Compressor Functional Check - Emerson Copeland Scroll ZRH49KJE Application Manuallines

One disadvantage of POE is that it is far more hygroscopic than mineral oil (see Fig. 10). Only
brief exposure to ambient air is needed for POE to absorb sufficient moisture to make it
unacceptable for use in a refrigeration system. Since POE holds moisture more readily than
mineral oil it is more difficult to remove it through the use of vacuum. Compressors supplied by
Copeland contain oil with low moisture content, and it may rise during the system assembling
process. Therefore it is recommended that a properly sized filter-drier is installed in all POE
systems. This will maintain the moisture level in the oil to less than 50 ppm. If oil is charged into
a system, it is recommended to use POE with a moisture content no higher than 50 ppm.
Figure 10: Absorption of moisture in ester oil in comparison to mineral oil in ppm by weight at 25°C and 50%
relative humidity (h=hours)
If there is uncertainty as to the moisture content in the system, an oil sample should be taken
and tested for moisture. Sight glass/moisture indicators currently available can be used with the
HFC refrigerants and lubricants. The moisture indicator will just show the moisture contents of
the refrigerant. The actual moisture level of POE would be higher than the sight glass specifies.
This is a result of the high hygroscopicity of the POE oil. Oil samples would have to be taken
from the system and analysed to determine the actual moisture content of the lubricant. If the
moisture content of the oil in a refrigeration system reaches unacceptably high levels, corrosion
and copper plating may occur.
Copeland Horizontal Scroll
Rotalock valves should be periodically re-torqued to ensure that leak tightness is maintained.
6.4

Compressor functional check

A functional compressor test with the suction service valve closed to check how low the
compressor will pull suction pressure is not a good indication of how well a compressor is
performing. Such a test will almost certainly damage a scroll compressor.
The following diagnostic procedure should be used to evaluate whether a Copeland Scroll
compressor is working properly:
1. Proper voltage to the unit should be verified.
2. The normal checks of motor winding continuity and short to ground should be made to
determine if the inherent overload motor protector has opened or if an internal motor
short or ground fault has developed. If the protector has opened, the compressor must
be allowed to cool sufficiently to allow it to reset.
3. Proper indoor and outdoor blower/fan operation should be verified.
4. With service gauges connected to suction and discharge pressure fittings, turn on the
compressor. If suction pressure falls below normal levels, the system is either low on
charge or there is a flow blockage in the system.
5. If suction pressure does not drop and discharge pressure does not rise to normal levels,
reverse any two of the compressor power leads and reapply power to make sure
compressor was not wired to run in reverse direction.
6. To test if the compressor is pumping properly, the compressor current draw must be
compared to published compressor performance using the operating pressures and
voltage of the system. If the measured average current deviates more than ±15% from
published values, it may be an indication of a faulty compressor. A current imbalance
exceeding 15% of the average on the three phases should be investigated further.
C6.2.7/0302-1007/E
TM
compressors are fitted with an internal oil pump.
TM
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