McQuay PWA008 Installation Manual

BULLETIN NO. IM 105

MAY 1966

INSTALLATION AND

MAINTENANCE DATA

PWA

PACKAGED WATER CHILLER

7% THRU 60 TONS

INC. l 13600 INDUSTRIAL PARK BLVD., P.O. BOX 1551, MINNEAPOLIS, MINNESOTA 55440

PHONE:

377-9750

AREA CODE: 612

PRE-INSTALLATION

LOCATION

A.

Unit

is designed for indoor application and must
be located in an area where the surrounding am­bient temperatures are 40 F or above. A good rule
of thumb is to place units where ambients are at

least 5 degrees above the leaving water tempera-

t

urc

B.

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
protection during transfer.

A reasonably level and sufficiently strong floor

c.

is all that is required for the Seasonpak Water

Chiller. If necessary,
bers should be provided to transfer the weight of

the unit to the nearest beams. Figures 1 and 2

indicate the base plan for the chiller. Refer to

310VING AND PLACING THE UNIT, Page

foundation information.

additional structural mem-

9,

for

INSPECTION

When the equipment is received, all items should
be carefully checked to make sure that all crates and
cartons have been received. All units should be
carefully

damage should be reported immediately to the carrier
and a claim filed for damage.

inspected for damage when received. All

HANDLING

Every model PWA Seasonpak with water cooled
condensers (Arrangement
refrigerant charge. A holding charge is supplied in
condenserless models (Arrangements 2
shipment, the charge is contained in the condenser
and is isolated by the manual condenser liquid
valve and the compressor discharge service valve.

Should the unit be damaged allowing the refrigerant
to escape, there may be danger of suffocation in
the equipment area since the refrigerant will dis­place the air. Care should be taken to avoid rough
handling or shock due to dropping the unit. NEVER

LIFT, PUSH OR PULL UNlT FROM ANYTHING
OTHER THAN THE BASE. Refer to MOVING AND

PLACING UNIT, Pages 7
and 4 for further information.

1)

is supplied with a full

& 3).

thru

9, and Figures 3

For

SPACE REQUIREMENTS FOR
CONNECTIONS AND SERVICING

Dimensions of the unit are given in Figures 1 and

A.

2.

The chilled water piping for all units enters and

B.

leaves the cooler from the rear. A clearance of
2-3 feet should be provided for this piping and for
replacing the filter-driers or servicing the solenoid
valves.

The condenser water piping enters and leaves the

C.

shell from the ends. Work space must be provided

in case water regulating valves are being used and

for general servicing.

It is desirable to leave a small walk area on the

D.

end opposite that used for replacement of a cooler

tube. Figures 1 and 2 indicate the requirements

for

tube

replacement. Clearance for removing a
length of tube is required on one end only. The
cooler

tube is longer than the condenser, therefore,

the condenser tube replacement area need not

be considered.

ELECTRICAL

Simple three lead connection is all that is required
to connect power to the Seasonpak. Wiring should
conform with all local and national codes. The system
nameplate
with the power supply available. Check Electrical

section,

should be checked to be sure that it agrees

Pages

12 to 18, for further information.

WATER TEMPERATURE LIMITS

A. The maximum allowable water temperature to the

cooler must not exceed

stance, such as change over from heating to cool-

ing.

B. These units must not be operated when the enter-

ing water temperature is in excess of 90” F.

140’

F under any circum-

Page

4

MOVING ANDPLACING UNIT

MOVING THE UNIT

The light weight of the Seasonpak makes moving

A.

a simple matter. The

McQuay

Seasonpak is skidded
to protect the unit from being accidentally damaged
from any angle. Table 3 gives the approximate skid
dimens ions.

When moving the unit, dollies or simple pipe rollers

B.

can be used under the skid or under the base.
Always apply pressure to the base 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.

The

4"

C.

channel base is arranged on the skid so

that the fork of a standard fork lift truck can be

slid easily under (See Figure

3).

The forks of the

fork lift truck must be across both the front and
rear channels before lifting. Always use a fork
lift truck on the side opposite the control panel to
avoid damaging the controls. Never put the weight
of the unit against the condensers.

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

D.

from the skid or from the base as indicated in

Figure 4, Page 8. 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

E

unit in the upright horizontal position at all times.
Let unit down gently when lowering from
or off

rollers.

TABLE 3

OVERALL SHIPPING

the truck

SKID DIMENSIONS

MODEL

PWA008

PWAOlO
PWAOlS

PWA020
PWA025

PWAOSO

PWA041 121

PWA050 128

PWA060 128

LENGTH WIDTH

98
98

98
121
121
121

39
39
39
34
34

38%

38%
40’/,
40’4

FIGURE 3

MOVING UNIT WITH FORK LIFT

THE CONTROLS.

