McQuay WGS 130AA Installation Manual

Operating Manual

Group: Chiller Part Number: 330599503 Effective: October 2004 Supersedes: OM WGS

Water-Cooled Screw Compressor Chillers

WGS 130AW To WGS 190AW, Packaged Water-Cooled Chiller WGS 130AA To WGS 190AA, Chiller with Remote Condenser

120 to 200 Tons, 420 to 700 kW

R-134a, 60 Hz Software Version WGSD30101C

OM WGS-1

Table of Contents

Introduction........................................3

General Description .....................................3

Nomenclature...............................................3

Definitions...........................................4

Wiring Diagrams................................8

Control Panel Layout......................10

MicroTech II Controller..............13

System Arch itecture ...................................13

General Description ...................................14

Sequence of Operation ....................16

Start-Up and Shutdown...................22

Pre Start-up ................................................22

Start-up.......................................................22

Weekend or Temporary Shutdown.............23

Start-up after Temporary Shutdown...........23

Extended Shutdown....................................23

Start-up after Extended Shutdown..............23

Unit Controller.................................27

Unit Inputs/Outputs....................................27

Unit Setpoints.............................................27

Circuit Controller............................30

Circuit Inputs and Outputs .........................30

Circuit Setpoint Table ................................31

Alarms, W arnings, Events...............32

Stop Alarms (Shutdown)............................32

Events (Limit)............................................34

Unit Controller Functions...............35

Unit Enable ................................................36

Unit Mode Selection ..................................37

Unit States..................................................38

Evaporator Pump Control...........................39

Leaving Water Temperature (LWT) Reset..40

Planned Unit Capacity Overrides...............42

Condenser Pump and Tower Control..........43

Cooling Tower Control...............................44

Evaporative Condenser Control.................46

Circuit Controller Functions.......... 48

Refrigerant Calculations.............................48

Compressor Control...................................49

Internal Capacity Overrides........................52

Slide Positioning ........................................53

Expansion Valve Control............................55

Oil Heater Control......................................59

Starter Communications.............................59

Condenser Fan Control...............................61

Digital Output Control................................62

Using the Controller...................................63

Security ......................................................65

Entering Passwords....................................65

Editing Setpoints........................................65

Clearing Alarm s..........................................65

Menu Descriptions...........................66

Unit Controller...........................................66

Circuit Controller.......................................80

Editing Review...........................................86

BAS Interface...................................87

Troubleshooting Chart....................88

Troubleshooting Chart................................88

Unit controllers are LONMARK

certified with an optional L

communications module.

Illustrations and data cover McQuay International products at the time of publication and we reserve the right to

make changes in design and construction at anytime without notice.

 The following are trademarks or registered trademarks of their respective companies:

BACnet from ASHRAE; L

GeneSys, McQuay and MicroTech II from McQuay International.

2 WGS 130A to WGS 190A OM WGS-1

2004 McQuay International

ONMARK and LONWORKS from Echelon Corporation;

ONWORKS

Introduction

General Description

McQuay Model WGS water chillers are designed for indoor installations and are available with factory-mounted water-cooled condensers (Model WGS AW), or arranged for use with remote air-cooled or evaporative condensers (Model WGS AA). Each water-cooled unit (WGS-AW) is completely assembled and factory wired before factory evacuation, charging and testing. The units consist of two semi-hermetic rotary screw compressors, a two-circuit shell-and-tube evaporator, two shell-and-tube water-cooled condensers, and complete refrigerant piping.

Units manufactured for use with remote condensers (Models WGS-AA) have all refrigerant specialties factory-mounted and have two sets of connection points for refrigerant discharge and liquid lines to and from the remote condenser. Discharge valves are included

Each circuit’s liquid line components are manual liquid line shutoff valve, charging valve, filter-drier, liquid line solenoid valve, sight glass/moisture indicator, and electronic expansion valve.

The electrical control center includes a MicroTech II microprocessor control system and equipment protection and operating controls necessary for dependable, automatic operation.

The compressor circuits are equipped with individual circuit breakers and a unit disconnect switch is available as an option over the standard power block.

Water-Cooled Condensing

Rotary Screw Compressor

Nominal Capacity (Tons)

Global

Nomenclature

W G S 130 - A W

W = Water-Cooled Condenser A = Unit Less Condenser

Design Vintage

OM WGS-1 WGS 130A to 190A 3

Definitions

Active Setpoint

The active setpoint is the setting in effect at any given moment. This variation 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.

Active Capacity Limit

The active setpoint is the setting in effect at any given moment. Any one of several external inputs can limit a compressor’s capacity below its maximum value.

Condenser Recirc Timer

A timing function, with a 30-second default, that holds off any reading of condenser water for the duration of the timing setting. This delay allows the water sensors (especially water temperatures) to take a more accurate reading of the condenser water system conditions.

Condenser Saturated Temperature Target

The saturated condenser temperature target is calculated by first using the following equation:

Sat condenser temp target raw = 0.833(evaporator sat temp) + 68.34 The “raw” value is the initial calculated value. This value is then limited to a range defined

by the Condenser Saturated Temperature Target minimum and maximum setpoints. These setpoints simply cut off the value to a working range, and this range can be limited to a single value if the two setpoints are set to the same value.

CPU Error

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

Dead Band

The dead band is a set of values associated with a setpoint such that a change in the variable occurring within the dead band causes no action from the controller. For example, if a temperature setpoint is 44°F and it has a dead band of ± 2 degrees, nothing will happen until the measured temperature is less than 42°F or more than 46°F.

