

Ice delay will be visible only when unit mode is Ice.

VIEW UNIT STATUS (4)

1234 D.O. 0100 D.I. 1110

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.

OM AGSB-5 41

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.

VIEW CIR N STATUS(2) 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

VIEW REFRG CIR N (3) Suct Temp = XXX.X °F Disc Temp = XXX.X °F Liq Temp = XXX.X °F

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

42 OM AGSB-5

VIEW REFRG CIR N (5) 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 AGSB-5 43

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 1 0 degrees. F., the range i s 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 30 for reset options.

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

See page 17 for soft load and demand limit options.

44 OM AGSB-5

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)

CLOCK

dd/mmm/yyyy

hh:mm:ss

SET UNIT SPs (11) 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 (12) Protocol= Ident Number= Baud Rate=

SET UNIT SPs (13) Enter Password:0000

Active Password Level:none

Compressor (Circuit) Setpoints

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

SET COMP SPs (2) Max Comprs On = X Start-Start = XXmin Stop-Start = XXmin

OM AGSB-5 45

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

SET ALARM LIMITS (3) MinLiftDel= XXX sec

Low Subcool= XX.X°F High Disc Temp=XXX°F

SET ALARM LIMTIS (4) Highlift Delay=XXsec

Evap Freeze= XX.X°F Evap Flow Proof=XXX

SET SENSOR OFFSET OAT= XX.X°F Evap LWT= XX.X°F Evap EWT= XX.X°F

46 OM AGSB-5

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 37 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 26, Circuit Controller Screen Matrix

"TEST"

SCREENS

TEST

COMP

(1)

TEST

COMP

(2)

TEST

COMP

(3)

VIEW

UNIT (1)

VIEW

UNIT (2)

"VIEW" SCREENS "SET" SCREENS VIEW

CIR

(1)

VIEW

CIR (2)

VIEW

CIR (3)

VIEW

CIR (4)

VIEW

CIR (5)

VIEW

CIR (6)

VIEW

REFRG

(1)

VIEW

REFRG

(2)

VIEW

REFRG

(3)

VIEW

REFRG

(4)



VIEW

REFRG

VIEW FANS

(1)

VIEW FANS

(2)

SET

COMP

SPs SET

COMP

SPs (2)

SET

COMP

SPs (3)

SET

EXV SPs

(1)

SET

EXV SPs

(2)

SET

FANS

(1)

SET

FANS

(2)

SET

FANS(3)

SET

FANS

(4)



SET

FANS

(6)

SET

SENSOR

OFFSETS

(1)

SET

SENSOR

OFFSETS

(2)

SET

SENSOR

OFFSETS

(3)

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 AGSB-5 47

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

VIEW CIR STATUS (2) Hours = XXXXX Starts = XXXXX

VIEW CIR STATUS (3)

Digital Outputs

Output Number

12345678910 0000000000

The digital outputs in menu 3 and 4 and the analog outputs in menu 5 are defined in Table 2 and Table 4 beginning on page 10. “0”= Off, “1”= ON.

Output Status

VIEW CIR STATUS (4)

Digital Outputs 11 12 13 000

VIEW CIR STATUS (5)

Analog Outputs

(volts X 100)

1=XXXX 3=XXXX

VIEW CIR STATUS (6)

Digital Inputs 123456789 000000000

VIEW REFRIGERANT (1) Evap Press=XXX.X psi Cond Press=XXX.X psi Liq Press= XXX.X psi

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

48 OM AGSB-5

VIEW REFRIGERANT (3) Suct Temp = XXX.X °F Disc Temp = XXX.X °F Liq Temp = XXX.X °F

VIEW REFRIGERANT (4) Suct SH = XXX.X °F Disc SH= XXX.X °F Liquid SC= XXX.X °F

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

VIEW REFRIGERANT (6) MaxCondSatT=XXX.X°F

EXV Control=Pressure

VIEW REFRIGERANT (7) 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.

OM AGSB-5 49

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.XoF

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%

50 OM AGSB-5

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

XX X

Sensor Offsets

SET SENSOR OFFSET (1) Evap Press= XX.X psi Cond Press= XX.X psi Liq Press= XX.X psi

SET SENSOR OFFSET (2) Suct Temp= X.X F Disch Temp= X.X F Liq Temp= X.X F

SET SENSOR OFFSET (3) 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 AGSB-5 51

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.

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.

CAUTION

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.

52 OM AGSB-5

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 FanTrol Condenser Fan Control

The first condenser fan stage will be started along with the first compressor to provide initial condenser head pressure control. The MicroTech II controller will activate the remaining condenser fans as needed to maintain proper condenser pressure. The MicroTech II controller continuously monitors the condenser minus evaporator lift pressure and will adjust the number of operating condenser fans as required. 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 AGSB-5 53

Figure 10, AGS Piping Schematic

AIR

FLOW

SIGHT

GLASS

SOLENOID

VALVE

OIL

RETURN

TO RE AR OF

COMPRESSOR

SUCTION

STRAINER

SIGHT

GLASS

SCHRADER

BUTTERFLY VALVE

(OPTION)

BALL

VALVE

CHARGING

VALVE

DISCHARGE

TUBING

WATER OUT

RELIEF VALVE (EVAP SHELL )

WATER IN

SCHRADER

VALVE

ANGLE

VALVE

CHARGING

VALVE

OIL

SEPARATOR

AIR

FLOW

EXPANSION

VALVE

CHECK

VALVE

DISCHARGE

TUBING

CONDENSER

ASSEMBLY

RELIEF

VALVE

AIR

FLOW

CHARGING VA LVE

LIQUID SHUT-OFF VALVE

FILTER DRIER

SCHRADER VALVE

SIGHT GLASS

LIQUID

TUBING

CONDENSER

ASSEMBLY

SCHRADER (EACH DIS CH HEADER)

AIR

FLOW

Start-up and Shutdown

McQuayService personnel or factory authorized service agency

must perform initial start-up in order to activate warranty.

