Power conductors rated 1,000V or less can occupy the same raceway, cable, or enclosure if all conductors have an insulation voltage rating not less than the maximum circuit voltage.

Stumped by the Code? NEC Requirements for the Mixing of Conductors

Sept. 14, 2022

Answering your NEC questions.

All questions and answers are based on the 2020 NEC.

Q. What are the NEC rules related to the mixing of conductors of different systems in the same raceway, cable, or enclosure?

A. These requirements are outlined in Sec. 300.3(C).

(1) Mixing. Power conductors rated 1,000V or less can occupy the same raceway, cable, or enclosure if all conductors have an insulation voltage rating not less than the maximum circuit voltage (see Figure).

Author’s comment: Control, signaling, and communications wiring must be separated from power and lighting circuits so the higher-voltage conductors do not accidentally energize the control, signaling, or communications wiring. Reference the following Sections of the Code:

Class 1 control circuits [Sec. 725.48)]
Class 2 control circuits [Sec. 725.136(A)]
Communications circuits [Sec. 808.133(A)(1)(c)]
Coaxial cable [Sec. 820.133(A)]
Fire alarm circuits Sec. 760.136(A)]
Sound circuits [Sec. 640.9(C)]

Q. What are the Code rules relating to the protection of conductors as they exit raceways?

A. Raceways containing insulated circuit conductors 4 AWG and larger that enter a cabinet, box, enclosure, or raceway, must have the conductors protected as follows [Sec. 300.4(G)]:

(1) A fitting providing a smoothly rounded insulating surface.

(2) A listed metal fitting that has smoothly rounded edges.

(3) Separation from the fitting or raceway using an identified insulating material securely fastened in place.

(4) Threaded hubs or bosses that are an integral part of a cabinet, box, enclosure, or raceway that provide a smoothly rounded or flared entry for conductors.

Author’s comment: If an intermediate metal conduit (IMC) or rigid metal conduit (RMC) enters an enclosure without a connector, a bushing must be provided regardless of the conductor size [Sec. 342.46 and Sec. 344.46].

Q. What are the Code requirements for GFCI protection in mobile homes and manufactured homes?

A. Ground-fault circuit-interrupter (GFCI) protection must be provided as required in Sec. 210.8(A). GFCI protection is not required for other than 125V, 15A and 20A receptacles installed within a mobile or manufactured home in the following areas [Sec. 550.13(B)]:

(1) Compartments accessible from the outdoors.

(2) Bathroom areas.

(3) Kitchens, where receptacles are installed to serve countertop surfaces.

(4) Sinks, where within 6 ft from the top inside edge of the sink.

(5) Dishwasher outlets.

Q. What is the definition of shore power for marinas?

A. As shown in Sec. 555.2, shore power is defined as the electrical equipment required to power a floating vessel including, but not limited to, the receptacle and cords.

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.