DIN

Digital input, usually followed by a number designating the number of the input.

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

4 WGS 130A to 190A OM WGS

Evap Recirc Timer

A timing function, with a 30-second default, that holds off any reading of chilled water for the duration of the timing setting. This delay allows the chilled water sensors (especially water temperatures) to take a more accurate reading of the chilled water system conditions.

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.

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.

High Superheat Error

The degrees of temperature difference between 40°F and the actual discharge temperature.

Light load Stg Dn Point

The percent load point at which one of two operating compressors will shut off, transferring the unit load to the remaining compressor.

Load Limit

An external signal from the keypad, the BAS or a 4-20 ma signal that limits the compressor loading to a designated percent of full load. Frequently used to limit unit power input.

Load Balance

Load balance is a technique that equally distributes the total unit load among the running compressors.

Low Ambient Lockout

Prevents the unit from operating (or starting) at ambient temperatures below the setpoint.

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.

OM WGS-1 WGS 130A to 190A 5

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.

Milli-second

Maximum Saturated Condenser Temperature

The maximum saturated condenser temperature allowed is calculated based on the compressor operational envelope.

Normally closed - usually refers to a contactor or valve.

Normally open - usually refers to a contactor. or valve.

OAT

Outside ambient air temperature.

Offset

Offset is the difference between the actual value of a variable (such as temperature or pressure) and the reading shown on the microprocessor as a result of the sensor signal. See notes on page 32 for explanation of sensor off set.

pLAN

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

Rapid Stop

A compressor stop process that circumvents the normal pumpdown cycle.

Refrigerant Saturated Te mperature

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.

Soft Load

Soft Load is a control sub-routine that allows the chiller to load up gradually. It requires setpoint inputs of selecting it by Yes or No inputs, by selecting the percent load to start ramping up, and by selecting the time to ramp up to full load (up to 60 minutes).

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

6 WGS 130A to 190A OM WGS

Stage Up/Down Accumulator

The accumulator can be thought of as a bank storing occurrences that indicate the need for an additional fan.

Stageup/Stagedown Delta-T

Staging is the act of starting or stopping a compressor or fan when another is still operating. Startup and Stop is the act of starting the first compressor or fan and stopping the last compressor or fan. The Delta-T is the “dead band” on either side the setpoint in which no action is taken.

Stage Up Delay

The time delay from the start of the first compressor to the start of the second.

Startup Delta-T

Number of degrees above the LWT setpoint required to start the first compressor.

Stop Delta-T

Number of degrees below the LWT setpoint required for the last compressor to stop.

VAC

Volts, Alternating current, sometimes noted as vac.

VDC

Volts, Direct current, sometimes noted as vdc.

VFD

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

OM WGS-1 WGS 130A to 190A 7

Wiring Diagrams

Figure 1, WGS 130AW – 190AW Field Wiring Diagram (Optional Single Point Connection)

3 PHASE

POWER SUPPLY

DISCONNECT (BY OTHERS)

UNIT MAIN

TERMINAL BLOCK

GND LUG

TO COMPRESSOR(S)

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

FACTORY SUPPLIED ALARM

FIELD WIRED

ALARM BELL OPTION

ABR

LARM BELL RELAY

FUSED CO N T RO L

CIRCUIT TRANSFORMER

CHWR

EVAP. PUMP RELAY #1

(BY OTHERS)

120 VAC 1.0 AMP MAX

CHWR

EVAP. PUMP RELAY #2

(BY OTHERS)

120 VAC 1.0 AMP MAX

CWR

COND. PUMP RELAY #1

(BY OTHERS)

120 VAC 1.0 AMP MAX

CWR

COND. PUMP RELAY #2

(BY OTHERS)

120 VAC 1.0 AMP MAX

M11

TOWER FAN #1

(BY OTHERS)

120 VAC 1.0 AMP MAX

M12

TOWER FAN #2

(BY OTHERS)

120 VAC 1.0 AMP MAX

COOLING TOWER BYPASS

(BY OTHERS)

FU4 FU5

120 VAC

FU7

TB1

(115 VAC)

2 82

85 2

86 2

87 2

88 2

89 2

78 77

80 79

81 75

TB1-2

24 VAC

120 VAC

0-10VDC N

0-10VDC

BELL

LARM BELL

RELAY

COM NO

LARM BELL OPTION

TIME

REMOTE STOP

SWITCH

(BY OTHERS)

ICE MODE

SWITCH

(BY OTHERS)

EVAP. FLOW

SWITCH

(BY OTHERS)

*MANDATORY IF FACTORY FLOW SWITCH OPTION IS NOT SELECTED

COND. FLOW

SWITCH

(BY OTHERS)

*MANDATORY IF FACTORY FLOW SWITCH OPTION IS NOT SELECTED

CLOCK

NOR. OPEN PUMP AUX. CONTACTS (OPTIONAL)

4-20MA FOR

EVAP. WATER RESET

(BY OTHERS)

4-20MA FOR

DEMAND LIMIT

(BY OTHERS)

UTO

MANUAL UTO

MANUAL

OFF

TB1

(24 VAC OR 30 VDC)

60 66

IF REMOTE STOP CONTROL

897

IS USED, REMOVE LEAD 897 FROM TERM. 40 TO 53.

