McQuay SEASONCON ALP-055C Installation And Maintenance Data

INTRODUCTION

GENERAL DESCRIPTION

McQuay type ALP SEASONCON air cooled condensing units

are designed for outdoor installations and are compatible with

either air handling or chilled water systems. Each unit is

com-

pletely assembled and factory wired before evacuation, charg-

ing and testing, and comes complete and ready for installa-

tion. Each unit consists of twin air cooled condensers with

integral subcooler sections, multiple accessible hermetic

com-

pressors, complete discharge piping and suction connections

for connection to any air or water cooling evaporator.

The electrical control center includes all safety and

operating controls necessary for dependable automatic

operation except for the cooling thermostat since this is

somewhat dependent on the unit application. Condenser fan

motors are fused in all three conductor legs and started by

their own three-pole contactors. Compressors are not fused

but may be protected by optional circuit breakers, or by field

installed fused disconnect.

NOMENCLATURE

A L P

-

080 C

T

CESIGN

;/II’-~‘h*:,.;r

NOMINAL CAPACITY (TONS)

INSPECTION

When the equipment is received, all items should be carefully

be checked before unloading the unit

to

ba sure that it agrees

checked against the bill of lading to insure a complete ship- with the power supply available. Physical damage to unit after

ment. All units should be carefully inspected for damage upon

acceptance is not the responsibility of

McQuay.

arrival. All shipping damage should be reported to the

car-

NOTE: Unit shipping and operating

weights

are available

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

in the physical data tables on pages 10 and

1

1.

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 and coil surfaces are a potential

injury hazard. Avoid contact with them.

HANDLING

Care should be taken to avoid rough handling or shock due

to dropping the unit. Do not push or puli the unit from anything

other than the base, and block the pushing vehicle away from

the unit to prevent damage to the sheetmetal cabinet and end

frame (see Figure 1).

Never allow any part of the unit to fall during unloading or

Figure

1.

Suggested Pushing Arrangement

BLOCKING REQ’D.

ACROSS FULL WIDTH

I

i

n

moving as this may result in serious damage.

To lift the unit,

2%”

diameter lifting holes are provided in

the base of the unit. Spreader bars and cables should be ar-

ranged to prevent damage to the condenser coils or unit

cabinet (see Figure 2).

Figure 2. Suggested Lifting Arrangement

IM 269 I Page 3

LOCATION

Care should be taken in the location of the unit to provide

Minimum clearances as shown in Figure 3 will prevent most

proper airflow to the condenser, minimizing effects on

con-

discharge air recirculation to the condenser which will have

densing pressure.

a significant effect on unit performance.

SERVICE ACCESS

Each end of the unit must be accessible after installation for

periodic service work. Compressors, filter-driers, and manual

liquid line shutoff valves are accessible on each side of the

unit adjacent to the control box. High pressure, low pressure,

and motor protector controls are on the compressor. Most

other operational, safety and starting controls are located in

the unit control box.

On all ALP units the condenser fans and motors can be

removed from the top of the unit. A complete fan/motor

assembly should be removed for service.

CAUTION: Disconnect all power to unit while servicing

con-

denser fan motors.

Figure 3. Clearance Requirements

ALP-045C

thru 230C

6 FT. MIN. CLEARANCE

FOR AIR INLET

(1) Minimum clearance between units is 12 feet.

(2) Units must not be Installed in a pit that is deeper than the height of the unit.

(3) Minimum clearance on each side is 12 feet when installed in a pit.

6 FT. MIN. CLEARANCE

FOR AIR INLET

VIBRATION ISOLATORS

Vibration isolators are recommended for all roof mounted in-

stallations or wherever vibration transmission is a considera-

tion. Table 1 lists spring isolators for all ALP unit sizes. Figure

4 shows isolator locations in relation to the unit control center.

Figure 5 gives dimensions that are required to secure each

Table 1. Vibration Isolators (Spring)

Q?txJ

CPl-31 CPl-31

CPl-27 CPl-31 CPl-31

CPl-27

ioU@

CPl-32

CPl-28 CPl-32

CPl-32

CPl-28

OS@

CPl-32 CPl-32

CPl-28 CPl-32 CPl-32

CPl-28

low

CPl-32 CPl-32

CPl-28 CPl-32 CPl-32

CPl-28

?8W:

CP2-28

CP2-26

CP2-28 CP2-26 CP2-28

CP2-28

Z96Q

CP2-31

OgoC

CP2-31 CP2-31

CP2-31 CP2-31 CP2-31 CP2-31

McQuay isolator selection to the mounting surface. Table 3

shows the isolator loads at each location shown in Figure 4,

and the maximum loads for each McQuay selection are

shown in Table 2.