Page 7

MOVING AND PLACING UNIT

FIGURE 4

SUGGESTED RIGGING

Page

*--

PLACING THE UNIT

The small amount of vibration normally encountered
with the Seasonpak makes this unit particularly
able for basement or ground floor installations where
the unit can be bolted directly to the floor. The floor
construction should be such that the unit will not af­fect

the building structure, or transmit noise and
vibration into the structure. See VIBRATION ISOLA­TORS section for additional mounting information.
Hold down bolt locations are indicated in Figures 1
and 2, Page 5.

VIBRATION ISOLATORS AND

ELIMINATORS

A.

Rubber-in-shear or spring isolators can be fur- C
nished and field placed under each corner of the
package. It is recommended that a rubber-in-shear

8

desir-

NOTE: ALWAYS USE SPREADER

BARS TO PROTECT UNIT
FROM DAMAGE.

pad be used as the minimum isolation on all upper
level installations or areas in which vibration
transmission is a consideration.

B. Transfer the unit as indicated under MOVING THE

UNIT, or use the methods as indicated in Figures
3 and 4. In all cases, set the unit in place and
level with a spirit level. When spring type isolators
are required,
main side channels as shown in Figure 5. Founda­tion hold down bolt locations for vibration isolators
are given in Figure 6. 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 are recommended to avoid strain­ing the piping and transmitting vibration and noise.

install springs running under the

WATER

PIPING

GENERAL

A.

Piping practices

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 bc provided at the unit so

B.

that normal servicing can be accomplished without
draining the system.

It is recommended that temperature and pressure

c

indicators be installed at the inlet and outlet of

the

shclls’to aid in the normal checking and

vicing

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

D.

be made before filling the system.
Vibration eliminators are recommended in all lines

E.

connected to the Seasonpak.

vary considerably.

In most cases

CHILLED WATER PIPING

A.

Each cooler is provided with the connections as

indicated in Figures 1 and 2, Page 5. Also, a

NPT vent and S/4” NPT drain are provided.
Design

B.

the piping so that it 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 circuit. System pressures can be maintained
by using an expansion tank or a combination pres­sure relief and reducing valve.

ser-

114”

C.

All chilled water piping should be insulated to
prevent the nuisance of water dripping from the

lines.
vapor barrier type,it should be covered with a
moisture seal. Do not insulate piping until it has
been tested for leaks and until all vent and drain
connections have been extended beyond the pro-

posed insulation thickness to make them
accessible.

The chilled water thermostat is mounted inside

D.

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

installed in the return water line as shown in

Figure 7. The bulb well is supplied with a

NPT male thread. Carefully unsnap the well from
the

and slowly remove the bulb from the well. Install

into piping as indicated in Figure
the bulb, carefully remove it from the well so as
to not wipe off the heat conducting 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
unit; however, it is recommended that the bulb well
be placed as close to the cooler inlet as possible.
Insulate over thermostat well.

CAUTION: The thermostat bulb should not be

posed to water temperatwes above
will

If insulation is not of the self-contained

holding clips, remove the retaining bushing

7.

When installing

10

feet from the

140 F

since this

damage the control.

112”

ex-

Page 10

FIGURE 7 THERMOSTAT WELL

RETURN WATER

TO

COOLER

INSTALLATION

‘/I”

N.P.T.

BUSHING

(BY

OTHERS)

ELECTRICAL

FIELD WIRING

Only three main power leads need be hooked up to

A.

the standard packaged water chiller. From the
power connection block to the motor, the unit is
factory wired ready for operation. Table 5, Page
18, gives the recommended lead wire size when
only three conductors are used in a raceway. Refer
to the National Electrical Code for other type wire
or special instructions.
Although there is no specific requirement, inter--

B.

locking of a flow switch and the condenser pump
starter (or air cooled condenser fan) is suggested
for the most dependable and economical system
operation. The cooler pump should operate con­tinuously, even when the unit is not operating. 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

matic 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

C.

is interlocked by removing jumpers between termi-

nals 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 before power can be applied to

start this system. Note that the crankcase heaters

will be energized regardless of water flow. The

flow switch is recommended and does not

the shortcomings of interlocking the cooler pump

starter. A

water temperature of

flow switch must be used for leaving

STARTING SEQUENCE

(Refer to Diagrams 1 thru

&

14 and 12 & 14 on Sche-

32 F and lower.

4).

have

compressors are not operating. The indicator
lights should show the heaters on. Power is

also supplied to the main system On-Off switch,
Sl.
Closing switch Sl energizes System No. 1 and

3.

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

4.
2

indicates power to the system by lighting

the red “Power on” light.

Provided operating safety controls are closed

5

5.

(FSl, OPl,
overloads are used), power at terminal 3 will

energize safety light,

is ready to run.
Referring to the standard non-recycle,

6.

operation of the schematic wiring diagram,

relay R1

cannot reach compressor starter. Power can
reach
controlled by thermostat
pressor lead-lag switch (dual units only) and
the

pumpdown

When cooling is required. power is supplied to

7.
Terminal 4,

energizing relay

8.

