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Thread: 240.15 (B) interpretation

  1. #1
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    240.15 (B) interpretation

    We are doing an install that requires a dedicated circuit. One person says we can use a 12/4 cable for the 3 circuits needed in that same area and use single pole breakers.This I believe to be a violation. He went on to say, this will keep that 1 circuit dedicated. Hence, only the circuit with a fault will trtip, not the dedicated circuit. 240.15 (B) (2) states an " identified handle tie" is required in this senario (sharing a neutral). Question#1, What is the definition of the quote "identified handle tie"? I think it means an approved means is required to trip all 3 single pole breakers simultaneously (aka an approved breaker tie/ bridge for the 3 breakers instead of using a 3 pole breaker). If so, my 2nd question is, Would that nullify the dedicated circuit if the breakers were tied together (bridged)? For my last question, Is this the proper section to be refeering or is there other sections I missed? Thanks!

  2. #2
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    The handle ties would have to be an "identified" product. Meaning they don't have to be listed but would have to be something that meets the definition of "identify"

    Identified (as applied to equipment). Recognizable as
    suitable for the specific purpose, function, use, environment,
    application, and so forth, where described in a particular
    Code requirement.
    Also, a handle tie doesn't cause all the breakers to trip. They have an internal tripping mechanism. A MWBC requires all the breakers to be disconnected or turned off when working on a circuit. The tie is so that when working on the circuit(s) you have to turn all the circuits off when you flip the breaker. The breakers will all turn off with a tie but not trip. It is possible that a fault that trips one of the breakers could turn off another breaker but won't trip it.
    If you aim at nothing, you will hit it every time!

  3. #3
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    Quote Originally Posted by Little Bill View Post
    The tie is so that when working on the circuit(s) you have to turn all the circuits off when you flip the breaker so instead you just work on it hot rather than trying to figure out what the other circuits are and if they are ok to turn off . The breakers will all turn off with a tie but not trip. It is possible that a fault that trips one of the breakers could turn off another breaker but won't trip it.
    FIFY I hate that requirement.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #4
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    Quote Originally Posted by electrofelon View Post
    FIFY I hate that requirement.
    I never said I liked the rule, just that it is the rule.
    If you aim at nothing, you will hit it every time!

  5. #5
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    Quote Originally Posted by Hoodood View Post
    Question#1, What is the definition of the quote "identified handle tie"? I think it means an approved means is required to trip all 3 single pole breakers simultaneously (aka an approved breaker tie/ bridge for the 3 breakers instead of using a 3 pole breaker). If so, my 2nd question is, Would that nullify the dedicated circuit if the breakers were tied together (bridged)? For my last question, Is this the proper section to be refering or is there other sections I missed? Thanks!
    If you used single pole CB's for a MWBC then yes you would be required to use a handle-tie, Little Bill gave you the code reference from Article 100. Even with a MWBC handle tied together you still would have separate circuits.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #6
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    Thanks for the Article 100 answer.

    Quote Originally Posted by Little Bill View Post
    The handle ties would have to be an "identified" product. Meaning they don't have to be listed but would have to be something that meets the definition of "identify"



    Also, a handle tie doesn't cause all the breakers to trip. They have an internal tripping mechanism. A MWBC requires all the breakers to be disconnected or turned off when working on a circuit. The tie is so that when working on the circuit(s) you have to turn all the circuits off when you flip the breaker. The breakers will all turn off with a tie but not trip. It is possible that a fault that trips one of the breakers could turn off another breaker but won't trip it.
    Don't know why I didn't look there. Didn't think it would be there? Also, my bad for thinking other circuits would trip. You are on target, the handle tie would turn the other circuits off.
    Thanks again.
    Last edited by Hoodood; 03-10-18 at 08:13 AM.

  7. #7
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    More detail for this MWBC

    I apoligize for not being more specific. One of the circuits is for the elevator pit sump pump. So, although it has a dedicated circuit which is 1 of the 3 poles in the now handle tied breakers would this particular circuit be considered critical and therefore not be permitted in a MWBC to begin with. If another circuit trips it would turn off this critical circuit. So, with that in mind can this pump circuit be allowed in the MWBC or does it need to be isolated from such circuitry and be on its own single pole breaker?
    Thanks for the responses guys!

  8. #8
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    The NEC doesn't care if the sump pump is on a MWBC. Might not be the best design however.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  9. #9
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    Is the building 3 phase? I haven't seen if it is or isn't.
    Sometimes I don't know whether I'm the boxer or the bag.

  10. #10
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    Other codes

    Well said & noted. So I need to look into the elevator codes in order to clarify this issue. Especially since this install will be inspected by both the electrical & elevator AHJ's. Thanks again!

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