What's Wrong Here? Hint: Mismatched Conductors

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James Hooten, a service manager with Hargis Electric, LLC in Paris, Texas, thought everyone would like to see a photo of this 20kW heating unit one of his service techs fixed not so long ago. "It has a No. 3 THHN conductor feeding one of the breakers with a No. 10 solid conductor jumper to the other breaker," says Hooten. "It was connected to a 100A ITE breaker in the panel."

I would call attention to the requirements noted in 240.4 for protection of conductors, which states: "Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G). We can also point to a rule in Art. 424 [Fixed Electric Space-Heating Equipment]. Section 424.9 notes, "All fixed electric space-heating equipment shall be installed in an approved manner."

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