Code Q&A: NEC Requirements for Installing RMC Couplings and Connectors

Jan. 11, 2024

Test your knowledge of the NEC.

Q. What are the requirements for installing RMC couplings and connectors?

See answer below.

A. The requirements for installing RMC couplings and connectors are found in Sec. 344.42.

(A) Installation. Threadless couplings and connectors must be made up tight to maintain an effective ground-fault current path to safely conduct fault current in accordance with Sec. 250.4(A)(5), Sec. 250.96(A), and Sec. 300.10.

Author's comment: Loose locknuts have been found to burn clear before a fault was cleared because loose connections increase the impedance of the ground-fault current path.

If buried in masonry or concrete, threadless fittings must be of the concrete-tight type. If installed in wet locations, fittings must be listed for use in wet locations and prevent moisture or water from entering or accumulating within the enclosure in accordance with Sec. 314.15.

(B) Running Threads. Running threads are not permitted for the connection of couplings, but they are permitted at other locations.

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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.