Code Q&A: Disconnect Requirements

Your most pressing National Electrical Code (NEC) questions answered

June 21, 2012

Q. What are the disconnect requirements for a building or structure supplied by a feeder?

A. A single disconnecting means for a building/structure must have an ampere rating not less than the calculated load as determined by Art. 220. If the disconnecting means consists of more than one switch or circuit breaker, the combined ratings of the circuit breakers must not be less than the calculated load as determined by Art. 220. In addition, the disconnecting means must not be rated lower than [225.39]:

For installations consisting of a single branch circuit, the disconnecting means must have a rating of not less than 15A [225.39(A)].
For installations consisting of two 2-wire branch circuits, the feeder disconnecting means must have a rating of not less than 30A [225.39(B)].
For a one-family dwelling, the feeder disconnecting means must have a rating of not less than 100A, 3-wire [225.39(C)].
For all other installations, the feeder or branch-circuit disconnecting means must have a rating of not less than 60A [225.39(D)].

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.