Ecmweb 7563 7 9 15codeqalarge
Ecmweb 7563 7 9 15codeqalarge
Ecmweb 7563 7 9 15codeqalarge
Ecmweb 7563 7 9 15codeqalarge
Ecmweb 7563 7 9 15codeqalarge

Code Q&A: Mixing Conductors from Different Voltage Systems

July 9, 2015
NEC rules on installation of conductors from different voltage systems

Q. What are the rules related to the installation of conductors from different voltage systems — such as 120V, 208V, 240V, 277V, and 480V — in the same raceway or enclosure?

Find the Answer

A. If the premises wiring system contains branch circuits supplied from more than one voltage system, each ungrounded conductor must be identified by phase and system at all termination, connection, and splice points in accordance with Sec. 210.5(C)(1)(a) and (b) [210.5(C)(1)]. Identification can be by color coding, marking tape, tagging, or other means approved by the authority having jurisdiction [210.5(C)(1)(a)]. The method of identification must be documented in a manner that’s readily available or permanently posted at each branch circuit panelboard [210.5(C)(1)(b)].

When a premises has more than one voltage system supplying branch circuits, the ungrounded conductors must be identified by phase and system. This can be done by permanently posting an identification legend that describes the method used, such as color-coded marking tape or color-coded insulation.

Conductors with insulation that’s green or green with one or more yellow stripes can’t be used for an ungrounded or neutral conductor [250.119]. Although the NEC doesn’t require a specific color code for ungrounded conductors, electricians often use the following color system for power and lighting conductor identification:

• 120/240V, single-phase — black, red, and white

• 120/208V, 3-phase — black, red, blue, and white

• 120/240V, 3-phase — black, orange, blue, and white

• 277/480V, 3-phase — brown, orange, yellow, and gray; or, brown, purple, yellow, and gray

Power conductors of alternating-current and direct-current systems 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 [300.3(C)(1)].

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.

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