60 68

60 67

72 70

71 70

DWG. 330588201 REV . 0B

GND

8 WGS 130A to 190A OM WGS

Figure 2, WGS 130AA – 190AA Field Wiring Diagram (Remote Air-cooled Condenser)

UNIT MAIN

3 PHASE

POWER

SUPPLY

DISCONNECT

(BY OTHERS)

TERMINAL BLOCK

GND LUG

TO COMPRESSOR(S)

NOTE: ALL FIELD WIRING TO BE INSTALLED AS NEC CLASS 1 WIRING SYSTEM WITH CONDUCTOR RAT E D 60 0 V OLTS

FACTORY SUPPLIED ALARM

ALARM BELL OPTION

CIRCUIT #1

M11

CONDENSER FAN

CONTACTOR COIL #1

M12

CONDENSER FAN

CONTACTOR COIL #2

M13

CONDENSER FAN

CONTACTOR COIL #3

M14

CONDENSER FAN

CONTACTOR COIL #4

M15

CONDENSER FAN

CONTACTOR COIL #5

M16

CONDENSER FAN

CONTACTOR COIL #6

FIELD WIRED

TB6

144

145

146

145

148

145

150

145

152

145

154

145

REMOTE STOP

SWITCH

(BY OTHERS)

ICE MODE

SWITCH

(BY OTHERS)

ABR

ALARM BELL RELAY

NO1

NO2

NO3

NO4

NO5

NO6

FUSED CONTROL

CIRCUIT T RANSFORMER

EVAP. PUMP RELAY #1

120 VAC 1.0 AMP MAX

EVAP. PUMP RELAY #2

120 VAC 1.0 AMP MAX

120 VAC

(LOCATED ON

CONTROLLER)

120 VAC

(LOCATED ON

CONTROLLER)

120 VAC

TIME

CLOCK

UTO

MANUAL

UTO

MANUAL

OFF

CHWR

(BY OTHERS)

CHWR

(BY OTHERS)

J12

CIRCUIT

J13

CIRCUIT

FU4

120 VAC

FU7

TB1

(115 VAC)

CIRCUIT #2

CONDENSER FAN

CONT A CTOR COIL #1

CONDENSER FAN

CONTA CTOR COIL #2

CONDENSER FAN

CONTA CTOR COIL #3

CONDENSER FAN

CONT A CTOR COIL #4

CONDENSER FAN

CONTA CTOR COIL #5

CONDENSER FAN

CONTA CTOR COIL #6

TB1

(24 VAC)

FU5

TB1-2

120 VAC

24 VAC

BELL

LARM BELL OPTION

LARM BELL

RELAY

COM

TB7

244

245

246 245

248

245

250 245

252 245

254

245

NO1

NO2

NO3

NO4

NO5

NO6

M21

M22

M23

M24

M25

M26

IF REMOTE STOP CONTROL

897

IS USED, REMOVE LEAD 897 FROM TERM. 40 TO 53.

120 VAC

J12

(LOCATED ON

CIRCUIT

CONTROLLER)

J13

(LOCATED ON

CIRCUIT

CONTROLLER)

EVAP. FLOW

SWITCH

(BY OTHERS)

*MANDATORY IF FACTORY FLOW SWITCH OPTION IS NOT SELECTED.

NOR. OPEN PUMP AUX. CONTACTS (OPTIONAL)

4-20MA FOR

EVAP. WATER RESET

(BY OTHERS)

4-20MA FOR

DEMAND LIMIT

(BY OTHERS)

GND

DWG. 330588101 REV. 0C

OM WGS-1 WGS 130A to 190A 9

Control Panel Layout

Figure 3, Outer (Microprocessor) Panel

T2, Unit Controlle

T13, Circ#1 Controller

T14, Circ#1 Load Solenoid

T15, Circ#1 EXV Power

T23, Circ#2 Controlle

T24, Circ#2 Load Solenoid

T25, Circ#2 EXV Power

Unit Controller

MHPR11 &12, Mechanical High Pressure Rel ay

Circ#1 Controller

Circuit Breaker & Switch Panel

External Disconnect Handle

Circ#1 & 2 EXV Drivers

Circ#2 Controller

TB3, Circ#2 Controller Terminal Board

TB2, Circ#1 Controller Terminal Board

TB1 Unit Controller Terminal Board

NOTES:

1. Transformers T2 through T25 are class 100, 120V to 12V.

2. Switches for MHPR 11 and 12 (Mechanical High Pressure Switches) are located on the compressors.

3. Mechanical High Pressure Switches Open at 310 psi, Close at 250 psi.

10 WGS 130A to 190A OM WGS

Figure 4, Inner (Power) Panel (Opti onal Single-Point Power wi th Disconnect Switches

Shown)

Circ#1 Solid State Starter

Circ#2 Solid State Starter

SSS1 Bypass Contactor

SSS2 Bypass Contactor

Secondary Fuses

External Disconnect Handle

Circ#1 Circuit Breaker

Circ#2 Circuit Breaker

Unit Disconnect Switch W/ External Handle

T1, Supply Voltage to 120V Transf ormer

Primary Fuses

Outside (Microprocessor) Panel

OM WGS-1 WGS 130A to 190A 11

Figure 5, Circuit Breaker/Fuse Panel

Open Location

S1 Main Unit On-Off Switch

CS2, Circuit#2 On-Off Switch

CS1, Circuit#1 On-Off Switch

CB11 Circ#1 Circuit Breaker

CB12, Circ#1 Sump Heater

Open Locatio

CB21, Circ#2 Circui

CB22, Circ#2 Sump Heate

Open Locations

Location for Optional

115V Receptacle

OUTER PANEL INNER PANEL

T13T2 T14 T15 T23 T24 T25

UNIT

CONTROLLER

EXV.

