11. Vacuum Drying and Leakage Checking
OUTDOOR UNIT
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Purpose of vacuum drying
• Eliminating moisture in the system to prevent the phenomena of ice-blockage and copper oxidation.
Ice-blockage can cause abnormal operation of system, while copper oxide can damage the compressor.
• Eliminating the non-condensable gas (air) in the system to prevent the components from oxidizing,
pressure fluctuation, or bad heat exchange during the operation of system.
Selection of vacuum pump
•The vacuuming capability of the vacuum pump should be 756 mmHg or above.
•Precision of vacuum pump should reach 0.02 mmHg or above.
Operation procedure for vacuum drying
There are two kinds of vacuum drying that can be used depending on the environment, when the unit is
installed. These are ordinary vacuum drying and special vacuum drying. These consist of the following:
Ordinary vacuum drying
1. When conducting the first vacuum drying, connect pressure gauge to the infusing mouth of the gas pipe
and liquid pipe, and keep vacuum pump running for an hour (the degree of vacuum the pump should
reach is, -755mmHg).
2. If the vacuum pump can not reach -755 mmHg after 1 hour of drying, it indicates that there is moisture
or leakage in the pipeline system and will need to continue drying for half an hour.
3. If the vacuum pump still can not reach -755 mmHg after 1.5 hours of drying, check for leaks.
4. Leakage test: After the vacuum reaches -755 mmHg, stop vacuum drying and keep the system
pressurized for 1 hour. If the indicator of the vacuum gauge increases, this is an indication that there is still
moisture or a leak present.
Special vacuum drying
The special vacuum drying method should be used when:
1. Moisture is found while flushing the refrigerant pipe.
2. Installation is being conducted on a rainy day, because rain water could penetrate into the pipeline.
3. Install period is taking an extended amount of time, rain water or moisture could penetrate into the
pipeline.
NOTE:
Be sure to use a micron gauge during vacuuming that can hold under 800 microns. Pull down
to 500 microns.
