Compressor Replacement; Compressor Functional Check - Emerson Liebert Challenger iCOM 3000 Operation & Maintenance Manual

3.5

Compressor Replacement

Replacement compressors are available through your local Emerson office. Compressors are shipped
in reusable packaging. If unit is under warranty, complete and include Liebert Service Credit
Application (LSCA) with the compressor that is being returned. The original compressor should be
returned in the same packaging.
Before Replacing or Returning a Compressor
Be certain that the compressor is actually defective. At a minimum, recheck a compressor returned
from the field in the shop or depot for Hipot, winding resistance and ability to start before returning
it. More than one-third of compressors returned for warranty analysis are determined to have nothing
wrong. They were misdiagnosed in the field as being defective. Replacing working compressors
unnecessarily costs everyone.
3.5.1

Compressor Functional Check

The following diagnostic procedure should be used to evaluate whether the 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. Condenser glycol flow 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, either the system charge is low on 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. If pressures still do not move to normal values, system is properly
charged and solenoid valves function, the compressor is faulty. Reconnect the compressor leads as
originally configured and use normal diagnostic procedures to check operation of the reversing
valve.
6. To test if the compressor is pumping properly, the compressor current draw must be compared to
published compressor performance curves using the operating pressures and voltage of the
system. If the measured average current deviates more than ±15% from published values, a faulty
compressor may be indicated. A current imbalance exceeding 15% of the average on the three
phases should be investigated further.
Component Operation and Maintenance
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Liebert ® Challenger 3000