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 TM 55-1905-219-14-8
4-28. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
(g) Hand expansion valves in the refrigerant circuits permit manual operation when the automatic
control valves are isolated for service, inspection or repairs. After isolating the expansion and solenoid valves
by closing cut-out valves, a circuit can be operated by throttling the hand expansion valve. Crack hand
expansion valves open gradually (about 1/4 turn at a time) and not too much to avoid flooding coils and liquid
return to compressor.
(4)
Securing.
(a) Before stopping the compressor for any time longer than several minutes, the supply of liquid
refrigerant to the evaporator should be shut off. This will prevent flooding the evaporator and avoid liquid
refrigerant return to the compressor when restarting.
(b) If the solenoid valves at the evaporator are energized from the compressor motor controller, or
a king solenoid valve wired to the motor controller is provided, the solenoids automatically close and cut off the
flow of liquid to the evaporator when the controller STOP button is depressed.
(c) To secure a condensing unit, proceed as outlined below. If the plant consists of two or more
interconnected units, with the plant operating under split plant conditions, proceed as outlined below for each
unit.
NOTE
For extended periods of compressor shutdown, the system should be pumped down.
Refer to paragraph 4-28e(4).
1
Close main liquid line stop valve (dryer bypass or inlet valve).
2
Let compressor run until it cuts out on low pressure setting of low pressure control switch.
3
Stop compressor at motor controller. Depress STOP button.
4
Close compressor suction and discharge stop valves.
5
Secure condenser sea water circulating system. Open vents atop and drains at bottom of
water heads and drain condenser if there is danger of water freezing in condenser tubes.
6
All other valves of condensing unit may be closed.
4-838
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