Desert Aire Aura QS Installation And Operation Manual page 80

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.
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Alternative Evacuation Specified by Process
After components have been repaired or replace 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 method has
not been successful after 24 hours minimum using the standard procedure, the following alternative method
should be used.
1. 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.
2. 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.
3. Start vacuum pump and draw system to 1,500 microns or less.
4. 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.
5. Start vacuum pump and draw system to 500 microns. Seal system. System may rise to higher level,
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Desert Aire - QS/QV Manual
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.