National Electrical Installation Standards

Standards as High as Your Own

Wednesday, November 13, 2019


Re: CQD answer published Wednesday, November 6, 2019 - Emergency circuits

1) Totally disagree with Tuesdays answer.  the circuits are kept separate but may run the entire length of a row of lighting picking up the EM ballasts drops. He did not say they were Emergency Backed up circuits off a Standby generator which must be separated. Bill Schell

2) Good morning and thank you for your great work assisting by brother and sister electricians in the industry. Regarding the emergency wiring in the fixtures with the regular lighting circuit and beg to differ with your answer. It seems from 700.10 that the restriction is when the emergency power is from an "emergency source, or emergency distribution overcurrent protection." An emergency source would be a generator or battery back-up pack remote from the emergency light. However, when the power feeding the emergency ballast is also the circuit that feeds the lighting circuit then this would not fit the restriction of 700.10(B). All the best, Jeff Glanstein


Hey Bill and Jeff, thanks for your comments and the kind words. You are both correct - emergency source wiring must be kept entirely independent from all other wiring and equipment - unless permitted by the conditions of 700.10(B)(1) through (5). That is what our answer stated, or at least what we intended. The original question stated that there was 44 feet of light fixtures (luminaires), 2 of which are emergency lights. They wanted to run both normal circuits and the emergency circuits down the entire row and use the emergency circuits to supply the 2 emergency lights. That is not acceptable.

If you are thinking that there were emergency light ballasts (with internal rechargeable batteries) that would be acceptable, but there would not be emergency circuits (EM power) run through the entire row.

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