In this troubleshooting situation your customer is requesting a second opinion on a proposed repair to their air-to-air heat pump. They originally called for service when they noticed that the house wasn’t cooling down as they would like, and the technician who responded reported that, in his opinion, since the high and low side refrigeration system pressure differential wasn’t what he expected, the compressor was no longer able to pump properly. Due to the price of the proposed repair, they decided to call for a second opinion.

When you arrive in the mid-afternoon, you confirm that the coil temperature splits are inadequate and the system is unable to obtain the necessary comfort level. When you check the refrigeration system pressures, you also note some irregularity, which prompts you to follow up with a temperature test at the compressor discharge, and an entering and leaving temperature test at two of the reversing valve tubing connections (see Figure One). Your results are as follows:

  • Temperature on compressor discharge line: 200°F
  • Temperature on the line from the indoor coil to the reversing valve assembly: 50°F
  • Temperature on the compressor suction line exiting the reversing valve: 60°F

Your troubleshooting question: Have you confirmed the previous technician’s diagnosis, or have you determined that there is another component that could be responsible for the poor performance of this system?

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