Explore all the possible causes of compressor terminal burnout

Q I have a problem with a York a/c condenser model H2DA036506A. Compressor terminals (R-S-C) often burn out and the compressor always sweats because of condensation.

I reduced the refrigerant charge, but the customer complained about not enough cooling. I checked on the field suction, which was 65 psig. The discharge was 210 psig and the temperature outside was 80 F. The unit and the furnace filter are clean. Please advise me what to do.

A A compressor, much the same as any component in a refrigeration system, will begin to sweat when the temperature of its surface reaches dew point. Why your system is reaching dew point is the real
question. Improper airflow, refrigerant charge or an
incorrect metering device are the most common causes. Unfortunately, the information you've provided is not
complete enough to properly diagnose the root cause.

If I were on the jobsite, I would begin my troubleshooting by first checking system airflow. This can be done in a variety of ways, but the fastest and most common method would be to measure temperature rise, then use the sensible-heat formula to determine actual cfm. Your 3-ton unit should be delivering about 1,200 cfm. Low airflow is common and could be a major contributor to your problem.

Then I'd determine if I have an orifice or thermal expansion valve (TXV) as the metering device. If it's an orifice, I would check for proper superheat. To determine what the superheat should be, you'd need to know the outdoor dry-bulb temperature, along with wet- and dry-bulb temperatures of the air going across the evaporator, which typically are measured at the return-air opening.

You then would use a superheat calculator, which can be obtained from most air-conditioning wholesalers. If you have a TXV, I would check for proper subcooling.

If an orifice is being used as the metering device,
check the model number of the evaporator. Hopefully,
the match-up of the evaporator and condensing unit is correct, allowing you to use the data supplied with the unit to verify the correct orifice size. Many match-ups require the installer to switch the orifice shipped with
the evaporator to one shipped with the condensing unit.

You also can contact your local York distributor or branch. They can supply you with a troubleshooting information sheet. Once completed and returned, the local service manager can help resolve the problem.

Question from Djaja Husen , Ontario , Canada . Answer
by Jack Bartell, senior trainer, York International.