TM 9-4120-357-14
(b) With the suction line service valve closed, disconnect the vacuum pump and attach a
cylinder of
dry nitrogen.
Leave the connection to the suction service valve loose. Open the cylinder shutoff valve for a few seconds to purge the
line of air. Tighten connection, and crack suction line service valve open slightly to break vacuum. Leave in this con-
figuration until system reaches atmospheric pressure (760 MM) . Close the suction service valve and the cylinder shutoff
valve, and disconnect the nitrogen cylinder.
(c) Reconnect the vacuum pump to the suction line service valve gage port, and start the pump. Open the 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 the suction line service valve, and disconnect the vacuum
pump. Close the discharge line service valve, and remove the vacuum gage.
(d) Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve. Open the cylinder shutoff
valve for a few seconds to purge line of air. Tighten the service valve connection. Charge refrigeration system as di-
rected 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 gas (vapor) valves, connect the line to the
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 refrig-
erant 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 the 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 conditioner 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 compressor before opera-
tion in COOL mode. If knocking or pounding is heard at start of COOL mode, turn selec-
tor switch to OFF or VENTILATE at once and allow additional warm up time.
(e) With power connected to the air conditioner, turn the mode selector switch to cool. Turn the temperature control
thermostat to maximum decrease position. Temporarily prop front across panel across opening. With the compressor
operating, observe the sight-glass liquid indicator. If bubbles or milkiness appear, top off the refrigerant charge as fol-
lows:
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. Replace caps on both service valves.
h. Final Assembly. Final assembly of the air conditioner consists of replacing external grilles and panels.
Proceed as follows:
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