McQuay Seasonpak PWA-041A Installation And Maintenance Data

Brand: McQuay

Model: Seasonpak PWA-041A

Type: Installation And Maintenance Data

BULLETIN NO. IM 126

AUGUST 1969

INSTALLATION AND

MAINTENANCE DATA

PACKAGED WATER CHILLER

TYPE WHR

THRU 120 TONS

“McQUAY”

and

“SEASON PAK” are registered trademarks of

McQuay,

Inc., Minneapolis, Minnesota.

@ 1969

McQuay,

Inc.

TABLE OF CONTENTS

CONTROLS-CHECKING

..................................

CROSSREFERENCE

NEW TO OLD MO

.............

ELECTRICAL

.......................................

22-23

CONTROL CENTER SERVICE

...........................

26-27

ELECTRICALDATA

..................................

22-23

WIRING

...........................................

10-13

WIRING DIAGRAMS

...................................

14-21

MAINTENANCE......................................

26-29

MOVING

PLACING THE UNIT

..........................

NOMENCLATURE

.....................................

OPERATION

......................................... 24

PIPING

REFRIGERANT

....................................... 8-9

WATER............................................

6-7

PRE-INSTALLATION

.....................................

REPLACEMENT PARTS

...................................

SERVICE & MAINTENANCE

..............................

26-29

START-UP PROCEDURE

..................................

TROUBLE SHOOTING CHART.

............................

27-29

VIBRATION ISOLATORS

.................................

3-5

NOMENCLATURE

Nominal Capacity (Tons)

R_OsOA-

l+Basic

unit with water cooled condenser(s).

-2kBasic

unit with mounted receiver(s) in lieu of condenser(s).

-3&Basic

unit less condenser(s) or receiver(s).

CROSS REFERENCE

NEW TO OLD MODEL NUMBERS

New model numbers represent a

change

in model number designation

only, NOT a change in unit design or performance.

PRE-INSTALLATION

INSPECTION

with a full refrigerantcharge.A holding charge is sup-

When the equipment is received, all items should be

plied in condenserless models (Arrangements 2 & 3).

carefully checked to make sure that all crates and

For shipment, the charge is contained in the

conden-

cartons have been received. All units should be

care-

ser and is isolated by the manual condenser liquid

fully inspected for damage when received. All damage

valve and the compressor discharge service valve.

should be reported immediately to the carrier and a

Should the unit be damaged, allowing the refrigerant

claim filed for damage.

to escape, there may be danger of suffocation in the

equipment area since the refrigerant will displace the

HANDLING

air. Care

should

be taken to avoid rough handling or

shock due to dropping the unit. NEVER LIFT, PUSH

Every model WHR SEASONPAK water chiller with

OR PULL UNIT FROM ANYTHING OTHER THAN

water cooled condensers (Arrangement 1) is supplied

THE BASE.

MOVING AND PLACING THE UNIT

MOVING THE UNIT

The

McQUAY

SEASONPAK water chiller is mounted

on heavy wooden skids to protect the unit from ac-

cidental damage and to permit easy handling and mov-

ing.

It is recommended that

all

moving and handling be

performed with the skids under the unit when possible

and that the skids not be removed until the unit is in

the final location.

When moving the unit, dollies or simple rollers can

be used under the skids, or dollies alone can be used

under ends of the frame. Do not use pipe rollers under

the unit if the skids have been removed.

The 4”

channel base is arranged on the skid so

that the fork of a standard fork lift truck can be slid

easily under (See Figure 1). The forks of the fork lift

truck must be across both the front and rear channels

before

lifting.Never

put the weight of the unit against

the condensers.

In moving, always apply pressure to the base on

skids only and not to the piping or shells. A long bar

helps move the unit easily. Avoid dropping the unit at

the end of the roll.

If the unit must be hoisted, it is necessary to lift

from the skid or from the base as indicated in Figure

2, Page 3. A spreader bar must be used to protect the

control cabinet and other

areas

of the chiller.

Do not attach slings to piping or equipment. Move

unit in the upright horizontal position at all times.

Let unit down gently when iowering from the trucks or

rollers.

Page 2

FIGURE NO. 1

MOVING UNIT WITH FORK LIFT

NOTE:

ALWAYS LIFT ON SIDE OPPOSITE THE

CONTROL PANEL TO AVOID DAMAGING

THE CONTROLS.

