TM 9-4110-255-14
5-14. EVACUATING THE REFRIGERANT SYSTEM .
This task covers:
Evacuate
INITIAL SETUP
Tools:
Equipment Conditions:
Refrigeration Unit Service Tool Kit
4, Section III, Appendix B
Evacuate. The refrigeration system must be evacuated to remove all moisture and non-condensable before it
is charged.
(1)
Check that new dehydrator was installed. If not, install one (para 5-17).
(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 gage, compound gage, 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 gage. If gage needle moves
back and forth, you have a leak which must be located and corrected (para 5-13).
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 gage 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 5-13). 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 gage and compound gage valves.
(8)
Disconnect the vacuum hose from vacuum pump.
5-23