Each elevator shall have a means for disconnecting all ungrounded main power-supply conductors for each unit, _____.
a) excluding the emergency power system
b) including the emergency or standby power system
c) excluding the emergency power system if it is automatic
d) and the power supply may not be an emergency power system
See answer and applicable Code reference
The correct answer is: b) including the emergency or standby power system
Emergency and standby power requirements for elevators are outlined in Sec. 620.91 of the 2011 NEC. As per 620.91(C), "The disconnecting means required by 620.51 shall disconnect the elevator from both the emergency or standby power system and the normal power system. Where an additional power source is connected to the load side of the disconnecting means, which allows automatic movement of the car to permit evacuation of passengers, the disconnecting means required in 620.51 shall be provided with an auxiliary contact that is positively opened mechanically, and the opening shall not be solely dependent on springs. This contact shall cause the additional power source to be disconnected from its load when the disconnecting means is in the open position."
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.