McQuay WHS 155A Installation Manual

Installation, Operation and Maintenance Manual IOMM WHS

Water-Cooled Screw Compressor Chiller

WHS 155A - WHS 200A, R-22 WHS 220A, R-410A 60 Hertz

Group: Chiller Part Number:746462 Effective: November 1998

Supersedes: IM 692-1

Table of Contents

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

Receiving and Handling...............................................................................................................................3

Installation...................................................................................................................4

Location and Mounting....................................................................................................................................4

Compressor Condensation...............................................................................................................................4

Vibration Isolators..............................................................................................................................................4

Evaporator and Condenser Water Piping.......................................................................................................7

Water Treatment.................................................................................................................................................7

Head Pressure Control, Tower System...........................................................................................................7

Head Pressure Control, Well Water System ...................................................................................................8

Relief Valve Piping.............................................................................................................................................8

Temperature and Water Flow Limitations.......................................................................................................9

Startup With Cold Condenser Water..............................................................................................................9

Evaporator Freeze Protection...........................................................................................................................9

Condenser Protection and Design Considerations......................................................................................9

Chilled Water Thermostat.................................................................................................................................9

Refrigerant Charge...........................................................................................................................................10

Detection of Loss of Flow..............................................................................................................................10

Glycol Solutions...............................................................................................................................................10

Chilled Water Quantity....................................................................................................................................11

Evaporator and Condenser Water Flow and Pressure Drop...................................12

Physical Data.............................................................................................................16

Dimensional Data......................................................................................................18

Field Wiring...............................................................................................................22

General Information.....................................................................................................................................22

Pre-Start-up...............................................................................................................26

Sequence of Operation..............................................................................................26

Initial Conditions..............................................................................................................................................26

Off Conditions..................................................................................................................................................27

Alarm..................................................................................................................................................................27

Initial Start-up...................................................................................................................................................27

Load Recycle ....................................................................................................................................................28

Maintenance..............................................................................................................28

General..........................................................................................................................................................28

Compressor Maintenance..........................................................................................................................28

Lubrication...................................................................................................................................................28

Electrical Terminals......................................................................................................................................29

Condensers ..................................................................................................................................................29

Refrigerant Sightglass................................................................................................................................29

Lead-Lag.......................................................................................................................................................29

Preventative Maintenance Schedule ............................................................................................................30

"McQuay" is a registered trademark of McQuay International

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"Illustrations cover the general appearance of McQuay International products at the time of publication and we reserve the right to

make changes in design and construction at anytime without notice"

1997 McQuay International

2 WHS 155A- 220A IOMM WHS

Introduction

McQuay StarGate™ water-cooled chillers are completely assembled, factory wired, evacuated, charged, tested and ready for installation. Each unit consists of a water-cooled condenser with integral subcooler, dual accessible semi-hermetic single screw compressors with suction and discharge shutoff valves, replaceable tube shell-and-tube evaporator, and complete refrigerant piping. Liquid line components included are manual liquid line shutoff valves, charging valves, filter-dryers, liquid line solenoid valves, sightglass/moisture indicators, and electronic expansion valves. Other features include compressor heaters, and an advanced fully integrated microprocessor control system.

The electrical control center includes all safety and operating controls necessary for dependable automatic operation, (the high and low pressure controls are external from the electrical control center). Compressors are protected by solid-state overload protection and over temperature protection.

Receiving and Handling

Inspect the unit immediately after receipt for possible damage. The unit is shipped FOB factory and all claims for handling and shipping damage are the responsibility of the consignee. Leave the shipping skid in place until the unit is in final position. This will aid in handling the equipment. Use extreme care when rigging the equipment to prevent damage to the control center, or refrigerant piping. See Dimensional Data for the center of gravity of the unit.

Lift the unit by fastening the rigging hooks to the four corners of the evaporator where the rigging eyes are located (see Figure 1). Use spreader bars between the rigging lines to prevent damage to the control center.

Figure 1, Rigging Eyes

Rigging Eyes

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Installation

CAUTION

Installation must be performed by qualified personnel who are familiar with local codes, regulations, and experienced with this type of equipment.

Start-up by McQuayService is included on all units sold for installation within North America excluding Mexico. Two weeks prior notification of start-up is required. The contractor should obtain a copy of the Start-up Scheduled Request Form from the sales representative or from the nearest McQuayService office.

Location and Mounting

Mount the unit on level concrete or steel base. Service and tube pull clearance (at either end of the unit) is 14 feet (4.3 m). Evaporator and condenser tubes are rolled into the tube sheets to permit replacement. Clearance at the sides and other end, including the top, is 3 feet (1 m).

Make certain the floor or structural support is adequate to support the full operating weight of the complete unit. Optional rubber-in-shear pads, or spring isolators can be ordered for use under each corner of the base members. It is not necessary to bolt the unit to the mounting slab or frame work; although mounting holes are provided in the unit support at the four corners.

