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Thread: Corridor Emergency Egress Lighting via GTD20

  1. #11
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    So prior to 2014 NEC many engineers (me included) were using load control relays and branch circuit transfer devices for transferring 20A branch circuit emergency loads, then the 2014 NEC clarified that this was not acceptable, only it only addressed load control relays used as transfer devices and ignored branch circuit transfer devices. So the 2017 NEC has now addressed the latter, identifying them as Branch Circuit Emergency Lighting Transfer Switch (BCELTS).

    If I'm off on any of this please correct.

    So going forward in order to design per my original description I will need a BCELTS that is UL 1008 listed to the proper category, and that will only suffice if the project is being designed under the 2017 NEC (unless I can get something in writing from the AHJ permitting this prior to adoption of the 2017 NEC).

    I am appreciative of all the input, very helpful.

  2. #12
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    Quote Originally Posted by birtclp View Post
    So prior to 2014 NEC many engineers (me included) were using load control relays and branch circuit transfer devices for transferring 20A branch circuit emergency loads, then the 2014 NEC clarified that this was not acceptable, only it only addressed load control relays used as transfer devices and ignored branch circuit transfer devices. So the 2017 NEC has now addressed the latter, identifying them as Branch Circuit Emergency Lighting Transfer Switch (BCELTS).

    If I'm off on any of this please correct.

    So going forward in order to design per my original description I will need a BCELTS that is UL 1008 listed to the proper category, and that will only suffice if the project is being designed under the 2017 NEC (unless I can get something in writing from the AHJ permitting this prior to adoption of the 2017 NEC).

    I am appreciative of all the input, very helpful.
    I think that about sums it up. I know from experience that the whole issue of the proper use of load load control relays as permitted in the 2014 NEC is wildly misunderstood in the field by many.
    Help me understand something though... while the need for a load control relay in this day and age is obvious, what is the real advantage to using a BCELTS as allowed in 700.25 in the 2017 NEC? You have to wire back to the emergency panel anyway, so why not just power the lights from there in the first place? What am I missing here?

  3. #13
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    You can switch the entire circuit, for example all of the lights in an existing corridor can be wired via a single BCELTS, then you only bring a normal circuit and an emergency circuit to the BCELTS.

  4. #14
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    Quote Originally Posted by birtclp View Post
    You can switch the entire circuit, for example all of the lights in an existing corridor can be wired via a single BCELTS, then you only bring a normal circuit and an emergency circuit to the BCELTS.
    Yes, I get that but you can do this with just an ALCR to bypass local switching/controls and avoid having to wire to the normal panel at all. You just put the lights on the emergency circuit. I must be missing something here.

  5. #15
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    Aren't 2 separate power sources to the space required so tripping a single breaker will not leave space in dark? The control relay only senses normal power. If the emergency panel breaker is tripped all of the lights in the space turn off regardless of the status of normal power.

  6. #16
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    Quote Originally Posted by birtclp View Post
    Aren't 2 separate power sources to the space required so tripping a single breaker will not leave space in dark? The control relay only senses normal power. If the emergency panel breaker is tripped all of the lights in the space turn off regardless of the status of normal power.
    OK, now I see where you are coming from. I was thinking of, say, a typical arrangement where you have both normal and emergency fixtures in the same area and you don't have to meet this requirement. You're right, if all the lights in an area were on 1 branch circuit then a BCELTS could be an option.

  7. #17
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    How do you positively prevent accidental 3-way switch situation? If emergency one has tripped for some reason and forgotten about and it is turned off at normal panel for routine service work, how do you ensure circuit being worked on won't get energized when someone turns on the breaker in the emergency side?

  8. #18
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    Quote Originally Posted by Electric-Light View Post
    How do you positively prevent accidental 3-way switch situation? If emergency one has tripped for some reason and forgotten about and it is turned off at normal panel for routine service work, how do you ensure circuit being worked on won't get energized when someone turns on the breaker in the emergency side?
    As soon as they turned off the normal power, the emergency relay should switch over to the "emergency side". I would assume the emergency side would be connected on the load side of a emergency transfer switch.

    So the light fixture would remain on, even after the default source of normal power was turned off.

  9. #19
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    I would have two issues with your use of the GTD device to connect all lights in a corridor.

    1. That doesn't provide the 2 required separate lighting systems - a normal system, and an emergency system. At least that's what I remember the code requiring. By putting all the lights on the emergency you have eliminated any "normal" system.
    2. Only necessary, required egress lights can go on the emergency system. You can't just put all the lights on the emergency system. That gives a higher chance a ballast will short, or something will go wrong that will trip a branch breaker and shut off all the emergency lighting in one area.

    Now, if you pick every 3rd light and put it on the GTD, I would be good with that.

  10. #20
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    There is normal and emergency to the GTD20, which is located above the lay-in ceiling in the corridor. If a properly listed BCELTS (Branch Circuit Emergency Lighting Transfer Switch) were used then I believe this would meet intent of the requirement. If the normal power breaker is shut off then the BCELTS transfers to the emergency panel circuit, which is still energized.

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