LOCATION

Unit is designed for indoor application and must be

located in an area where the surrounding ambient tem-

peratures are 40F or above. A good rule of thumb is

to place units where ambients are at least 5 degrees

above the leaving water temperature.

Because of the electric control devices, the units

should not be exposed to the weather. A plastic cover

over the control box is supplied as temporary protec-

tion during transfer.

A reasonably level and sufficiently strong floor is

all that is required for the SEASONPAK water chiller.

If necessary, additional structural members should be

provided to transfer the weight of the unit to the near-

est beams. Refer to Page 4 for foundation information.

SPACE REQUIREMENTS FOR CONNECTIONS

AND SERVICING

The c h i I led water piping for all units enters and

leaves the cooler from the rear. A clearance of 3 to 4

feet should be provided for this piping and for replac-

ing the fi Iter-driers, for servicing the solenoid valves,

or for changing the compressors, should it ever be-

come necessary.

The condenser water piping enters and leaves the

shell from the ends. Work space must be provided in

case water regulating valves are being used and for

general servicing.

Clearance should be provided for removing cooler

tubes on one end of the unit as specified in Table 1.

Condenser tubes cannot be replaced. It is also desir-

able to leave a small walk area on the end opposite

that used for replacement of a cooler tube.

MINIMUM CLEARANCE FOR COOLER TUBE RE-

MOVAL MEASURED FROM CENTER LINE OF

CHILLED WATER CONNECTION ON EITHER END

TABLE NO. 1

MINIMUM CLEARANCE

UNIT SIZE

MINIMUM CLEARANCE

007A THRU 015A 72”

020A THRU 041A

96”

050A THRU 070A

108”

080A

120”

FIGURE NO. 2

SUGGESTED RIGGING

OTE:ALWAYS USE SPREADER

BARS TO PROTECT UNIT

FROM DAMAGE.

PLACING THE UNIT

The small amount of vibration normally encountered

with the SEASONPAK water chiller makes this unit

particularly desirable for basement or ground floor in-

stallations where the unit can be bolted directly to

the floor. The floor construction should be such that

the unit wi II not affect the bui

lding

structure, or trans-

mit noise and vibration into the structure. See VI-

BRATION ISOLATORS section for additional mount-

ing information. Hold down bolt locations are indicated

in Figures 3 and 4, Page 4.

VIBRATION ISOLATORS

Rubber-in-shear or spring isolators can be furnished

and field placed under each corner of the package. It

is recommended that a rubber-in-shear pad be used as

the minimum isolation on all upper level installations

or areas in which vibration transmission is a consid-

eration.

Transfer the unit as indicated under MOVING THE

UNIT, or use the methods as indicated in Figures 1

and 2. In all cases, set the unit in place and level

with a spirit level. When spring type isolators are re-

quired, install springs running under the main side

channels. Foundation hold down bolt locations for vi-

bration isolators are given in Figures 3 & 4. A

rubber-

anti -skid pad should be standard under isolators if

hold down bolts are not used.

Vibration eliminators in all water piping connected

to the SEASONPAK water chiller are recommended to

avoid straining the piping and transmitting vibration

and noise.

090A THRU

1OOA

1 OX”

110A

THRU

120A

132"

Page 3

WATER PIPING

GENERAL

Piping practices vary considerably. In most cases,

codes,

local ordinances and established practices

govern the selection and installation of piping. Local

building and safety codes and ordinances should be

studied and complied with.

Shut-off valves should be provided at the unit so

that normal servicing can be accomplished without

draining the system.

It is recommended that temperature and pressure in-

dicators be installed at the inlet and outlet of the

shells to aid in the normal checking and servicing of

the unit. Also, the installation of wire mesh strainers

at the pump suction will protect the pump and shells

from foreign matter.

A preliminary leak check of the water piping should

made before filling the system.

Vibration eliminators are recommended in all lines

connected to the SEASONPAK water chiller.

CHILLED WATER PIPING

The water flow entering the cooler must always be on

the end nearest the expansion valves and cooler re-

frigerant connections to assure proper expansion valve

operation and unit capacity.

Design the piping so that is has a minimum number

of changes in elevation. Include manual or automatic

vent valves at the high points of the chilled water

piping, so that air can be vented from the water cir-

cuit. System pressures can be maintained by using an

expansion tank or a combination pressure relief and

reducing valve.

