Servicing the Refrigerant System - TM-5-4120-273-150058

TM 5-4120-273-15

slightly to purge hose. Tighten connection at

refrigerant from the system. Refer to paragraph

charging valve. Open shutoff valve and backseat

5-21b for instructions for discharging the system.

charging valve.

b. After discharging the system allow the tub-

(d) Refrigerant drum must be in up-right

ing to warm to the ambient temperature before

position to allow only gaseous refrigerant to en-

opening the system; this delay will help prevent

ter system.

the formation of condensation on the inside wall

(e) Start unit.

of the tubing. Plug or cap all openings as a part

is removed to minimize the entry of dirt and mois-

(f) TO speed up charging, set refrigerant

drum in warm water, Never use a heating torch

ture into the system.

for this purpose.

c. Use a silver solder on all soldered connec-

tions. Silver solder (or equivalent) with a 50 per-

(g) Observe slight glass (fig. 3-13) at the

time of charging, and even though flash gas is ap-

cent silver capacity and a melting point of approx-

parent, shutoff refrigerant flow and observe sight

imately 1,300F. is recommended. Continually

glass for a period of 10 to 20 minutes. If at the

pass dry nitrogen through the tubing or connec-

end of this time period the sight glass is not free

tions being soldered to prevent formation of

from the flash gas, admit a small amount of

harmful copper oxides.

charge and observe for the same time period. Re-

peat this operation until sight glass is clear.

5-21. Servicing the Refrigerant System

(h) Frontseat charging valves and close

a. Testing Refrigerant System for Leaks. Refer

refrigerant drum shutoff valve. Stop the unit and

to paragraph 3-45b, and test refrigerant system

disconnect manifold hoses from charging valves,

for leaks.

install caps.

b. Releasing Refrigerant for Service. Release

(2) Weight method. With this method you

refrigerant slowly to a well vented atmosphere.

are charging the unit with liquid.

Adjust the release so that a vaporized discharge

(a) Evacuate the system, paragraph 5-21,

is made to avoid loss of refrigerant oil.

(b) Connect a bottle of refrigerant-22 to

c. Evacuating the Refrigerant System.

discharge high side access fitting, figure 3-6.

(1) General. Opening the system to the at-

mosphere will cause entry of air and moisture into

(d) Invent charging cylinder and open

the system. After any servicing operation, when

valve on refrigerant bottle and allow refrigerant

the system is opened, the entire system should be

to flow through system.

evacuated before a recharging with refrigerant,

(e) Periodically weigh bottle until it is

(2) Evacuation.

lighter by amount needed in system, must be exact

(a) Connect hose assemblies of evacuation

amount.

gage manifold to discharge valve access fitting

Caution: Total amount of charge must

and to the suction access fitting of unit, reference

be exactly 53 oz.

figure 3-6.

(b) Connect vacuum pump to center hose

5-22. Wiring Harness and Wire Leads

of gage manifold.

a. General. The electrical circuits in the refrig-

crons.

eration unit are completed by individual wire

(d) Break vacuum by admitting refriger-

leads or by leads laced or enclosed to form a wir-

ant, para 5-21d (1).

ing harness. When testing, repairing, or replac-

ing the individual wires or Harnesses refer to the

Caution: Do not use the compound gauge as

wiring diagram (fig. 1-5).

an indicator for satisfactory vacuum pressure.

b. Inspection. Inspect the wiring insulation for

d. Charging the Refrigerant System. There are

cracks and frayed material. Pay particular atten-

two preferred methods used to charge the refrig-

tion to the wires passing through holes in the

erant system.

frame or over rough edges. If inspection reveals

(1) Sight glass method.

a broken or cut wire, and the break in the wire is

exposed, the wire must be repaired (d below). If

(a) Evacuate the system, paragraph 5-21.

the break in a wire is in a harness or inaccessible

(b) Remove cap from suction tube charg-

area, replace wire (e below).

ing valve.

c. Testing. Test a wire for continuity by discon-

( c ) Connect hose from refrigeration

necting each end from the component or compo-

charging hookup loosely to suction tube charging

nents to which it is connected. Touch the test

valve. Open refrigerant drum shutoff valve

5-4