Midea MPM1-10CEN1-BB6 Technical & Service Manual page 25

Acetylene Welder
Electronic Halogen Leak Detector (G.E. Type H-6 or equivalent.)
Accurate refrigerant charge measuring device such as:
a. Balance Scales - 1/2 oz. accuracy
b. Charging Board - 1/2 oz. accuracy
High Pressure Gauge - (0 - 400 lbs.)
Low Pressure Gauge - (30 - 150 lbs.)
Vacuum Gauge - (0 - 1000 microns)
9.2.2 Equipment must be capable of:
Recovery CFC's as low as 5%.
Evacuation from both the high side and low side of the system simultaneously.
Introducing refrigerant charge into high side of the system.
Accurately weighing the refrigerant charge actually introduced into the system.
Facilities for flowing nitrogen through refrigeration tubing during all brazing processes.
9.2.3 Hermetic compressor replacement.
The following procedure applies when replacing components in the sealed refrigeration circuit
or repairing refrigerant leaks. (Include Compressor, condenser, evaporator, capillary tube,
refrigerant leaks, etc.)
Recover the refrigerant from the system at the process tube located on the high side of
the system by installing a line tap on the process tube. Apply gauge from process tube to EPA
approved gauges from process tube to EPA approved recovery system. Recover CFCs in system
to at least 5%.
Cut the process tube below pinch off on the suction side of the compressor.
Connect the line from the nitrogen tank to the suction process tube.
Drift dry nitrogen through the system and unsolder the more distant connection first.
(Filter drier, high side process tube, etc.)
Replace inoperative component, and always install a new filter drier. Drift dry nitrogen
through the system when making these connections.
Pressurize system to 30 PSIG with proper refrigerant and boost refrigerant pressure to
150 PSIG with dry nitrogen.
Leak test complete system with electric halogen leak detector, correcting any leaks found.
Reduce the system to zero gauge pressure.
Connect vacuum pump to high side and low side of system with deep vacuum hoses, or
copper tubing. (Do not use regular hoses.)
Evacuate system to maximum absolute holding pressure of 200 microns or less. NOTE:
This process can be speeded up by use of heat lamps, or by breaking the vacuum with
refrigerant or dry nitrogen at 5,000 microns. Pressure system to 5 PSIG and leave in system a
minimum of 10 minutes. Recover refrigerant, and proceed with evacuation of a pressure of
200 microns or a minimum of 10%.
Break vacuum by charging system from the high side with the correct amount of
refrigerant specified. This will prevent boiling the oil out of the crankcase.
NOTE: If the entire charge will not enter the high side, allow the remainder to enter the low side
in small increments while operating the unit.
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Basic test procedure