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Code Q&A: Motor Controller Ratings

March 3, 2016

NEC requirements for motor controllers

Q. What is the Code requirement for the rating of a motor controller?

Find the Answer

A. The controller must have one of the following ratings [430.83(A)]:

1) Horsepower rating — controllers, other than circuit breakers and molded-case switches, must have a horsepower rating not less than that of the motor.

2) Circuit breakers — a circuit breaker can serve as a motor controller [430.111]. Note: Circuit breakers aren’t required to be horsepower rated.

3) Molded-case switch — a molded-case switch, rated in amperes, can serve as a motor controller. Note: A molded-case switch isn’t required to be horsepower rated.

As noted in Sec. 430.83(C)(2), for stationary motors rated at 2 hp or less, the controller can be a general-use alternating-current snap switch, where the motor full-load current rating isn’t more than 80% of the ampere rating of the switch. Note: A general-use snap switch is a general-use switch constructed for installation in device boxes or on box covers [Art. 100].

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.