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Code Q&A: Protection Rules for NM Cable and EMT

Sept. 8, 2022

Test your knowledge of the NEC.

Based on the 2020 NEC.

Q. What are the Code rules relating to the protection of nonmetallic-sheathed cable and electrical nonmetallic tubing through metal framing members?

See answer below.

A. If Type NM cables pass through factory or field-made openings in metal framing members, the cable must be protected by listed bushings or listed grommets that cover all metal edges. The protection fitting must be securely fastened in the opening before the installation of the cable [Sec. 300.4(B)(1)].

If nails or screws are likely to penetrate Type NM cable or electrical nonmetallic tubing, a steel sleeve, steel plate, or steel clip not less than 1⁄16 in. in thickness must be installed to protect the cable or tubing [Sec. 300.4(B)(2)].

Exception: A listed and marked steel plate less than 1⁄16 in. thick that provides equal or better protection against nail or screw penetration is permitted.

These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code.

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.