Table 2. Spring-flex Isolators

Gray

W/2

White Stripes

Gray W/Orange Stripe

Gray W/Green Stripe

Gray W/2 Yellow Stripes

477927A-26

600

477927A-27

750

477927A-26

900

477927A-31

1100

Page 4

/

IM 269

REFRIGERANT

PIPING

GENERAL

Piping design, sizing and installation information presented

in ASHRAE Handbooks should, where applicable, be followed

in the design and installation of piping. McQuay type ALP

condensing units are adaptable to either chilled water or air

handling air conditioning applications. The only restriction on

applications is that the evaporator be selected for a system

using refrigerant R-22.

REFRIGERANT PIPING

Piping between the condensing unit and the cooling coil must

be designed and installed to minimize pressure drop, pre-

vent liquid refrigerant carryover to the compressor and to

assure a continuous return of compressor oil from the system.

Piping sketches and tables are not intended to provide infor-

mation on all of the possible arrangements. For example,

when dual circuit evaporators are used with an unloading

compressor, two liquid line solenoid valves may be used to

reduce coil capacity with compressor unloading. Note

especially that dual circuit evaporators should not be piped

with common liquid and suction lines to more than one com-

pressor circuit. Separate evaporators, evaporator circuits and

piping must be run for each compressor circuit.

Piping recommendations include:

1. The use of type K or L clean copper tubing. All ioints should

be thoroughly cleaned and brazed with high temperature

solder.

Piping sizes should be based on temperature/pressure

limitations as recommended in the following paragraphs.

Under no circumstances should pipe size be based upon

the coil or condensing unit piping connection size.

Suction line piping pressure drop should not exceed the

pressure equivalent of

2”

F (3 psi) per 100 feet of equivalent

pipe length. After the suction line size has been deter-

mined, the vertical suction risers should be checked to

verify that oil will be carried up the riser and back to the

compressor. The suction line(s) should be pitched in the

direction of refrigerant flow and adequately supported.

Lines should be free draining and fully insulated between

the evaporator(s) and the compressor. Table 7, page 8,

shows piping information for units operating at suction

temperatures between

40” F and 45” F and a condenser

entering air temperature of 95” F. If operating conditions

are expected to vary substantially from these operating

levels, the pipe sizing should be rechecked.

Vertical suction risers should be checked using Table 5

to determine the minimum tonnage required to carry oil

up suction risers of various sizes.

The liquid line should be sized for a pressure drop not to

exceed the pressure equivalent of

2°F

(6 psi) saturated

temperature. The liquid line(s) on all units must include

a liquid solenoid valve wired into the circuit as shown on

the applicable unit wiring diagrams.

The control circuit for all compressors has been de-

signed to include a

pumpdown

cycle. The use of a liquid

line solenoid is required for proper unit operation. In ad-

dition, a filter-drier should be located between the liquid

line service valve and the solenoid valve and a combina-

tion moisture indicator/sightglass should be located in the

liquid line ahead of the expansion valve.

Suggested piping arrangements are shown on page 7. All

multiple compressor units require a separate refrigerant

circuit for each compressor. The figures shown are for an

air handling installation, but all components shown are

recommended for chilled water vessel installations except

that a refrigerant distributor is not usually required for

shell-

and-tube evaporators.

If dual suction risers are used:

Double risers are sized so that their combined

cross-

sectional internal area will allow full load unit operation

without excessive pressure drop (see notes, Table 7). Riser

“A” is sized to provide adequate suction gas velocity for

proper oil return at minimum load conditions. This riser

becomes effective only when the trap shown in riser

“B”

fills itself with oil. It should be emphasized that the trap

shown in riser “B” should be designed to contain a

minimum internal volume to keep the total system oil re-

quirements at a minimum. Table 7 gives recommended

line sizes for both single and double suction lines and for

liquid lines.

The combined cross-sectional areas of the two risers

must be capable of maintaining adequate refrigerant

velocity for oil return at full unit tonnage.

The extra riser should be of a smaller diameter than

the main riser. The extra riser must include its own trap

at the bottom and should enter the main suction header

at twelve o’clock.

The trap serving the extra riser must be as short as fit-

tings permit. A “U” fitting or the combination of a

90”

standard

"L"

and a 90” street-l is recommended.

