National Electrical Code

Code Q&A

Feb. 27, 2007

Q. If the secondary conductors of a transformer are less than 10 feet in length, do the secondary conductors have to terminate in a main breaker? A. You can run secondary conductors up to 10 feet without overcurrent protection, if they comply with ...

Mike Holt

Q. If the secondary conductors of a transformer are less than 10 feet in length, do the secondary conductors have to terminate in a main breaker?

A. You can run secondary conductors up to 10 feet without overcurrent protection, if they comply with 240.21(C)(2). However, you must provide overcurrent protection for lighting and appliance branch-circuit panelboards. This protection is required to be located on the secondary side of the transformer [408.36(D)], as shown in the Figure.

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.