Vacuum Drying And Leakage Checking - Midea MUBU-12HRFN1-M Service Manual

b. Continuously infusing water until water
level alarmed, check whether the drainage
pump could discharge water at once. If
water level does not decline under warning
water level 3 minutes later, it shall cause
shutdown of unit. When this situation
happens, the normal startup only can be
recovered by turning down power supply
and eliminating accumulated water.
Note: Drain plug at the main water-containing
plate is used for eliminating accumulated water
in water-containing plate when maintaining air
conditioner fault. During normal operation, the
plug shall be filled in to prevent leakage.
12.5.4 Insulation work of drainage pipe
Refer the introduction to the insulation
engineering parts.
12.6 Vacuum Drying and Leakage
Checking
12.6.1 Purpose of vacuum drying

Eliminating moisture in system to prevent
the phenomena of ice-blockage and copper
oxidation.
Ice-blockage
operation of system, while copper oxide
shall damage compressor.

Eliminating the non-condensable gas (air)
in system to prevent the components
oxidizing, pressure fluctuation and bad heat
exchange during the operation of system.
12.6.2 Selection of vacuum pump

The ultimate vacuum degree of vacuum
pump shall be -756mmHg or above.

Precision of vacuum pump shall reach
0.02mmHg or above.
12.6.3 Operation procedure for vacuum
drying
shall cause abnormal
Due to different construction environment, two
kinds of vacuum drying ways could be chosen,
namely ordinary vacuum drying and special
vacuum drying.
1 Ordinary vacuum drying

When conduct
connect pressure gauge to the infusing
mouth of gas pipe and liquid pipe, and
keep vacuum pump running for 1hour
(vacuum degree of vacuum pump shall be
reached -755mmHg).

If the vacuum degree of vacuum pump
could not reach -755mmHg after 1 hour of
drying, it indicates that there is moisture or
leakage in pipeline system and need to go
on with drying for half an hour.

If the vacuum degree of vacuum pump still
could not reach -755mmHg after 1.5 hours
of drying, check whether there is leakage
source.

Leakage test: After the vacuum degree
reaches -755mmHg, stop vacuum drying
and keep the pressure for 1 hour. If the
indicator of vacuum gauge does not go up,
it is qualified. If going up, it indicates that
there is moisture or leak source.
2 Special vacuum drying
The special vacuum drying method shall be
adopted when:

Finding moisture during flushing refrigerant
pipe.

Conducting construction on rainy day,
because rain water might penetrated into
pipeline.

Construction period is long, and rain water
might penetrated into pipeline.

Rain water might penetrate into pipeline
during construction.
48
first vacuum drying,