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 TM 55-1905-219-14-8
4-28. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
interchanger liquid bypass valve is closed. If a heat interchanger is not installed, close cut-out
valves installed upstream of solenoid and thermal expansion valves at the evaporator(s).
2
Weigh an empty refrigerant-12 drum.
3
Place empty drum on deck at an angle slightly above horizontal with drum valve at high end.
4
Connect drum to drain valve with a flexible drain line identical to charging line. Tighten
connection at drain valve. Purge air from drain line by momentarily cracking open
drain valve
and tighten connection at drum.
5
With compressor operating automatically, open drum valve and drain valve. Liquid refrigerant
will flow into drum.
6
Weigh drum while filling with refrigerant and compare with weight of empty drum obtained in
step 2. Drum should be filled only to its rated weight of liquid refrigerant. To fill drum
to its
rated capacity, immerse it in an ice water bath. Cooling of drum will also permit rapid
of refrigerant.
CAUTION
Never fill a drum beyond its rated capacity. Damage may result from excessive
hydraulic pressure upon temperature rise.
7
When required amount of refrigerant has been removed, close drain valve and drum valve.
Loosen drain line connections, allow any liquid refrigerant in drain line to evaporate,
and
remove drain line. Store filled refrigerant drum.
8
When removing only some refrigerant to correct system overcharge, open liquid supply to
evaporator(s) shut off in step 1 and resume normal system operation.
9
If entire refrigerant charge is to be removed, attach new drum as per step 4 and repeat draining
operation. If may be necessary to pump down system several times to insure complete
removal of refrigerant.
4-843
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