All chilled water piping should be insulated to pre-

vent the nuisance of water dripping from the lines. If

insulation is not of the self-contained vapor barrier

type, it should be covered with a moisture seal. Do not

insulate piping until it has been tested for leaks and

drain connections have been extended beyond the pro-

FIGURE NO. 7

TO COOI.ER

posed insulation thickness to make them accessible.

CHILLED WATER THERMOSTAT

WHR-008A

thru 060A

The chilled water thermostat

is mounted inside the control console and the control

bulb, capillary tubing and control bulb immersion well

are attached to the unit with spring clips, The control

bulb well

must be

field inserted in the first tee install-

ed in the return water line as shown in Figure 7. The

bulb well is supplied with a

1/2"

NPT male thread.

Carefully unsnap the well from the holding clips, re-

move the retaining bushing and

slowly remove the bulb

from the well. Install into piping as indicated in Fig-

ure 7. When installing the bulb, carefully remove it

from the well so as to not wipe off the heat

conduct-

ing compound supplied in the well. After installing

the well, carefully insert the bulb and seal in with

the excess compound. Insert the retaining gasket

and

sealing bushing and clip or tape the cap tube to the

water line. Care should be taken not to break or kink

the charged capillary tubing. Sufficient cap tube length

is provided for bulb insertion up to 10 feet from the

unit; however, it is recommended that the bulb well

be placed as close to the cooler inlet as possible.

Insulate over thermostat well.

WHR-070A thru 120A

The chilled water thermostat

is mounted inside the control console. The control

bulb is mounted in a well, located in the return water

connection to the unit. Care should be taken not to

kink or break the charged capillary tubing when work-

ing around the unit. It is also advisable to check the

cap tube before running the unit to be sure that it is

firmly anchored and not rubbing on the frame or any

other component.

CAUTION: The thermostat bulb should not be exposed

to water temperatures above 140F since this will

damage the control.

THERMOSTAT WELL INSTALLATION

RETURN WATER

‘h’

N.P.T.

Page 6

CONDENSER

WATER PIPING

General

_.-

For the best performance, the condenser water inlet

is established as the bottom connection of the con-

denser.

Water cooled condensers may be piped for well

water applications, or for use in conjunction with a

cooling tower. Cooling tower applications should in-

clude a small amount of waste circulating water to

prevent building up of solids in the tower basin.

Head Pressure Control

Some means of controlling operating head pressure

must be

provided.

A three way pressure actuated water

regulating valve is recommended for cooling tower ap-

plication, as indicated in Figure 8. This arrange-

ment wi II maintain a constant condensing pressure, re-

gardless of temperature conditions and assures enough

head pressure for proper thermal expansion valve op-

eration. Full water flow is assured to the tower with

this arrangement.

Well Water

Where well water is used for condensing refrigerant, a

direct acting water regulating valve is

recommended-

See Figure 9. The valve is n

orma

I ly installed at

the outlet of the condenser. On shut down, the valve

will close and, in this way, prevents water siphoning

out of the condenser. Siphoning causes drying of the

water side of the condenser and rapid buildup of foul-

ing. When no valve is used, a loop at the outlet end

is recommended

See Figure 9.

WATER REGULATING VALVES (EACH CONDENSER)

FIGURE NO. 8

3 WAY WATER

REGULATING VALVES

COi:lNG

TOWER

PURGE

MAIN

CONDENSER

WATER SUPPLY

FROM PUMP

PASS

LANCING

VALVES OR COCKS

FIGURE NO. 9

LOOP REQUIRED WHEN NO

REGULATING VALVE

USED

TO DRAIN

FROM MAIN

CONDENSER

PUMP

DIRECT ACTING WATER

REGULATING VALVE

COOLING TOWER SYSTEM

WELL WATER COOLING SYSTEM

WATER FLOW SAFETY SWITCH (OPTIONAL)

A water flow safety switch is available as optional

equipment for all Type WHR chillers. The flow switch

must

be field installed and wired into the SEASONPAK

water chiller control center as indicated on the draw-

ings.

The flow switch should be installed in a horizontal

run in either the supply or return chilled water piping

as follows:

1. Apply pipe sealing compound to only the threads of

the switch and screw unit into D’ x D’ x

1”

reducing

tee(See Figure 10). The flow arrow must be pointed

FIGURE NO. 10

FLOW SWITCH

--._,

PADDLE

FLOW SWITCH

in the correct direction.

