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17
AIR PURGING
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
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.
Air purging with vacuum
pump
Preparation
■
Check that each tube(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
cylinder valve when the gauge reading
reached 150 P.S.I.G. Next, test for leaks with
liquid soap.
Lo Hi
Indoor unit
Outdoor unit
Manifold valve
Charge hose
Nitrogen gas
cylinder(in vertical
standing position)
Pressure
gauge
A
B
■
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.
CAUTION
CAUTION