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 TM 55-1905-220-14-11
5-143. COMPRESSOR - HVAC - MAINTENANCE INSTRUCTIONS (Continued).
LOCATION
ITEM
ACTION
REMARKS
OVERHAUL - SAFETY PRECAUTIONS
Wear goggles to prevent liquid R-12 from getting into the eyes when charging,
purging or opening the system for repairs.
1. Operating.
a. Never start a compressor without making sure that any shutoff valve between the compressor and
the condenser is open.
b. Do not jack or turn the compressor by hand when power is on.
c. Whenever the compressor motor is first started, the operator should stand by the switch and start
the motor in short, intermittent spurts until it is certain that the compressor is operating properly. If possible, the
compressor should be turned over several times BY hand, to clear the cylinders of any oil that may have
collected there during shipment or erection. When starting up the compressor, avoid rapid pumping down of
the low side pressure. The operator should also be certain that liquid refrigerant is not being returned to the
compressor. Liquid return will be indicated by the crankcase and cylinder being relatively cold, sweating or
frosted.
d. In case of severe vibration or unusual noise, stop the unit and investigate.
e. When isolating any part of the system in which there is liquid refrigerant, close the cut-out valve on
inlet side of the part to be isolated and allow the compressor to remove all liquid refrigerant. This will be
indicated by a sudden chilling of the part being isolated. When the part begins to get warm again it may be
considered devoid of liquid refrigerant. Close valve on outlet side of isolated part before opening bypass
valves, if provided.
f Never open any part of the system which is under a vacuum. If this is done, air and moisture will be
drawn into the system and are almost certain to cause trouble at some later date. The section to be opened
should be under 1 - 2 psig (6.9 - 13.8 kPa) pressure to prevent the admission of air and moisture into the
system.
5-1482
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