McQuay WHR040 Installation Manual

INTRODUCTION

This manual covers only the mechanical aspects of WHR chillers equipped with the
trol. All of the operating, safety control and installation requirements of the

MicroTech

MicroTech

reciprocating chiller con-

control are coveted in the separate

Installation and Maintenance Bulletin 493, which must be consulted before startup and operation is attempted.

GENERAL

McQuay Type WHR SEASONPAK water chillers are de­signed for indoor installations and are compatible with either
air or water as a condensing medium. Each unit is complete­ly assembled and factory wired before evacuation, charging
and testing. Each unit consists of multiple accessible hermetic
compressors, replaceable tube dual circuit shell-and-tube
evaporator, water cooled condenser, and complete or partial
refrigerant piping depending on the condensing medium.

Liquid line components that are included are manual liquid
line shutoff valves, charging valves, filter-driers, liquid line
solenoid valves,

sightglass/moisture indicators, and balance

DESCRIPTION

port type thermal expansion valves. Other features include
compressor crankcase heaters, recycling

pumpdown
“on” or “off” seasons, compressor lead-lag switch to alter­nate the compressor starting sequence, and sequenced star­ting of compressors.

The electrical control center includes. all safety and operat-

ing controls necessary for dependable automatic operation.

Compressors are not fused, but may be protected by op­tional circuit breakers, or may rely on the field installed
fused disconnect for protection.

NOMENCLATURE

W HR

- 040

D W

-

Nominal Capacity (Tons)

Basic Unit with Single Water Cooled

H

-

Basic Unit with Dual Water Cooled Condensers per Refrigerant Circuit

Condenser per Refrigerant Circuit

INSPECTION

When the equipment is received, all items should be careful-

ly checked against the bill of lading to insure a complete

ship-
ment. All units should be carefully inspected for damage upon
arrival. All shipping damage should be reported to the

car-

rier and a claim should be filed. The unit serial plate should

be checked before unloading the unit to be sure that it agrees

with the power supply available. Physical damage to unit after

acceptance is not the responsibility of McQuay.

NOTE: Unit shipping and operating weights are available

in the physical data table (pages 21 through 23).

during

INSTALLATION

NOTE: Installation and maintenance are to be performed only by qualified personnel who are familiar with local codes
and regulations, and experienced with this type of equipment. CAUTION: Sharp edges are a potential injury hazard.
Avoid contact.

HANDLING

Every model WHR SEASONPAK water chiller with water
cooled condensers (Arrangements W and H) is supplied with
a full refrigerant charge. A holding charge is supplied in

con­denserless models (Arrangement A). For shipment the charge
is contained in the condenser and is isolated by the manual
condenser liquid valve and the compressor discharge ser­vice valve.

MOVING

The McQuay SEASONPAK water chiller is mounted on heavy
wooden skids to protect the unit from accidental damage and
to permit easy handling and moving.

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.

Never put the weight of the unit against the control box.

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 the unit
by attaching cables or chains at the lifting holes in the
evaporator tube sheets. Spreader bars must be used to pro­tect the control cabinet and other areas of the chiller (see

Figure 1).

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. Avoid expos­ing an open flame to refrigerant. Care should be taken to avoid
rough handling or shock due to dropping the unit. NEVER

LIFT, PUSH OR PULL UNIT FROM ANYTHING OTHER

THAN THE BASE.

THE UNIT

Figure 1.

I

IM 508 / Page 3

Do not attach slings to piping or equipment. Move unit in
the upright horizontal position at all times. Set unit down gently
when lowering from the trucks or rollers.

240D,

NOTE: On unit sizes 120 through

ordered with the

LOCATION

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
temperature.

Because of the electrical control devices, the units should

not be exposed to the weather. A plastic cover over the

con-

optional acoustical enclosure, there will be extension brackets
attached to the evaporator tube sheets. These brackets will

be used for hoisting the unit and should be removed when
unit is in place.

trol box is supplied as temporary protection 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 nearest beams.

NOTE: Unit shipping and operating weights are available
in the physical data table, pages 21 through 23.

SPACE REQUIREMENTS FOR

The chilled water piping for all units enters and leaves the
cooler from the rear, with the control box side being the front
side of the unit. A clearance of 3 to 4 feet should be pro­vided for this piping and for replacing the filter-driers, for ser­vicing the solenoid valves, or for changing the compressors,

should it ever become 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 cleaning condenser tubes
or for removing cooler tubes on one end of the unit as
specified in Table 1. It is also necessary to leave a work area
on the end opposite that used for replacement of a cooler tube.