When
close and open the liquid line solenoid valve
LLSl.

9.

If low pressure control

ing of

the low side building up pressure which will
close

Meanwhile, time delay TD 3

10.
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.

HP1 and MPl or

and R3 are normally open, and power

starter only by energizing Rl which is

switch S3.

through water thermostat

Rl,

indicator light LT5.

Rl relay is energized, contact Rl will

LLSl

will allow refrigerant to flow into

LPl

and the compressor will start.

OLl

when external

indicating the system

TCl

through the com-

LPl

is open, the open-

is timing the

pumpdown

TC1

A. Variations or options in the control system will

change the basic wiring diagrams slightly, however,
the sequence of events will be similar.

B. 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 completely 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
to terminal 25. The power from 25 is fed thru
NC contacts to relay
the compressor crankcase heaters, when the

Ll

and L2 is fed through fuse

R3

and R4 to energize

Fl

OFF

CYCLE

Referring to the schematic wiring diagrams, when
thermostat
terminal No. 4 (or No. 10 for second system), will be

broken opening relay
solenoid, and indicator light LT5. The compressor will
continue to operate through t.he contacts of R3 relay.

Note that

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,
This locks the compressor off the line until the ther­mostat
and Rl and closing

TCl

is satisfied, the electrical circuit to

Rl

de-energizing the liquid line

R3

relay is now energized through its own

LPl

will open and de-energize R3 relay.

TCl

calls for cooling again, energizing

LPl.

LLSl

Page 13

START UP PROCEDURE

Do not start the Seasonpak until the following steps
have been completed.

A. Check all auxiliary components of the installation.

B. Open the compressor suction and discharge shut

off valves until back seated. Back seating the

valve closes the gauge ports and, if gauges are
provided,
toward the closed position.

caps.

Open the manual liquid line shut off valve at the

C.

condenser.

D.

If water regulating valves are provided, connect
their capillary to the manual valves provided on
the condensers and open the manual valves.

Check to see that the water temperature thermostat

E.

is installed in the entering water line, that the
thermostat well is full of heat conducting compound
and that the bulb is secured with the retaining
fitting.

close valve one turn from full open,

Always

replace seal

Check the compressor oil level. Prior to start-up,

F.

the oil level should be in the oil sight-glass.

Fill the water system. The cooler circuits should

G.

be filled with clean non-corrosive water.

Check the main system “on-off’ switch to see that

II.

it is in the
switches should be thrown to the “auto” position.

Check resets of all safety controls.

J.

K.

Throw the main power disconnect to “On”.

L. Start the auxiliary equipment for the installation.

M. Set the circuit breakers to “On”.

N.

Start the system by pushing the system “On-Off’

rocker switch to “On”.

“off’ position. The pump down

OPERATION

During full load operation, check the compressor oil
level. It should be at the center of the oil sight glass
during operation.

A. Check the refrigerant charge frequently at the

moisture/liquid indicator. A steady clear glass
of liquid refrigerant indicates sufficient charge.
A green colored button in the center of the mois­ture indicator indicates a dry system (should mois­ture enter the refrigerant, the color will turn yel-

low). The button was green before it left the
factory and should be green after period of opera­tion on start up.

B. Check the temperature control thermostat by ob-

serving operation at reduced loads. The thermostat

is factory set for 44F leaving chilled water tem­perature when the entering temperature is 54F.
Refer to CHECKING CONTROLS section, Pages 20
and 21.

Check voltage and amperage of the compressor

C.

motor.

Adjust water regulating valve for discharge pres-

D.

sures between 200 and 230 psig for the most econ­omical operating pressure.

Close gauge ports on valves when gauge readings

E.

are not required. This will prolong the gauge life.

Page

19

CHECKING CONTROLS

All controls are checked and adjusted prior to
leaving the factory. However, after the unit has op­erated satisfactorily for a reasonable length of time, a
check of the operation and safety controls can be
made as indicated below:

A.

OIL PRESSURE SAFETY SWITCH - The oil fail­ure pressure switch is activated by a low pressure
differential between the oil pressure and the crank­case pressure. Upon start up, the normally closed
pressure actuated contact of this control opens
when the pressure differential increases to about

I5 psig. If oil pressure does not reach this differen-

tial, the thermal time delay remains energized and

opens a bi-metallic safety contact, de-energizing

the complete control circuit. If pressure reaches

the prescribed differential within 120 seconds, the

thermal time delay is de-energized and the control

circuit remains closed. If during the operation,

the oil pressure differential falls below 10 psig,
the thermal time delay is again energized and the
control will shut down the compressor.

