Airwell VVFA Series Service Manual page 28

• The outdoor gas pipe and the refrigerant distributing pipe, as well the refrigerant distributing pipe and the branch
pipe should be welded with hard solder.
• Weld the pipe at the same time charge the nitrogen. Or it will cause
a number of impurity (a film of oxidation) to clog the capillary and the
expansion valve, further cause the deadly failure.
• Protect the pipe end against the water, impurity into the pipes
(welding after being flat, or being sealed with adhesive tape).
Flat
Brazing
• The refrigerant pipe should be clean. The nitrogen should flow
under the pressure of about 0.2Mpa and when charging the
nitrogen, stop up the end of the pipe by hand to enhance the
pressure in the pipe, then loose the hand (meanwhile stop up the
other end).
• When connecting the pipes, close the valves fully.
• When welding the valve and the pipes, use the wet cloth to cool down the
valve and the pipes.
(6) Leakage test
1. The outdoor unit has been executed the leakage test in the factory. After connecting the distributing pipe, execute
the leakage test from the outdoor check valve and the indoor. Besides, while testing, the valves should be close.
2. Refer to the below figure to charge the nitrogen into the unit to take a test. Never use the chlorin, oxygen,
flammable gas in the leakage test. Apply pressure both on the gas pipe and the liquid pipe.
3. Apply the pressure step by step to the target pressure.
a. Apply the pressure to 0.5MPa for more than 5 minutes, confirm if pressure goes down.
b. Apply the pressure to 1.5MPa for more than 5 minutes, confirm if pressure goes down.
c. Apply the pressure to the target pressure (4.0MPa), record the temp. and the pressure.
d. Leave it at 4.0MPa for over 1 day, if pressure does not go down, the test is passed. Meanwhile, when the
temp. changes for 1degree, pressure will change 0.01MPa as well. Correct the pressure.
e. After confirmation of a~d, if pressure goes
down, there is leakage. Check the brazing
position, flared position by laying on the soap.
modify the leakage point and take another
leakage test.
4. After leakage test, must execute the evacuation.
(7) Evacuation
Evacute at the check valve of liquid stop valve and
both sides of the gas stop valve.
Operation procedure:
Adhesive tape
Nitrogen
After reaching -101KPa or
less (below -755mmHg), let
the vacuum pump running
continuously for over 1hour.
If vacuum pointer arises, it shows there is water or leakage in the
system, please check and modify it, and then evacuate again.
26
Seal the pipe end with
adhesive tape or the stopper
to increase the resistance, fill
up the pipe with nitrogen.
<N2>
Taping
Only nitrogen gas
can be used
1st side 2nd side
Source valve
0.2MPa
Check valve
To indoor
Gauge manifold
Lo Hi
Lo handle Hi handle
Leave it for over 1
hour, vacuum pointer
does not arise.
Brazing
Hand
Gas pipe
Gas pipe
Check hole
Outdoor