SYSVRF2 IM

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5.7 Gastightness test
To prevent faults caused by refrigerant leakage, a gastightness test
should be performed before system commissioning.
Allow time for nitrogen to flow as far as the opening at indoor unit
A.
Flush the first opening:
Using suitable material, such as a bag or cloth, press firmly
against the opening at indoor unit A.
When the pressure becomes too high to block with your hand,
suddenly remove your hand allowing gas to rush out.
Repeatedly flush in this manner until no further dirt or moisture
is emitted from the piping. Use a clean cloth to check for dirt or
moisture being emitted. Seal the opening once it has been
flushed.
Flush the other openings in the same manner, working in
sequence from indoor unit A towards the outdoor units. Refer to
Figure 5-14.
Once flushing is complete, seal all openings to prevent dust and
moisture from entering.
Fig.5-15
Fig.5-13
Fig.5-14
Outdoor unit
Indoor unit
Nitrogen
Liquid pipe
Gas pipe
Liquid side
stop valve
Gas side of stop valve
CAUTION
6.
7.
8.
9.
The gastightness test procedure is as follows:
Once the piping system is complete and the indoor and outdoor
units have been connected, vacuum the piping to -0.1MPa.
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.
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 distinctly.
If there are no small leakages, charge the piping with nitrogen at
4MPa 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 gastightness test. If the observed pressure is
lower than the adjusted reference pressure, the piping has a micro
leakage.
If the leakage
is detected, refer to following part “Leak detection”.
Once the leak has been found and fixed, the gastightness test
should be repeated.
If not continuing straight to vacuum drying once the gastightness
test is complete, reduce the system pressure to 0.5-0.8MPa and
leave the system pressurized until ready to carry out the vacuum
drying procedure
1.
2.
3.
4.
5.
6.
a)
b)
c)
liquid pipe
gas pipe
Outdoor
unit
Nitrogen gas cylinder
Indoor
unit A
Indoor
unit B
Only dry nitrogen should be used for gastightness testing. Oxygen,
air, flammable gases and toxic gases must not be used for
gastightness testing. Use of such gases may result in fire or
explosion.
Make sure that all the outdoor unit stop valves are firmly closed
5.8 Vacuum drying
Vacuum drying should be performed in order to remove moisture and
non-condensable gases from the system. Removing moisture
prevents ice formation and oxidization of copper piping or other
internal components. The presence of ice particles in the system
would cause abnormal operation, whilst particles of oxidized copper
can cause compressor damage. The presence of non-condensable
gases in the system would lead to pressure fluctuations and poor
heat exchange performance.
Vacuum drying also provides additional leak detection (in addition to
the gastightness test).
The general methods for identifying the source of a leak are as
follows:
Audio detection: relatively large leaks are audible.
Touch detection: place your hand at joints to feel for escaping gas.
Soapy water detection: small leaks can be detected by the
formation of bubbles when soapy water is applied to a joint.
1.
2.
3.
Leak detection