Table 1. Minimum recommended clearance requirements

0

Minimum clearance required for removal and replacement of cooler tubes

(either end).

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 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

struc-

ture, or transmit noise and vibration into the structure. See

CONNECTIONS AND SERVICING

Figure 2. Clearance requirements

FRONT

0'

I

20

vibration isolator section for additional mounting information.

240D,

NOTE: On the WHR 120D thru

shipping bolts are
used to secure the compressor rails to the evaporator
brackets. Remove these and discard after unit is mounted and
before unit is started.

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

tion transmission is a consideration.

Transfer the unit as indicated under “Moving the Unit.” In
all cases, set the unit in place and level with a spirit level.
When spring type isolators are required, install springs run­ning under the main unit supports. Adjust spring type mount­ings so that upper housing clears lower housing by at least

l/4 ”

and not more than

l/z “.

A rubber anti-skid pad should be

used 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.

I

Page 4

IM 508

VIBRATION ISOLATORS

Figure 3. Isolator Locations

vibra-

;04

REPlR

a

30

Table 3. Spring Flex Isolators

Figure 4. Spring Flex Mountings

POSITIONING PIN

ADJUST MOUNTING SO UPPER
HOUSING CLEAR3 LOWER HOUSING

SY

‘/2”

DIA

AT LEAST %S 8 NOT

ACOUSTICAL NON-SKID

NEOPRENEPAD

WATER PIPING

GENERAL

Since regional piping practices vary considerably, local or­dinances and practices will govern the selection and installa­tion of piping. In all cases local building and safety codes and
ordinances should be studied and complied with.

All piping should be installed and supported to prevent the
unit connections from bearing any strain or weight of the
system piping.

Vibration eliminators in all water piping connected to the
unit are recommended to avoid straining the piping and
transmitting pump noise and vibration to the building
structure.

It is recommended that temperature and pressure indicators

be installed within 3 feet of the inlet and outlet of the shells

to aid in the normal checking and servicing of the unit.

A strainer or some means of removing foreign matter from

Figure 5. Single Neoprene-in-Shear

Mounting

“S” DIA

POSITIONING PIN

“D” D,A

the water before it enters the unit or the pump is recom­mended. It should be placed far enough upstream to prevent
cavitation at the pump inlet (consult pump manufacturer for
recommendations). The use of a strainer will prolong pump
life and thus keep system performance up.

A preliminary leak check of the water piping should be

made before filling the system.

Shutoff valves should be provided at the unit so that nor­mal servicing can be accomplished without draining the
system.

A WATER FLOW SWITCH OR PRESSURE DIFFERENTIAL
SWITCH MUST BE MOUNTED IN THE WATER LINES TO
THE EVAPORATOR TO ASSURE WATER FLOW BEFORE
STARTING THE UNIT

CHILLED WATER PIPING

The water flow entering the cooler must always be on the end

nearest the expansion valves and cooler refrigerant connec-

tions to assure proper expansion valve operation and unit

capacity (see pages 16 thru 20).

Design 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

Page 6

I

IM 508

maintained by using an expansion tank or a combination
pressure relief and reducing valve.

All chilled water piping should be insulated to prevent con­densation on the lines. If insulation is not of the self-contained
vapor barrier type, it should be covered with a vapor seal.
Piping should not be insulated until completely leak tested.

Vent and drain connections must extend beyond pro­posed insulation thickness for accessibility.

CHILLED WATER SENSOR

On units WHR-040D thru

240D.

the chilled water sensor is
factory installed in the leaving water connection on the
evaporator. For detailed specifications regarding the chilled
water sensor or any other sensors/transducers, refer to IM 493.
Care should be taken not to damage the sensor cable or lead­wires when working around the unit. It is also advisable to
check the leadwire before running the unit to be sure that it

is firmly anchored and not rubbing on the frame or any other
component. Should the sensor ever be removed from the well
for servicing, care should be taken as not to wipe off the heat

conducting compound supplied in the well.

NOTE: See IM 493 for additional thermostat information.
CAUTION: The thermostat bulb should not be exposed to

water temperatures above 125°F since this will damage the

control.

