6.4 Air purging with vacuum pump
Air and moisture in the refrigerant system have undesirable effects as below:
● Pressure in the system rises.
● Operating current rises.
● Cooling or heating efficiency drops.
● Moisture in the refrigerant circuit may freeze and block capillary tubing.
● Water may lead to corrosion of parts in the refrigerant system.
Therefore, the indoor units and the pipes between indoor and outdoor units must be leak tested and
evacuated to remove gas and moisture from the system.
Air purging with vacuum pump
(Indoor unit)
(Liquid side)
(Gas side)
Vacuum
pump
Vacuum
pump
adaptor
Lo Hi
Handle Hi
Two-way valve
Close
Manifold valve
Compound meter
Pressure
gauge
-76cmHg
Handle Lo
Charge hose
Charge hose
(Outdoor unit)
Close
Three-way valve
Procedure
1. Completely tighten the flare nuts of the indoor and outdoor units, connect the manifold valve
charge.
2. Connect the charge hose connection to the vacuum pump.
3. Fully open the handle Lo of the manifold valve.
4. Operate the vacuum pump to evacuate. After starting evacuation, slightly loose the flare nut of the
Lo valve on the gas pipe side and check the air is entering. (Operation noise of the vacuum pump
changes and a compound meter indicates 0 stead of minutes)
5. After the evacuation is complete, fully close the handle Lo valve of the manifold valve and stop the
operation of the vacuum pump. Make evacuation for 15 minutes or more and check the compound
meter indicates -76cmHg.
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