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Thread: Emergency Lighting

  1. #1
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    Emergency Lighting

    I've got a code question/concern. In my experience, lighting legally required for egress of a building is usually fed from an "emergency (700)" (Life Safety) Branch. Where lighting for, say, an office suite which the occupants may use during a prolonged power outage is fed from an "optional standby (702)" branch. I've got a situation where the engineer has put the entire building lighting on the "Emergency" branch. There is only one transfer switch and no "optional standby" branch. Intuition says that this is wrong, but I can't find a code reference that specifically prohibits this practice.

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    Quote Originally Posted by IMFOTP View Post
    I've got a code question/concern. In my experience, lighting legally required for egress of a building is usually fed from an "emergency (700)" (Life Safety) Branch. Where lighting for, say, an office suite which the occupants may use during a prolonged power outage is fed from an "optional standby (702)" branch. I've got a situation where the engineer has put the entire building lighting on the "Emergency" branch. There is only one transfer switch and no "optional standby" branch. Intuition says that this is wrong, but I can't find a code reference that specifically prohibits this practice.
    Why is he going to so much trouble? Why not use battery backup units??

  3. #3
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    Because they want to keep the building illuminated during a power outage. They have a generator, no battery packs.

  4. #4
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    They either need to add battery packs or another transfer switch and panelboard for Art 700 loads.
    The more they overthink the plumbing, the easier it is to stop up the drain

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    That was my thought, but there doesn't seem to be a code reference to back that up. Yes, common sense would say if they want to put the whole building on backup illumination they would need 2 transfer switches. One for emergency and one for standby. But I can't find code verbiage that prohibits them for going ahead and put the whole building lighting on the emergency transfer switch, which is what's happening here.

  6. #6
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    Quote Originally Posted by IMFOTP View Post
    That was my thought, but there doesn't seem to be a code reference to back that up. Yes, common sense would say if they want to put the whole building on backup illumination they would need 2 transfer switches. One for emergency and one for standby. But I can't find code verbiage that prohibits them for going ahead and put the whole building lighting on the emergency transfer switch, which is what's happening here.
    I think if you read the definition at 700.2 closely it basically says that if you have a mixture of 700 and non-700 loads, you can't just treat them all as 700 loads. Only legally required loads can go on a 700 ATS. The egress lighting is legally required. Task lighting to keep things humming along is not. Only the first can go on the 700 ATS. Or, install battery backup units and use the generator for the 702 loads, including any task lighting.

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    The more they overthink the plumbing, the easier it is to stop up the drain

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    Quote Originally Posted by gadfly56 View Post
    I think if you read the definition at 700.2 closely it basically says that if you have a mixture of 700 and non-700 loads, you can't just treat them all as 700 loads.
    I agree, thanks!

  9. #9
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    Just playing devil's advocate, how can you define which lights are emergency and which are not? If all that is on the transfer switch is lighting, then couldn't it all be considered egress lighting? We are given a minimum FC level for egress, but not a maximum.

  10. #10
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    Quote Originally Posted by jcbabb View Post
    Just playing devil's advocate, how can you define which lights are emergency and which are not? If all that is on the transfer switch is lighting, then couldn't it all be considered egress lighting? We are given a minimum FC level for egress, but not a maximum.
    Egress lighting is along the path of travel and it's only at low levels that don't accommodate actual work getting done. The real point is, if the lighting is out, lots of other things probably aren't working either. Emergency lighting is supposed to allow safe evacuation of a facility, period. Otherwise, get a whole building backup and be done. But you'll still need emergency lighting (dang!).

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