FLOW

A WATER FLOW SWITCH MUST SE MOUNTED in either the

entering or leaving water line to insure that there will be ade-

quate water flow and cooling load to the evaporator before

the unit can start. This will safeguard against slugging the

compressors on startup. It also serves to shut down the unit

in the event that water flow is interrupted to guard against

evaporator freeze-up.

A flow switch is available from under ordering number

1750338-00. It is a “paddle” type switch and adaptable to any

pipe size from

1”

to 6” nominal. Certain minimum flow rates
are required to close the switch and are listed in Table 6. In­stallation should be as shown in Figure 7. The flow switch
should be wired per actual unit wiring diagram found on the
inside of the unit control panel door or refer to IM 493.

Apply pipe sealing compound to only the threads of the
switch and screw unit into

Figure

7).

The flow arrow must be pointed in the correct

D”x D”x 1”

reducing tee (see

direction.

Piping should provide a straight length before and after

the flow switch of at least five times the pipe diameter.
Trim flow switch paddle if needed to fit the pipe diameter.

Make sure paddle does not hang up in pipe.

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 should be con­nected according to the wiring diagram (see wiring diagram
inside control box door).

Table

Figure 6.

SWITCH

Fioure 7.

5.

Thermostat Well Installation

TEMPERATURE SENSOR

LOCATICJN

FLOW SWITCH

VIEW FROM END OF COOLER

Table 6. Flow Switch Minimum Flow Rates

1

1%

l'h 12.70

2 18.80
2%
3
4
5

24.30

30.00

39.70

58.70

6.00

9.80

IM 508 I Page 7

GLYCOL SOLUTIONS

The system glycol capacity, glycol solution flow rate in gpm,
and pressure drop through the cooler may be calculated

us-

ing the following formulas and table.

-

CAPACITY

Capacity is reduced from that with plain
water. To find the reduced value multiply the chiller’s water
system tonnage by the capacity correction factor C to find
the chiller’s capacity in the glycol system.

/I T)

GPM -To determine gpm (or

knowing n T (or gpm)

and tons:

Glvcol gp:pm = 24 x Tons (WW

,

AT

x G (from table)

PRESSURE DROP -To determine glycol pressure drop
through the cooler, enter the water pressure drop graph
on page 9 at the glycol gpm. Multiply the water pressure
drop found there by P to obtain corrected glycol pressure
drop.

Test coolant with a clean accurate glycol solution hydrometer
(similar to that found in service stations) to determine freez­ing point. Then obtain percent glycol from the freezing point
table below.

0

1

10

1

20
30
40
50

CONDENSER

j

1.000

1

32°F

24'F
15'F

-12°F 0.968

-33°F 0.964

-

1

1.000

/

1

0.990

0.981

4°F 0.974

0.994

'

0.988

0.984

0.981 1.13

0.980

The use of a glycol solution in the heat

1.00

1

1.01

1.04

1.08

1.20

1.00

1

1.06

1

1.12

1.18

1.24

1.30

recovery condensers will not affect heat recovery capacity.

1.30

1.25

PERCENT BY VOLUME

lb

% ETHYLENE GLYCOL BY WEIGHT

i0

3b

1.20

100

4-o

Page 8 I IM 508

CONDENSER

WATER PIPING

GENERAL - For proper performance, the condenser water

must enter the bottom connection of the condenser. Water
cooled condensers may be piped for use with cooling towers,
well water or heat recovery applications. Cooling tower ap­plications should be made with consideration to freeze pro­tection and scaling problems. For specific applications, con­tact cooling tower manufacturer for equipment characteristics
and limitations.

HEAD PRESSURE CONTROL, TOWER SYSTEM

-

Some
means of controlling operating head pressure must be pro­vided. Minimum condensing temperature allowed is 80°F.

Minimum entering tower condenser water temperature is
70°F. Typical systems are shown in Figures 8 and 9. In Figure
8, a three-way pressure actuator water regulating valve is

used for cooling applications, In Figure 9 the capacity of the
cooling tower is controlled through damper and/or fan

COOLING TOWER SYSTEMS-HEAD PRESSURE CONTROL

Figure 8. 3-Way Water Valve

TO

COOLING

REGULATING VALVES

modulation. These typical systems, depending on the specific
application, must maintain a constant condensing pressure,
regardless of temperature conditions and must assure
enough head pressure for proper thermal expansion valve
operation. Note also that both systems assure full water flow

to the tower.

