McQuay WGZ 030AW Installation Manual

Operating Manual

Water-Cooled Scroll Compressor Chillers

WGZ 030AW To WGZ 120AW, Packaged Water-Cooled Chiller WGZ 030AA To WGZ 120AA, Chiller with Remote Condenser 30 to 120 Tons, 105 to 420 kW

Software Version WGZD20102C 60 Hz, R-22, R-407C

OM WGZ-2

Group: Chiller Part Number: 331374501 Effective: March 2005 Supercedes: OM WGZ-1

Table of Contents

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

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

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

Water Pressure Drop..............................3

Operating Limits....................................6

Components...........................................6

Unit Configuration ............................7

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

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

Motor Protection Module....................10

Start-Up and Shutdown...................11

Pre Start-up.......................................... 11

Start-up................................................11

Weekend or Temporary Shutdown ......12

Start-up after Temporary Shutdown....12

Extended Shutdown.............................12

Start-up after Extended Shutdown ......13

Low Ambient Start ..............................13

Fan High Ambient Rapid Start............14

Sequence of Operation ....................14

Start-up/Compressor Staging...............14

MicroTech II Controller .................18

Controller Software Version................18

General Description.............................18

Setpoints..............................................21

Protection (Shutdown) Alarms............22

Event (Limit) Alarms...........................23

Staging Parameters..............................26

Capacity Overrides..............................26

Digital Output Control ........................27

Analog Output Control........................28

Using the Controller............................31

Menu Screens......................................34

Menu Descriptions ..............................34

Optional Controls............................51

Phase/Voltage Monitor (Optional) ......51

Hot Gas Bypass (Optional) .................51

Troubleshooting Chart.........................52

Warranty Statement........................53

Manufactured in an ISO Certified facility

"McQuay" is a registered trademark of McQuay International

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.

2 WGZ 030A through 120A OM WGZ-2

Introduction

)

General Description

McQuay Type WGZ water chillers are designed for indoor installations and are available with watercooled condensers (Model AW), or arranged for use with remote air-cooled or evaporative condensers (Model AA). Each water-cooled unit is completely assembled and factory wired before evacuation, charging and testing. They consist of hermetic scroll compressors, brazed-plate evaporator, watercooled condenser (WGZ-AW), and complete refrigerant piping.

Units manufactured for use with remote condensers (Models WGZ-AA) have all refrigerant specialties factory-mounted and connection points for refrigerant discharge and liquid lines.

Liquid line components that are included are manual liquid line shutoff valves, charging valves, filterdriers, liquid line solenoid valves, sight glass/moisture indicators, and thermal expansion valves. Other features include compressor crankcase heaters, and a MicroTech II¥ microprocessor controller.

The electrical control center includes all equipment protection and operating controls necessary for dependable automatic operation.

The compressors are not fused as standard, but can be protected by optional circuit breakers or fuses, or can rely on a field-installed, fused disconnect switch for protection.

BOOT & BIOS

BOOT Version: 3.0F BIOS Version 3.56

Manuals: Information in unit initial installation and routine maintenance is contained in Installation and Maintenance Manual IMM WGZ-2.

Nomenclature

W G Z 100 - A W

Water-Cooled

Global

Scroll Compressor

W = Water-Cooled Condenser

Design Vintage

ominal Capacity (Tons

Water Pressure Drop

Water flow rates should be maintained as closely as possible to job design values. The vessel flow rat es mu st f al l be twe en t he mi nimu m and maxi mum values shown on the appropriate evaporator and condenser curves.

Measure the water pressure drop through the vessels at field-installed pressure taps and check the flow rate using the following tables. Do not include valves or strainers in these readings.

The evaporator flow rates and pressure drops shown on the following page are for full load design purposes. The maximum flow rate and pressure drop are based on a 6-degree temperature drop. Avoid higher flow rates with resulting lower temperature drops to prevent potential control problems resulting from very small control bands and limited start up/shut off temperature changes.

The minimum flow and pressure drop is based on a full load evaporator temperature drop of 16degrees.

Minimum Part Load Flow Rates: This full load design minimum flow is not to be confused with the part load minimum flow rate that must be maintained for chillers operating in variable primary flow pumping systems. As chiller capacity drops, the flow rate is reduced proportionally. See the following table for the part load minimum flow rates.

