RJ150-30 / Operations and Maintenance Manual
Mobile Aircraft Air Conditioner
Trailer Mounted, Cool Mode Only
______________________________________________________________________________
SECTION 2 - 1
JANUARY 20, 2004
PAGE 20
A small portable vacuum pump designed for the type of refrigerant used in the
system should be used for evacuation. Do not use the refrigeration system
compressor as a vacuum pump.
Manifold gauges may be used to connect the vacuum pump to the
refrigeration system service/test valves. (See Figure 3) For larger systems
and larger vacuum pumps, copper tubing or vacuum hoses of 1/4-inch
minimum inside diameter are recommended for high vacuum work. The
following procedures are for use with a small vacuum pump connected
through manifold gauges.
Triple evacuation is strongly recommended for all field installed systems
because of the increased risk of contamination expected under actual
operating conditions.
(1) Attach the common connection on the manifold gauges to the suction
connection on the vacuum pump.
(2) Connect the high- and low-pressure connections on the manifold gauges
to the service valves on the high- and low-pressure sides of the system
respectively.
(3) With the valves on the manifold gauges closed (front-seated), open the
service valves and adjust to a point approximately midway between the
front-seat and back-seat position.
(4) Start the vacuum pump and gradually open the valves on the manifold
gauges. It may be necessary to restrict the vacuum pump suction
pressure using the manifold gauges to avoid overloading the vacuum
pump motor.
(5) Continue evacuation until the desired vacuum reading is obtained on both
gauges.
(6) When evacuation is complete, close the valves on the manifold gauges
tightly, remove the line from the vacuum pump and connect it to a
refrigerant cylinder.
(7) Loosen the common hose connection at the manifold gauges, crack the
refrigerant cylinder valve to purge the hose and retighten the hose
connection.
(8) Crack the valves on the manifold gauges until the system pressure rises
to 2 psig.
(9) Close the refrigerant cylinder valve and the valves on the manifold
gauges.
For triple evacuation, the above procedure should be performed three times,
evacuating twice to 500 microns and the last time for eight hours to ensure
complete system evacuation.
When triple evacuation is complete, the system is ready for recharging.
Perform
Charging Refrigerant
procedure, paragraph 3.F. in this Section. If
