There are several ways a compressor motor can fail. One of these ways is a compressor burnout. This happens when the compressor motor catastrophically fails. If a compressor does burn out, the oil becomes extremely acidic. If all this acid is not removed when the compressor is replaced, the high acid levels will attack the new compressor and cause another compressor motor burn-out in a short period of time.hvac classes

  1. You must first determine how bad of a burnout there has been. Mild burnouts, where the acidic contamination is mild and not widespread, it may be economical to save the refrigerant charge (although not recommended). If there has been a severe burnout, the oil will be discolored, there is an acidic smell, and components are contaminated throughout the system. Avoid breathing acidic vapors and prevent skin contact with contaminated compressor oil.
  2. Thoroughly clean or replace all system components such as the TXV, check valve, reversing valve, strainers, and filter driers.
  3. Install the new compressor and make a complete electrical check.
  4. Make sure the suction line is clean near the compressor. Install an over-sized liquid line filter-drier and a suction line filter-drier.
  5. Pressure test and leak test the system according to standard HVAC practices or the manufacturer’s recommendations.
  6. Triple evacuate the system to 200 microns (minimum). Break each vacuum with clean, dry refrigerant at 0 psig.
  7. Recharge the system through a filter-drier.
  8. Start the system and put it into operation. Measure and record the pressure (temperature) drop across the suction line filter-drier. Record this measurement for future reference.
  9. Replace the filter-drier if the pressure (temperature) drop exceeds 3F.
  10. Observe the system operation for the first 4 hours. Repeat step 9 until there is no pressure (temperature) drop across the filter-drier.
  11. After 48 hours of operation, use an acid test kit to check the acidity of the oil. If the oil tests positive for acid, replace both the liquid and suction line filter-driers.
  12. Check the system again after two weeks operation. If the oil is discolored or acidic, replace both the liquid and suction line filter-driers.
  13. Clean up is complete when the oil is clean and odor free and the acid test results are negative.

Things such as moisture, non-condensables, and overheating are preventable causes of motor burn out. Proper evacuation and charging and proper system maintenance (replacing filter, cleaning condensers, and properly adjusted controls) will prevent many burnouts from occurring.

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by Ron Walker

Ron Walker
Ron Walker

After retiring from the U.S. Marines and achieving his B.S. degree, Ron Walker entered the HVAC field. He has been an HVAC technician, service manager, and business owner. Working as a service manager, he spent many years training HVAC technicians to be more technically competent and really understand their trade. His passion for teaching and helping others resulted in the creation of HVAC Training Solutions, LLC.