HEAD PRESSURE CONTROL, WELL WATER SYSTEM

-

Where well water is used for condensing refrigerant, a direct
acting water regulating valve is recommended (see Figure

10). The valve is normally installed at the outlet of the con-

denser. On shutdown, the valve will close and, in this way,

prevent water siphoning out of the condenser. Siphoning

causes drying of the waterside of the condenser and rapid

build-up of fouling. When no valve is used, a loop at the outlet
end is recommended (See Figure 10).

Figure

9. Fan

Modulation

COOLING TOWER

BYPASS

BALANCING

VALVES OR COCKS

Figure 10. Well Water Cooling System

I

LOOP REOUIAED WHEN

REGULATING VALVE IS USED

DIRECT
REGULATING VALVE

NO

ACTlNG

WATER

Page 10 I IM 508

Single circuit heat recovery employs a standard water
cooled chiller equipped with heavier electrical components
and a 380 psig high pressure limit switch. These modifica-

tions allow leaving condenser water temperatures up to 135°F

for building or process heating applications.

A typical heat recovery arrangement will include a closed
circuit cooling tower used to reject unwanted condenser heat
to the outdoor ambient air. The cooling tower should be
sized to reject all the condenser heat during summer design
operation. This insures proper operation in the

nonheat­recovery mode. Use of a closed circuit tower is normally re­quired in order to prevent fouling of heating coils in the heat
recovery loop. Condenser water remains free of contamina­tion from minerals and impurities normally contained in make­up water in an open cooling tower.

If a closed circuit cooling tower is to be located in an am­bient temperature below freezing, protection against coil and
sump freeze-up must be provided. Coil freeze protection can
be provided by using a glycol solution or by maintaining a
heat load on the coil

at all times and maintaining water flow

through the coil. Sump water freeze protection can be pro­vided by locating the spray water circulating pump and sump
tank inside a heated space or by placing heating coils in the
sump. Head pressure and water temperature are normally
controlled by the tower capacity control. Adequate capacity
control is usually obtained by fan cycling and regulating
dampers located in the fan discharge. This will maintain a
constant tower water temperature. Consult the closed circuit

manufacturer for information on specific applications.

An auxiliary heat

source is necessary if the available con-

denser heat is not sufficient to satisfy all of the heat load.
The auxiliary heat source must be located between the con­denser and the heat load and the control should be inter-

locked with the closed circuit tower to prevent auxiliary
heating while rejecting heat to the ambient.

When the heating load is satisfied, a two-position, three-

way valve is set to divert condenser water around the heat

load and the auxiliary heat source. Whether operating in sum­mer or winter, the chiller is always controlled by the cooling
load and not the heating load.

-

TYPICAL OPERATION

On a call for cooling, the chiller
starts and hot condenser water flows through the diverting
valve to the closed circuit cooling tower rejecting heat to the
outdoors. The tower dampers modulate to maintain a pro-

per entering condenser water temperature which will give ef-

ficient operation by means of the proportional controller T2

located in the outlet fluid line of the tower.

When a heating load is sensed by mode switch

Tl,

the
three-way valve is switched to allow condenser water to flow
through the heating circuit. The proportional controller T2 is

also reset upwards to give the desired water temperature for
heat recovery. The unused condenser heat will be rejected
out through the closed circuit tower. If the condenser heat
of rejection cannot satisfy the heating load after an ap­propriate delay, the auxiliary heat source will be activated.

Figure

11. Typical Single Condenser (Per Refrigerant Circuit) Heat Recovery

PUMP

HEATRECOVERY

CONDENSER

TWO POSITION

DIVERTING VALVE

COOLING LOAD

NOTE: The schematic shows one refrigerant circuit. Models with two refrigerant circuits have two condensers

IM

508 I Page 11

DUAL CONDENSER HEAT RECOVERY - ARRANGEMENT H

Dual condenser heat recovery chiller models have two water
cooled condensers per refrigerant circuit. The upper con­denser is the heat recovery condenser and is piped into the
building’s hot water system. The lower condenser is the tower
condenser and is piped to an open cooling tower. Condens­ing is done in either the tower condenser or heat recovery
condenser, or partial condensing is done in each. The tower
and heat recovery water circuits are independent and do not

intermix. This use of an open tower and the closed heat

recovery loop prevents fouling of the building’s heating

system.

