Code Q&A: NEC Requirements for Installing Conductors in Parallel Inside Wireways

Aug. 24, 2023

Test your knowledge of the NEC.

Q. What are the NEC requirements for installing conductors in parallel inside wireways?

See answer below.

A. The requirements for installing conductors in parallel inside wireways are found in Sec. 376.20. Where conductors are installed in parallel as permitted in Sec. 310.10(G), the parallel conductors must be installed in groups consisting of not more than one conductor per phase or neutral conductor to prevent current imbalance in the paralleled conductors due to inductive reactance (Figure).

metal wireways conductors connected in parallel

Note: The purpose of having all parallel conductor sets within the same group is to prevent current imbalance in the paralleled conductors due to inductive reactance.

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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.