To check the control, jumper the Freezestat

terminals L

off position. Throw control circuit to “On” to

pull in contactor. The contactor should drop out

and the safety indicator light should go out after

approximately 120 seconds or less. After checking

the control, wait approximately 2 to 3 minutes and

then reset control manually. The compressor can

then be started. Repeated successive operations

of the control will require a longer period before

it can be reset, since the bi-metal will get hotter

and will take more time to cool.

& M

and trip the circuit breaker to the

the end of the
psig and automatically reset at approximately 60
psig. The control can be checked by throwing the

individual

tion and observing the cut-out point on the gauge.
FREEZESTAT

D.

control connected to the low side of the system

and is set to shut down the system when the pres-

sure drops low enough to be dangerous as far as
cooler freeze up is concerned. The control is fac­tory set at 52 to 53 psig. When dropping to this

point,

the

tacts of this control will close, energizing a 220

volt heater. This causes the normally closed bi-

metallic relay switch of this control to open after

a delay of approximately 90 seconds, or less,

stopping

line so 1 en o id valve. The time delay prevents

nuisance trip out on momentary low suction pres-

sure and permits the operation of the system on a

“pumpdown cycle”.

The control must, be checked while the system
is operating. To check the control, install a volt
meter or
of the low pressure freeze control. There should
be a voltage indication or the test light will glow
indicating the contacts are opened. Throw the
pump down switch to the manual position and check
the pressure at which the test light goes out or
the volt meter goes to zero. In actual operation,
the compressor will shut down and the safety light
will go out. The control can be manually reset in
about 2 minutes.

pumpdown

pumpdown

-

The Freezestat is a pressure type

normally open pressure actuated con-

the

compressor and closing the liquid

220

volt light across terminal Tl and T2

cycle. It will open at 35

switches to the manual posi-

Page 20

B.

HlGH

PRESSURE CONTROL - The high pressure

switch will shut down the compressor and close
the liquid line solenoid valve when the compressor
discharge pressure reaches 270 psig for water
cooled units, or 360 psig for air cooled units. To
check the control, slowly throttle the condenser
inlet water or shut down the condenser fan. Ob-

serve the cut out point. During testing stand by
the System “On-Off’ switch to shut down the
unit should the safety device malfunction. Be sure
the gauges used are accurate.

The water cooled condensers are supplied with

a 300 psig relief valve and the discharge pressure
during the test must be kept below 270 psig. For
Aircooled Condenser operation the relief valve
will be set for 400 psig.

The control can be manually reset at approxi-

mately 70 psig below the cut out point.

LOW PRESSURE CONTROL

C

switch is connected to the low side of the system
and its purpose is to shut down the compressor at

-

This pressure

E. THERMOSTAT

packaged chillers are factory calibrated for use
in the return water line to the cooler inlet. The
thermostat bulb is installed in a well in the re­turn water line in order to be more stable under
temperature changes due to load conditions. Figure

7. Page 10 illustrates the recommended method
of installing the bulb and well in the return water
line. The return water does not change temperature
as rapidly as the outlet because of the “fly wheel
effect” of the total water system. This results in a
stable, non-recycling control of the outlet water

temperature.

Normally the thermostat requires no adjustment

in the field other than the dial setting for the
required control point. The control is preset at the
factory to maintain a 44 F average leaving water
temperature throughout the loading and unloading

sequence of the unit based on a full load cooling
range of 10 F. It should be realized however, that
there will be a fluctuation in the leaving water

-

The thermostats supplied on all

CHECKING CONTROLS

temperature as the unit cycles, unloads and loads.
The magnitude of fluctuation will decrease as the
number of capacity control

On a two stage thermostat, the dial setting in­dicates the average leaving water
that the control will maintain. At a 44 F setting
the high stage should actuate at approximately
51 F return water and 41 F leaving based on 10”
cooling range. The low stage will open at 46 F

return or 41 F leaving

As the water warms up, the low stage should

cut in at approximately 49 F which is the inlet
and outlet temperature with the unit off and the
high stage should operate at
leaving.

These settings may be checked by operating
the unit and slowly regulating the load from full
to minimum and return. It may then be necessary
to adjust the dial and/or differential between
switches to obtain

On a four stage thermostat, the dial setting
indicates

the cut out point of the low stage switch

these values.

steps

increases.

(5” TD

or 50% capacity).

54

F return or 49 F

temperature

which represents the average leaving water temper­ature desired. The high stage or
be

actuated at approximately 51 F return water

#3

temperature,

which is the dial
approximately 2 F higher than the cut out on each
switch.

These settings may be checked by operating
the unit and slowly reducing the load. The four
stage thermostat has a fixed switch
and fixed differential between switches. DO NOT
make

any

is a

preset

must

be

made using a screw driver in

gear

below

by turning the large numbered dial.

at 49 F, #2 at 47 F and #1 at 45 F

setting. The

adjustments other than the dial as this

precision control. This dial adjustment

the dial. Do not attempt the adjustment

#4

switch should

cut in point will be

differential

the

slotted

FIGURE 10

TWO STAGE FOUR STAGE

THERMOSTAT

BULB

THERMOSTATS

1

Page 21

SYSTEM COMPONENTS

COMBINATION FILTER DRIER

A.

