Steve Miles is the general manager of Jerry Kelly Heating and Air Conditioning in St. Louis. He has seen his share of misdiagnosed unitary air conditioners and heat pumps — the company offers free second opinions for potential customers who have already had their systems checked by other contractors.
Many system misdiagnoses, he agrees, unduly condemn the compressor. If it’s under warranty, the replaced compressor may undergo a teardown to find the cause of the failure. When no failure is found — the compressor would work if put into another system — manufacturers such as Copeland Corp. (an Emerson Climate Technologies company) give it a tag reading “No Defect Found” (NDF).