Posted by: Denny Bell on July 04, 2001 at 17:41:27

I installed the AC unit for my second floor in the attic of my home. Every spring for the past 3 years the transformer would burn out early in the season, sometimes in the first week, sometimes in the first month. The attic is ventilated, but still gets quite warm. Could this be the cause of the transformer failure?

Answer:
Thanks, there was no temperature rise figure on the transformer, so I wasn't sure how high was too high. There are no other transformers on that 240v circuit. The only other transformers I know of are for the doorbell and the other AC unit. Could the attic heat affect the fan motor in such a way as to cause a surge or lag strong enough to cause the problem? Other than the compressor and a few control boards there isn't anything else on the circuit.

You will not need to be concerned with the temperature rise on the transformer as it will work well at over 220F. It is the amperage draw and voltage coming out of the transformer that you need to measure. The length of the wire run and the size of the wires attached can cause problems. The coil in the unit that closes to make the compressor and fan run can have shorting problems that draw too much current for the transformer to handle. The voltage should be near that stated on the transformer and the current should not exceed that rated on the transformer.