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Thread: Emergency Lighting on Generator

  1. #1
    Join Date
    Aug 2015
    Cincinnati, OH

    Emergency Lighting on Generator

    I'm going to try to explain this to the best of my ability. See attached sketch for reference -

    I have always worked with individual lights/exit signs with internal battery packs so this is a new area for me. I'm searching through 700 and trying to get an answer for my question, but no luck as of yet. Is a set up like this permissible per code?

    Basically the idea is to serve an emergency panel from a genset and ATS. In the example I'm showing normal lighting in a room fed from a separate panel (panel A) and a dedicated emergency circuit coming from the emergency panel (panel X).
    The potential issue I see with this is that if you lose power somewhere downstream of the ATS or downstream of panel X (EM branch circuits), that would be a way in which you would not be guaranteeing egress lighting in these areas. So then if you lost the normal lighting circuit in that area you would have a situation where there would be no lighting at all. Is this just accepted in the code as a "that's a very unlikely situation" or is this not allowed per code?

    Can someone offer any clarification or point me in the right direction here?

    - Drew
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    Where sin increased, grace abounded all the more
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  2. #2
    Join Date
    Nov 2017
    Colorado & New Mexico
    I don't see a code problem with that setup. The no-lights situation you describe would require two separate circuit failures to happen within the 90 minutes you're required to provide egress lighting.

    Side note - if your generator is providing the only emergency power to a life safety load (like egress lighting), it needs to meet performance standards for a "Level 1" power source as defined in NFPA 110. Nothing too exotic in there, but mention it to your generator supplier.

  3. #3
    Join Date
    Jun 2003
    That would be a typical setup for emergency lighting. Odds are a failure won't happen on both the emergency side and the normal side at the same time.

    In addition to the comment about the generator and ATS being a Level 1 system, you won't be able to put any non-emergency loads on that ATS.

    If the client wants any non-emergency loads backed up (any receptacles, computer UPS's, heating or AC, or almost anything besides the exit and emergency lighting or the fire alarm panel) you will need to add a second ATS.

  4. #4
    Join Date
    Feb 2004
    Austin, TX
    It's just as likely that your battery back up lights will fail as the scenario you described, in fact, we recently had a utility power outage and therefore, many employees did not leave the building and the batteries failed within 1-1/2 hours as expected but nonetheless, the employees who stayed behind were complaining that the emergency lights had went out!
    Electrical Project Coordinator

    "Communication, its a wonderful thing, when it happens."

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