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TM 9-4110-257-14
5-11.
EVACUATING THE REFRIGERANT SYSTEM.
This task covers:
Evacuate
INITIAL SETUP
Tools:
Refrigeration Unit Service Tool Kit
4, Section III, Appendix B
Equipment Conditions:
Refrigerant system discharged (para. 5-7).
Evacuate.
The refrigeration system must be evacuated to remove all moisture and non-condensables before it
is charged.
(1) Check that new dehydrator was installed. If not, install one (para. 5-14).
(2) Check that service manifold charge valve is closed.
(3) Connect the vacuum hose to vacuum pump and start pump.
(4) Open service manifold high pressure gauge, compound gauge, and vacuum valves.
(5) Run vacuum pump until at least 29 inches of mercury is measured on compound gage. Continue running
vacuum pump for one more hour, while observing the compound gauge. If gage needle moves back and forth,
you have a leak which must be located and corrected (para. 5-10).
NOTE
Inability to reach and hold 29 inches of mercury may indicate either a
leak or a problem with the vacuum pump.
(6) Close service manifold vacuum valve and stop vacuum pump. Note reading on compound gauge and observe
for 10 minutes. If pressure rises, moisture may still be in the system or a leak exists. If pressure rose, repeat
evacuation and re-check. If the pressure rise occurs again at the same speed, a leak is in the system and must
be found (para. 5-10). If the pressure rise was slower the second time, moisture remains in the system and the
evacuation process must be repeated until there is no rise.
(7) Close service manifold high pressure gauge and compound gauge valves.
(8) Disconnect the vacuum hose from vacuum pump.
5-20
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