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6. AIR PURGING
Air and moisture in the refrigerant system may 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 refrigerant
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 a Vacuum Pump (for Test Run)
Preparation
Check that each tube (both liquid and gas tubes) between the
indoor and outdoor units have been properly connected and all
wiring for the test run has been completed. Remove the valve
caps from both the gas and liquid service valves on the outdoor
unit. Note that both liquid and gas tube service valves on the
outdoor unit are kept closed at this stage.
Leak test
(1) With the service valves on the outdoor unit closed, remove
the 1/4 in. flare nut and its bonnet on the gas tube service
valve. (Save for reuse.)
(2) Attach a manifold valve (with pressure gauges) and dry
nitrogen gas cylinder to this service port with charge hoses.
Use a manifold valve for air purging. If it
is not available, use a stop valve for this
CAUTION
purpose. The "Lo" knob of the manifold
valve must always be kept closed.
(3) Pressurize the system to no more than 3.80 MPa with dry
nitrogen gas and close the cylinder valve when the gauge
reading reaches 3.80 MPa. Then, test for leaks with liquid
soap.
To avoid nitrogen entering the refrigerant
system in a liquid state, the top of
the cylinder must be higher than the
CAUTION
bottom when you pressurize the system.
Usually, the cylinder is used in a vertical
standing position.
Manifold gauge
Vacuum pump
Manifold valve
Pressure
gauge
Lo
Cylinder
valve
Gas
tube
Liquid
tube
39
Outlet
Inlet
Hi
Charge hose
Nitrogen gas cylinder
(In vertical standing
position)
Open
Close
Outdoor unit
Open
Close
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