National Electrical Installation Standards

Standards as High as Your Own

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Thursday, March 17, 2022

Question:

Thanks for this Code Question Page!

Is a main bonding jumper required to be installed in a transformer or in the first panel supplied by a transformer?

Thank you.

Paul Charles

A

Answer:

Paul,

You might want to check the term you are referring to in the question. A main bonding jumper is located at the service, by definition in Article 100. A system bonding jumper is often installed in a transformer (separately derived system) enclosure or at the first equipment supplied by the transformer secondary. The term system bonding jumper is also defined in Article 100. The NEC permits this connection to be made either at the source enclosure or at the first system overcurrent device enclosure as indicated in Section 250.30(A)(2).

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