Each refrigerant circuit is furnished with a full
flow replaceable core type filter-drier. In the
drier installed in all Seasonpaks, the filters are
attached to the flange end cap

core assembly has a solid plate at the inlet end
and a plate with a gasket and fine mesh screen
at the outlet. During assembly, a spring at the
inlet end is compressed which holds the core in
place and exerts a force on the gasket at the outlet
end to prevent bypassing. CAUTION

refrigerant before removing end flange.

B. A condenser manual liquid line shut-off valve is

provided for isolating the charge in the condenser,
but also serves as the point from which the liquid
line can be pumped out. With the line free of liquid,
the filterdrier core can be easily replaced.

by

tie rods. The

LIQUID LINE SOLENOID

A.

Each refrigerant circuit is furnished with a liquid
line solenoid for automatic
All valves have epoxy-clad water proof coil as-

semblies for standard 220 volt AC
ice. The valve is completely serviceable without

removing valve body from the. line. The coils are

easily removed without “pumping-out” the liquid
line. All valves have a manual operation stem at
the side which allows you to open the valve and
operate the system in case of a coil malfunction.
Manual stem should be turned
clockwise to open bypass port.

CAUTION: Unit cannot be pumped down with valve

in manually opened position. Operator or

man should standby to shut unit off.

pumpdown

-

60 cycle

1/2

turn counter-

LIQUID SIGHT GLASS AND
MOISTURE INDICATOR

A. The color of the moisture indicator button is an

indication of the dryness of the system and is

extremely important when the system has been

serviced. Immediately after the system has been
opened for service, the element button may indicate
a chartreuse or yellow color. It is recommended
that the equipment operate for about 12 hours to
allow this system to reach equilibrium before
deciding if the system requires a change of drier
cores.

B. The following table is a guide to the moisture

content of the system.

Color Indication

Green
Chartreuse Caution
Yellow

C. Bubbles in the sight glass at constant full load

conditions indicate a shortage of refrigerant, a

Dry

Wet

filter-

-

Pump out

operation.

ser-

service-

plugged filter or a restriction in the liquid line.
However

sight glass during changing conditions.

it is not unusual to see bubbles in the

WATER FLOW SAFETY SWITCH

water flow safety switch is available as optional

A. A

equipment for all Model PWA chillers. The flow
switch must be field installed and wired into the
Scasonpak

ings

.

1. The flow switch should be installed in a hori­zontal run of piping as follows:

a. Adjust the flow switch paddle to the size

b. Apply pipe sealing compound to only the

c. Piping should provide for a straight length

2.

CAII’TION:
a.

b. The

control center as indicated on the draw-

of’ pipe in which it is to be used. (See Fig­ure 11).

threads of the switch and screw unit into

a

D”

x D” x 1” reducing tee (See Figure 12).

The

flow arrow must be pointed in the cor-

rect direction.

before and after the flow switch of at least
5 times the pipe diameter.

Make

sure the

is pointed in the proper direction of flow.

flow
control voltage and should only be connected
according to the wiring diagram (See
Diagram inside control box door).

arrow

on the side of the switch

switch is designed to handle the

THERMAL EXPANSION VALVE

Each thermal expansion valve is adjusted for 8 to

A.

10 degrees superheat at the factory before ship­ment. The valve performs only one very simple
function; it keeps the evaporator supplied with
the proper amount of refrigerant to satisfy the
load conditions. Normal suction superheat will
be maintained by the expansion valve and it need
not be adjusted in the field.

The sensing bulb, of the thermal expansion valve

B.

is

installed
line from the cooler. The bulb is held on by two
clamps around the suction line to assure firm con­tact with the line. The line is then insulated to
remove the effect of surrounding ambients. In case
the bulb need be removed, simply slice the in­sulation on each side of the bulb, remove the clips
and then remove the capillary tubing that runs
along the suction line from the valve.

In the event the valve itself

C.

not necessary to remove the
line. All power assemblies
and

replaced.

in the closest straight run of suction

needs service, it is
valve body from the

are easily removed

Wiring

Page

22

SYSTEM COMPONENTS

FIGURE 11

FLOW SWITCH

PADDLE

FS4-3 FLOW SWITCH

COMPRESSOR

FIGURE 12

FLOW DIRECTION

4

VIEW FROM END OF COOLER

STRAIGHT PIPE

FOR AT LEAST

TEE

Dv x

D” x

1”

A.

The reciprocating semi-hermetic compressor(s)
are complete with suction and discharge service
valves, integral force feed lubrication system, oil
sight glass,oil charging connection, crankcase
heater and initial oil charge.

