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How to Troubleshoot a Copeland Sentronic

Many Copeland Sentronic compressor problems can be solved by knowing how the oil is maintained and used within the unit. The compressor must have sufficient oil lubrication, for example. Its oil pressure must also be stable and fall within a certain range above the crankcase pressure. A clear suction filter matters as does the lack of visible oil foam. By researching these and a few other areas first, your troubleshooting may quickly reveal the source of the problem.

Step 1

Check for leaks, faulty system design and bad pipework. Inadequate lubrication could cause the main moving parts to fail.

Step 2

Verify that the net oil pressure is stable and between 1.05 and 4.25 more than the crankcase pressure. Connect a pressure gauge to the oil pump and connect another pressure gauge to the crankcase to read the net oil pressure. A blocked suction filter will cause abnormal operating conditions.

Step 3

Check to see if oil foam is visible in the compressor oil sight glass. If it is, oil pressure will not build up sufficiently. Fit a pump down system or crankcase heater to reduce bearing failure. Fitting this part will also help reduce refrigerant migration when the compressor is off for a longer period of time.

Step 4

Verify that the suction superheat is 10K higher. If the superheat is too low, cylinder wall and rod, valve plate and piston damage could occur. Replace the expansion valve and correctly mount the sensor bulb. Increase the refrigeration lines if they are too short by installing an accumulator or heat exchanger.

Step 5

Check for acid formation. When oil comes in contact with acid, moving parts will be damaged; motor burn-out will occur in extreme cases. Change the oil and install a suction filter designed to remove acid.

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