2. Piping should provide for a straight length before

and after the flow switch of at least 5 times the

pipe diameter.

CAUTION: Make sure the arrow on the side of the

switch is pointed in the proper direction of flow.

The flow switch is designed to handle the control

voltage and shouldonly be connected according to the

wiring diagram (See Wiring Diagram inside control

box door).

PIPE SECTION

FLOW DIRECTION

TEE

D’

VIEW FROM END OF COOLER

Page 7

REFRIGERANT PIPING

REMOTE AIR COOLED CONDENSERS

For remote condenser application, such as an air

cooled condenser, the chillers, with and without

mounted receivers, are shipped containing a Refriger-

ant-22 holding charge. It is important that the unit be

kept tightly closed until the remote condenser is in-

stalled, piped to the unit and the high side evacuated.

Refrigerant piping,to and from the remote unit,

should be sized and installed according to the latest

ASHRAE

Guide. It is important that the piping be

properly supported with sound and vibration insulation

between tubing and hangerand that the discharge lines

be looped at the condenser and trapped at the com-

pressor to prevent refrigerant liquid from draining into

the compressor discharge manifold. Looping the dis-

charge line also provides greater line flexibility.

The discharge gas valve, liquid line

solenoid,filter-

drier and moisture indicators are all provided as stan-

dard equipment with the SEASONPAK water chiller,

whether installed with remote or factory mounted re-

ceivers.

After the equipment is properly installed, the unit

may be charged with Refrigerant-22, then run at de-

sign load conditions, adding charge until the liquid

line sight-glass is clear, with no bubbles flowing to

expansion valve. Total operating charge will depend

on the air cooled condenser used and the length of

external piping, but generally will be equal to the

water cooled charge shown in Table 9, Page 26. With

SEASONTROL low ambient control on air cooled

units, additional charge must then be added, as re-

quired (but not to exceed receiver pumpdown capacity)

UNIT LESS CONDENSER

SEASONPAK water chillers without condensers or

with mounted receivers require field piping to a re-

mote condenser of some type. As mentioned under the

REMOTE CONDENSER section above, refrigerant

piping should be sized and installed according to the

latest ASHRAE Guide. The design of refrigerant pip-

ing when using air cooled condensers involves a num-

ber of considerations not commonly associated with

other types of condensing equipment. The following

discussion is intended for use as a general guide to

sound, economical and trouble-free piping of air cool-

ed condensers.

On remote condenser applications, discharge line

mufflers are recommended. The mufflers should be in-

stalled as close to the compressor discharge as pos-

sible, If oil separators are used, they will usually

perform the same function as a muffler and will elim-

inate the need for one. A muffler wi II reduce discharge

line pulsations; particularly those which occur during

unloaded compressor operation

Discharge lines must be designed to handle oil

properly and to protect the compressor from damage

that may result from condensing liquid refrigerant in

the line during shutdown. Total friction loss for dis-

charge lines of

3 psi is considered good design. Care-

ful consideration must be given for sizing vertical

risers to insure that gas velocities are sufficient at

all operat,ing conditions to carry oil. If the velocity

in a vertical discharge riser is too low, considerable

oil may collect in the riser and the horizontal header,

causing the compressor to lose its oil and resultant

damage due to lack of lubrication.

Another danger is when the compressor load is in-

creased, the oil that had collected during reduced

loads may be carried as a slug through the system

and back to the evaporator, where a sudden increase

of oil concentration may cause

slopover

and damage

to the compressor.

Any horizontal run of discharge piping should be

pitched away from the compressor approximately

1/4"

per foot or more. This is necessary to move by gravity

any oil lying in the header. Oil pockets must be

avoided as oil needed in the compressor would

col-

lect

at such points and the compressor crankcase may

become starved.

It is recommended that any discharge lines coming

into a horizontal discharge header rise above the

center line of the discharge header. This is necessary

to prevent any oil or condensed liquid from draining

to the top heads when the compressor is not running.

In designing liquid line, it is important that the

liquid reach the expansion valve with a minimum of

flash gas since this gas will reduce the capacity of

the valve. Because “flashing” can be caused by a

pressure drop in the liquid lines, the pressure losses

due to friction and changes in static head should be

kept to a minimum.