The motor is of the hermetic induction type, 1750

B.

rpm, gas cooled, with inherent thermal protection
and supplementary overload protection, where re­quired. The standard unit is wired for

across-the­line starting. Part winding starting is available
as an option.

The compressor is pre-wired and ready to run.

C.

Suction and discharge service valves are closed
during shipment and must be opened. just prior
to start up. Gauge connections on suction and
discharge valves are closed when the valve stem
is back seated in the full open position. To in­crease the life of any gauges supplied, the suction
and discharge valve should be back seated except
when readings are required. Always replace valve
caps with gaskets in place.
The safety control piping connection to the com-

D.

pressor includes the oil failure switch-high pres­sure oil connection at the oil pump discharge; the
oil failure switch-low pressure connection at the
compressor crankcase: the high pressure safety
connection at the discharge manifold; and the low
pressure and freeze safety connection at the suc­tion chamber on the motor end of the compressor.

Shut off valves are never installed in these con­trol lines.
The compressor is pre-charged with sufficient oil
for normal operation. In case oil is required, or

if unit requires additional oil after installation
with a remote air cooled condenser, the compressor
may be pumped out on

pumpdown

cycle, valves
closed and oil charged through the filler plug
on the side of the compressor oil sump. The plug
must ‘be replaced with a sealer and leak checked
during operation.

A compressor crankcase heater, internal or ex­ternal, is provided to minimize refrigerant accumu-

lation in the oil during the off-cycle of the com­pressor. Excessive refrigerant in the crankcase
dilutes the oil causing excessive foaming, oil loss,
and in extreme cases, bearing washout and pos-

sible failure. The heaters are energized at all
times when the unit is shut down. During prolonged

shut downs, when the electrical power may be shut

off, close the suction and discharge service valves
to prevent migration of the refrigerant to the oil
and reopen the valves just prior to start up.

Except for minor repairs, such as replacing a

suction or discharge reed valve, the compressor

is not generally repaired in the field. Exchange
compressors are stocked in warehouses throughout
the country and the damaged compressor is turned

in for credit.

Page

23

SHELLS

SYSTEM COMPONENTS

A. Both the cooler and condenser shells are

constructed and stamped and are of the straight
through tube type with replaceable tubes.

ASME

WATER COOLER

A. The water cooler is of the direct expansion type

with removeable internally finned tubes and heavy
terneplate baffles. The copper tubes are individual­ly rolled into heavy duty, steel tube sheets and
sealed by a cast steel refrigerant head.

B. The water nozzles which enter and leave the shell

are at the rear of the unit. No special attention

UNIT LESS CONDENSER

Seasonpaks supplied without condensers or with
mounted receivers require field piping to a remote
condenser of some type. As mentioned under the
REMOTE CONDENSER section of this manual, re­frigerant piping should be sized and installed ac­cording to the Latest

-of refrigerant piping when using air cooled condensers
involves a number 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 cooled condensers.

A. On remote condenser applications having distances

of more than 20 feet between compressor or con­denser, a discharge line muffler is recommended.
The muffler should be installed as close to the
compressor discharge as possible. If an oil separa­tor is used, it will usually perform the same func­tion as a muffler and will eliminate the need for
one. A muffler will reduce discharge line pulsa­tions; particularly those which occur during un­loaded compressor operation.

B. 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 shut down. Total friction loss
for discharge lines of 3 psi is considered good
design. Careful consideration must be given to
sizing vertical risers to insure that gas velocities

are sufficient at all operating conditions to carry

oil. If the velocity in a vertical discharge riser

ASHRAE

Guide. The design

is required for the cooler except
tered

water should be supplied.

that clean,

CONDENSER

A.BThe condensers are of the shell

tube type with integral, externally finned copper
tubes, brazed into heavy-duty tube sheets. The
tube sheets are then epoxy coated on the water

side to protect the metal surfaces. Water heads
are rust-resistant, cast iron. Each condenser has
full refrigerant
with a purge valve and relief valve, according to
ASA-B9.

Each cooler and condenser is supplied with drain
and vent connections.

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

C

increased, the oil that had collected during re-

duced loads may be carried as a slug through the

system and back to the evaporator, where a sudden
increase of oil concentration may cause

and damage to the compressor.

Any horizontal run of discharge piping should be

D

pitched away from the compressor approximately

li4”

gravity any oil lying in the header. Oil pockets
must be avoided as oil needed in the compressor
would collect at such points and the compressor

crankcase may become starved.

It is recommended

E

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.

F.

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 line, the pressure

1 code.

per ft. or more. This is necessary to move by

pumpdown

that

any discharge lines coming

capacity and is supplied

and replaceable

slopover

fil-

Page 24

UNIT LESS CONDENSER

losses due to friction and changes in static head
should be kept to a minimum.

size

A good policy to follow is to
from the condenser to the receiver for sewer flow
operation. This allows any gas formed in the re­ceiver to vent
bottled up in the receiver. Traps in this liquid

drain line should be avoided.

