Service Manual 29
Air PurgingAir purging With Vacuum Pump
Lo Hi
Indoor unit
Outdoor unit
Manifold valve
Charge hose
Nitrogen gas
cylinder(in vertical
standing position)
Pressure
gauge
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 refrigeration 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.

Preparation

• Check that each tubing(both liquid and gas side
tubes) between the indoor and outdoor units have
been properly 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.

Leak test

• Connect the manifold valve(with pressure gauges)
and dry nitrogen gas cylinder to this service port
with charge hoses.
• Pressurize the system to no more than 150
P.S.I.G. with dry nitrogen gas and close the cylin-
der valve when the gauge reading reached 150
P.S.I.G. Next, test for leaks with liquid soap.
• 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.
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.
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.
Installation