The liquid line from the condenser to the receiver

MUST be sized for sewer flow operation (100

fpm/ve-

locity

or less) and MUST be sloped to the receiver

with no traps in the line.

Any shut off valve in this

line must have an orifice area equal to the inside area

of the line. Free drainage in this line is essential to

permit gas from the receiver to vent back to the con-

denser. Failure to adequately size and slope this line

wi II force liquid to back up into the condenser causing

high head pressure and bubbling sight glass.

A check valve should be installed in the liquid line

on installations that require operation at outside am-

bients below 60F. This prevents liquid migration to

the condenser and helps maintain a supply of refriger-

ant in the receiver for initial start up.

Typical Arrangements

Figure No. 11,

Page 9 illustrates a typical piping

arrangement involving a remote air cooled condenser

located at a higher elevation than the compressor and

receiver. This arrangement is commonly encountered

when the air cooled condenser is on a roof and the

compressor and receiver are on grade level or in a

basement equipment room.

In this case,

the design of the discharge line is

very critical. If properly sized for full load condition,

the gas velocity might be too low at reduced loads to

carry oil up through the discharge line and condenser

coil. Reducing the discharge line size would increase

the gasvelocity sufficiently at reduced load condi-

tions; however,

when operating at

full

load, the line

might be greatly undersized and thereby create an ex-

cessive refrigerant pressure drop. This condition can

be overcome in one of the two following ways:

1. The discharge line may be properly sized for the

desired pressure drop at full load condition and an

oil separator installed at the bottom of the trap on

the discharge line from the compressor.

Page 8

2. A double riser discharge line may be used as shown

in Figure 12, Page 9. Line “A” should be sized

to carry the

oil

at minimum load condition and line

‘(

B”

should be sized so that at the full load con-

dition both lines would carry oil.

The above two points are particularly important in

applications where the refrigerant receiver is directly

beneath the air cooled condensers. If two unlike air

cooled condensers or unequal piping is used, the re-

sultant unequal refrigerant pressure drop may cause

liquid to build up in one of the condenser coils, there-

by reducing its effective capacity.

Notice in all illustrations, the hot gas line is loop-

ed at the bottom and top of the vertical run. This is

done to prevent oil and condensed refrigerant from

flowing back into the compressor and causing damage

The highest point in the discharge line should always

be above the highest point in the condenser coi I; and

it is advisable to include a purging vent at this point

to release noncondensibles from the system.

Figure No. 13, below, i I I us t ra te s another very

common application where the air cooled condenser is

located on essentially the same level as the compress-

FIGURE NO. 11

PURGE

VALVE

DISCHARGE LINE

HECK VALVE

LIQUID LINE

FIGURE NO. 13

DISCHARGE LINE

TO EVAPORATOR

RECEIVER

LrQuro

LINE

(EVAPORATORS

or and receiver. The discharge line piping in this

case is not too critical. The principal problem en-

countered with this arrangement is that there is fre-

quently insufficient vertical distance to allow free

drainage of liquid refrigerant from the condenser coil

to the receiver.

To guard against gas binding in the receiver and

liquid buildup in the condenser coil, which are com-

mon to this arrangement, be certain that the receiver

is located as far below the condenser outlet as pos-

sible. The liquid line should be free of any traps or

loops and, if there are any horizontal runs, they

should be pitched down toward the receiver.

Figure No. 14, below, illustrates a third very

common application where two or more separate air

cooled condensers are piped together on a single

compressor.

First of all, it is very important that the two air

cooled condensers have the same capacity so that the

refrigerant pressure drop through each unit is equal.

Secondly, the piping should be arranged so that the

lengths of run to and from each air cooled condenser

are equal.