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.

NOTICE

CAUTION

4. Start the auxiliary equipment for the installation by turning on the time clock, and/or

remote on/off switch, and chilled water pump.

54 OM AGSB-5

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 AGSB-5 55

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 20

F 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 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 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.

56 OM AGSB-5

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 shutdown occurs, or will continue through periods below freezing ambient

temperatures, protect the chiller vessel from freezing. See Freeze-Up Protection in

this manual for 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 equi pped) as well as the liq uid l ine 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 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 imm ersion heaters if the system is drained of

fluids as this can cause the heaters to burn out.

used in the system, drain all water from the unit evaporator and chilled

Start-up A fter 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 tig ht for good elec tr ic al cont ac t.

2. Check the voltage of the unit power supply and see that it is within the ±10% toler ance 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 AGSB-5 57

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 12 on page 64.

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.

58 OM AGSB-5

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.

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 27, Freeze Protection

Temperature

°F (°C)

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 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.

Ethylene Glycol Propylene Glycol Ethylene Glycol Propylene Glycol

For Freeze Protection For Burst Protection

Percent Volume Glycol Concentration Required

°F lower than the expected lowest ambient temperature. Inhibitor levels

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 AGSB-5 59

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.

60 OM AGSB-5

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 11 on page 62.

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 AGSB-5 61

Figure 11, Discharge Superheat vs. Pressure Lift

Discharge Superheat vs. Pressure Lift

34/44

Discharge S uperheat (F)

44/54 54/64 64/74

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)

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.

62 OM AGSB-5

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 28, Standard Protocol Data

BACnet®/IP

BACnet MSTP RS485 (TBD)

ModbusRTU RS-485 (TBD)

NOTE: For additional information on the protocol data available through the BACnet or LonTalk communications modules, reference ED 15062, MicroTech II Chiller Unit

Controller Protocol Information.

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:

Protocol Physical Layer Data Rate Controller Other

Reference ED 15057:

BACnet PICS

Reference ED 15057:

BACnet PICS

LONMARK® Chiller

Functional Profile

LonTalk®

Ethernet 10 Base-T 10 Megabits/sec Color graphics SBC

pCO

Unit Controller

FTT-10A 78kbits/sec

pCO

Unit Controller

pCO

Unit Controller

• 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 McQuayService office, or from the McQuay Technical Response Center, located in Staunton, Virginia (540-248-0711).

The above are trademarks or registered trademarks of their respective companies: BACnet from the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., LonTalk, LONMARK and LONWORKS from Echelon Corporation, and Modbus and ModbusRTU from Schneider Electric.

OM AGSB-5 63

Field Wiring Diagram

UNIT MAIN

Figure 12, Typical Field Wiring Diagram

DISCONNECT (BY OTHERS)

3 PHASE

POWER

SUPPLY

FUSED CONTROL

CIRCUIT TRANSFORMER

TERMINAL BLOCK

GND LUG

TO COMPRESSOR(S)

AND FAN MOTORS

NOTE: ALL FIELD WIRING TO BE INSTALLED AS NEC CLASS 1 WIRING SYSTEM WITH CONDUCTOR RATED 600 VOLTS

ALARM BELL OPTION

REMOTE STOP

SWITCH

(BY OTHERS)

ICE MODE

SWITCH

(BY OTHERS)

FACTORY SUPPLIED ALARM

CHW FLOW SWITCH

---MANDATORY–(BY OTHERS)

FIELD WIRED

ALARM BELL RELAY

TIME

CLOCK

NOR. OPEN PUMP AUX. CONTACTS (OPTIONAL)

4-20MA FOR CHW RESET

(BY OTHERS)

4-20MA FOR

DEMAND LIMIT

(BY OTHERS)

UTO

MANUAL

UTO

MANUAL

CHW PUMP RELAY #1

(BY OTHERS)

120 VAC 1.0 AMP MAX

CHW PUMP RELAY #2

(BY OTHERS)

120 VAC 1.0 AMP MAX

OFF

120 VAC

(24 VAC OR 30 VDC)

24 VAC

TB1

(115 VAC)

82 2

85 2

TB1

69 70

TB1-2

120 VAC

24 VAC

897

CONTROLLER

Rx-/Tx-

GND

IF REMOTE STOP CONTROL IS USED, REMOVE LEAD 897 FROM TERM. 40 TO 53.

J11

BLACK

*COMMUNICATIO

GND

WHITE

GREEN

PORT

LABEL DWG. 330803901 REV. 0D

64 OM AGSB-5

This document contains the most current product information as of this printing. For the most up-todate product information, please go to www.mcquay.com.

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