Code Q&A

Feb. 7, 2008

What are the Code requirements for bonding bushings on 277V or 480V branch and feeder and circuits?

Q. What are the Code requirements for bonding bushings on 277V or 480V branch and feeder and circuits?

A.Metal raceways or cables containing 277V and/or 480V branch or feeder circuits terminating at ringed knockouts must be bonded to the metal enclosure with a bonding jumper sized in accordance with 250.122, based on the rating of the circuit overcurrent device [250.102(D)]. A bonding jumper isn’t required where ringed knockouts aren’t encountered or where the box is listed to provide a reliable bonding connection as in a typical 4 square outlet box [250.97].

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.