3
.8 Air purging
3.8.1 Air purging
Air and moisture remaining in the refrigerant system
have undesirable effects as indicated below.
1) Pressure in the system rises.
2) Operating current rises.
3) Cooling(or heating) efficiency drops.
4) Moisture in the refrigerant circuit may freeze and
block capillary tubing.
5) 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 evacuated to
remove any noncondensables and moisture from the
system.
3.8.2 Air purging with vacuum pump
A. 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.
B. 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 cylinder 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 con-
nector at the nitrogen cylinder. When the system pres-
sure 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.
CAUTION
CAUTION
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