The suction line leaving the coil should also include a

trap if the expansion valve control bulb is to be on the

horizontal section leaving the coil outlet. See the pip-

ing sketches on page 7.

Table 5. Minimum tonnage (R-22) to carry oil up

suction riser at 40

o

F saturated suction.

NOTE: When compressor minimum tonnage is less than shown in the above

table for a given line size, double suction risers will be required.

Table 6. Equivalent feet of straight tubing for copper fittings and valves

Page 6 I IM 269

Figure 6. SINGLE CIRCUIT EVAPORATOR

-

RECOMMENDED PIPING

If Row Split Coils Are Used, Duplicate The Piping

CONDENSING UNIT ABOVE THE EVAPORATOR

CONDENSING UNIT BELOW THE EVAPORATOR

Figure 7. DUAL CIRCUIT EVAPORATOR (FACE SPLIT)

-

RECOMMENDED PIPING

_d”

\

_,

D”Ai

RISER

L

-.-

1

~~

iVP4NSlON

Lla.,vt

;:

CONTROL

BULBS

SUCTION

TRAP

L

FXPANSlOlv

VALVE

‘S~FIPIV

TO

LlNt

\.__

_--

SHORT

AS

$1

!

-,m

.R‘iP

-

TONTROL BLLRS

--

i’

“IUD

INSULnrE

FITTINGS

PERMIT

SMORT

*s

STRAP

TO

LlhE

F

TT,rvi,S

PFPMll

4ND

US”L4TE

NOTES:

1.

Piping shown is for one compressor circuit; second circuit is similar. Must have separate piping for each compressor circuit.

2.

Trap for double suction riser should be as small in horizontal direction as fittings will allow.

3.

The thermal expansion valve equalizer line should be placed just past the thermal sensing bulb on the side or top of the pipe.

4. A separate expansion valve is required for each distributor and mounted per manufacturer’s recommendations.

(See additional notes under recommended line sizes, Table 7.)

REFRIGERANT PIPING CONNECTIONS

Refrigerant piping connections will be made at the

com-

unit. When piping, allow room for the unit disconnect and field

pressor end of the unit. Suction and liquid lines should be

wiring to the unit. Figures 8 and 9 show piping connections

routed through the compressor enclosure on each side of the

and sizes for each ALP model.

IM 269

/ Page 7

Table 7. Recommended line sizes

c

1

vi-1

5/a

2%

1%

15.3 23.6

IYe-

% 2%

1

‘/s

18.5

29.1

14.7 29.0

t

17.9 35 3

1%--15/g

a!¶

1

‘/a

t

5/8-2’/8

25/n

%

15/s--2’h 2%

1%

16.6 37.6

15h--2’h

2%

1

YE

16.6 37.6

1%

33.2

48.9

t

%-2’/a

1%-2%

2% 1%

36.1 56.1

t5/8-2’/!¶

I$

2%-25/s 3%

1%

33.0

56.9

2’/8-2%

irr:

.%-25/n

3% 1%

33.4 66.7

2’%-2%

tc

I 2%-25/n

I

3%

t

% 33.9 73.6

2%-25/e

E

f

2%-25/e

I

3%

1%

37.9

82.5

2%-25/s

3%

1

=/n

34.4 90.4 2%-25/a

~,I

,

II

,

.”

._

,

3’/a

1%

C

3%

I

2%

I

35.9

99.6

1

2+-31/s

I

35/s

2%

w

1

Wi-3%

1

3%

1

2%

1

40.0

111.1

1

Wi-3%

1

3% 2%

NOTES:

Recommended line sizes shown in the above table are based on the unit

for oil entrainment should be checked and where necessary double

suc-

operating conditions between 40°F and 45°F saturated suction temperature

tion risers should be utilized. See Table 5.

page

6.

and condenser entering air temperature of 95°F. per 100 ft. equivalent length

of tubing. When design conditions vary, the table values should be rechecked.

1. Liquid and suction lines based on a recommended equivalent pressure

drop of 2°F (3 psi for suction line, 6 psi for liquid line) per 100 ft. of

equivalent length.

4.

5.

2. When refrigerant required to charge a circuit exceeds the

pumpdown

capacity of that circuit the use of a separate refrigerant storage receiver

will be required. The pumpdown capacity (shown in Table 10) is based

on the condenser 90% full at 90°F.

3.

Wherever vertical rise occurs in the suction piping, the minimum tonnage

6.

