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Fig. 7-1
Fig. 7-2
Fig. 7-3
7. 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
5/16" 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.
(3) Pressurize the system to no more than 469 psig (33 kgf/cm
2
G)
with dry nitrogen gas and close the cylinder valve when the
gauge reading reaches 469 psig (33 kgf/cm
2
G). Then, test for
leaks with liquid soap.
Manifold gauge
Outlet
Inlet
Vacuum pump
Manifold valve
Pressure
gauge
Lo Hi
Charge hose
Outdoor unit
Close
Open
Liquid
tube
Gas
tube
Balance
tube
Nitrogen gas cylinder
(In vertical standing
position)
Close
Open
Close
Open
Cylinder
valve
CAUTION
CAUTION
To avoid nitrogen entering the
refrigerant system in a liquid state, the
top of the cylinder must be higher than
the bottom when you pressurize the
system. Usually, the cylinder is used in
a vertical standing position.
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 closed.
07-007 W-2WAY_II_NA 1/23/07 6:09 PM Page 67