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mixed with oil Alternative process should not be considered if there is chance of free water entering
the system or the system was open for any significant time.
Charging
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Testing and Final Diagnosis
Check the oil level in the compressor after the system has been running for 24 hours. Oil may have
been contaminated in the liquid refrigerant when recovered from the system. Most of this oil will be
returned if the recovered refrigerant is used. If new refrigerant is added, additional oil should be
added based on the following ratio:
New Refrigerant Charge Added, lbs. x 0.352 = Oil charge, oz.
It is of critical importance to ensure that the system is operating as expected before the unit is
returned to normal service. Test component replaced and function of the system. Many times a
separate component in the system may have set a condition that causes a failure of another.
Thoroughly test systems to ensure repeat failures do not occur. Note: Compressors supplied with an
oil sight glass should be viewed and filled to 75% capacity.
44
Desert Aire - LW Manual
Charge should be weighed into the system using a scale. In cases where the full charge was
recovered, weigh in the charge with the recovered refrigerant and add the
appropriate amount to meet the rating plate and field charge (if applicable). This should be
placed in the high side of the system.
In cases where the full charge cannot be added to the system high side, the charge can be
added to the low side of the system only when compressors are energized. If this is required,
the compressors should be energized and the charge should be slowly metered into the
suction line as far as possible upstream of the compressor. If the unit is equipped with an
accumulator, the charge needs to be added to the port upstream of this location.
The bulkhead fittings on the side of the unit should not be used for charge addition. Monitor
superheat at the compressor suction inlet using the bulkhead fitting and a temperature sensor
on the suction line near the compressor. Superheat should not drop below 10 degrees during
the process of adding charge.
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