Tech Talk: High Output Voltage for Transformers

Q. My 75 VA 120:24 volt control transformer has a high output voltage. It reads as high as 28.3 volts with a 123 volt input. The load is only 8 VA on the transformer. Why is the output voltage so high?

A. A control transformer will have a higher output at a no-load or low load condition. A typical transformer with a 24 or 25 volt secondary rating will output 28 to 29 volts with no load. As the load increases, the output will lower to rated voltage at a full load. You need to either add load to the existing transformer or use a smaller VA transformer.

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