5-17. EVACUATING THE SYSTEM.
Before the system is charged with refrigerant, it must be completely
evacuated to exhaust water vapor, non-condensible gases and other
impurities which would prevent the system from operating.
The following instructions are provided for use by refrigeration
shops furnished with only the most basic equipment.
sophisticated equipment, such as two-valve or four-valve service
manifolds is available, it should be used by making appropriate
modifications to these instructions.
a. Connect a vacuum pump to the suction service valve and a vacuum
gauge to the discharge service valve. Start the pump and open both
service valves. Operate the vacuum pump until pressure in the
system is reduced to 500 microns. Close the suction service valve
and turn the vacuum pump off. Let the unit stand in this condition
for at least one hour. If the system holds the vacuum without
change of pressure, continue with step B.
If the 500-micron vacuum
cannot be held for one hour, break the vacuum with dry nitrogen and
check for leaks. If 500-micron vacuum cannot be achieved, one or
more of the following reasons may account for the problem.
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