126 RT-SVX34C-EN
Maintenance
If a motor burn out has occurred, change the oil in both compressors in a tandem set. This will
require that the oil equalizer tube be removed to suck the oil out of the oil sump. A catch pan must
be used to catch the oil when the compressor oil equalizer line is loosened.
Note: Refrigerant oil is detrimental to some roofing materials. Care must be taken to protect the
roof from oil leaks or spills.
Charge the new oil into the Schrader valve on the shell of the compressor. Do to the moisture
absorption properties of POE oil, do not use POE oil from a previously opened container. Also
discard any excess oil from the container that is not used.
Compressor Replacements
Electrical Phasing
If it becomes necessary to replace a compressor, it is very important to review and follow the
Electrical Phasing procedure described in the startup procedure of this manual.
If the compressors are allowed to run backward for even a very short period of time, internal
compressor damage may occur and compressor life may be reduced. If allowed to run backwards
for an extended period of time the motor windings can overheat and cause the motor winding
thermostats to open. This will cause a "compressor trip" diagnostic and stop the compressor
If a scroll compressor is rotating backwards, it will not pump and a loud rattling sound can be
observed. Check the electrical phasing at the compressor terminal box. If the phasing is correct,
before condemning the compressor, interchange any two leads to check the internal motor
phasing.
Precision Suction Restrictor
Tandem manifold compressors that have unequal capacity sizes utilize a precision suction
restrictor Figure 59, p. 126 to balance the oil levels in the compressors. This restrictor is placed in
the smaller capacity compressor. When replacing this compressor, it is imperative that the proper
restrictor is selected from those provided with the replacement compressor. See Table 70, p. 127
and Figure 60, p. 127
When the compressors are restarted, verify that correct oil levels are obtained with both
compressors operating.
Compressor model Oil amount
CSHD142-161 7.0 pts
CSHD183 7.6 pts
CSHN250 14.2 pts
Figure 59. Precision Suction Restrictor
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