Compressor Replacement; Start-Up Of A New Or Replacement Compressor; Lubrication And Oil Removal - Emerson Copeland Scroll ZR24KRE Application Manuallines

6.4.1 Compressor replacement

In the case of a motor burnout, the majority of contaminated oil will be removed with the compressor.
The rest of the oil is cleaned through the use of suction and liquid line filter driers. A 100% activated
alumina suction line filter drier is recommended but must be removed after 72 hours. When a single
compressor or tandem is exchanged in the field, it is possible that a major portion of the oil may still
be in the system. While this may not affect the reliability of the replacement compressor, the extra oil
will add to rotor drag and increase power usage.

6.4.2 Start-up of a new or replacement compressor

Rapid charging only on the suction side of a scroll-equipped system can occasionally result in a
temporary no-start condition for the compressor. The reason for this is that, if the flanks of the scrolls
happen to be in a sealed position, rapid pressurisation of the low side without opposing high-side
pressure can cause the scrolls to seal axially. As a result, until the pressures eventually equalise,
the scrolls can be held tightly together preventing rotation. The best way to avoid this situation is to
charge on both the high and low sides simultaneously at a rate which does not result in axial loading
of the scrolls.
A minimum suction pressure specified in the published operating envelope must be maintained
during charging. Allowing the suction pressure to drop below that value may overheat the scrolls and
cause early drive bearing and moving parts damage. Never install a system in the field and leave it
unattended when it has no charge, a holding charge, or with the service valves closed without
securely electrically locking out the system. This will prevent unauthorised personnel from
accidentally operating the system and potentially ruining the compressor by operating with no
refrigerant. Do not start the compressor while the system is in a deep vacuum. Internal arcing
may occur when a scroll compressor is started in a vacuum causing burnout of the internal lead
connections.

Lubrication and oil removal

6.5
CAUTION
Chemical reaction! Compressor destruction! Do not mix up ester oils with
mineral oil and/or alkyl benzene when used with chlorine-free (HFC)
refrigerants.
The compressor is supplied with an initial oil charge. The standard oil charge for use with refrigerants
R450A and R513A is a polyolester (POE) lubricant Emkarate RL 32 3MAF. In the field the oil level
could be topped up with Mobil EAL Arctic 22 CC if 3MAF is not available. See nameplate for original
oil charge shown in litres. A field recharge is from 0.05 to 0.1 litre less.
One disadvantage of POE is that it is far more hygroscopic than mineral oil (see Figure 23). 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 Emerson 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 23: 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 the moisture content of the oil in a refrigeration system reaches unacceptably high levels, corrosion
and copper plating may occur. The system should be evacuated down to 0.3 mbar or lower. If there
is uncertainty as to the moisture content in the system, an oil sample should be taken and tested for
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