37
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 (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 all 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.
The balance tube leak test is not necessary if only 1 outdoor unit is installed.
Leak test
(1) With the service valves on the outdoor unit closed, remove the 5/16"
(7.94mm) 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.
The balance tube leak test is not necessary if only 1 outdoor unit is
installed.
CAUTION
CAUTION
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.
(3) Pressurize the system to no more than 484 psig (3.34MPa {33.1 k
g
f/cm
2
G})
with dry nitrogen gas and close the cylinder valve when the gauge reading
reaches 484 psig (3.34MPa {33.1 k
g
f/cm
2
G}).
Then, test for leaks with liquid soap.
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.
Manifold gauge
Vacuum pump
Outlet
Inlet
Charge hose
Open
Open
Open
Close
Close
Outdoor unit
Close
Pressure
gauge
Cylinder
valve
Gas
tube
Liquid
tube
Balance
tube
Nitrogen gas cylinder
(In vertical standing
position)
Manifold valve
00_302411_EN.indd 37
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