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8.Flush the other openings in the same manner, working
in sequence from indoor unit A towards the outdoor
units. Refer to Figure 5.27.
9.Once flushing is complete, seal all openings to prevent
dust and moisture from entering.
liquid pipe
gas pipe
Outdoor
unit
Indoor
Indoor
unit A
unit B
5.6 Gas Tightness Test
To prevent faults caused by refrigerant leakage, a gas
tightness test should be performed before system
commissioning.
CAUTION
Only dry nitrogen should be used for gas
tightness testing. Oxygen, air, flammable
gases and toxic gases must not be used for
gas tightness testing. Use of such gases may
result in fire or explosion.
Make sure that all the outdoor unit stop
valves are firmly closed.
The gas tightness test procedure is as follows:
1.Charge the indoor piping with nitrogen at 0.3Mpa
through the needle valves on the liquid and gas stop
valves and leave for at least 3 minutes (do not open the
liquid or gas stop valves). Observe the pressure gauge
to check for large leakages. If there is a large leakage,
the pressure gauge will drop quickly.
2.If there are no large leakages, charge the piping with
nitrogen at 1.5Mpa and leave for at least 3 minutes.
Observe the pressure gauge to check for small
leakages. If there is a small leakage, the pressure gauge
will drop noticeably.
3.If there are no small leakages, charge the piping with
nitrogen at 4.2 MPa and leave for at least 24 hours to
check for micro leakages. Micro leakages are difficult to
detect. To check for micro leakages, allow for any
change in ambient temperature over the test period by
adjusting the reference pressure by 0.01Mpa per 1°C of
temperature difference. Adjusted reference pressure =
Pressure at pressurization + (temperature at observation
– temperature at pressurization) x 0.01Mpa. Compare
the observed pressure with the adjusted reference
pressure. If they are the same, the piping has passed the
gas tightness test. If the observed pressure is lower than
the adjusted reference pressure, the piping has a micro
leak.
4.If leakage is detected, refer to the section of the
manual titled "Leak detection". Once the leak has been
found and fixed, the gas tightness test should be
repeated.
Figure 5.27
5.If not continuing straight to vacuum drying once the
gas tightness test is complete, reduce the system
pressure
pressurized until ready to carry out the vacuum drying
procedure.
Figure 5.28
Gas side of
stop valve
Liquid side of
stop valve
Nitrogen
Leak detection
The general methods for identifying the source of a leak
are as follows:
1. Audio detection: relatively large leaks are audible.
2. Touch detection: place your hand at joints to feel for
escaping gas.
3. Soapy water detection: small leaks can be detected by
the formation of bubbles when soapy water is applied to
a joint.
35
to
0.5-0.8MPa
and
leave
Outdoor unit
Gas pipe
Liquid pipe
the
system
Indoor unit
Figure 5.29
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