Code Q&A

Q. Can a single transfer switch be used to supply both emergency and non-emergency loads, such as a UPS for telecom equipment? A. No, a single transfer switch is not permitted to serve emergency and non-emergency loads . However, a single generator is ...

Mike Holt

July 23, 2004

Q. Can a single transfer switch be used to supply both emergency and non-emergency loads, such as a UPS for telecom equipment?

A. No, a single transfer switch is not permitted to serve emergency and non-emergency loads [700.6(D)]. However, a single generator is permitted to serve emergency and non-emergency loads, provided multiple transfer switches are used, and automatic load shedding ensures adequate power for the emergency loads [700.5(B)] (Figure below).

The building feeder disconnecting means is permitted to be locked closed if there is concern that the opening of the readily accessible disconnect could result in a hazard to persons or property, lets say because of vandals or terrorism.

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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.