DRIVER

CIRCUIT CONTROLLER

MODBUS CARD

CONVERTER BOARD

EXV.

DRIVER

CIRCUIT CONTROLLER

TB1

TB11 TB21

MHPR1MHPR

CS1

S1S

REC

OPTION

CS2

CB11 CB12 SP CB21 CB22

SP FU7

SINGLE

POINT

CIR. #1

DS HANDLE (MULTI-

POINT)

CIR. #2

DS HANDLE (MULTI-

POINT)

SSS #1 SSS #2

CT2

F U 5

CONTACTOR

CT1

THERM-

ISTOR CARD

BYPASS

C B 1

(DS1 DS2

MULTIPOINT

POWER)

CT3

C B 2

CONTR.

BRD.

CT3

F U 6

F U 4

CONTR.

BRD.

CT2

DS1

CONTACTOR

CT1

THERM-

ISTOR CARD

BYPASS

G N D

330589001 REV. 00 - Legen

12 WGS 130A to 190A OM WGS

MicroTech II Controller

System A rchitecture

The WGS 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

and communicates with the other controllers. It is located in the control panel and is labeled “UNIT CONTROL”.

• Circuit Controllers

settings specific to the circuit. The controllers are located in the control panel 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 down the compressor, or entire unit, 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.

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

for each compressor/circuit that control compressor functions and

BAS Interface-

Modbus, BACnet,

Lonworks

Chiller

RS485/

LON

Unit Controller

4x20 LCD

Carel pLAN

Circuit Controller

Solid

State

Starter

RS485 RS485

Circuit Control l e r

4x20 LCD

Solid

State

Starter

PLAN A ddressing

The pLAN (proprietary local area network) addressing is based on a commonly used scheme among all applications using pLAN networked MicroTech II controllers. Only three addresses are needed, and are designated as shown in the following table.

Controller Address Dip Sw 1 Position Dip Sw 2 Position Dip Sw 3 Position

Unit 5 Up Down Up Circuit 1 1 Up Down Down Circuit 2 2 Down Up Down

The Dip switches are located on the upper front of the controller above the screen.

OM WGS-1 WGS 130A to 190A 13

General Description

The MicroTech II controller’s design permits the chiller to run more efficiently, and it simplifies troubleshooting if a system failure occurs. Every MicroTech II controller is programmed and tested prior to shipment to assist in a trouble-free start-up. The MicroTech II controller can be used to cycle fans on remote air-cooled condensers for head pressure control when the setpoint Water Cooled=N is selected in one of the setpoint menu screens. Water Cooled=Y sets the chiller for operation with the water-cooled condenser and activates settings for cooling tower control. Remote evaporative condensers will have to have self-contained, on-board, head pressure control systems.

Units of measure

Version “C”, as described in this manual, supports metric (SI) units of measure.

Inch-Pound SI

°F to 0.1°F °C to 0.1°C

psi to 0.1 psi KPa to 1.0 kPa

Distributed Control

The WGS units have three MicroTech II microprocessors, a Unit Controller plus a Circuit Controller for each of the two circuits. The Circuit Controllers are independent such that either one will operate its circuit if the other Circuit Controller is out of service.

Operator-friendly

The MicroTech II controller menu structure is separated into three distinct categories, which provide the operator or service technician with a full description of the following:

1. Current unit status

2. Control parameters (setpoint settings and adjustment). Security protection prevents unauthorized changing of the setpoints and control parameters.

3. Alarm notification and clearing

The MicroTech II controller continuously performs self-diagnostic checks, monitoring system temperatures, pressures and protection devices, and will automatically shut down a refrigerant circuit or the entire unit if a fault occurs. The cause of the shutdown and date stamp are retained in memory and can be easily displayed in plain English for operator review, which is an extremely useful feature for troubleshooting. In addition to displaying alarm diagnostics, the MicroTech II controller also provides the operator with a warning of pre-alarm limit conditions.

Staging

The two screw compressors are loaded and staged on and off as a function of leaving chilled water temperature, number of starts and run-hours. See Sequence of Operation beginning on page 13.

Equipment Protection

The unit is protected by alarms that shut it down and require manual reset, and also by limit alarms that limit unit operation in response to some out-of-ordinary condition. Shutdown alarms activate an alarm signal that can be wired to a remote device.

14 WGS 130A to 190A OM WGS

Unit Enable Selection

(4)

Enables unit operation from local keypad or digital input.

Unit Mode Selection

Selects standard cooling, ice, glycol, or test operation mode.

Keypad/Display

A 4-line by 20-character/line liquid crystal display and 6-key keypad is mounted on each controller. Its layout is shown below.

Figure 6, Keypad and Display in MENU Mode

Air Condi ti oni ng

Key to Screen Pathway

ALARM

VIEW

Arrow Keys

SET

"Enter" Key and Green Comp. Run Light

Red Alarm Light

Menu Key

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 RIGHT Cancel 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).

OM WGS-1 WGS 130A to 190A 15

Sequence of Operation

Compressor Heaters

With the control power on, 120V power is applied through the control circuit Fuse FU7 to the compressor oil separator heater (HTR-OIL SEP).