Table 1, Minimum Part Load

WGZ Model 030 035 040 045 050 055 060 070 080 090 100 110 120

Min.Part Load GPM

30 33 38 43 47 53 58 67 74 83 91 102 113

Flow Rates

OM WGZ-2 WGZ 030A through 120A 3

Figure 1, Evaporator Pressure Drop, WGZ 030 – WGZ 120

)

Flow Rate (L/s)

1.9 2.5 3.2 3.8 4.4 5.0 5.7 6.3

12.6 18.9

25.2

31.5 37.9

44.2 120

WGZ 040

WGZ 050

WGZ 060

WGZ 080

WGZ 030

Pressure Drop (kPa)

9 8 7

Pressure Drop (ft of water)

WGZ 100 - 120

30 27

24 21

WGZ 035

WGZ 055

WGZ 090

WGZ 045

WGZ 070

WGZ

Model

030 035 040 045 050 055 060 070 080 090 100 110 120

30 40 50 60 70 80 90 100 200 300 400 500 600

Flow Rate (GPM

Minimum Flow Nominal Flow Maximum Flow

Inch-Pound S.I. Inch-Pound S.I. Inch-Pound S.I.

GPM Ft. L/S kPa GPM Ft. L/S kPa GPM Ft. L/S kPa

45.5 1.85 2.87 5.54 75.8 5.15 4.78 15.40 126.3 14.31 7.97 42.77

50.3 1.76 3.17 5.27 83.8 4.90 5.29 14.65 139.7 13.62 8.81 40.70

57.7 1.83 3.64 5.46 96.2 5.07 6.07 15.15 160.3 14.08 10.12 42.10

63.7 1.71 4.02 5.10 106.1 4.74 6.69 14.17 176.8 13.16 11.16 39.35

70.0 1.70 4.41 5.08 116.6 4.72 7.36 14.12 194.3 13.12 12.26 39.21

78.2 1.70 4.93 5.08 130.3 4.72 8.22 14.10 217.2 13.11 13.70 39.17

85.8 1.67 5.41 5.00 143.0 4.65 9.02 13.90 238.3 12.91 15.04 38.60

97.9 1.75 6.18 5.24 163.2 4.87 10.30 14.54 272.0 13.51 17.16 40.40

112.3 1.86 7.09 5.56 187.2 5.17 11.81 15.45 312.0 14.36 19.68 42.92

123.5 1.91 7.79 5.70 205.9 5.29 12.99 15.82 343.2 14.71 21.65 43.96

134.9 2.14 8.51 6.39 224.9 5.94 14.19 17.74 374.8 16.49 23.65 49.29

152.9 2.75 9.65 8.21 254.9 7.63 16.08 22.79 424.8 21.18 26.80 63.31

168.8 3.34 10.65 9.99 281.3 9.29 17.75 27.76 468.8 25.80 29.58 77.11

700

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

4 WGZ 030A through 120A OM WGZ-2

Figure 2, Condenser Pressure Drop, WGZ 030 – WGZ 120

Flow Rate (L/s)

1.9 2.5 3.2 3.8 4.4 5.0 5.7 6.3

70 60

12.6 18.9

25.2

31.5 37.9

44.2 210

180

WGZ 050, 055

WGZ 080

WGZ 090

150

120

WGZ 040, 045

Pressure Drop (kPa)

WGZ 030, 035

9 8

Pressure Drop (ft of water)

7 6

WGZ 070

WGZ 100 - 120

30 27

24 21

WGZ

Model

030 035 040 045 050 055 060 070 080 090 100 110 120

WGZ 060

30 40 50 60 70 80 90 100 200 300 400 500 600

Flow Rate (GPM)

700

Minimum Flow Nominal Flow Maximum Flow

Inch-Pound S.I. Inch-Pound S.I. Inch-Pound S.I.