Table 8. Liquid line accessory kits (when supplied by McQuay)

Wherever vertical rise occurs in the suction piping on a system

with

hot

gas bypass, double suction risers may not be needed as the velocity of

suction gas is increased at minimum load conditions.

Total equivalent feet for a given piping layout must include the equivalent

length of straight pipe for fittings, valves and specialties added to the total

run of straight pipe.

Piping design,

sizing

and installation information presented in

ASHRAE

Handbooks should, where applicable, be followed in the design and In-

stallation of piping.

886-580896A-06

.” ,”

i

886~580896A-09 1%

1

‘/a

886~580896A-10

1

‘/s

1

‘/s

l&2

886-580896A-10

1%

l’/a

l&2

886-580896A-11

1%

I

23oc

182

886~580896A-11

1%

NOTE:

%

Larger capacity expansion valve in liquid line accessory kit is used for

circuit

#2.

,-

,_

._

1

‘/a

1

‘/a

1

Yi

1

‘h

1

‘/a

1%

1

‘h

1

‘/a

1%

1

‘h

1%

t

‘/s

1

‘/a

1%

LIQUID LINE COMPONENTS

McQuay has available a “Liquid Line Accessory Kit” for each

ALP unit size. The kit does not include tubing. Table 8 shows

the ordering number to be used for each ALP unit size. The

components in these kits are:

1. Sealed core filter-driers (ALP-170 thru 230C have

replaceable core filter-driers).

2. Refrigerant solenoid valves.

3. Refrigerant

sightglass/moisture indicators.

4. Expansion valves (one per circuit).

HOLDING CHARGE

The Model ALP condensing unit is shipped with a holding

charge of refrigerant. At the time the unit was received a visual

inspection of the unit piping should have been made to be

sure no breakage had occurred or that fittings might have

been loosened. A pressure check should indicate a positive

pressure in the unit. If no pressure is evident, the unit will

have to be leak tested and the leak repaired. This should be

Page 8

/

IM 269

noted and reported to your McQuay sales representative or

freight carrier if the loss is due to shipping damage.

PRESSURE TESTING

No pressure testing is necessary unless damage was in-

curred during shipment or rigging. Damage may be deter-

mined by a visual inspection of the exterior piping assuming

no breakage has occurred or fittings have loosened. Pressure

gauges should show a positive pressure. If no pressure is

evident on the gauges, a leak has probably occurred releas-

ing all or part of the refrigerant charge. In this case, the unit

should be leak tested to locate the leak.

LEAK TESTING

In the case of loss of the refrigerant holding charge, the unit

should be checked for leaks prior to charging the complete

system. If the full charge was lost, leak testing can be done

by charging the refrigerant into the unit to build the pressure

to approximately 10 psig and adding sufficient dry nitrogen

to bring the pressure to a maximum of 125 psig. The unit

should then be leak tested with a Halide or electronic leak

detector. After making any necessary repair, the system

should be evacuated as described in the following

paragraphs.

CAUTION: Do not use oxygen to build up pressure. A

serious explosion could be the result.

EVACUATION

After it has been determined that the unit is tight and there

are no refrigerant leaks, the system should be evacuated.

The use of a vacuum pump with a pumping capacity of ap-

proximately 3 cu.

ft./min.

and the ability to reduce the vacuum

in the unit to at least

1

millimeter (1000 microns) is recom-

mended.

The first pull down will remove about 90% of the

non-

condensibles, the second about 90% of that remaining

from the first pull down and after the third only 1

/1

0 of 1

o/o

non-condensibles will remain.

Table 12, page 10, shows the relationship between pressure,

microns, atmospheres, and the boiling point of water.

A mercury manometer, electronic or other type of micron

gauge should be connected to the unit at a point remote

from the vacuum pump. For readings below 1 millimeter,

an electronic or other micron gauge should be used.

The triple evacuation method is recommended and is par-

ticularly helpful if the vacuum pump is unable to obtain

the desired

1

millimeter of vacuum. The system is first

evacuated to approximately 29 inches of mercury. Enough

refrigerant vapor is then added to the system to bring the

pressure up to 0 pounds.

Then the system is once again evacuated to 29 inches

of vacuum. This procedure is repeated three times. This

method can be most effective by holding system pressure

at 0 pounds for a minimum of 1 hour between evacuations.

