Chapter 6. REFRIGERATION SYSTEM REPAIR

TM 5-4110-217-14

CHAPTER 6

REFRIGERATION SYSTEM REPAIR

Section I. SERVICING REFRIGERATION SYSTEM

blocks above large electric light bulb If heat from other

6-1. Pumping Down.

sources is used, be sure that temperature is not raised

Before the refrigeration system can be opened for

above 175F.

maintenance, as much refrigerant as possible must be

liquefied and removed from tubing and other

6-3. Adding Refrigerant.

components and placed in the receiver tank in the

condenser compartment The procedure involved in

transferring refrigerant to the receiver tank Is known as

NOTE

pumping down To pump down the system, proceed as

Whenever available, use recycled

follows

refrigerant

for

charging

the

a Be sure that compressor suction and discharge

refrigeration system.

valves are open.

b. Close receiver outlet valve by turning valve

When refrigerant passing through sight glass

stem clockwise as far as it will go.

appears frothy during normal operation of refrigeration

c. Operate unit until suction pressure gauge

unit, the system needs additional refrigerant. A normal

registers between 0-and 1-pound per square inch

refrigerant charge consists of 14 pounds of R12 This

amount of R-12 is in the unit when shipment Is made If

d. Shut off machine and observe suction pressure

additional refrigerant is required, it indicates that a leak

gauge If pressure rebuilds appreciably, again

has developed in the system In this case, test for leak

operate machine until pressure is between 0- and

(para 6-9), repair faulty connection, and add refrigerant

1-pound per square inch. Repeat this step until

as follows:

pressure no longer rebuilds appreciably

a. Turn stem of suction service valve

e. Close receiver inlet valve by turning valve stem

counterclockwise as far as possible

clockwise as far as it will go

b. Connect line from R-12 charging drum to the

6-2.

Opening System.

connection of compressor service valve.

Leave

connection loose at compressor suction valve and open

Before opening the refrigeration system, the

charging drum outlet valve long enough to purge all air

pressure in the system should be known If the system is

from the charging line through the loose connection.

open under high pressure, excessive loss of refrigerant

will occur; if opened under vacuum, air is drawn into the

CAUTION

equipment and causes future operating difficulties. If

Avoid bodily contact with or

pressure gauge indicates a vacuum after system has

inhaling of refrigerant gas. When in

been pumped down, cautiously open receiver outlet

an enclosed area, be sure of proper

valve enough to build a slight pressure in the system

ventilation.

Breathing

When a positive pressure Is assured, the part of system

Refrigerant 12 for long periods of

to be opened should be shut off from remainder of

time

could

injurious

system. Thus, If the compressor is to be removed,

personnel.

compressor suction and discharge valves should be

Tighten charging line connection at compressor suction

closed after system Is pumped down. In opening the

valve

system, observe the following precautions

c. Turn stem of suction service valve clockwise 3

Clean and dry equipment at the point to be

or 4 turns

opened Use a clean, lint-free cloth for this purpose.

d. Open charging drum outlet valve one or two

b. Open the necessary joints and plug and cover

turns.

opening to prevent dirt from entering.

e. Snap start switch to ON position.

c. After opening the system, do not touch internal

f. Operate unit while observing sight glass.

parts unless hands are thoroughly dry and clean.

When frothiness disappears, turn suction service valve

If a spare part is to be installed, clean and dry

counterclockwise as far as It will go Allow unit to operate

the part as follows:

a while to see if sight glass remains clear If not, add

more R-12

(1) Clean the part by brushing it while

g. Close outlet valve of charging drum and back-

immersed in an approved cleaning solvent.

seat suction service valve

(2) Dry the part with heat by placing part on

Change 5 6-1