G

TYPlCAL ARRANGEMENTS
Page 26 illustrates a typical piping arrangement
involving a remote Aircon located at a higher

elevation than the compressor and receiver. This

arrangement is commonly encountered when the
Aircon 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
dition. the gas velocity might he too low at reduced

loads to carry oil up through the discharge line

and condenser coil. Reducing the discharge line

size

would increase the gas velocity sufficiently
at reduced load conditions; however, when operat­ing at full load, the
sized and thereby create an excessive refrigerant
pressure drop. This condition can
one of the two following ways:

1. The discharge line may
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.

2. A double riser discharge line may be used as
shown in Figure 14, Page 26. Line “A” should

be sized to carry the oil at minimum load con-

dition and line
at the full load condition both lines would

carry oil.

back to the condenser without being

sized

line

might be greatly under-

“B”

should be sized so that

the liquid line

-

Figure No. 13,

for full load con-

be

overcome in

be

properly sized for

unlike air cooled condensers or unequal piping is

used, the
drop may cause liquid to build up in one of the
condenser
capacity.

looped at the bottom and top of the vertical run.
This is done to prevent oil and condensed
erant from flowing back into
causing damage. The highest point in the

line should always be above the highest point

in the
a purging vent at this point to

s ihI< from

common

on

and

casrx

encountercxd

is

frccl

denser cx)i I to the receiver.

liquid buildup in the
common to this arrangement.
receiver is located as far below
outlet
of any
tal run:, they should be pitched down toward the

receiver.

common application where two or more separate
Aircons

Aircons
frigerant pressure drop through each unit is equal.

resultant unequal refrigerant pressure

coils, thereby

Notice

in all illustrations, the hot gas

cxondcnsrr coil; and it is advisable to include

the

system,

Figure

No.

15. Page> 26

application where the Aircon is located

cssc,ntialIy

rc~~civer.

is not

frcqucntly insuff’icic>nt

drai

To guard against gas binding in the receiver and

as possible. The liquid line should be free

traps

Figure No.

arc piped together on a single compressor.

First of all, it is very important that the two

have the same capacity so that the

the same

The dischargcl

t,oo

critical. The principal problem

with this arrangement is that

nag<>

of 1

or loops, and if

iqu

16,

Page 26 illustrates a third very

reducing

illustrates another very

lcvc~l

vertical

id rcfr

condenser

there

its effective

the compressor

discharge

rclcasc

as

lint

igclrant from

coil, which arc

noncondcIi-

the

comprcssoI

piping in this

distance

be certain

arc any horizon-

to allow

the

that the

the

condenser

line

rcfrig-

and

thcrc

co~i-

is

rc-

The above two points are particularly important

in applications where the refrigerant receiver is
directly beneath the air cooled condensers. If two

Secondly, the piping should be arranged so that
the lengths of run to and from each Aircon are
equal.

Page 25

SERVICE INFORMATION

FIGURE 18

PROBLEM

lompressor

Compressor noisy or
vibrating.

High Discharge Pressure

will not run.

a) Main switch open.

Circuit breakers open.

b) Fuse Blown.

c)

Thermal overloads tripped or fuses

blown.
d) Defective contactor or coil.
e)

System shut down by safety de-

vices.
f)

No cooling required.
g) Liquid line solenoid will not open.
h)

Motor electrical trouble.

i)

Loose wiring.

(I) Flooding of refrigerant into

crankcase.

*b) Improper piping support on

charge

c)

worn compressor.

a) Condenser water insufficient or

temperature too high.

b) Fouled condenser tubes

cooled condenser). Clogged
nozzles (evaporative condenser).

Dirty tube and fin surface (air
cooled condenser).

c) Non-condensibles in system.

“d)

System overcharged with refrigerant.

e)

Discharge shut off valve partially

closed.

*f) Condenser undersized.

l g) High ambient conditions.

Low Discharge Pressure

High Suction Pressure

a) Faulty condenser temperature

regulation.

b) Suction shut-off valve partially

closed.
c) Insufficient refrigerant in system.
d) Low suction pressure.

e) Compressor operating unloaded.

*f)

Condenser too large.

*g) Low ambient conditions.

a) Excessive load.
b) Expansion

TROUBLE SYSTEM CHART

POSSIBLE CAUSES

a) Close switch.

b) Check electrical circuits and motor winding

for shorts or grounds. investigate for pos­sible overloading. Replace fuse or reset

breakers

c) Overloads are auto. reset. Check unit

ly when unit comes back on line.

d)

Repdir

e)

Determine type and cause of shut-down and

correct it before resetting safety switch.

f) None. Wait until unit calls for cooling.

g) Repair or replace coil.

h)

Check motor for opens, short circuit, or burn-

out.