GPM Ft. L/S kPa GPM Ft. L/S kPa GPM Ft. L/S kPa

56.9 2.66 3.59 7.96 94.8 7.40 5.98 22.11 158.0 20.55 9.97 61.43

62.8 3.25 3.96 9.71 104.7 9.02 6.61 26.97 174.5 25.07 11.01 74.93

72.2 2.83 4.55 8.45 120.3 7.85 7.59 23.46 200.5 21.80 12.65 65.17

79.6 3.43 5.02 10.26 132.6 9.54 8.37 28.51 221.0 26.49 13.94 79.18

87.5 3.02 5.52 9.02 145.8 8.38 9.20 25.05 243.0 23.28 15.33 69.58

97.7 3.77 6.17 11.26 162.9 10.46 10.28 31.27 271.5 29.06 17.13 86.85

107.3 3.38 6.77 10.11 178.8 9.39 11.28 28.07 298.0 26.09 18.80 77.97

122.4 3.45 7.72 10.31 204.0 9.58 12.87 28.64 340.0 26.62 21.45 79.56

140.4 3.92 8.86 11.72 234.0 10.89 14.76 32.56 390.0 30.26 24.61 90.45

154.4 3.95 9.74 11.81 257.4 10.97 16.24 32.80 429.0 30.48 27.07 91.11

168.7 3.55 10.64 10.62 281.1 9.87 17.73 29.50 468.5 27.41 29.56 81.94

191.2 4.56 12.06 13.64 318.6 12.68 20.10 37.89 531.0 35.21 33.50 105.26

211.0 5.56 13.31 16.61 351.6 15.44 22.18 46.15 586.0 42.89 36.97 128.19

OM WGZ-2 WGZ 030A through 120A 5

Operating Limits

• Maximum allowable condenser water pressure is 232 psig (1599 kPa).

• Maximum allowable cooler water pressure is 363 psig (2509 kPa).

• Maximum design saturated discharge temperature is 140°F (60°C).

• Maximum allowable water temperature to cooler in a non-operating cycle is 100°F

(37.8°C). Maximum entering water temperature for operating cycle is 90°F (32.2°C) (during system changeover from heating to cooling cycle).

• Minimum leaving water temperature from the cooler without freeze protection is 40°F

(4.4°C).

• Minimum entering tower condenser water temperature is 60°F (15.6°C).

Components

Figure 3, Compressor Locations

Evaporator and

423

Evaporator

Condenser Connections

Circuit 2 Circuit 1

Control Panel

Table 2, Major Components

Unit

Size

030 ZR90K3 ZR90K3 ZR11M3 ZR11M3 AC250-70DQ C1010-046 OVE-20-CP100 OVE-20-CP100 035 ZR11M3 ZR11M3 ZR11M3 ZR11M3 AC250-78DQ C1010-046 OVE-20-CP100 OVE-20-CP100 040 ZR12M3 ZR12M3 ZR12M3 ZR12M3 AC250-90DQ C1010-058 OVE-20-CP100 OVE-20-CP100 045 ZR12M3 ZR12M3 ZR16M3 ZR16M3 AC250-102DQ C1010-058 OVE-30-CP100 OVE-30-CP100 050 ZR16M3 ZR16M3 ZR16M3 ZR16M3 AC250-114DQ C1010-070 OVE-30-CP100 OVE-30-CP100 055 ZR16M3 ZR16M3 ZR19M3 ZR19M3 AC250-130DQ C1010-070 OVE-30-CP100 Y929-VCP100 060 ZR19M3 ZR19M3 ZR19M3 ZR19M3 AC250-146DQ C1410-078 Y929-VCP100 Y929-VCP100 070 ZR19M3 ZR19M3 ZR250KC ZR250KC AC250-166DQ C1410-090 OVE-40-CP100 OVE-40-CP100 080 ZR250KC ZR250KC ZR250KC ZR250KC AC250-194DQ C1410-098 OVE-40-CP100 OVE-40-CP100 090 ZR250KC ZR250KC ZR300KC ZR300KC AC250-230DQ C1410-110 OVE-55-CP100 OVE-55-CP100 100 ZR300KC ZR300KC ZR300KC ZR300KC AC250-250DQ C1410-122 OVE-55-CP100 OVE-55-CP100 110 ZR300KC ZR300KC ZR380KC ZR380KC AC250-250DQ C1410-122 OVE-55-CP100 OVE-70-CP100 120 ZR380KC ZR380KC ZR380KC ZR380KC AC250-250DQ C1410-122 OVE-70-CP100 OVE-70-CP100

System #1 System #2 Expansion Valve

Comp. #1 Comp. #3 Comp. #2 Comp. #4

Evap.

