Heatcraft Mohave, Installation & Operation Manual, Page: 48 / 76

48
Leak Testing
After all lines are connected, the entire system must be leak tested. The complete
system should be pressurized to not more than 150 psig with refrigerant and
dry nitrogen (or dry CO
2
). The use of an electronic type leak detector is highly
recommended because of its greater sensitivity to small leaks. As a further check
it is recommended that this pressure be held for a minimum of 12 hours and then
rechecked. For a satisfactory installation, the system must be leak tight.
Line Insulation
After the final leak test, refrigerant lines exposed to high ambient conditions should
be insulated to reduce heat pickup and prevent the formation of flash gas in the liquid
lines. Suction lines must always be insulated with 3/4" wall Armstrong “Armaflex” or
equal. When required, Liquid lines should be insulated with 1/2 inch wall insulation or
better. The insulation located in outdoor environments should be protected from UV
exposure to prevent deterioration of insulating value.
Evacuation
CAUTION: Do not use the refrigeration compressor
to evacuate the system. Do not start the
compressor while it is in a vacuum.
A good, deep vacuum pump should be connected to both the low and high side
evacuation valves with copper tube or high vacuum hoses (1/4" ID minimum). If the
compressor has service valves, they should remain closed. A deep vacuum gauge
capable of registering pressure in microns should be attached to the system for
pressure readings.
A shut off valve between the gauge connection and vacuum pump should be
provided to allow the system pressure to be checked after evacuation. Do not turn off
vacuum pump when connected to an evacuated system before closing shut off valve.
The vacuum pump should be operated until a pressure of 1,500 microns absolute
pressure is reached — at which time the vacuum should be broken with the
refrigerant to be used in the system through a drier until the system pressure rises
above “0” psig.
NOTE: Refrigerant used during evacuation cannot be vented.
Reclaim all used refrigerant. EPA regulations are constantly
being updated to ensure your procedure follows correct
regulations.
Repeat this operation a second time.
Open the compressor service valves and evacuate the entire system to 500 microns
absolute pressure. Raise the pressure to 2 psig with the refrigerant and remove the
vacuum pump.
Evacuation & Leak Detection
Due to the smaller molecule size of HFC’s, they will tend to leak more readily than
CFC’s. Consequently, it is of the utmost importance that proper system evacuation
and leak detection procedures be employed.
Copeland recommends a minimum evacuation to 500 microns. In addition, a vacuum
decay test is strongly recommended to assure there is not a large pressure differential
between the system and vacuum pump. Good evacuation processes include frequent
vacuum pump oil changes and large diameter, short hose connections to both high
and low sides of the system preferably using bronze braided hose.
Leak detection can be carried out in the conventional manner.
If HCFC or CFC tracer gas is used, care must be taken to completely remove all
traces of the gas prior to introducing HFC’s.
Electronic leak detectors are now available that will sense HFC’s. This is considered
preferable since it removes the possibility of chlorine remaining in the system after
leak testing with HCFC’s and/or CFC’s. There is a view that even small quantities
of chlorine may act as a catalyst encouraging copper plating and/or corrosion and
should therefore be avoided.
Within the last several years, manufacturers have developed fluorescent dye leak
detection systems for use with refrigerants. These dyes mix with the lubricant and,
when exposed to an ultraviolet light “fluoresce,” indicates the location of leaks.
Copeland has tested and approved the Rigid “System Safe” dye and found it to be
compatible with the compressor materials in systems.
Evacuation & Leak Detection
NOTE: The Hot Gas Control Board may be powered up and set
on“EVAC” Mode during Evacuation. In this mode, all of the
system valves are energized. See Page 47.