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    EM Lighting

    Not sure the way they show this is correct. So panel E1LP4A is an emergency panel fed from emergency side of ATS. Why would they label some fixtures EM and some not if fed from same emergency panel and circuit? The EM ones don't require battery backup. Not sure why they differentiate.
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    #2
    Anyone make sense of this?

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      #3
      If it's not a mistake then my only guess is that besides the EM lighting circuit they want some of the fixtures with battery backup.
      Rob

      Moderator

      All responses based on the 2017 NEC unless otherwise noted

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        #4
        Maybe redundancy so that if the breaker/fuse protecting that panel (or circuit) trips/blows, emergency lighting will kick on in that area, even if the entire store hasn't lost power?
        I'm offended.

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          #5
          The only reason I can see for this would be redundancy.

          Typically you would just run a normal circuit to a fixture with battery backup, or use a UL924 emergency lighting relay so the emergency circuit powers the emergency fixtures and switches with the normal fixtures.

          The only time I would use redundancy with an emergency circuit like this would be in egress stairwells. In a normal office space it seems unnecessary and may have been a mistake.

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            #6
            It's all about the switching. The EM ones have to come on when you're on emergency, even if they're switched off. See 700.20.
            Alternate current
            Line to ground and ground to line
            Current alternates

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