Vessel

Size

Cond.

Vessel

Size

System #1 System #2

6 WGZ 030A through 120A OM WGZ-2

Unit Configuration

The chiller unit has two refrigerant circuits, two tandem scroll compressors (total of four), a single two-circuited brazed plate evaporator, a single two-circuited water-cooled condenser, interconnecting refrigerant piping and a control panel with associated sensors and transducers.

Figure 4, Schematic Piping Diagram (One of Two Circuits)

Chilled

Water

LWT

Evaporator

Legend:

Temperature Sensor

Pressure Transducer

Pressure (High Pressure Cutout)

Condenser

F-D

Comp

Relief Valve Schrader Fitting Thermal Expansion Valve

Comp

Condenser

Water

Temperataure Sensor, Leaving

LWT

Chilled Water Control

Solenoid Valve

F-D

Filter-Drier

Sight Glass / Moisture Indicator

Charging Valve

Angle Valve

Ball Valve

OM WGZ-2 WGZ 030A through 120A 7

Field Wiring Diagrams

SCO

Figure 5, WGZ 030AW – 120AW Field Wiring Diagram

3 PHASE

POWER

SUPPLY

FIELD

SUPPLIED

OPTION

CONTROL POWER

FACTORY SUPPLIED ALARM

FIELD WIRED

LARM BELL

OPTION

REMOTE STOP SWITCH

(BY OTHERS)

ICE MODE SWITCH

(BY OTHERS)

CHW FLOW SWITCH

--MANDATORY-(BY OTHERS)

CDW FLOW SWITCH

--MANDATORY-(BY OTHERS)

4-20 MA FOR

CHW RESET

(BY OTHERS)

4-20 MA FOR DEMAND LIMIT (BY OTHERS)

NNECT

(BY OTHERS)

DISCONNECT

(BY OTHERS)

120VAC

CDW PUMP RELA Y

(BY OTHERS)

120 VAC 1.0 AMP MAX

TOWER FAN #1 COIL

(BY OTHERS)

120 VAC 1.0 AMP MAX

ALARM BELL

RELAY

TIME CLOCK

UNIT MAIN

TERMINAL BLOCK

FUSED CONTROL

CIRCUIT

TRANSFORMER

10A

FUSE

(BY OTHERS)

CHW PUMP RELA Y

(BY OTHERS)

120 VAC 1. 0 AMP MAX

TOWER FAN #2 COI L

(BY OTHERS)

120 VAC 1. 0 AMP MAX

OFF

UTO

MANUAL

OFF

UTO

MANUAL

NOR. OPEN PUMP A UX. CONTACTS (OPTIONAL)

NOR. OPEN PUMP AUX.

CONTACTS (OPTIONAL)

GND LUG

120 VAC

TB1

CONTROLLER

J15-N08

TB1-12

J16-N09

TB1-12

J16-N10

TB2

TO COMPRESSOR(S)

TB1-20

CONTROL CIRCUIT

FUSE

2 11 14

GND

40 53

IF REMOTE STOP CONTROL

897

IS USED, REMOVE LEAD 897

FROM TERM 40 TO 53.

IF ICE MODE IS USED

900

REMOVE LEAD

FROM TERM 42 TO 55.

33 43

CONTROLLER

Rx-/Tx-

Rx+/Tx+

53 38 48 49

GND

38 50 51

GND

120VAC

J11

GND

120 VAC

COMMUNICATIO

2 3

330258901-R4

PORT

8 WGZ 030A through 120A OM WGZ-2

Figure 6, WGZ 030AA – 120AA Field Wiring Diagram (Remote Condenser)

UNIT MAIN

3 PHASE

FIELD

SUPPLIED

OPTION

REMOTE STOP SWITCH

NOTE: CONDENSER FAN MOTORS CAN ALSO BE CONTROLLED BY PRESSURE SWITCHES ON THE CONDENSER.