Compressor Condensation

Condensation occurs on the compressor surface when the temperature of the compressor surface is lower than the ambient dew point temperature. Drain pans with drain connections are provided underneath each compressor to collect the condensate. The compressor motor housing extends past the drain pans. Install a floor drain close to the unit to collect condensate from motor housing and condensate pans.

Vibration Isolators

Waffle type vibration isolator pads are shipped with the unit for field installation. These pads provide minimal isolation. Vibration isolators are recommended on all upper level installations where vibration transmission is a consideration. When vibration isolators are used, install springs under the main unit supports. Adjust spring so the upper housing clears lower housing by at least 1/4” (6mm) and not more than 1/2” (13mm). If hold-down bolts are not used, install a rubber anti-skid under isolators. Install vibration eliminators in water piping to reduce piping strain, vibration, and noise. Table 1 lists spring and rubber-in-shear isolators for all WHS unit sizes.

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Table 1, Vibration Isolators (WHS 155A - 200A)

Isolator Isolator Per Location

1 2 3 4

Rubber-in-Shear RP-4 RP-4 RP-4 RP-4

Spring CP-4-28 CP-4-28 CP-4-28 CP-4-28

Figure 2, Isolator location

Table 2, Isolators (WHS 220A)

Color Recom.

Isolator Type Of McQuay Max Ld

Stripe Part No. Lb. (Kg)

Rubber-In-Shear RP-4 Green 0021639803 3300 (1497)

Spring CP-4-28 Green 0058051328 3600 (1633)

Note: The spring is fully compressed at about 5400 lb (2449 Kg).

Figure 3 and Figure 4 give dimensions required to secure each McQuay isolator section to the mounting surface. The maximum loads for each unit are shown in Table 3.

Figure 3 , Rubber-in-Shear Isolator

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Figure 4, Spring Flex Isolator

Table 3, Corner Weights for Standard Shell Units lb (kg)

WHS Unit U X V W

155-200 2105 (953) 2475 (1121) 2477 (1122) 2913 (1320)

220 2564 (1161) 3060 (1386) 2935 (1330) 3501 (1586)

Figure 5, Corner Weight Locations

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Evaporator and Condenser Water Piping

WHS evaporators and condensers are equipped with either victaulic or flange connections. The installing contractor must provide matching connections.

CAUTION

Remove the solid-state temperature sensor and thermostat bulbs from the wells to prevent damage to those components when welding on the victaulic or flange connections.

Connect the condenser with the inlet water entering at the bottom to maximize subcooling. The condenser water will discharge from the top connection.

Support piping to reduce weight and strain on the fittings and connections. Be sure piping is adequately insulated. Install a cleanable 20-mesh water strainer in evaporator and condenser water piping. Install enough shutoff valves to permit draining water from the evaporator or condenser without draining the complete system.

CAUTION

Freeze Notice: The evaporator and condenser are not self-draining. Both must be blown out.

Include thermometers at the inlet and outlet connections and air vents at the high points of piping. The water heads can be interchanged (end for end) allowing water connections to be made at either end of the unit. Use new head gaskets when interchanging water heads. When water pump noise is objectionable, use rubber isolation sections at both the inlet and outlet of the pump. Vibration eliminator sections in the condenser inlet and outlet water lines are not normally required. Where noise and vibration are critical, and unit is mounted on spring isolators, flexible piping connections are necessary.

Water Treatment

If unit is operating with a cooling tower, clean and flush cooling tower. Make sure tower "blowdown" or bleedoff is operating. Atmospheric air contains many contaminants which increases the need for water treatment. The use of untreated water may result in corrosion, erosion, sliming, scaling, or algae formation. A water treatment service is recommended. McQuay International is not responsible for damage or faulty operation from untreated or improperly treated water.

Head Pressure Control, Tower System

The minimum entering water temperature to the condenser must not be lower than 75°F (23.9°C) at full tower water flow. If lower temperature water is used, the flow must be reduced proportionally. Use a three-way bypass valve around the tower to modulate the condenser water flow. Figure 6 shows a three-way pressure actuator water regulating valve used for cooling applications. This regulating valve will assure an adequate condensing pressure if the inlet condenser water temperature falls below 75°F (23.9°C). An optional AOX-4 board located in the MicroTech panel will control a cooling tower bypass valve or a variable speed condenser pump.

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Head Pressure Control, Well Water System

When using city or well water for condensing refrigerant, install a normally closed direct acting water regulating valve in the outlet piping of the condenser. This regulating valve will assure an adequate condensing pressure if the inlet condenser water temperature falls below 75°F (23.9°C). The condenser service valve provides a pressure tap for the regulating valve. The valve can modulate in response to head pressure. On shutdown, the valve closes, preventing water from siphoning out of the condenser. Siphoning causes condenser waterside drying and accelerates fouling. If a valve is not used, Figure 7 illustrates the recommendation of a loop at the outlet. Size the loop height (H) to offset the negative pressure caused by the siphoning effect. A vacuum breaker may be required.