A subcooling circuit is provided in the tower condenser to
provide optimum cooling efficiency. When the unit is
operating on maximum heat recovery, the cooling tower will
be modulated down to its minimum capacity, usually about
5% of full capacity. This provides subcooling for the system
during heat recovery operation. Water can be heated up to

135°F in the heat recovery condensers to satisfy a heating

load. If all of the condenser heat of rejection cannot be

used, the remainder is rejected out through the cooling tower.

The cooling tower should be sized to reject all of the con­denser heat during summer operation. Freeze protection for
the cooling tower must be provided if it is to operate in below
freezing temperatures, Adequate capacity control must be

provided to maintain a constant water temperature leaving
the cooling tower. Head pressure and water temperature are
controlled by the tower capacity control. Fan cycling and

modulating fan discharge dampers should be used. Consult

the cooling tower manufacturer for information on specific
applications.

If the available condenser heat cannot satisfy all of the heat
load, an auxiliary heat source must be provided. The aux­iliary heat source should be located between the heat
recovery condenser and the heat load and interlocked with
the cooling tower so that auxiliary heat is not being supplied
unless the cooling tower is modulated down all the way. The
chiller operation is always controlled by the building’s cool­ing load and not the heating load.

TYPICAL OPERATION

-

On a call for cooling the chiller
starts. If a heating load is sensed by mode switch Tl , the heat
recovery water pump Pl will start and the cooling tower
dampers will modulate to control the heat recovery condenser
by means of proportional temperature controller T3. If max­imum heat recovery is required, the tower dampers close and

only

the fans shut off. The tower will then provide

subcool-

ing. If more heat is required than the heat recovery con­densers can provide, the auxiliary heat source is activated.

When mode switch Tl senses that a heating load no longer
exists, the heat recovery pump shuts off and the cooling tower
modulates to control the entering tower condenser water
temperature by means of proportional controller T2 and a sen­sor located in the tower sump. Proportional controller T2 is
set at a temperature lower than T3 to provide optimum
efficiency.

Figure

12. Typical Dual Condenser (Per Circuit) Heat Recovery

COOLING TOWER

COOLER

PUMP

Page 12

‘&k’

NOTE: The schematic shows one refrigerant circuit. Heat recovery WHR models with two refrigerant circuits

/

IM 508

have two heat recovery condensers and two tower condensers.

------j

REFRIGERANT PIPING

UNIT WITH REMOTE CONDENSER-ARRANGEMENT A

General

cooled condenser, the chillers are shipped containing a
Refrigerant 22 holding charge. It is important that the unit be
kept tightly closed until the remote condenser is installed,
piped to the unit and the high side evacuated.

sized and installed according to the latest
book. It is important that the piping be properly suported with
sound and vibration isolation between tubing and hanger and
that the discharge lines be looped at the condenser and
trapped at the compressor to prevent refrigerant and oil from
draining into the compressor discharge manifold. Looping the
discharge line also provides greater line flexibility.

drier(s), moisture indicator(s), and thermostatic expansion
valve(s) are all provided as standard equipment with the

SEASONPAK water chiller.
condenserless units (Arrangement A) between the liquid line

filter-drier and remote condenser.
charged with Refrigerant 22, then run at design load condi-

tions, adding charge until the liquid line sightglass is clear,

with no bubbles flowing to the expansion valve. Total operating
charge will depend on the air cooled condenser used and
the length of external piping, but generally will be similar to
the water cooled charge shown in Tables 16, 17, and 18, pages
21 through 23.

densers), the installer is required to record the refrigerant
charge by stamping the total charge and the charge per cir­cuit on the serial plate in the appropriate blocks provided for
this purpose.

piping to a remote condenser of some type. The design 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.

and to protect the compressor from damage that may result
from condensing liquid refrigerant in the line during shutdown.
Total friction loss for discharge lines of 3 to 6 psi is considered
good design. Careful consideration must be given for sizing

each section of piping to insure that gas velocities are suffi­cient at all operating conditions to carry oil. If the velocity in
a vertical discharge riser is too low, considerable oil may col-

lect in the riser and the horizontal header, causing the com-

pressor to lose its oil and result in damage due to lack of

lubrication. When the compressor load is increased, the oil
that had collected during reduced loads may be carried as
a slug through the system and back to the compressor, where

a sudden increase of oil concentration may cause liquid slug­ging and damage to the compressor.

away from the compressor approximately l/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 collect at such points and the compressor crankcase

may become starved.

horizontal discharge header rise above the center line of the

-

For remote condenser application such as an air

Refrigerant piping, to and from the remote unit, should be

The discharge gas valve(s), liquid line solenoid(s), filter-

A liquid line shutoff valve must be added in the field on

After the equipment is properly installed, the unit may be

NOTE: On the Arrangement A units (units with remote con-

SEASONPAK water chillers without condensers require field

Discharge lines must be designed to handle oil properly

Any horizontal run of discharge piping should be pitched

It is recommended that any discharge lines coming into a

ASHRAE

Hand-

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 lines it is important that the liquid reach
the expansion valve with no presence 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.