CONTROL POWER

(BY OTHERS)

ICE MODE SWITCH

(BY OTHERS)

CHW FLOW SWITCH

4-20 MA FOR

CHW RESET

(BY OTHERS)

4-20 MA FOR DEMAND LIMIT (BY OTHERS)

330259001-R4

DISCONNECT

(BY OTHERS)

POWER SUPPLY

FUSED CONTROL TRANSFORMER

DISCONNECT

(BY OTHERS)

120VAC

FACTORY SUPPLIED ALARM

FIELD WIRED

ALARM BELL

OPTION

ALARM BELL RELAY

TIME

CLOCK

UTO ON

--MANDATORY--

(BY OTHERS)

LIQUID LINE #1 SOLENOID

LIQUID LINE #2 SOLENOID

OPTIONAL

HOT GAS BYPASS #1 SOLENOID

HOT GAS BYPASS #2 SOLENOID

FAN MOTOR #1 COIL

FAN MOTOR #2 COIL

FAN MOTO R #3 COIL

FAN MOTO R #4 COIL

FAN MOTOR #5 COIL

FAN MOTO R #6 COIL

FAN MOTO R #7 COIL

FAN MOTOR #8 COIL

TERMINAL BLOCK

CIRCUIT

10A

FUSE

(BY OTHERS)

CHW PUMP RELAY

(BY OTHERS)

120 VAC 1.0 AMP MAX

OFF

UTO

MANUAL

OFF

MANUAL

NOR. OPEN PUMP AUX. CONTACTS (OPTIONAL)

24 VAC AMP MAX

(BY OTHERS)

120 VAC 1.0 AMP MAX

(BY OTHERS)

120 VAC 1.0 AMP MAX

(BY OTHERS)

120 VAC 1.0 AMP MAX

(BY OTHERS)

120 VAC 1.0 AMP MAX

(BY OTHERS)

120 VAC 1.0 AMP MAX

(BY OTHERS)

VAC 1.0 AMP MAX

120 VAC

(BY OTHERS)

GND LUG

TB1

2 11 14

TB2

38 48

38 50

TB3

CONTROLLER

J15-N08

TB1-12

J16-N09

J16-N010

J16-N011

J18-N013

J22-N016

J22-N017

J22-N018

TO COMPRESSOR(S)

TB1-20

CONTROL

CIRCUIT

FUSE

120 VAC

120VAC

GND

IF REMOTE STOP CONTROL

897

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

IF ICE MODE IS USED

900

REMOVE LEAD FROM TERM 42 TO 55.

CONTROLLER

J11

GND

1 2 3

24 VAC

120 VAC

Rx-/TxRx+/Tx+

GND

COMMUNICATIO

PORT

OM WGZ-2 WGZ 030A through 120A 9

Control Panel Layout

Figure 7, Typical Control Panel

MicroTech II Unit

Controller

(3) 24V Controller Transformers

Terminal Strips

S1, PS1, PS2

(4) Compressor

Grounding Lug

Switches

Contactors

110V Control

Space for Optional Circuit Breakers and Multi-point Connection

Disconnect Switch

NOTES:

1. Additional space provided in the upper right section for extra components required for optional multiple point power connection and optional circuit breakers.

2. Front door has opening on top for access to the MicroTech II controller for viewing display and making keypad entries without opening the panel door.

Motor Protection Module

The motor protection system consists of an external control module, located on each compressor, connected to a series of thermistors located in the motor windings and the compressor discharge port. If the windings experience an over-temperature condition or the discharge temperature is excessive, the module will trip and shut off the compressor for a 30-minute time delay.

10 WGZ 030A through 120A OM WGZ-2

Start-Up and Shutdown

Pre Start-up

1. The chilled-water system should be flushed and cleaned. Proper water treatment is required to prevent corrosion and organic growth.

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

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

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

5. 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.

6. Check to see that the evaporator water thermostat sensor is securely installed.

7. Making sure control stop switch S1 is open (off) and pumpdown switches PS1 and PS2 are on “manual pumpdown,” place the main power and control disconnect switches to “on.” This will energize the crankcase heaters. Wait a minimum of 12 hours before starting the unit.

8. Check compressor oil level. Prior to start-up, the oil level should cover at least onethird of the oil sight glass located in the equalizing line between the compressors or on the compressor.

9. Note the water pressure drop across evaporator and condenser on pages Error! Bookmark not defined. and Error! Bookmark not defined. and check that water flow is correct per the system 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 3%. 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.

