Code Q&A: Enclosure Mounting Rules

Jan. 3, 2013

Your most pressing National Electrical Code (NEC) questions answered

Q. What Code section requires that enclosures containing overcurrent protection devices must be mounted vertically?

A. Section 240.33 of the 2011 NEC requires that enclosures containing overcurrent devices must be mounted in a vertical position unless this isn't practical. Circuit-breaker enclosures can be mounted horizontally if the circuit breaker is installed in accordance with 240.81.

Section 240.81 specifies that where circuit breaker handles are operated vertically, the "up" position of the handle must be in the ON position. So, in effect, an enclosure that contains one row of circuit breakers can be mounted horizontally, but an enclosure that contains a panelboard with multiple circuit breakers on opposite sides of each other will have to be mounted vertically.

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.