Startup/Compressor Staging

During Cool Mode the following must be true to start a circuit operating. The evaporator and condenser pump (WGS-AW only) outputs must be energized and flow must be established for a period of time defined by the evaporator recirculate setpoint. Established flow will be detected by evaporator and condenser water flow switches. The water temperature leaving the evaporator must be greater than the Active Leaving Water Temperature setpoint, plus the Startup Delta-T, before a circuit will start. The first circuit to start is determined by sequence number. The lowest sequence numbered circuit will start first. If all sequence numbers are the same (default), then the circuit with the fewest number of starts will start first. During operation, the slide valves for loading and unloading will be pulsed until the active leaving water temperature setpoint is maintained. The second circuit start will occur once the first circuit has loaded to 75% slide capacity or is in Capacity Limit and the water temperature leaving the evaporator is greater than the active leaving water temperature Setpoint plus Stage Delta-T. The circuits will load or unload simultaneously through a continuous capacity control to maintain the evaporator leaving water temperature. If all sequence numbers are the same, the circuit with the most run hours will be shut down first. The circuit with the most run hours will stop when the water temperature leaving the evaporator is less than the Active Leaving Water Temperature Setpoint minus Stage Delta-T. The last remaining circuit will shut down when the water temperature leaving the evaporator is lower than the Active Leaving Water Temperature Setpoint minus the Stop Delta-T.

Automatic Pumpdown

The Model WGS chiller has two separate refrigerant circuits so the refrigerant charge is stored in the condenser when the circuit is off. Pumpdown to the condenser helps keep refrigerant from migrating to the compressor. It also helps establish a pressure differential on start for oil flow. In a normal shutdown, each circuit will close its expansion valve, causing the evaporator pressure to reach a low-pressure setpoint. Once this setpoint is reached, or a specified amount of time has elapsed, the running circuit will be shut down.

Chilled Water and Condenser Water Pumps

The chiller’s MicroTech II controller has a total of four pump outputs, two for the evaporator and two for the condenser (WGS-AW only). There is a manual setting in the software for the user to select either pump output 1 or 2. It is recommended that the chiller’s outputs control the water pumps, as this will offer the most protection for the unit.

Cooling Tower Control

The MicroTech II controller can control the cooling tower fans and/or a tower bypass valve. This provides a simple and direct method to control the unit’s discharge pressure. Programming directions and the sequence of operation can be found on page 44. Some means of discharge pressure control is recommended and must be installed if the entering condenser water temperature to the condenser can fall below 60°F.

Condenser Fan Control

The MicroTech II controller can be programmed to cycle air-cooled condenser fans on and off based on the discharge pressure. Details are on page 61.

16 WGS 130A to 190A OM WGS

Unit Controller Sequence of Operation

Unit power up

Unit in Off state

The chiller may be disabled via the unit switch, the remote switch, the keypad enable setting, or the BAS network. In addition, the chiller will be disabled if both circuits are disabled, either because of an alarm or the circuit pumpdown switch on

each circuit, or if there is a unit alarm. If the chiller is disabled, the unit status display will reflect this and also show why it is disabled.

Is unit enabled?

Yes

Evaporator pump output on

Is flow present?

Yes

Wait for chilled water loop to

recirculate.

If the unit switch is off, the unit status will be disabled due to network command, the unit status will be the remote switch is open, the unit status will be alarm is active, the unit status will be are enabled, the unit status will be

Off:All Cir Dis abl e d

Off:Unit Switch

Off:Remote Switch

Off:Unit Alarm

. If the chiller is

Off:BAS Disa bl e

. When a unit

. In cases where no circuits

If the chiller is enabled, then the unit will be in the Auto state and the evaporator water pump output will be activated.

The chiller will then wait for the flow switch to close, during which time the unit status will be

Auto:Wait for flow

After establishing flow, the chiller will wait some time to allow the chilled water loop to recirculate for an accurate reading of the leaving water temperature. The unit status during this time is

Auto:Evap Recirc

. When

Keep evaporator pump

output on while unit is

enabled.

The chiller is now ready to start if enough load is present. If the LWT is not high

Is there enough load to

start chiller?

Yes

enough to start, the unit status will be If the LWT is high enough to start, the unit status will be

Auto:Wait Evap Flow

Auto

OM WGS-1 WGS 130A to 190A 17

Is unit watercooled?

Yes

If the unit is configured as watercooled, the condenser pump will need to be started. Otherwise, the unit can start the first circuit at this point.

Condenser pump output on

Is flow present?

Yes

Wait for condenser water

loop to recirculate.

Keep condenser pump

output on while u n it is

enabled and load is present.

Start first circuit.

Load/unload as needed to

satisfy load.

Is more capacity

needed to satisfy load?

If load is present, the condenser water pump output will be activated.

The chiller will then wait for the condenser flow switch to close, during which time the unit status will be

Auto:Wait Cond Flow

After establishing condenser flow, the chiller will wait some time to allow the condenser water loop to recirculate and guarantee consistent flow. The unit status during this time is

Auto:Cond Recirc

Once the condenser flow has been present for enough time, the unit status will become

Auto

. The tower control logic will start working to control the condenser water temperature, using outputs from the unit controller to control tower fans, bypass valves, and vfd's as determined by the tower set points.

The first circuit to start is generally the one with the least number of starts, or circuit one if there is a tie. This circuit will go through its start sequence at this point.

A number of fans may be started with the compressor based on the OAT. Fan stages will be added/removed as needed to control condenser pressure. The EXV will begin controlling at this point as well. The compressor cannot start loading until it has at least 22

discharge superheat for more than 30 seconds.

The first circuit will load and unload as needed in an attempt to satisfy the load. It will eventually get to a point where it is considered to be at full load. A circuit is at

full load when it reaches 75% slide target, it reaches the max slide target setting, or it encounters a problem and is running in an inhibited state.