Start-up

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

2. Open the two manual liquid line shutoff valves.

3. Check to see that the unit circuit breakers are in the “off” position.

4. Check to see that the pumpdown switches, PS1 and PS2, are in the “manual pumpdown” position and the control system switch S1 is in the “off” position.

5. Put the main power and control circuit disconnects to the “on” position.

OM WGZ-2 WGZ 030A through 120A 11

6. Verify crankcase heaters have operated for at least 12 hours prior to start-up. Crankcase should be warm to the touch.

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

8. 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.

9. Check resets of all equipment protection controls.

10. Switch on the unit circuit breakers.

11. Set pumpdown switches PS1 and PS2 to “auto” for restart and normal operation.

12. Start the system by setting the system switch S1 to on.

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

14. After system performance has stabilized, it is necessary that the “Compressorized Equipment Warranty Form” (Form No. 206036A) be completed to establish commencement of the warranty period. Be sure to list the pressure drop across both vessels. This form is shipped with the unit and after completion should be returned to the McQuayService Department through your sales representative.

Weekend or Temporary Shutdown

Move pumpdown switches PS1 and PS2 to the “manual pumpdown” position. After the compressors have pumped down, turn off the chilled water pump. Note: With the unit in this condition, it will not restart until these switches are turned back on. The unit has onetime pumpdown. It is important that the compressors pump down before the water flow to the unit is interrupted to avoid freeze-up in the evaporator.

Leave S1 on and power to the unit so that the crankcase heaters will remain energized.

Start-up after Temporary Shutdown

1. Start the water pumps.

2. With the control system switch S1 in the “on” position, move the pumpdown switches PS1 and PS2 to the “auto pumpdown” position.

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

4. Check compressor crankcase heaters.

Extended Shutdown

1. Close the manual liquid line shutoff valves.

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

3. Turn off all power to the unit.

4. Move the control service switch S1 to the “off” position.

5. Close the discharge shutoff valves on the compressor(s) and the liquid outlet valves at the condenser.

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. Do not leave the vessels or piping open to the atmosphere over the shutdown period.

12 WGZ 030A through 120A OM WGZ-2

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.

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 pumpdown switches PS1 and PS2 are in the “manual shutdown” position and the control system switch S1 is in the “off” position.

7. Put the main power and control circuit disconnects to the “on” position.

8. Allow the crankcase 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. Check resets of all equipment protection controls.

13. Switch the unit circuit breakers to “on.”

14. Start the system by setting the system switch S1 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.

15. Set pumpdown switches PS1 and PS2 to the “auto pumpdown” position for restart and normal operation.

16. After running the unit for a short time, check the oil level in the compressor oil sight glass or in the compressor’s equalizing lines for flashing, indicating possible refrigerant in the oil.

Low Ambient Start

The low ambient start logic is for starting units with remote air-cooled condensers during periods of low ambient air temperatures.

A low ambient start takes place if the saturated condenser temperature is less than 85.0°F when the first compressor starts. The low ambient start is active for a time defined by the Low OAT Start Timer set point. This set point is found on screen three in the alarm set points menus.

During the low ambient start, the freezestat logic for the low-pressure stop alarm and the low-pressure events are disabled. The low-pressure stop alarm can still be triggered if the evaporator pressure drops below 5.0 psi at any time while the circuit is in the ‘Run’ state. Also, during the low ambient start, the second compressor is not allowed to start. The evaporator pressure is checked at the end of the low ambient start time frame. If the pressure is less than the low pressure unload set point, then the low ambient start is not successful and the compressor will shut off. This will not be a manual reset alarm until three consecutive attempts have failed. The circuit alarm triggered after the third failed

OM WGZ-2 WGZ 030A through 120A 13

attempt is a Low OAT Restart fault. The Low OAT Restart faults are Circuit alarms so each circuit will attempt to start either compressor three times before the Low OAT Restart fault is indicated.

Fan High Ambient Rapid Start

The following logic exists to get condenser fans started earlier than normal during unit starts with warm ambient air temperatures.

• If the outside air temperature higher than 75.0°F the condenser fan staging logic changes to bring on the first fan on when the condenser pressure is greater than 140 psi.

• The standard condenser fan staging logic would start the first condenser fan when the condenser pressure is higher than 200.0 psi.

