National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, October 13, 2021

Question:

Hello and thanks for the NEC work here. My question relates to the mounting of grounding lugs inside dry-type transformer enclosures. Can the grounding bar be installed on the bottom mesh of a transformer enclosure if the paint is wire brushed to bare metal?

Thanks for you opinions on this.

Ellen Hearn

A

Answer:

Greetings Ellen,

Thanks for the comments and the question. Section 450.10 indicates that where separate equipment grounding conductors and supply-side bonding jumpers are installed, a terminal bar for all grounding and bonding conductor connections shall be secured inside the transformer enclosure. The terminal bar shall be bonded to the enclosure in accordance with 250.12 and shall not be installed on or over any vented portion of the enclosure. There is an exception that says where a dry-type transformer is equipped with wire-type connections (leads), the grounding and bonding connections shall be permitted to be connected together using any of the methods in 250.8 and shall be bonded to the enclosure if of metal.

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