If a single circuit is not enough to satisfy the load, the second circuit will need to be started.

Yes

Has the stage up time

delay expired?

Yes

A minimum time must pass between the start of the first circuit and the second circuit.

18 WGS 130A to 190A OM WGS

The second circuit will go through its start sequence at this point.

Start second circuit.

Load/unload as needed to

satisfy load.

Can one circuit handle

the load?

Yes

Shut down one circuit.

Load/unload as needed to

satisfy load.

discharge superheat for more than 30 seconds.

Both circuits will now load/unload as needed to satisfy the load. In addition, they will load balance so that both circuits are providing nearly equal capacity.

As the load drops off, the circuits will unload accordingly. If the LWT gets low enough, or both circuits unload enough, one circuit can shut off.

The first circuit to shut off is generally the one with the most run hours. The circuit will do a pumpdown by closing the EXV and continuing to run the compressor until it reaches the pumpdown pressure or exceeds the pumpdown time limit. Then, the compressor and all fans will be turned off.

The single running circuit will load/unload as needed to satisfy the load.

With one circuit running, the load may drop off to the point where even minimum

Is load satisfied?

Yes

unit capacity is too much. The load has been satisfied when the LWT drops below the shutdown point. At this time the only running circuit can shut down.

The last circuit running now shuts down. The circuit will do a pumpdown by closing the EXV and continuing to run the compressor until it reaches the pumpdown

Shut down last circuit.

pressure or exceeds the pumpdown time limit. Then, the compressor and all fans will be turned off.

The unit should be ready to start again when the LWT gets high enough. The unit

Turn off condenser pump

and tower control.

status at this time will be

Auto:Wait for load

The condenser pump and tower control outputs are turned off until the LWT is high enough to start again.

OM WGS-1 WGS 130A to 190A 19

Circuit Controller Sequence of Operation

Unit power up

Circuit is in Off state

Next on?

Yes

Stage up now?

Yes

When the circuit is in the Off state the EXV is closed, compressor is off, and all fans are off. The oil heater will be on at this time as long as oil is detected in the separator.

If the compressor is ready to start when needed, the circuit status will be

Off:Ready

. When the circuit switch is off, the circuit cannot start and the status will

Off:Pumpdown Switch

If this compressor has the least starts, the other compressor is disabled for some reason, or the other compressor is already running, then this compressor will be designated as the next one on.

If there is a need for more cooling capacity , the compressor designated as next on can start.

Is unit watercooled?

Yes

Preopen EXV

Start Compressor

If the unit is configured as watercooled, then the EXV preopen process must be performed. Otherwise, this is skipped and the compressor can be sta rted.

At this point, the EXV will perform a preopen. While the compressor is off, the EXV is opened for a period of time to prime the evapora tor an d avoid low pressure at startup. The circuit status will display

EXV Preopen

When the compressor starts, the EXV will open (if not already open) and hold at 3000 steps for 15 seconds.

If the unit is aircooled, depending on the OAT, a number of fans may be started with the compressor to keep condenser pressure from climbing too fast.

The circuit status will normally be

Run: Disc SH Low

after the compressor starts.

20 WGS 130A to 190A OM WGS

Run Compressor

Next off?

Yes

Stage down now?

Yes

When in the Run state, the compressor will load/unload as needed to satisfy the load. The compressor will also load/unload to load balance with the other compressor if it is running and not in a limited condition. However, it cannot load up until the discharge superheat has been over 22 F for at least 30 seconds. After this, the circuit status will be

Run:Normal

The EXV will operate in either Pressure Control or Superheat Control. In Pressure Control, the evaporator pressure is controlled to a target pressure, which is adjusted based on LWT and discharge superheat. In Superheat Control, the suction

superheat is controlled to a target that varies with discharge superheat. If unit is aircooled, fans will be staged on and off to control the condenser pressure.

The condenser pressure is controlled to a target that is based on evaporator pressure, with the target getting higher as the evaporator pressure gets higher.

If this compressor has the most run hours or the other compressor is already off, then this compressor will be designated as the next one off.

If less cooling capacity is needed, the compressor designated as next off can shut down. This condition may arise when either the LWT has dropped far enough below the active set point or both circuits are running at a low capacity.

When the circuit does a normal shutdown, a pumpdown is performed. The EXV is closed while the compressor continues to run. As soon as the pumpdown is initiated, the compressor is unloaded to the minimum. The condenser fans continue to control normally during this process. The circuit status during this time

Run:Pumpdown

Pumpdown circuit

After the evaporator pressure drops below the pumpdown pressure or enough time has passed, the compressor and fans are shut off to end the pumpdown process. The circuit status will normally be

Off:Cycle Timers

at this time.

OM WGS-1 WGS 130A to 190A 21

Start-Up and Shutdown

Pre Start-up

1. Flush and clean the chilled-water system. Proper water treatment is required to prevent corrosion and organic growth.

Failure to flush and clean system and provide water treatment can damage the unit.

2. With the main disconnect open, check all electrical connections in control panel and starter to be sure they are tight and provide good electrical contact. Connections are tightened at the factory, but can loosen enough in shipment to cause a malfunction.

Lock and tag out all power sources when checking connections. Electrical shock can

3. Check and inspect all water piping. Make sure flow direction is correct and that piping is made to the correct connection on evaporator and condenser.

4. Check that refrigerant piping on remote condensers is connected to the correct circuits and not crossed and has been properly leak tested and evacuated.

