83003702.K Operating Instruction
Type KPC 108-L-U/S
page 41
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Single-Stage Hermetic Compliant SCROLL Motor-Compressor
Type ZR xx K3E-TWD-561
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 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 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.
If pressures still do not move to normal values, either the reversing valve (if so equipped) or 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 average measured
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 may indicate a voltage imbalance and should be
investigated further.
7. Before replacing or returning a compressor: Be certain that the compressor is actually defective. More than one-
third of compressors returned to Copeland were misdiagnosed in the field as being defective.
Unbrazing System Components and Service Brazing Procedure
Caution! Before opening a system it is important to remove all refrigerant from both the high and low side. If the
refrigerant charge is removed from a scroll-equipped unit by bleeding the high side only, it is possible for the scrolls to seal,
preventing pressure equalization through the compressor. This may leave the low side shell and suction line tubing
pressurized. If a brazing torch is then applied to the low side while the low side shell and suction line contains
pressure, the pressurized refrigerant and oil mixture could ignite when it escapes and contacts the brazing flame. It is
important to check both the high and low side with manifold gauges before unbrazing. If compressor removal is
required, the compressor should be cut out of system rather than unbrazed.
Copeland Scroll compressors have copper plated steel suction and discharge tubes. Due to the different thermal
properties of steel and copper, brazing procedures may have to be changed from those commonly used. It is
important to flow nitrogen through the system while brazing all joints during the system assembly process. Nitrogen
displaces the air and prevents the formation of copper oxides in the system. The copper oxide flakes can be swept through the
system and block screens such as those protecting capillary tubes, thermal expansion valves, and accumulator oil
return holes. The blockage is capable of doing damage resulting in compressor failure.
The copper-coated steel tubes on scroll compressors can be brazed in approximately the same manner as any copper tube.
Recommended brazing materials: Any silfos material is recommended, preferably with a minimum of 5% silver. However, 0%
silver is acceptable.
