Code Q&A: Rules When Mixing Conductor Types in Same Raceway

June 11, 2015

NEC rules on installation of conductors

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Q. What are the rules related to the installation of conductors under 50V with conductors from 120V, 208V, 240V, 277V, and 480V systems in the same raceway or enclosure?

Find the Answer

A. Class 1 circuit conductors can be installed with associated power conductors [725.48(B)(1)] if all conductors have an insulation voltage rating not less than the maximum circuit voltage [300.3(C)(1)]. A Class 2 circuit that’s been reclassified as a Class 1 circuit [725.130(A), Exception No. 2] can be installed with associated power conductors [725.48(B)(1)] if all conductors have an insulation voltage rating not less than the maximum circuit voltage [300.3(C)(1)] (Figure).

Control, signal, and communications wiring must be separated from power and lighting circuits so the higher-voltage conductors don’t accidentally energize the control, signal, or communications wiring.

Note 2: PV system conductors, both direct current and alternating current, are permitted to be installed in the same raceways, outlet and junction boxes, or similar fittings with each other, but they must be kept entirely independent of all other non-PV system wiring [690.31(B)].

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.