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  1. #1
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    Circuit breakers as switches

    I looked a job today where twelve GE circuit breakers are being used to control 120v florescent lighting in a warehouse. These breakers are worn and one has totally failed. If my understanding is correct, the only time a breaker can be used to control lighting is if they are marked for "switch duty" (SWD).

    The owner is asking me to put in 12 toggle switches to control the lighting so he can avoid using the breakers. He specifically does not want a lighting contactor. There is plenty of room to do this near the surface-mounted panel, however I'm running up against the derating rules. If I run two short pieces of conduit with 12 conductors each (12 switch legs in, 12 out) to a switch box, I have to derate 50%. Since I want 20 amp circuits, I would have to run #10 which seems like a pain.

    The switch box could be 6 4x4 deep boxes chase nippled together with 2 switches each. Or I could use two pole switches and switch two circuits at a time with less boxes.

    An alternative I'm considering is mounting a 12 slot Cutler-Hammer subpanel with SWD breakers, but the same derating rules apply as far as I know. I can be a few inches away from the main panel.

    Suggestions?

  2. #2
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    Derating only applies when your raceways exceed 24" so short sections between your components will eliminate the need to derate the conductors. The old CB's were generally listed as switch duty (SWD), newer ones are typically listed as HID for high intensity discharge lighting.

    240.83(D) Used as Switches. Circuit breakers used as switches in120-volt and 277-volt fluorescent lighting circuits shall be
    listed and shall be marked SWD or HID. Circuit breakers
    used as switches in high-intensity discharge lighting cir-
    cuits shall be listed and shall be marked as HID.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    Quote Originally Posted by infinity View Post
    Derating only applies when your raceways exceed 24" so short sections between your components will eliminate the need to derate the conductors. The old CB's were generally listed as switch duty (SWD), newer ones are typically listed as HID for high intensity discharge lighting.
    So if I run 24" to the first 4x4 box and then I have several boxes chase nippled together, do I have to derate the wires that go to the furthest box since the total length would exceed 24"?

  4. #4
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    Quote Originally Posted by Coppersmith View Post
    So if I run 24" to the first 4x4 box and then I have several boxes chase nippled together, do I have to derate the wires that go to the furthest box since the total length would exceed 24"?
    I don't see how it could be properly interpreted that way. The nipple ends at the box and then a new one starts.

    Personally, I would like to see someone use this provision to run a crap load of wires in a conduit using 24" nipples between boxes just to see what a picky inspector could do about it.
    Bob

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    Quote Originally Posted by petersonra View Post
    I don't see how it could be properly interpreted that way. The nipple ends at the box and then a new one starts.

    Personally, I would like to see someone use this provision to run a crap load of wires in a conduit using 24" nipples between boxes just to see what a picky inspector could do about it.
    I've ran from an exterior panel into a house and ran all the romex home runs through a 1-1/2 chase nipple. The inspector tried calling me and saying I had too many wires in it (23) but they fit and the code was on my side so I won.


    Sent from my iPhone using Tapatalk

  6. #6
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    Quote Originally Posted by Coppersmith View Post
    So if I run 24" to the first 4x4 box and then I have several boxes chase nippled together, do I have to derate the wires that go to the furthest box since the total length would exceed 24"?
    I don't remember the wording, but I know the 24" rule only mentions raceways. If you read it carefully you could run two feet of pipe, install a box, run two more feet of pipe, and so on. I'm sure that's not what was meant to be allowed, but it is how the section reads.
    Once in a while you get shown the light
    In the strangest of places if you look at it right. Robert Hunter

  7. #7
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    Quote Originally Posted by ActionDave View Post
    I don't remember the wording, but I know the 24" rule only mentions raceways. If you read it carefully you could run two feet of pipe, install a box, run two more feet of pipe, and so on. I'm sure that's not what was meant to be allowed, but it is how the section reads.

    I agree, that's how it's worded.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    While I would not wire lights w/o switches in the circuit, just utilizing the breakers, now that it is wired that way, what's the big deal with replacing the breakers every so often? 12 1p 20A GE breakers arent expensive and the labor is nil compared to adding onto the circuit.

    If you really want the switches, why not just run 3 pieces of conduit to a switchbox instead of 2? 12 switch = 24 CCC/3 = 8/pipe = 70% derating x30A = 21A, still enough for a 20A breaker
    Electricians do it until it Hertz!

  9. #9
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    Quote Originally Posted by JFletcher View Post
    If you really want the switches, why not just run 3 pieces of conduit to a switchbox instead of 2? 12 switch = 24 CCC/3 = 8/pipe = 70% derating x30A = 21A, still enough for a 20A breaker
    I hadn't thought of that.

    As others have mentioned, the point seems moot if I stay within 24" which I can.

  10. #10
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    Quote Originally Posted by JFletcher View Post
    While I would not wire lights w/o switches in the circuit, just utilizing the breakers, now that it is wired that way, what's the big deal with replacing the breakers every so often? 12 1p 20A GE breakers arent expensive and the labor is nil compared to adding onto the circuit.
    +1

    GE plug on breakers are not much more expensive then a 20 amp spec grade switch is.

    Throw lighting contactors into the mix and total installation/possible maintenance cost jumps pretty fast.

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