National Electrical Installation Standards

Standards as High as Your Own

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Monday, May 7, 2018

Question:

I have a lug that has a 1/2 hole on a load side of a breaker...can I use a 3/8 bolt?

Jerry Marquez

A

Answer:

Hey Jerry thanks for your question. The general rules for electrical connections are in 110.14 but there is not specific wording regarding terminal hole size and fastener size. Manufacturers make terminal connectors with different size holes and it is logical that the fastener match the nominal hole size. Torque values can also be related to fastener sizes and are now covered in 110.14 (D). Electrical connections are commonly listed products so the instructions included must also be followed as stated in 110.3(B). Unless the manufacturer(s) provide specific instructions for using smaller fastener sizes it seems that using a fastener that is the same size as the terminal hole is necessary.

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