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 TM 55-1905-219-14-11
5-144. REFRIGERATOR/FREEZER - MAINTENANCE INSTRUCTIONS
(Continued).
LOCATION
ITEM
ACTION
REMARKS
SERVICE (Cont)
b.
To increase or decrease the pressure setting refer to back pressure control instruction sheet.
3.
Refrigerant.
NOTE
Freon 12 refrigerant is used.
a.
Low refrigerant in the system.
(1)
Should a compressor operate for too long a period, or too often, it is generally due to the refrigerant
supply being low, even though the temperature may be cold enough.
(2)
When the refrigerant is a little low, the head pressure may be below normal with the machine running;
when the supply is very low, the pressure may drop considerably within 10 or 15 minutes after the compressor stops.
The suction or back pressure may be higher than normal, while the machine is idle and drops more quickly than it -should
when the compressor starts, and may continue to be lower than normal with the apparatus in operation.
(3)
In case of low refrigerant, first locate the cause which is almost certain to be a leak. Do not add any
refrigerant until the leak has been found and repaired.
b.
How to add refrigerant.
(1)
Weigh the service cylinder before and after adding refrigerant, as this is the only way to determine how
much refrigerant has been added.
(2)
Be sure the low side suction valve is turned ail the way to the left to close the gauge port. Install a
compound gauge hose on one end, and connect the center hose from the manifold to the refrigerant cylinder. Before
finally tightening the connection, crack the service valve to purge air in the regular way. Attach the pressure gauge to the
high-side valve.
(3)
Warm the refrigerant service cylinder by putting it into a pail of warm water, or by using hot cloths. Do
not use a blow torch. Place cylinder in an upright position with valve at top to admit refrigerant vapor. Do not allow liquid
to enter compressor crankcase.
5-1460
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