38
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.
n
Air Purging with a Vacuum Pump (for Test Run)
Preparation
Check that each tube 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 all service ports on the
outdoor unit.
Note that all service valves on the outdoor unit are kept
closed at this stage.
The balance tube leak test is not necessary if only 1
outdoor unit is installed.
Leak test
(1) Attach a manifold valve (with pressure gauges) and
dry nitrogen gas cylinder to all service ports with
charge hoses.
The balance tube leak test is not necessary if only 1
outdoor unit is installed.
(2) Pressurize the system to no more than 484 psig
(3.34 MPa) {33.1 k
g
f/cm
2
G} with dry nitrogen gas
and close the cylinder valve when the gauge reading
reaches 484 psig (3.34 MPa) {33.1 k
g
f/cm
2
G}. Then,
test for leaks with liquid soap.
Use a manifold valve for air
purging. If it is not available,
use a stop valve for this
purpose. The “Lo” knob of the
manifold valve must always
be kept closed.
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.
Manifold gauge
Vacuum pump
Lo
Hi
Manifold valve
Charge hose
Cylinder
valve
Open
Close
Close
Close
Close
Open
Open
Open
Nitrogen gas cylinder
(In vertical standing
position)
Pressure
gauge
Suction
tube
Discharge
tube
Outdoor unit
Liquid
tube
Balance
tube
Outlet
Inlet
ex.)Type 72
Service port cap
Valve cap
Service port cap
Flare nut
Flare nut
CAUTION
CAUTION
CAUTION
CAUTION
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