5. Open all water flow valves to the condenser and evaporator.

6. Flush the cooling tower and system piping to be sure the system is clean. Start evaporator pump and manually start condenser pump and cooling tower. Check all piping for leaks. Vent the air from the evaporator and condenser water circuit, as well as from the entire water system. The cooler circuit should contain clean, treated, noncorrosive water.

7. Check to see that the evaporator water temperature sensor is securely installed.

8. Make sure the unit control switch S1 is open OFF and the circuit switches CS1 and CS2 are open. Place the main power disconnect switch to ON. This will energize the compressor sump heaters. Wait a minimum of 12 hours before starting the unit.

9. Measure the water pressure drop across the evaporator and condenser, and check that water flow is correct (on pages 25 and 26) per the design flow rates.

10. Check the actual line voltage to the unit to make sure it is the same as called for on the compressor nameplate, within + 10%, and that phase voltage unbalance does not exceed 2%. Verify that adequate power supply and capacity is available to handle load.

11. Make sure all wiring and fuses are of the proper size. Also make sure that all interlock wiring is completed per McQuay diagrams.

12. Verify that all mechanical and electrical inspections by code authorities have been completed.

13. Make sure all auxiliary load and control equipment is operative and that an adequate cooling load is available for initial start-up.

CAUTION

cause severe personal injury or death.

Start-up

1. Open the compressor discharge shutoff valves until backseated. Replace valve seal caps.

2. Open the two manual liquid line shutoff valves (king valves).

22 WGS 130A to 190A OM WGS

3. Verify that the compressor sump heaters have operated for at least 12 hours prior to start-up. Crankcase should be warm to the touch.

4. Check that the MicroTech II controller is set to the desired chilled water temperature.

5. Start the system auxiliary equipment for the installation by turning on the time clock, ambient thermostat and/or remote on/off switch and water pumps.

6. Switch on the unit circuit breakers.

7. Set circuit switches CS1 and CS2 to ON for normal operation.

8. Start the system by setting the unit system switch S1 to ON.

9. After running the unit for a short time, check the oil level in each compressor, rotation of condenser fans (if any), and check for flashing in the refrigerant sight glass.

Weekend or Temporary Shutdown

Move circuit switches CS1 and CS2 to the OFF pumpdown position. After the compressors have shut off, turn off the chilled water pump if not on automatic control from the chiller controller or building automation system (BAS). With the unit in this condition, it will not restart until these switches are turned back on.

Leave on the power to the unit (disconnect closed) so that the sump heaters will remain energized.

Start-up after Temporary Shutdown

1. Start the water pumps.

2. Check compressor sump heaters. Compressors should be warm to the touch.

3. With the unit switch S1 in the ON position, move the circuit switches CS1 and CS2 to the ON position.

4. Observe the unit operation for a short time, noting unusual sounds or possible cycling of compressors.

Extended Shutdown

1. Close the manual liquid line shutoff valves.

2. After the compressors have shut down, turn off the water pumps.

3. Turn off all power to the unit.

4. Move the unit control switch S1 to the OFF position.

5. Close the discharge shutoff valves.

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

7. Drain all water from the unit evaporator, condenser and chilled water piping if the unit is to be shut down during the winter and exposed to below-freezing temperatures. To help prevent excessive corrosion, do not leave the vessels or piping open to the atmosphere over the shutdown period.

Start-up after Extended Shutdown

1. Inspect all equipment to see that it is in satisfactory operating condition.

2. Remove all debris that has collected on the surface of the condenser coils (remote condenser models) or check the cooling tower, if present.

OM WGS-1 WGS 130A to 190A 23

3. Open the compressor discharge valves until backseated. Always replace valve seal caps.

4. Open the manual liquid line shutoff valves.

5. Check circuit breakers. They must be in the OFF position.

6. Check to see that the circuit switches CS1 and CS2 and the unit control switch S1 are in the OFF position.

7. Close the main power disconnect switch. The circuit disconnects switches should be off.

8. Allow the sump heaters to operate for at least 12 hours prior to start-up.

9. Start the chilled water pump and purge the water piping as well as the evaporator in the unit.

10. Start the system auxiliary equipment for the installation by turning on the time clock, ambient thermostat and/or remote on/off switch.

11. Check that the MicroTech II controller is set to the desired chilled water temperature.

12. Switch the unit circuit breakers to ON.

13. Start the system by setting the system switch S1 and the circuit switches to ON.

CAUTION

Most relays and terminals in the control center are powered when S1 is

closed and the control circuit disconnect i s on. Therefore, do not close S1

until ready for start-up or serious equipment damage can occur.

14. After running the unit for a short time, check the oil level in the compressor oil sight glass and check the liquid line sight glass for bubbles.

24 WGS 130A to 190A OM WGS

Figure 7, Evaporator Pressure Drop WGS 130 – WGS 190

(

)

Flow Rate (L/s)

6131925323844505763

126

180

9 8

Pressure Drop (ft of water)

6 5

WGS 130, 140

WGS 160, 170, 190

150

120

30 27

24 21

Pressure Drop

kPa

100 200 300 400 500 600 700

800

900

1000

2000

Flow Rate (GPM)

Minimum Flow Nominal Flow Maximum Flow

WGS Model

130AW/AA 140AW/AA 160AW/AA 170AW/AA 190AW/AA

Note: Minimum, nominal, an d maximum flows are at a 16°F, 10°F, and 6°F chilled water temperature range respectively and at ARI tons.