CHARGING THE SYSTEM

Model ALP condensing units are leak tested at the factory

and shipped with a holding charge of refrigerant. In the event

the refrigerant charge has been lost due to shipping damage,

the system should be charged with enough refrigerant to raise

the unit pressure to 30 psig after first repairing the leaks and

evacuating the svstem.

After all refrigerant piping is complete and the system has

been evacuated, it can be charged as described in the

paragraphs following. Connect the refrigerant drum to the

gauge port on the liquid shutoff valve and purge the charg-

ing line between the refrigerant cylinder and the valve.

Then open the valve to the mid-position.

If the system is under a vacuum, stand the refrigerant drum

with the connection up and open the drum and break the

vacuum with refrigerant gas.

With a system gas pressure higher than the equivalent

of a freezing temperature, invert the charging cylinder and

elevate the drum above the condenser. With the drum in

this position, valves open and liquid refrigerant will flow

into the condenser. Approximately 75% of the total require-

ment estimated for the unit can be charged in this manner.

After 75% of the required charge has entered the con-

denser, reconnect the refrigerant drum and charging line

to the suction side of the system. Again purge the con-

necting line, stand the drum with the connection up, and

place the service valve

in

the open position.

IMPORTANT: At this point charging procedure should be

interrupted and prestart checks made before attempting to

complete the refrigerant charge. See startup procedures on

page 48.

NOTE: It is recommended that the total operating charge

per circuit be stamped on the unit nameplate for future

reference.

HOT GAS BYPASS COMPONENTS

McQuay offers a “Hot Gas Bypass Accessory Kit” for each

ALP unit size. Each kit includes a solenoid valve, a hot gas

bypass valve and an instruction drawing. See page 55 for

hot gas bypass operation.

Table 9. Hot gas bypass kits

REFRIGERANT CHARGE

Each ALP condensing unit is designed for use with R-22.

Table 10 lists approximate refrigerant charges for operation

of the unit. Additional refrigerant will be needed for the system

piping and evaporator. Estimated total operating charge

should be calculated before charging system. See Table 11

for weight of refrigerant in copper lines.

CAUTION: Total operating charge per circuit should not

exceed the condenser

pumpdown

capacity per circuit. A li-

quid receiver on each refrigerant circuit could be used in this

situation. Refer to the

ASHRAE

Handbook for the design and

installation of piping and components.

Table 10. Approximate refrigerant charge

NOTE: Condenser

pumpdown

capacity is based on ANWASHAAE Standard

15-1978 rating of 90% full of liquid at 90°F. To convert values to the older

ARI

standard (80% full at 80°F). multiply

pumpdown

capacity by 0 888.

Table 11. Weight of refrigerant R-22 in copper lines

(Pounds Per 100 Feet of Type L Tubing)

is/8

1

1.237

1

88.0

1

4.62

1

1.190 1.770

2’h

2.147 153.0 8.04 2.06 3 060

2%

3.312 236.0 12.4 3.18 4.720

31/a

4.728 336.0 17.7 4.55 6.750

3%

6.398 456 0 24.0 6.15 9.140

4’ia

1

8.313

1

592.0

1

31.1

1

8.00

1

11.190

IM

269 I Page

9

FIELD WIRING

Wiring must comply with all applicable codes and ordinances.

Warranty is voided if wiring is not in accordance with specifi-

cations. An open fuse indicates a short, ground or overload.

Before replacing a fuse or restarting a compressor or fan

motor, the trouble must be found and corrected.

Copper wire is required for all power lead terminations at

the unit while either aluminum or copper can be used for all

other wiring.

ALP units may be ordered with internal power wiring for

either single or multiple point power connection. If single point

power connection is ordered, a single large power terminal

block or non-fused disconnect switch is provided and wiring

within the unit is sized in accordance with the National Elec-

trical Code. A single field supplied disconnect is required.

An optional factory mounted transformer may be provided.

If multiple point wiring is ordered, three power connections,

one per compressor circuit plus one for condenser fans, are

required and wiring with the unit is sized in accordance with

the National Electrical Code. Separate field supplied discon-

nects are required for each of the three circuits. A single

power block is provided for all of the condenser fans and the

optional

115V

control transformer.

CAUTION: Internal power wiring to the compressors for

the single point versus the the multiple point option are dif-

ferent. It is imperative that the proper field wiring be in-

stalled according to the way the unit is built.

Figures

10,

11 and 12 show typical field wiring that is re-

quired for unit installation. Items that require field wiring are

liquid line solenoids (SV1 and

SV2),

optional hot gas bypass

solenoid (SV5) and the cooling thermostat as well as the unit

power supply.

