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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 evac-
uated 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 properly
connected and all wiring for the test run has been com-
pleted. 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.
Manifold valve
Pressure
gauge
-35-
Indoor unit
Outdoor unit
Lo
Hi
Charge hose
Nitrogen gas
cylinder(in vertical
standing position)
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