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Evacuation
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Alternative Evacuation Specified by Process
After components have been repaired or replaced evacuation procedure should take place. Very
small amounts of refrigerant may still be mixed with the oil in the system. Out-gassing of this
refrigerant may interfere with the evacuation and vacuum decay testing.
IF, AND ONLY IF, a unit has been previously charged with refrigerant, and standard evacuation
methods has not been successful after 24 hours minimum using the standard procedure, the
following alternative method should be used.
1.
2.
3.
4.
5.
It is anticipated that the system was clean and tight from the original process and refrigerant only is
Carefully inspect pump and related equipment before connecting to system. Ensuring
gaskets are in good condition and pump is capable of low vacuum levels can save time.
Connect pump(s) to as many locations as possible ensuring all locations are well sealed.
If a field charge will be required, connecting a refrigerant tank to the system with a good valve
is recommended. Any hose connections requiring purging of non-condensable can be done
at this point.
Evacuate the line and remote condenser to 400 microns measured at a point on the system
furthest away from the pump.
-
Note that a gauge installed on the pump or in close proximity will give a lower reading
while the unit is being evacuated.
-
A deep vacuum gauge should be used to evaluate the pressure. Compound
manifold gauges do not allow for enough accuracy at the pressures required.
-
The system should be able to hold a vacuum under 500 microns for more than 10
minutes.
-
If pressure continuously rises at a rapid rate there is likely a system leak. Review all
piping connections and correct before continuing evacuation.
-
Pressure rising above 500 microns and tending to stabilize at a higher pressure
indicates the system has moisture above specifications. Continue evacuation until
500 microns or lower can be held for a minimum of 10 minutes.
Check vacuum level. It should be a maximum of 1,500 microns absolute pressure. If this is
not the case, review system for leaks and continue evacuation process until 1,500 microns is
achieved.
Purge system with nitrogen to atmospheric pressure (0 gauge pressure). Ensure all portions
of systems are at this pressure. Seal system and wait 10 minutes.
Start vacuum pump and draw system to 1,500 microns or less.
Purge system with nitrogen to atmospheric pressure (0 gauge pressure). Ensure all portions
of systems are at this pressure. Seal system and wait 10 minutes.
Start vacuum pump and draw system to 500 microns. Seal system. System may rise to
higher level, but should not rise above 1000 microns in 10 minutes timeframe. If successful,
continue evacuation or check for leaks.
43
Desert Aire - LW Manual
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