National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, January 30, 2019

Question:

Hi Charlie, is there any rule about stranded vs solid thhn and lug nuts? I constantly find lugs with stranded wire jammed in and was once told they are only for solid and to use a crimp on terminal to connect

Christopher Walters

A

Answer:

Hey Christopher thanks for your question. "Lug nuts" is a term commonly used to describe the fasteners used to secure wheels to vehicles so I am not completely sure which specific type of electric termination you are refereeing to.

Pressure connectors (lugs) and terminals must generally be Identified (as that term is defined in Article 100) for the specific type of conductor they are intended to be used with, as stated in 110.14. Detailed information should be included with the manufacturer's instructions. Wire binding screws, or studs and nuts, with upturned lugs or the equivalent are allowed for 10 AWG and smaller conductors as stated in 110.14(A).

More information about markings for solid and stranded conductors and other details is available at:

http://productspec.ul.com/document.php?id=ZMVV.GuideInfo

If this isn't the information you are looking for please send in a follow up question.

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ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

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