7. AIR PURGING
Air and moisture in the refrigerant system may have undesirable effects as indicated 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 unit and tubing between the indoor and outdoor unit must be leak tested and evacuated to remove any noncondensables and moisture from the system.
■Air Purging with a Vacuum Pump (for Test Run) Preparation
Check that each tube (both liquid and gas tubes) between the indoor and outdoor units has been properly connected and all wiring for the test run has been completed. Remove the valve caps from both the gas tube and liquid tube service valves on the outdoor unit. Note that both liquid and gas tube service valves on the outdoor unit are kept closed at this stage.
Manifold gauge
Fig.
Vacuum pump
Outlet
Inlet
Fig.
Manifold valve
Leak test
(1)Attach a manifold valve (with pressure gauges) and dry nitrogen gas cylinder to this service port with charge hoses.
CAUTION | Use a manifold valve for air | |
purging. If it is not available, use | ||
| ||
| ||
| a stop valve for this purpose. The | |
| “Hi” knob of the manifold valve | |
| must always be kept closed. |
(2)Pressurize the system to no more than
512 psig (36 kgf/cm2G) with dry nitrogen gas and close the cylinder valve when the gauge reading reaches 512 psig (36 kgf/cm2G). Then, test for leaks with liquid soap.
CAUTION | To avoid nitrogen entering the | |
refrigerant system in a liquid state, | ||
| ||
| ||
| the top of the cylinder must be | |
| higher than the bottom when you | |
| pressurize the system. Usually, | |
| the cylinder is used in a vertical | |
| standing position. (Refer to the | |
| previous page.) |
Pressure gauge
Gas tube
Liquid tube
Lo 
Hi
Charge hose
Cylinder valve
Nitrogen gas cylinder (In vertical standing position)
Service port ø5/16"
Open
Close
Outdoor unit
Open
Close
Fig.
65