Flow Rate Pressure Drop Flow Rate Pressure Drop Flow Rate Pressure Drop

gpm L/s Ft. kPa gpm L/s Ft. kPa gpm L/s Ft. kPa

195 12.3 5.8 17.4 312 19.7 13.5 40.4 520 32.9 33.9 101.1 211 13.4 6.7 20.0 338 21.4 15.6 46.6 563 35.6 39.0 116.5 235 14.9 4.6 13.8 376 23.8 10.8 32.3 627 39.7 27.3 81.6 254 16.1 5.3 15.9 407 25.8 12.5 37.3 678 42.9 31.6 94.2 273 17.3 6.1 18.1 437 27.7 14.2 42.5 728 46.1 35.9 107.2

OM WGS-1 WGS 130A to 190A 25

Figure 8, Condenser Pressure Drop WGS 130 – WGS 190

Flow Rate (L/s)

6131925323844505763

126

180

rop (ft of water)

ressure

WGS

Model

130AW 140AW 160AW 170AW 190AW

WGS

Model

130AW 140AW 160AW 170AW 190AW

WGS 170, 190

150

120

with Manifold

WGS 130, 140, 160

with Manifold

9 8

7 6

WGS 170, 190

30 27

24 21

without Manifold

WGS 130, 140, 160

100 200 300 400 500 600 700

without Manifold

800

900

1000

2000

Flow Rate (GPM)

Pressure Drop Without Optional Condenser Manifold

Minimum Flow Nominal Flow Maximum Flow

Flow Rate Pressure Drop Flow Rate Pressure Drop Flow Rate Pressure Drop

gpm L/s Ft. kPa gpm L/s Ft. kPa gpm L/s Ft. kPa

304 19.2 4.1 12.2 390 24.7 6.5 19.3 650 41.1 16.0 47.9 304 19.2 4.1 12.2 422 26.7 7.4 22.2 704 44.5 18.5 55.1 304 19.2 4.1 12.2 470 29.8 9.0 26.9 784 49.6 22.4 66.8 372 23.5 4.3 12.8 509 32.2 7.9 23.7 848 53.7 19.8 59.1 372 23.5 4.3 12.8 546 34.6 9.0 26.9 911 57.6 22.5 67.1

Pressure Drop With Optional Condenser Manifold

Minimum Flow Nominal Flow Maximum Flow

Flow Rate Pressure Drop Flow Rate Pressure Drop Flow Rate Pressure Drop

gpm L/s Ft. kPa gpm L/s Ft. kPa gpm L/s Ft. kPa

304 19.2 4.7 14.0 390 24.7 7.4 22.0 650 41.1 18.5 55.1 304 19.2 4.7 14.0 422 26.7 8.5 25.3 704 44.5 21.3 63.5 304 19.2 4.7 14.0 470 29.8 10.3 30.7 784 49.6 25.8 77.1 372 23.5 5.3 15.8 509 32.2 9.4 28.1 848 53.7 23.8 71.1 372 23.5 5.3 15.8 546 34.6 10.7 32.0 911 57.6 27.1 80.9

Pressure Drop (kPa)

26 WGS 130A to 190A OM WGS

Unit Controller

Unit Inputs/Outputs

Table 1, Analog Inputs

# Description Signal Source Range 1

2 3 4

C1 = Refrigerant Circuit #1, C2 = Refrigerant Circuit #2, UT = Unit

Table 2, Analog Outputs

# Description Output Signal Range 1

2 3 4

Table 3, Digital Inputs

# Description Signal Signal 1

2 3 4 5 6 7 8

Condenser EWT or Outdoor Ambient Temp. Demand Limit 4-20 mA Current 0 to 100% limit

Chilled Water Reset 4-20 mA Current Leaving Evaporator Water Temp. Thermister (10k@25°C) -58 to 212°F

Entering Evaporator Water Temp. Thermister (10k@25°C) -58 to 212°F

Cooling Tower Bypass Valve Position 0 to 10 VDC 0 to 100% Cooling Tower VFD Speed 0 to 10 VDC 0 to 100% Open Open

Unit Switch 0 VAC (Stop) 24 VAC (On) Remote Switch 0 VAC (Stop) 24 VAC (Start) Evaporator Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow) Mode Switch 0 VAC (Cool) 24 VAC (Ice) Condenser Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow) Open Open Open

Thermister (10k@25°C) -58 to 212°F

0 to 10 degrees

60°F max.

Table 4, Digital Outputs

# Description Load Output OFF Output ON

Evaporator Water Pump 1 Pump Contactor Pump OFF Pump ON

Evaporator Water Pump 2 Pump Contactor Pump OFF Pump ON

Condenser Water Pump 1 Pump Contactor Pump OFF Pump ON

Condenser Water Pump 2 Pump Contactor Pump OFF Pump ON

Tower Fan 1 Fan Contactor Fan OFF Fan ON

Tower Fan 2 Fan Contactor Fan OFF Fan ON

Remote Run Status All Circuits Off Any Circuit On

Alarm Remote Alarm No alarm Stop alarm

Unit Setpoints

The following parameters are retained during power off, are factory set to the Default value, and can be adjusted to any value in the Range column.

The Type defines whether the setpoint is part of a coordinated set of duplicate setpoints in different controllers. Types are as follows:

N = Normal setpoint – Not copied from, or copied to, any other controller M = Master setpoint – Setpoint is copied to all controllers in the “Sent To” column

The PW (password) column indicates the password level that must be active in order to change the setpoint. Passwords are as follows:

O = Operator [0100] M = Manager (8745)

OM WGS-1 WGS 130A to 190A 27

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