LG RCWW Operation & Maintenance Manual page 81

Vacuum drying and vacuum test
• If the machine is exposed to the air for a considerable period, or it is found that moisture is in the machine, orrefrig-
erant pressure is lost due to leakage, vacuum drying work should be done to remove moisture in the machine com-
pletely.
!
WARNING
Do not start the compressor motor or oil pump motor, or conduct insulation resistance test during the vacuum
drying work.
Even though it is a momentary rotation for checking the rotation, the electrical insulation may be damaged and
cause serious damage.
• Generally, the vacuum drying work is carried out at room temperature.
The higher the room temperature, the faster the pace of vacuum drying work.
To remove the moisture by evaporating it at a low room temperature, a stronger vacuum is required.
Vacuum drying procedure is as follows:
1) Connect a high-capacity vacuum pump (approximately more than 120 LPM) to the valve for refrigerant charging.
To minimize the resistance of the gas flow, make the piping from the pump to the machine shorter in length and
wider in diameter as much as possible.
2) To measure the vacuum, use the pressure value on a microcomputer or pressure gauge when installed.
3) During vacuum work, open all of the shutoff valves except the ones connected to the ambient air.
4) When the vacuum pump is running in the ambient temperature of 15.6°C or above outside the machine, and the
pressure indicates 756mmHg, operate the vacuum pump for about 2 hours further.
If the cabin pressure is kept lower than 756 mmHg, the moisture concentrated in the machine will freeze to ice
and this ice will evaporate slower thus the vacuum drying work will be delayed. In such case, if hot water is avail-
able, make the hot water flow through the evaporator and condenser, and then operate the vacuum pump.
5) Close the valve of the vacuum pump and stop the pump, and then record the vacuum gauge value.
When reading the vacuum level, if the ambient temperature changes, convert the temperature change into pres-
sure following the equation below:
6) After waiting about 4 hours, read the value of the vacuum gauge. If the value has not been changed, the vacuum
drying work is completed.
If leakage rate is 0.1mmHg/h (=0.1 Torr/h) or less, the machine is regarded as fully tightened.
If the value of the vacuum gauge went up, repeat paragraphs 4) and 5) above.
7) Upon conducting the vacuum drying work several times, if its value continues to change, increase the pressure
in the machine to over 9~9.5kg/cm2.G before conducting the leakage test.
After repairing the leaking areas, perform the vacuum drying work again.
t
2
△P + (760 + H)x
t
273+
H: Pressure inside the machine before test(mmHg)
t1: Ambient temperature before test(°C)
t2: Ambient temperature after test(°C)
t
1
-
mmHg
t
2 273+ 1
6. Commissioning
81