TM 9-4120-357-14
f. With suction line service valve closed, disconnect vacuum pump and attach cylinder of
dry nitrogen. Leave the
connection to the cylinder shutoff valve loose for a few seconds and purge the line of air. Tighten connection, and crack
suction line service valve open slightly to break vacuum. Leave in this configuration until system reaches atmospheric
pressure (760 MM), then close suction service valve and cylinder shutoff valve, and disconnect nitrogen cylinder.
g. Reconnect vacuum pump to suction line service valve gage port, and start pump. Open suction line service
valve, and again pump until a 500-Micron vacuum is achieved. This double evacuation will remove all traces of water
vapor from the system. Close suction line service valve, and remove vacuum gage.
h. Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve, and turn cylinder shutoff
valve on for a few seconds to purge line of air. Tighten service valve connection. Charge refrigeration system as directed
in the following steps:
(1) Place the refrigerant cylinder on a scale of sufficient capacity, with the shutoff valve down, or suspend the
cylinder from a spring scale or beam scale, with the valve end down.
NOTE
If cylinder is equipped with both liquid and vapor valves, connect line to liquid
valve.
(2) Weigh the cylinder, and record the weight.
(3) Open the discharge line service valve, and slightly open the refrigerant cylinder shutoff valve. Liquid re-
frigerant will be sucked into the refrigeration system rapidly at first, then more slowly as pressures begin to equalize.
When 25 pounds (11.4 KG) of refrigerant have flowed into refrigeration system, as indicated by the scale, close the dis-
charge line service valve and the cylinder shutoff valve.
WARNING
Hearing protection must be worn when maintenance is performed while air condi-
tioner is in operation. Failure to heed this warning can result in hearing loss or
injury.
CAUTION
Connect power to unit as soon as possible after charging or any period when
power has been disconnected. Allow heater time to vaporize refrigerant in com-
pressor before operation in COOL mode. If knocking or pounding is heard at start
of COOL mode, turn selector switch to OFF or VENTILATE at once and allow addi-
tional warm up time.
i. With power connected to the air conditioner, turn mode selector switch to cool, and turn temperature control
thermostat to maximum decrease position. With compressor operating, observe the sight-glass liquid indicator. If bub-
bles or milkiness appear, top off the refrigerant charge as follows:
(1) Connect a cylinder of refrigerant, R22, loosely to the gage port of the suction line service valve. Open the
cylinder shutoff valve for a few seconds to purge air from the line. Tighten the connection. Leave the cylinder upright, or
connect line to vapor valve.
(2) With the air conditioner compressor operating, open the suction line service valve and the cylinder shutoff
valve to charge refrigerant gas into the system, while observing the sight-glass liquid indicator.
(3) When liquid in sight-glass indicator runs clear and free of bubbles, close the suction line service valve and
the cylinder shutoff valve.
(4) Disconnect refrigerant cylinder, and replace caps on both service valves.
5-9.
Compressor Motor Burnout.
Burnout of a compressor motor is indicated by lack of continuity of the motor windings and the condition of compressor
oil, which must be determined after the compressor has been removed from the refrigeration system. Causes of com-
pressor motor burnout include the following:
a. Low line voltage, which causes motor winding to overheat. Before burning out completely, the overheated
windings cause chemical breakdown of the refrigerant and the oil to form sludge and other system contaminants.
5-9