• The last condenser fan on each circuit will not shut down until the condenser pressure drops below 140.0 psi regardless of the outside air temperature

Sequence of Operation

The following sequence of operation is typical for WGZ water chiller models. The sequence can vary slightly depending upon options.

Compressor Heaters

With the control circuit power on and the control stop switch S1 off, 115V power is applied through the control circuit fuse Fl to the compressor crankcase heaters HTR1, HTR2, HTR3, and HTR4.

Start-up/Compressor Staging

When compressors start and stop. Stage Up Temp is the LWT temperature at which the next compressor to start will stage up

(start) after at least one compressor on the unit has started and is running. Start Up Temp is the LWT at which the first compressor starts. The start up temperature

equals the stage up temperature plus the Start Delta temperature. A high Start Delta will keep the unit off longer and reduce unit cycling at low loads. However, this high Start Delta will cause a larger excursion from the LWT setpoint before the unit starts.

Stated another way, the Start Delta is the number of degrees above the Evap LWT setpoint, plus ½ the Dead Band, that determines when the first compressor starts. The Start Delta is in effect for only the first start after all compressors have been off. Additional compressor starts and stops are determined by the LWT in respect to the dead band only. The dead band is automatically set of 30% of the EvapDeltaT selected in menu 3. The following sequence would occur for the settings shown below:

EvapDelta T=10.0°F Dead Band=3.0°F StartDelta=5.0°F StopDelta=2.0°F LWT=40.0°F

Figure 8, Staging/Starting Temperatures

EWT

Evap Delta-T Set

LWT Set

50.0°F

10.0°F

40.0°F

Start Del ta T

½DB

46.5°

41.5°

40.0°

38.5°

For a warm start-up (no compressors running), the first compressor will start at any temperature above

46.5°F. Each subsequent compressor will start after the Stage Up Timer has timed out and if the temperature is above the

14 WGZ 030A through 120A OM WGZ-2

dead band, 41.5°F in this case. If the LWT stays above 41.5°F, all of three remaining compressors will eventually stage on after the Stage Up Timer times out between each stage.

At some point, the chilled water temperature will be dropping and begin to approach the point when compressors should begin staging off, which is the LWT setpoint minus ½ of the Dead Band, 38.5°F in this case. If the LWT remains below LWT setpoint minus ½ Dead Band and the Stage Down Timer times out, additional compressor will stage off. The last compressor will stage off when the LWT falls below the LWT Setpoint minus ½ the Dead Band minus the Stop Delta T. The stop Delta T is in effect for only the last compressor running.

If the temperature climbs above 38.5°F all running compressors will remain on. No compressor staging occurs within the Dead Band. The next-on compressor will start when the chilled water temperature reaches 41.5°F and the Stage Up Timer times out.

However, in some circumstances this methodology can cause the LWT to drop to dangerously low levels, with the evaporating temperature below the freeze point, before stopping. In the example shown in Figure 8, the Shutdown Temp (last compressor off) would be 36°F.

This would result in a refrigerant evaporating temperature approaching freezing, so the rule is amended to read:

If the Cool Leaving Water Temperature (LWT) set point is less than half the Control Band above 39.0° F the Stage Down temperature is calculated as:

Stage Down Temperature = Cool LWT – (Cool LWT - 39.0

Shutdown Temperature = Cool LWT – (Cool LWT - 39.0

F), and the

F) – Stop Delta T

This keeps the Stage Down Temp above 39°F and the Shutdown Temp above 36°F, as the maximum Stop Delta T allowed is 3-degrees.

Which compressor starts and stops. One compressor per circuit will start before starting the second compressor on any circuit. In other words, the compressor with the lowest number of starts will start first. The compressor with the lowest number of starts on the other circuit will start next, so that one compressor on each circuit will be running. The third compressor on will be the compressor on either circuit with the fewest starts. The remaining compressor will be the last on. If a circuit is unavailable for any reason, the second compressor. on the operating circuit will stage on. Only two compressors (on the one circuit) will be operating.

There is a 150 second delay after power-up before any compressor is allowed to start. When staging down, one compressor on each circuit will be left on until each circuit has

only one compressor running. In other words, the compressor, on either circuit, with the most run-hours will stop first. The compressor with the most run-hours on the other circuit will stop next. One compressor on each circuit will be running. The third compressor off will be the one, on either circuit, with the most run-hours. The remaining compressor will be the last off. See the following description of pumpdown.