FIGURE NO. 12

PURGE

VALVE

LIQUID LINE

RECEIVER-

TiAp

(EVAPORATORS

FIGURE NO. 14

PURGE

VALVE

I I

CONDENSER

(

EVAPORATOR

CHECKVALVE

Page 9

ELECTRICAL

MODELS WHR-008A THRU 060A

FIGURE NO. 15

FREEZESTAT (MANUAL RESET) 8. COMPRESSOR STARTING CONTACTORS

2. OIL FAILURE SWITCH (MANUAL RESET)

9. CONTROL CIRCUIT FUSE

3. LEAD LAG SWITCH 10. CIRCUIT BREAKERS

4. CONTROL RELAYS (BEHIND PANEL)

11. POWER CONNECTION TERMINAL BLOCK

5. WATER CONTROL THERMOSTAT 12. INDICATOR LIGHTS

6. HIGH (MANUAL RESET) AND LOW PRESSURE CUTOUTS

7. CONTROL SYSTEM ON -OFF SWITCH

FIGURE NO. 16

MODELS WHR-070A THRU 120A

1. FREEZESTAT (MANUAL RESET) 7. CONTROL SYSTEM ON

-OFF

SWITCH

2. OIL FAILURE SWITCH (MANUAL RESET)

8. COMPRESSOR STARTING CONTACTORS

LEAD LAG SWITCH 9. CONTROL CIRCUIT FUSE

CONTROL RELAYS (BEHIND PANEL) 10. CIRCUIT BREAKERS

WATER CONTROL THERMOSTAT

11. POWER CONNECTION TERMINAL BLOCK

HIGH (MANUAL RESET) AND LOW PRESSURE CUTOUTS 12. INDICATOR LIGHTS

Page 10

ELECTRICAL

MODELS WHR-008A THRU 060A

FIELD WIRING

Only three main power leads need be hooked up to the

chiller on Models WHR-008A thru 060A. Models WHR-

070A thru 120A have a dual control panel, each sec-

tion handling one circuit of the unit and require separ-

ate service connections to each panel. Table 8, Page

22 gives the recommended lead wire size when only

three conductors are used in a raceway. Refer to the

National Electrical Code for othertype wire or special

instructions.

Although there is no specific requirement,

inter-

locking of a flow switch and the condenser pump start-

er (or air cooled condenser fan) is suggested for the

most dependable and economical system operation.

The cooler pump should operate continuously,

when the unit is not operating.

even

The condenser pump should be field interlocked by

connecting the pump starter coil to terminal 7 and

terminal 12 as shown on Schematic Wiring Diagrams 1

and 2 and terminals 8 & 14 and 12

14 on Schematic

Wiring Diagrams 3 and 4, Pages 14 thru 17. This

cycles the condenser pump (or air cooled condenser

fan) with the compressor.

Referring to Diagrams 1 thru 4, the flow switch is

interlocked by removing jumpers between terminals 13

and 14 for single units and 25 and 26 for dual units,

and wiring the switch contacts into the system as is

shown on the Schematic Wiring Diagrams. When so

wired, the chilled water pump must be operating be-

fore power can be applied to start this system.

Note

that the crankcase heaters will be energized regard-

less of water flow. The flow switch is recommended

and does not have the shortcomings of interlocking the

the cooler pump starter.

A flow switch must be used

for leaving water temperature of 42 F and lower.

STARTING SEQUENCE

(Refer to Diagrams 1 thru 4)

Variations or options

in the control system will

change the basic wiring diagrams slightly, however,

the sequence of events will be similar.

The following starting sequence is for dual com-

pressor units. The sequence for single compressor

units is identical except for the obvious reference to

the second unit. Once the system ON-OFF switch is

pushed on the ON position, the unit will operate com-

pletely automatically.

1. Check or throw to “auto” position switches S3

and S4 (pumpdown switches). Switch is in “auto”

position during normal operation.

2. With main power on,

power to the control circuit

from L1 and L2 is fed through fuse

to terminal

COMPRESSOR LOCATION

WHR-020A THRU 060A

FIGURE NO. 17

TOP VIEW OF UNIT

Models

WHR-OO8A thru 015A are

single compressor units.

10.

25. The power from 25 is fed thru NC contacts to

relay R3 and R4 to energizethe compressor crank-

case heaters, when the compressors are not

oper-

ating. The indicator lights should show the heaters

on. Power is also supplied to the main system On-

Off switch,

S1.

Closing switch

energizes System No. 1 and

System No. 2.

Referring to System No. 1, power at terminal 2 in-

dicates power to the system by lighting the red

“Power on” liaht.

Provided

operating

safety controls are closed

(FS1,

OP1,

HP1 and

MP1

OL1

when external

overloads are used), power at terminal 3 will ener-

gize safety light, indicating the system is ready

to run.

Referring to the standard non-recycle, pumpdown

operation of the Schematic Wiring Diagram, relay

and R3 are normally open and power cannot

reach compressor starter. Power can reach starter

only by energizing

which is controlled by ther-

mostat

TC1

through the compressor lead-lag switch

(dual units only) and the pumpdown switch S3.

