5. Air Purging
1) Air purging
Air and moisture remaining in the refrigerant system 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 refrigera- tion system.
Therefore, the indoor unit and tubing between the indoor and outdoor unit must be leak tested and evacu- ated to remove any noncondensables and moisture from the system.
2)Air purging with vacuum pump
1.Preparation
•Check that each tube(both liquid and gas side tubes) between the indoor and outdoor units have been prop- erly connected and all wiring for the test run has been completed. Remove the service valve caps from both the gas and the liquid side on the outdoor unit. Note that both the liquid and the gas side service valves on the outdoor unit are kept closed at this stage.
2. Leak test
•Connect the manifold valve(with pressure gauges) and dry nitrogen gas cylinder to this service port with charge hoses.
CAUTION
Be sure to 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 close.
•Pressurize the system to no more than 150 P.S.I.G. with dry nitrogen gas and close the cylinder valve when the gauge reading reached 150 P.S.I.G. Next, 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 its bottom when you pressurize the system. Usually, the cylinder is used in a vertical standing position.
•Do a leak test of all joints of the tubing(both indoor and outdoor) and both gas and liquid side service valves.
Bubbles indicate a leak. Be sure to wipe off the soap with a clean cloth.
•After the system is found to be free of leaks, relieve the nitrogen pressure by loosening the charge hose connector at the nitrogen cylinder. When the system pressure is reduced to normal, disconnect the hose from the cylinder.
Indoor unit
Outdoor unit
Manifold valve
Pressure | Lo Hi | |
gauge | ||
|
Charge hose
Nitrogen gas cylinder(in vertical standing position)