Figure 10. Typical field wiring diagram for ALP-045C

-

08OC

with 4 steps of capacity control

FIELD WIRING TERMINAL

---

FIELD WIRING

-

FACTORY WIRING

-

OPTIONAL FACTORY WIRING

BK

BLACK WIRING (LINE)

WH

WHlTE

WIRING

(NEUTRALI

Page 14

I

IM 269

Table 18. Capacity reduction

SVl + Comp. 1 + Comp. 3 (R3 energized)

,‘:

SV2 + Comp. 2 + Comp. 4 (R4 energized)

SW

+Comp. 1,

Ul.

U2

SV2 + Comp. 2,

Ul,

U2

SVI

+

Comp. 1

(Ul,

U2

de-energized)

t7lac,

i

SV2

+

Comp. 2

(Ul,

U2 de-energized)

a?$#!&

m

SVl

+

Comp.

1,

Ul,

U2

+ Comp. 3 (R3 energized)

SV2 + Comp. 2,

Ul,

U2

+ Comp. 4 (R4 energized)

SVl

+

Comp. 1 + Comp. 3

(Ul,

U2

de-energized)

Stage 3

Stage 5

Stage 4

Stage 6

Stage

1

Stag-e

1

Stage 2

Stage 3

Stage 4

_I

Stage 4

-

..-_I

Stage 5

-

Stage 5

--

1

SV2

+

Comp.

2

+

Comp.4

(Ul,

UZ

Stage

6

Stage

6

de-energized)

1

I

NOTES:

1.

Compressor staging for units with suction pressure controlled unloaders and unloaders controlled from a remote source

(discharge

air, return water, etc.) is the same.

2. See page 54 for more information on unloaders controlled from suction pressure.

WATER PIPING FOR CHILLED WATER APPLICATIONS

Due to the variety of piping practices, it is advisable to follow the recommendations of local

authorities. They can supply the installer with the proper building and safety codes required

for a safe and proper installation.

FLOW SWITCH FOR CHILLED WATER APPLICATIONS

A WATER FLOW SWITCH MUST BE MOUNTED in either

the entering or leaving water line to insure that there will be

adequate 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 McQuay under ordering

number

860-175033B-00.

It is a “paddle” type switch and

adaptable to any pipe size from 1” to 6” nominal. Certain

Table 19. Flow switch minimum flow rates

Figure 13.

Page 18 /

IM

269

minimum flow rates are required to close the switch and are

listed in Table 18. Installation should be as shown in Figure

13.

Electrical connections in the unit control center should be

made at terminals 5 and 6. The normally open contacts of

the flow switch should be wired between these two terminals.

There is also a set of normally closed contacts on the switch

that could be used

for an indicator light or an alarm to in-

dicate when a “no

flow” condition exists.

EVAPORATOR FAN INTERLOCK FOR AIR HANDLER COIL INSTALLATIONS

It is important to interlock the air handler evaporator fan with

the condensing unit control to insure that there will be a

cool-

purpose. Remove the jumpers between terminals 111 and

11.2 for circuit 1 and 211 and 212 for circuit 2. Use these ter-

ing load on the evaporator before the unit can start to

pre-

minals for the evaporator fan interlock contacts. Be sure to

vent compressor slugging. A pair of terminals for each

refrigerant circuit is available in the unit control center for this

keep circuits separate by using two contacts on dual circuit

machines.

UNIT LAYOUT

&

PRINCIPLES OF OPERATION

Figure 14. Major Component Locations

The figures below illustrate component locations within the unit for each unit size.

COMPRESSOR No. 1

-

COMPRESSOR No. 1

I

L---J

COMPRESSOR No. 2

-/

TOP VIEW OF UNIT

COMPRESSOR No. 2

J

\_

COMPRESSOR No. 4

CONTROLCENTER

All electrical controls are enclosed in a weatherproof control

center with keylocked, hinged access doors. The control

center is composed of two separate compartments, line

voltage and control voltage. All of the line voltage

com-

ponents, except for the input terminals of the PVM, are

located in the compartment on the right side of the unit. The

control voltage components are located on the left side with

the live terminals located behind a deadfront panel. This

pro-

tects service personnel from live terminals when accessing

the adjustable and resettable controls.

IM 269 I Page

19

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McQuay SEASONCON ALP-055C Installation And Maintenance Data

McQuay SEASONCON ALP-055C Installation And Maintenance Data

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