8. LEAK TEST, EVACUATION AND
ADDITIONAL REFRIGERANT
CHARGE
Perform an air-tightness test for this package A/C. Check that
there is no leakage from any of the connections.
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. (Figs. 8-1 and
8-2)
Manifold gauge
Fig. 8-1
■ 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 has 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. (Fig. 8-3)
Vacuum pump
Outlet
Inlet
Fig. 8-2
Manifold valve
Lo
Pressure
gauge
Gas tube
Liquid tube
● The refrigerant charge at the time of shipment is only
guaranteed sufficient for a tubing length of up to 30 m. The
tubing may exceed this length, up to the maximum permitted
length; however, an additional charge is necessary for
the amount that the tubing exceeds 30 m. (No additional
refrigerating machine oil is needed.)
8-1. Leak Test
(1) With the service valves on the outdoor unit closed, remove
the 7.94 mm 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.
CAUTION
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.
(3) Pressurize the system up to 4.15 MPa (42 kgf/cm
dry nitrogen gas and close the cylinder valve when the
gauge reading reaches 4.15 MPa (42 kgf/cm
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
the bottom when you pressurize the system. Usually, the
cylinder is used in a vertical standing position.
(4) Do a leak test of all joints of the tubing (both indoor and
outdoor) and both gas and liquid service valves. Bubbles
indicate a leak. Wipe off the soap with a clean cloth after a
leak test.
(5) 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.
50
Hi
Charge hose
Cylinder
valve
Nitrogen gas cylinder
(In vertical standing
position)
Open
Close
Outdoor unit
Close
Fig. 8-3
2
G) with
2
G). Then,