Table 3, Staging in Cool and Glycol Mode

Description Occurs When: Action Taken

Stage #1 ON (See Notes Below) Stage #2 ON After Stage Up Delay times out then, LVG Evap

Stage #3 ON After Stage Up Delay times out, then LVG Evap Stage #4 ON After Stage Up Delay times out then, LVG Evap

Lvg Evap T > Evap LWT SP + (DB/ 2) + S t artup

Delta T T > Evap LWT SP + (DB/2) T > Evap LWT SP + (DB/2) T > Evap LWT SP + (DB/2)

Available compressor with l east starts, ON Available compressor on the other circuit with least starts, ON Available compressor on ei ther circuit with least starts, ON Remaining compressor, ON

Continued next page.

OM WGZ-2 WGZ 030A through 120A 15

Description Occurs When: Action Taken

Stage #4 OFF After Stage Down Delay times out then, LVG

Evap T < Evap LWT SP – (CB/2)

Stage #3 OFF After Stage Down Delay times out then, LVG

Evap T < Evap LWT SP – (DB/2)

Stage #2 OFF After Stage Down Delay times out then, LVG

Evap T < Evap LWT SP – (DB/2)

Stage #1 OFF After Stage Down Delay times out then, LVG

Evap T < Evap LWT SP – (DB/2)-StopDelta T

Note 1: DB (Dead Band) = Evap W ater Delta T x .3

Compressor with most run hours, OFF Compressor on the other ci rcuit with most run hours, OFF Compressor on either circuit with most run hours, OFF Remaining compressor, OFF

Manual Compressor Disable Logic

Logic is available that allows the operator to manually enable and disable compressors. When a compressor is disabled, it is considered unavailable to start in the staging logic. This allows a damaged compressor to be taken offline while the remaining compressor can still provide some cooling

• The Compressor Disable set points are found on Compressor Set Points screens three and four.

• A running compressor cannot be disabled until it has been shutdown.

• If all of the compressors on a circuit are disabled, then the circuit will be disabled.

• If both circuits have all of their compressors disabled, then the Unit State will remain

Off

Automatic Pumpdown

WGZ units are equipped with single pumpdown control. When the last compressor running on either circuit is ready to shut off, the liquid line solenoid valve (LLSV) is closed first and the compressor continues to run until the pumpdown pressure is reached, at which time the compressor shuts off. The shut off pressure is set at 15 psi below the Low Evaporator pressure Unload setpoint.

When the first compressor on a circuit starts, the LLSV opens simultaneously.

Manual Pumpdown

When the Pumpdown Switch is in the pumpdown position, Compressor #3 or #4 (depending on circuit) will shut off. Then the Liquid Line and Hot Gas Bypass Valves will close. The operating compressor will pump out the refrigerant. When the Suction Pressure is at 40 psig, the compressor will stop.

Chilled Water and Condenser Water Pumps

The chiller MicroTech II controller can be programmed to start and stop the system chilled water and condenser water pumps. They may also be controlled by the BAS or manually. Programming directions and the sequence of operation can be found beginning on page 30.

Cooling Tower Control

The cooling tower fans and/or the tower bypass valve can be controlled by the MicroTech II controller. 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 must be installed if the condenser water temperature can fall below 60°F (16°C).

16 WGZ 030A through 120A OM WGZ-2

Condenser Fan Control

Model AA chillers equipped with air-cooled or evaporative-cooled condensers usually require some form of discharge pressure control. The MicroTech II controller can be programmed to provide this function by cycling condenser fans based on the unit discharge pressure. Directions on the pressure settings can be found on page 44.

ICE

In ICE mode, the compressors stage to 100% load until the LWT is less than the ICE LWT SP. Then Compressors #3 and #4 shut down. Following that, Compressors #1 and #2 shut down after going through normal pumpdown on both circuits. There is a programmable, start-to-start, Ice Mode Start Delay that limits the frequency of starts when in the ice mode. The timer can be manually cleared to force a restart.

OM WGZ-2 WGZ 030A through 120A 17

+ 37 hidden pages