Low-Voltage Transformers

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Transformers with VA ratings of 40 VA and above usually have an internal fuse built into the secondary windings. This makes it imperative for the service technician not to short across the secondary with a screwdriver (to see if it “sparks”). If the secondary is shorted for any reason, the fuse will open and the transformer will have to be replaced. Regardless of the type of fuse, remember that if you find an open fuse, something must have caused the excessive current. Look for the trouble elsewhere in the circuit.

EXCERPT FROM ELECTRICITY FOR HVACR TECHNICIANS available from the online store at RSES (Refrigeration Service Engineers Society) The HVACR Training Authority

2 thoughts on “Low-Voltage Transformers”

  1. Whenever I come across a shorted out transformer, I always look for a short to ground before installing a new transformer and connecting it to power. When installing the new transformer I install an inline 3 amp fuse on the secondary side of the transformer to protect the new transformer in the event that I missed locating the short that caused the original transforer to fail.

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