Figure 6, Bypass valve

Figure 7, Well Water System

Relief Valve Piping

Follow the requirements of ANSI/ASHRAE Standard 15-1994 for relief valve piping. The condenser relief valve assembly consists of a tree valve and two relief valves. The tree valve must be fully front or back seated to ensure only one relief valve is available for discharge.

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Temperature and Water Flow Limitations

WHS units are designed to operate in conditions from 20°F (-6.7°C) to 50°F (10°C) leaving water temperature on the evaporator side and 75°F (23.9°C) to 95°F (35°C) entering water temperature on the condenser side.

Glycol in the evaporator is required on all applications below 40°F (4.4°C) leaving evaporator fluid temperature. The maximum allowable water temperature to the cooler in a non-operating cycle is 105°F (40.6°C). The non-operating leaving condenser water temperature maximum is 115°F (46.1°C). Flow rates below the minimum values shown in the evaporator and condenser pressure drop curves may cause freeze-up problems, scaling and poor control. Flow rates above the maximum values shown in the evaporator and condenser pressure drop curves will result in unacceptable pressure drops, excessive nozzle and tube erosion and possibly cause tube failure.

Startup With Cold Condenser Water

WHS screw compressor chillers are designed to permit startup with elevated chilled water temperatures and cold condenser water. Following a weekend shutdown, for example, in relatively cool, low wet bulb ambient, the building chilled water temperature could be 70°F to 80°F (21°C to 27°C) with a condenser water temperature of 55°F (13°C). Start up under these conditions is expected. If the cooling load is excessive, or condenser water temperatures substantially less, modification of alarm timer settings by the McQuayService Technician may be required.

Evaporator Freeze Protection

When freeze protection is a concern, do the following:

1. If the unit will not be operated during the winter, drain and flush the evaporator and chilled water

piping with glycol. Drain and vent connections are provided on the evaporator.

2. When using a cooling tower, add glycol solution to the chilled water system. Freeze point should

be approximately 10°F (5.6°C) below minimum design ambient temperature.

Note: Freeze damage is not considered a warranty failure and is not the responsibility of McQuay International.

3. Insulate field water piping, especially on the chilled water side.

Condenser Protection and Design Considerations

If pond or river water is used as a condensing medium and the water valves leak, the condenser and liquid line refrigerant temperature could drop below the equipment room temperature on the "off" cycle. This problem occurs when cold water continues to circulate through the condenser and the unit remains off due to satisfied cooling load. If this occurs:

1. Cycle the condenser pump off with the unit.

2. Verify the liquid line solenoid valves are operating properly.

Chilled Water Thermostat

The WHS water-cooled chiller is equipped with the MicroTech leaving water controller. Be careful when working around the unit to avoid damaging lead wires and sensor cables. Check lead wires before running the unit. Avoid rubbing the lead wires on the frame or other components. Verify the lead wires are firmly anchored. If the sensor is removed from the well for servicing, do not wipe off the heat conducting compound supplied in the well.

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Refrigerant Charge

All units are designed for use with R-22 or R-410A and are shipped with a full operating charge. The operating charge for each unit is shown in the Physical Data Table.

Detection of Loss of Flow

NOTE: Water pressure differential switches are not recommended for outdoor applications.

The preferred means for detecting loss of flow is the use of factory-mounted pressure differential switches for the evaporator and condenser.

A flow switch is available from McQuay (part number 00175033-00). It is a “paddle” type switch and adaptable to any pipe size from 3” (76mm) to 8” (203mm) nominal. Two flow switches are required. Mount the flow switch in either the entering or leaving water line of the evaporator and condenser. Certain minimum flow rates are required to close the switch and are listed in Table 4. Installation should be as shown in Figure 8.

Figure 8, Flow Switch

Connect the normally open contacts of the flow switch in the unit control center at terminals 62 and

63. Flow switch contact must be suitable for 24 VAC, low current (16ma).

Table 4, Flow Switch Minimum Flow Rates

Nominal Pipe Size Min. Required Flow to

(inches) Activate Switch - GPM (L/s)

5 58.7 (3.7) 6 79.2 (5)

Glycol Solutions

A glycol anti-freeze solution is required for operation below 40°F leaving chilled fluid temperature. The introduction of a glycol solution reduces the capacity of the chiller and any air handling equipment. Contact the local McQuay sales office for determination of the affect of glycol on the chiller capacity, power input and pressure drop.

CAUTION

Use industrial grade glycols only. Do not use an automotive grade antifreeze. Automotive antifreeze contains inhibitors that will cause plating on the copper tubes within the chiller evaporator. The type and handling of glycol used must be consistent with local codes.

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