National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, March 18, 2020

Question:

Thanks for this forum. It provides useful information. I have a question pertaining to emergency generators installed for a commercial building. When the utility power fails, is there a maximum time that emergency generator power must be restored so people are not left stranded in the dark? I can't seem to find a rule that clarifies this. Thanks for you help on it.

Thomas Seneca

A

Answer:

Hi Thomas, thanks for the nice comments and participating in Code Question of the Day. This is a fairly simple question at face value,  the answer is going to be short and simple too. The answer is yes, the NEC does specify a maximum time for emergency power/lighting transfer and it is 10 seconds. For an emergency system, this requirement is found in Section 700.12. Hope this is useful.

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IMPORTANT NOTICE: Unless the question requests a response based on a specific edition, all answers are based on the latest edition of NFPA 70® National Electrical Code®.

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