1)

Check all wire junctions. Tighten

terminal screws.

a) Check setting of expansion valve.

or liquid line.

valve

overfeeding.

dis-

(woter-

spray

b) Relocate, add, or remove hangers.

c)

Replace.

o)

Reodiust

ways to increase water supply.

b) Clean.

c) Purge the non-condensibles,
d) Remove excess.
e)

open valve.

f)

Check

operation.

g) Check condenser rating tables against the

operation.

a) Check condenser control operation.

b) Open valve.

c) Check for leaks. Repair and add charge.

d) See Corrective Steps for low suction

pressure below.

e) See Corrective Steps for failure of corn-

pressor

f)

Check condenser rating table against the

operation.

g) Check condenser rating tables against the

operation.

a) Reduce load or add additional equipment.
b) Check remote bulb. Regulate superheat.

POSSIBLE CORRECTIVE STEPS

after fault is corrected.

close-

or replace.

all

water regulating valve. Investigate

condenser rating tables against the

to load up below.

Low Suction Pressure

*Remote condenser models.

28Poge

c)

Compressor unloaders open.

of

a) Lack
b) Evaporator dirty.
c)

Clogged liquid line filter-drier.

d) Clogged suction line or corn-

e) Expansion valve malfunctioning.

refrigerant.

pressor

suction gas strainers.

c) See Corrective Steps below for failure of

compressor to load up.

a) Check for leaks. Repoir and add charge.

b) Clean chemically.

c) Replace cartridge(s).

d) Clean strainers.

e) Check and reset for proper superheat.

Replace if

necessary

SERVICE INFORMATION

FIGURE 18

PROBLEM

f)

Low Suction Pressure
(Continued)

Compressor will not
unload or load up.

Compressor
Loading-Unloading
Intervals too short.

Little or no oil

pressure.

_

Compressor loses oi I.

Condensing temperature too low.

g)

Compressor will not unload.

h) Insufficient water flow.

a) Defective capacity control.
b)

Unloader mechanism defective.

c)

Faulty thermostat stage or broken

copiliory

d) Stages not set for application.

a) Erratic water thermostat.
b)

Insufficient water flow.

a)

Clogged suction oil strainer.

b) Excessive liquid in crankcase.

c)

Oil pressure gouge defective.

d) Low-oil pressure safety switch

defective.
e) Worn oil pump.
f)

Oil pump reversing gear stuck in

wrong position.

g)

Worn bearings.

h)

Low oil level.

i)

Loose fitting on oil lines.

k)

Pump housing gasket leaks.

I)

Flooding of refrigerant into

crankcase.

a) Lack of refrigerant

*b)

Velocity in risers too low.

*c)

Oil trapped in line.

d)

Excessive compression ring

blow-by.

TROUBLE SYSTEM CHART

POSSIBLE CAUSES

f) Check means for regulating condensing

temperature.

g)

See Corrective Steps for failure of compres-

sor to unload.

h) Adiust gpm.

a) Replace.
b)

Replace.

c)

Replace.

tube.

d) Reset thermostat setting to fit application.

a) Replace.
b) Adiust

a) Clean.
b)

Check crankcase heater. Reset expansion

valve for higher superheat. Check liquid line
solenoid valve operation.

c)

Repotr

when taking readings.

d)

Replace.

e) Replace.

f)

Reverse direction of compressor rotation.

g)

Replace compressor.

h)

Add oil.

i)

Check and tighten system.

k)

Replace gasket.

I)

Adjust thermal expansion valve.

a) Check for leaks and repair. Add

refrigerant.

b)

Check riser sizes.

c)

Check pitch of lines and refrigerant

velocities.

d)

Replace compressor.

POSSIBLE CORRECTIVE STEPS

gpm.

or replace. Keep valve closed except

Motor overload
circuit breakers open.

Compressor thermal

protector switch open

Freeze protection opens.

-Kemote

condenser models.

relays

or

a)

Low voltage during high

conditions.

b) Defective or grounded wiring in

motor or power circuits.

c) Loose power wiring.
d)

High condensing temperature.

e) Power line fault causing

voltage.

anced

f)

High ambient temperature around

the overload

g)

Failure of second starter to pull

in on part-winding start systems.

a) Operating beyond design

ditions.

b)

Discharge valve partially shut.

c)

Blown valve plate gasket.

a) Thermostat set too low.
b)

Low water flow.

c)

Low suction pressure.

relay.

load

unbal-

con-

a) Check supply voltage for excessive line

drop.

b)

Replace compressor-motor.

c)

Check all connections and tighten.

d) See Corrective Steps for high discharge

pressure.

e)

Check supply voltage. Notify power

pany.

Do not start until fault is corrected.

f)

Provide ventilation to reduce heat.

g)

Repair or replace starter or time delay

mechanism.

a) Add facilities so that conditions are

within allowable limits.

b)

Open valve.

c)

Replace gasket.

a) Reset to 40 F or above.

b) Adjust
c)

see “Low

gpm.

suction pressure.”

com-

Page 29