Refrigeration Maintenance
112
Unit Evacuation
NOTE: The electrical system must be energized
throughout this procedure.
1. Close the isolation valve at the thermistor to
isolate the vacuum gauge. Turn the vacuum
gauge on to warm it up.
2. Open the compressor service valves and the
receiver outlet valve.
3. Observe the gauge manifold. If the system
pressure is more than 5 psig (35 kPa), loosen
the hose at the receiver outlet valve to vent the
excess pressure, then tighten the hose.
4. Replace and tighten the valve stem caps on all
three service valves.
5. Open the vacuum valve at the vacuum pump
and start the pump.
6. After evacuating the system for 5 minutes,
open the isolation valve at the thermistor to
access the vacuum gauge.
7. Evacuate the system to 500 microns. Back
seat the suction service valve and then
continue to evacuate the system for one
additional hour.
8. After the hour of additional evacuation time,
open the suction service valve. The vacuum
gauge reading will rise. Continue to evacuate
the system back down to 500 microns. When
the system reaches 500 microns, back seat the
suction service valve, close the vacuum valve
at the vacuum pump, and stop the pump.
9. Observe the reading on the vacuum gauge for
5 minutes. The pressure should not exceed
2000 microns. If the pressure exceeds 2000
microns in 5 minutes, a leak is present, or
additional evacuation time is required.
10. If the vacuum level is acceptable, start the
pump and open the vacuum valve. Evacuate
the system for 5 minutes to remove the
pressure rise. Close the vacuum valve and stop
the pump. Observe the vacuum gauge to
confirm that the system remains in a deep
vacuum.
11. Close the isolation valve at the thermistor. The
unit is now ready to charge.
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