When cooling is required, power is supplied to

terminal 4 through water thermostat

TC1

energiz-

ing relay

R1,

indicator light LT5.

When

relay is energized, contact

will close

and open the liquid line solenoid valve

LLS1.

If low pressure control

LP1

is open, the opening

LLS1

will allow refrigerant to flow into the low

side building up pressure which will close

LP1

and the compressor will start.

Meanwhile, time delay TD3 is timing the second

compressor. After the time delay closes, power is

fed to control system No. 2 and the same sequence

of starting for the second compressor is repeated.

OFF CYCLE

Referring to the Schematic Wiring Diagrams

when

thermostat

TC1

is satisfied, the electrical

circuit

terminal No. 4 (or No. 10 for second system), will be

broken opening relay

de-energizing the liquid line

solenoid and indicator light LT5. The compressor wi II

continue to operate through the contacts of R3 relay.

Note that R3 relay is now energized through its own

contacts and the compressor is on the pumpdown

cycle. When the compressor has pumped most of the

liquid refrigerant from the cooler, the low pressure

cut out,

LP1

will open and de-energize R3 relay. This

locks the compressor off the line until the thermostat

TC1

calls for cooling again, energizing

LLS1

and

and closing LPI.

COMPRESSOR HORSEPOWER

TABLE NO. 6

MODEL

NUMBER

COMPRESS

OR NOMINAL HP

-3MP.

COMP.

WHR-008A

WHR.OlOA

WHR-015A

WHC

. . ...1-020A

WUS-025A

II.

WIJ’C

,J-030A

Whn-vr,

nr,

WHR-050A

2.5

WHR-060A

Paoe

ELECTRICAL

MODELS WHR-070A THRU 120A

FIELD WIRING

3. Close all circuit breakers in both

panels.

Power leads must be run into each panel and be con-

nected to the power terminal block. Table 8, Page 22

gives the recommended lead wire size for each circuit

which is based on the use of 3 conductors in a race-

way. Refer to the National Electric Code for other

type wire or special instructions. All Field wiring

must comply with Local, State and National Electric

Codes.

Close control circuit system switch

located on

the outside face of the Left Hand panel.

From the power connection block to the contactors,

overloads and compressor motors, the wiring is fac-

tory installed, ready for operation.

Red power lights

LT1

and LT2 will be energized.

Circuit

(odd numbered components) will be

energized thru safety controls (Freeze & High

Pressure Controls) and safety light LT3 wi II

light as controls are closed (Normal position).

All compressor motor overload protector relays

MP1

& MP3 will be energized closing contacts

in safety circuit.

Although there is no specific requirement, inter-

locking of a flow switch and the condenser pump

starter (or air cooled condenser fan) is suggested for

the mostdependable and economical system operation.

The cooler pump should operate continuously, even

when the unit is not operating.

Close pump down switch S3 (Auto Position).

Switch

on thermostat

TC1

closes (due to in-

crease in entering water temperature to cooler) and

followina sequence occurs.

The condenser pump or air cooled condenser fan

should be Field interlocked by connecting toterminals

8, 12, 36, 40 and 14 & 42 in the following manner, and

as indicated in Diagrams 5 and 6.

If the tower or air cooled condenser has only one

pump or fan, jumper terminals 8, 12, 36 and 40 and

connect the motor starter

coil

to any one of these

terminals, and also to terminal 14

42. Power at

these terminals is 220V; therefore, the pump or fan

motor starter coil must be 220 volts.

If two towers or air cooled condensers are used (one

for each circuit), connect one pump or fan starter to

terminals (8 and 12) and 14 and the other pump or fan

to terminals (36 and 40) and 42.

Connecting the unit as indicated above will provide

tower pump or condenser fan operation when any com-

pressor is operating.

Referring to Diagrams 5 and 6, the flow switch is

interlocked by removing jumper between terminals 25

and 26 and wiring the switch contacts into the system

as is shown on the Schematic Wiring Diagrams. When

so wired, the chilled water pump must be operating

before power can be applied to start this system. Note

that the crankcase heaters will be energized regard-

less of water flow. The flow switch is recommended

and does not have the shortcomings of interlocking

the cooler pump starter. A flow switch must be used

for leaving water temperoture of 42 F and lower.

Energizes

10 second time delay relay

TD1

provide a delay on starting circuit #2.