A check valve must be installed in the liquid line in all ap­plications where the ambient temperature can get below the
equipment room temperature. This prevents liquid migration
to the condenser, helps maintain a supply of refrigerant in the
liquid line for initial startup and keeps liquid line pressure high
enough on “off” cycle to keep the expansion valve closed.

On systems as described above, a relief valve or relief type
check valve must be used in the liquid line as shown in pip­ing systems (Figure 14) to relieve dangerous hydraulic

pressures that could be created as cool liquid refrigerant in
the line between the check valve and expansion or shutoff
valve warms up. A relief device is also recommended in the

hot gas piping at the condenser coil as shown in Figures 14
through 16.

Typical Arrangements

ing 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 gas velocity sufficiently at re­duced load conditions; however, when operating at full load,

the line might be greatly undersized and thereby create an

excessive refrigerant pressure drop. If this condition occurs,
it 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.

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

Figure 15, page 15. Line ‘A” should be sized to carry the
oil at a minimum load condition and line
sized so that at the full load condition, both lines would
carry oil properly.

Notice in all illustrations that the hot gas line is looped 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 coil; it is advisable to include a purging vent
at this point to release noncondensables from the system.

Figure 16 illustrates another very common application
where the air cooled condenser is located on essentially the
same level as the compressor and receiver. The discharge
line piping in this case is not too critical. The principal pro­blem encountered with this arrangement is that there is fre­quently insufficient vertical distance to allow free drainage of
liquid refrigerant from the condenser coil to the receiver.

Figure 14 illustrates a typical pip-

-

“B”

should be

IM 508

/ Page 13

UNIT WITH FACTORY MOUNTED CONDENSER(S)

Units with factory mounted condensers are provided with
complete refrigerant piping and full operating refrigerant
charge at the factory.

There is a remote possibility on Arrangement W units utiliz­ing low temperature pond or river water as a condensing
medium, and if the water valves leak, that the condenser and

liquid line refrigerant temperature could get below the equip­ment room temperature on the off cycle. This could open the

expansion valve and cause recycling pumpdown. This

prob-

RELIEF VALVE PIPING

The ANSMASHRAE Standard 15-1978 specifies that pressure

relief valves on vessels containing Group 1 refrigerants (R-12,

R-22 and R-500) “shall discharge to the atmosphere at a loca­tion not less than 15 feet above the adjoining ground level
and not less than 20 feet from any window, ventilation open-

ing or exit in any building.” The piping must be provided with

a rain cap at the outside terminating point and a drain at the

low point on the vent piping to prevent water buildup on the

atmospheric side of the relief valve. In addition, a flexible pipe

section should be installed in the line to eliminate any piping

stress on the relief valve(s).

The size of the discharge pipe from the pressure relief valve
shall not be less than the size of the pressure relief outlet.
When two or more vessels are piped together, the common
header and piping to the atmosphere shall not be less than
the sum of the area of the relief valve outlets connected to
the header. Fittings should be provided to permit vent pip­ing to be easily disconnected for inspection or replacement
of the relief valve.

only arises during periods when cold water continues to

lem
circulate through the condenser and the unit remains off due
to satisfied cooling load.

If this condition occurs:

1.2.Cycle the condenser pump off with the unit.
Check the liquid line solenoid valve for proper operation.
If these valves are closing liquid tight as designed, no
recycling of

Figure

13. Relief Valve Piping

pumpdown

should occur.

NOTE: Provide adequate fittings in piping to permit repair
or replacement of relief valve.

REFRIGERANT PIPING

Figure 14. Condenser Above Compressor and Receiver

REM3 VALVE

SUBCOOLER HOOKUP

RELIEF

VALVE

OUTDOORS OR TO CONDENSER

SIDE OF IIOUID LINE CHECK

(VENT TO

VALVE)

PURGE

VALVE

GHECK VALVE’
iPREFERRED,

DISCHARGE LINE

RELIEF VALVE

(SET AT 4%

PSI1

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