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Dehydration is readily accomplished at room temperatures. Use of a cold trap (Figure 29)
may substantially reduce the time required to complete the dehydration. The higher the room
temperature, the faster dehydration takes place. At low room temperatures, a very deep
vacuum is required for boiling off any moisture. If low ambient temperatures are involved,
contact a qualified service representative for the dehydration techniques required.
Perform dehydration as follows:
1. Connect a high capacity vacuum pump (5 cfm [.002 m
3
/s] or larger is recommended) to the
refrigerant charging valve (Figure 2A or Figure 2B). Tubing from the pump to the machine
should be as short and as large a diameter as possible to provide least resistance to gas
flow.
2. Use an absolute pressure manometer or a wet bulb vacuum indicator to measure the
vacuum. Open the shutoff valve to the vacuum indicator only when taking a reading. Leave
the valve open for 3 minutes to allow the indicator vacuum to equalize with the machine
vacuum.
Do not start or megohm test the compressor motor or oil pump motor, even for a
rotation check, if the machine is under dehydration vacuum. Insulation break-
down and severe damage may result.
WARNING
!
WARNING