Energizes light LT5, indicating stage 1 cooling

is required.

Energizes TD3 10 second delay relay to provide

delayed start of compressor

1B.

Energizes run relay

closing contacts to open

liquid line solenoid

LLS1,

allowing liquid re-

frigerant to flow into cooler.

Low side pressure will increase closing Low

pressure switch

LP1

energizing compressor con-

tactors

Ml and M3 and starting compressor motor

1A (Left Hand).

Non-recycle relay R3 is energized closing con-

tacts R3.

If oil pressure does not build up T2 contact in

oi I pressure,

safety control

OP1

will close,

energizing a heater in the control. If pressure

does not build up in 120 seconds, the heater wi II

cause the contacts

OP1

to open and shut down

the compressor.

If suction pressure does not build up to 56 psi,

the T2 contact in freeze control will close and

open contacts

FS1

after 60 seconds.

7.With a further increase in inlet water temperature,

thermostat switch

will close. If 10 seconds has

elapsed since switch #1 closed, contacts TD3 in

time delay relay will be closed.

a. Light LT7 will be energized, indicating that

STARTING SEQUENCE

(Refer to Diagrams 5

cooling on stage 2 is required.

b. Relay R5 is energized, closing contacts R5

energizing contactors

& M7 starting com-

pressor motor 1B (Left Center).

A further increase in water temperature will close

thermostats 3 and 4, starting compressors 2A and

2B in a similar manner.

Variations or options in the control systems will

change the basic wiring diagrams slightly; however,

the sequence of events will be similar.

The following starting sequence covers one circuit

of a two circuit, four compressor model. The second

circuit operates in a similar manner.

1. Close the main disconnect switches to both cir-

cuits 1 and 2.

9.When compressor contactors Ml, M3,

and M7

are eneraized.

relays

R3 and R7 are eneraized.

2. Power for the control circuit is taken from circuit

power terminal block; therefore, circuit

dis-

connect must be closed to run the unit.

The

normally

closed contacts on R3

will

open

whenever compressor is operating, thus turning

off the compressor crankcase heaters.

The normally open contacts R3 and R7 will

close whenever the compressor is operating,

which will run the cooling tower pump or air

cooled condenser fan when connected as in-

structed in Field Wiring section.

Page 12

MODELS WHR-070A THRU 120A (Continued)

OFF CYCLE

(Refer to Diagrams 5 & 6)

On a decrease in entering water temperature thermo-

stat

(TC1),

stage

will be satisfied and the con-

tacts will open.

1. LT7 cooling light will turn off.

2. R5 relay will be de-energized, contacts R5 will

open and de-energize

contactors

& M7.

3. Compressor 1B will turn off immediately.

A further decrease in entering water temperature

wi II open thermostat contacts

#1.

relay will be de-energized, opening contacts

which allows the liquid line solenoid to close.

2. Refrigerant flow to the evaporator will be shut off

and the unit will begin to pump down.

3. The compressor will continue to operate thru

pump-

down relay R3 since

is open.

4. The suction pressure will drop until low pressure

switch

LP1

opens.

Contactors

Ml & M3 and relay

R3 will open and compressor 1A will turn off and

stay off until relay

is again energized thru the

thermostat.

In the event compressor 1A is off on oil pressure

safety

(OP1)

or motor overload protection MP1, then

compressor 1B will serve as the pumpdown compress-

or.

Again thermostat

will open and de-energize re-

lay R5 and open contacts R5.

The compressor 1B will continue to operate thru

pumpdown relay R7. R7 will be in the circuit in

this case since the auxiliary contact on

con-

tactor

is closed.

thermostat will open on further decrease in

water temperature, closing the liquid line solenoid

(LLS1)

thru

relay.

Compressor 1B will continue to run until the cir-

cuit is opened by low pressure control

LP1.

FIGURE 18

COMPRESSOR LOCATION

(REFERENCE TO ELECTRICAL DIAGRAMS 1 & 2)

COMP.

COMP. 20

COMP. 2A

CONTROL

PANEL NO. 1

CONTROL

PANEL NO. 2

TOP VIEW OF UNIT

TABLE 7 COMPRESSOR HORSE POWER

Page 13

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McQuay Seasonpak PWA-041A Installation And Maintenance Data

McQuay Seasonpak PWA-041A Installation And Maintenance Data

McQuay Seasonpak PWA-041A Installation And Maintenance Data

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