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 TM 55-1905-219-14-11
5-140. 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. 4 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.
5-1412
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