Figure. Each disconnecting means must be lockable in the open position per 110.25 [445.18].

Code Q&A: Standby Generator Requirements in Other Than Dwelling Units

April 13, 2022

Test your knowledge of the NEC.

All questions and answers are based on the 2020 NEC.

Q. What are the Code rules for disconnecting means and emergency shutdown of standby generators, other than in one- and two-family dwelling units?

See answer below.

A. Follow these requirements as outlined in Sec. 445.18:

(A) Generators, other than cord-and-plug-connected portable generators, must have one or more disconnecting means. Each disconnecting means must simultaneously open all associated phase conductors. Each disconnecting means must be lockable in the open position per Sec. 110.25 [445.18] (Figure).

(B) Generators must have provisions to shut down the prime mover. The means of shutdown must comply with all the following:

(1) Be equipped with provisions to disable all prime mover start control circuits to render the prime mover incapable of starting.

(2) Initiate a shutdown mechanism that requires a mechanical reset. The provisions to shut down the prime mover are permitted to satisfy the requirements of Sec. 445.18(A) where it is capable of being locked in the open position per Sec. 110.25.

(C) Generators with a greater than 15kW rating must be provided with a remote emergency stop switch to shut down the prime mover. The remote emergency stop switch must be located outside the equipment room or generator enclosure and must also meet the requirements of Sec. 445.18(B)(1) and (B)(2).

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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.