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Thread: Feeder circuit vs. branch circuit begins

  1. #1
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    Feeder circuit vs. branch circuit begins

    Hi,

    I have been searching around to get an explanation why this is an issue with some inspectors wheres others have another opinion on where the branch circuit begins from the perspective of NEC and UL508A panels.
    The problem is when it comes to having several branch circuits breakers in series. Some inspectors point out that the branch circuits begins after the last branch circuit breaker due to the code says so.
    I do not understand why it is an issue to not begin at the first branch circuit breaker. There the branch begins and all circuit breakers after this branch circuit breaker is just additional protection for specific circuits within its branch.
    I have been speaking to two guys at UL and also been in contact with Intertek. As I understands it is an issue if you strict go by the wording in the code/standard.

    NFPA 70:
    Feeder. All circuit conductors between the service equipment,
    the source of a separately derived system, or other
    power supply source and the final branch-circuit overcurrent
    device.

    Why do I want to have two branch circuit breakers in-line.
    To get as quick as possible the branch circuit spacing per distances in UL508A §10.
    To protect the EMI filter for the panel.
    Power switch -> CB1 -> EMI -> CB(x) -> Motor controller
    After EMI filter there can be several CB's for several motor controllers.

    How do you build your panels to follow the feeder description in NFPA 70 or NFPA79?

  2. #2
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    The code is pretty clear as is UL 508a. It's not a branch circuit until the final overcurrent protection device. The exception would be if you use a circuit breaker that is not rated for branch circuit protection.
    Bob

  3. #3
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    Incidentally, if you want to have closer spacings in a feeder circuit you can. You just have to have insulation on the live parts. For instance, it is not unusual for fuse blocks or power distribution blocks that use crimped on compression lugs to have the exposed lug stick out over the metal panel and be within an inch of that surface. The answer is to insulate it so there is no path to grounded metal that is less than an inch. Or you can put some insulation on the panel.
    Bob

  4. #4
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    Yes the standard/code says so the branch starts at the final overcurrent protection device.
    But in a real world without the code wording. Why is it so?
    For example in your industrial facility you have in the feeder entrance into building.
    In the building you have a panel board with branch fuses or circuit breakers to different floors.
    On the floors you may have additional panel boards with branch fuses or circuit breakers for different wall outlets.
    So from the fuse and forward it is a branch, the power wall outlet does not have to comply with the feeder spacing's.
    Now you connect the product to the wall outlet and the product contains a branch fuse or circuit breaker.
    Suddenly the power wall outlet is a feeder circuit because you have a branch fuse or circuit breaker up front from it.

    It is something with this UL508A and code in I do not understand. I have tried to talk to UL but it is very hard to get good answers.



  5. #5
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    Any OCPD in the load equipment itself does not count since it is part of the load and not part of the fixed building wiring system.
    As for more than one OCPD along a circuit that serves only one load, you either have several feeder runs in series with only one branch run. Or at least one of the OCPDs, especially if it is not an approved branch/feeder breaker, may be ignored as an "auxiliary" OCPD.

    Sent from my XT1585 using Tapatalk

  6. #6
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    Quote Originally Posted by larsahl View Post
    Yes the standard/code says so the branch starts at the final overcurrent protection device.
    But in a real world without the code wording. Why is it so?
    For example in your industrial facility you have in the feeder entrance into building.
    In the building you have a panel board with branch fuses or circuit breakers to different floors.
    On the floors you may have additional panel boards with branch fuses or circuit breakers for different wall outlets.
    So from the fuse and forward it is a branch, the power wall outlet does not have to comply with the feeder spacing's.
    Now you connect the product to the wall outlet and the product contains a branch fuse or circuit breaker.
    Suddenly the power wall outlet is a feeder circuit because you have a branch fuse or circuit breaker up front from it.

    It is something with this UL508A and code in I do not understand. I have tried to talk to UL but it is very hard to get good answers.


    The reason we give things names is because it is easier than describing what said thing is every time we try communicate said thing to another person. Language has it's flaws but it's the best we got for now.
    Last edited by ActionDave; 07-13-17 at 04:54 AM.
    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 GoldDigger View Post
    Any OCPD in the load equipment itself does not count since it is part of the load and not part of the fixed building wiring system.
    As for more than one OCPD along a circuit that serves only one load, you either have several feeder runs in series with only one branch run. Or at least one of the OCPDs, especially if it is not an approved branch/feeder breaker, may be ignored as an "auxiliary" OCPD.

    Sent from my XT1585 using Tapatalk
    I think you will find the correct term is supplementary.

    This is well defined in article 100.

    Overcurrent Protective Device, Branch-Circuit. A device
    capable of providing protection for service, feeder, and
    branch circuits and equipment over the full range of overcurrents
    between its rated current and its interrupting rating.
    Branch-circuit overcurrent protective devices are provided
    with interrupting ratings appropriate for the intended
    use but no less than 5000 amperes.

    Overcurrent Protective Device, Supplementary. A device
    intended to provide limited overcurrent protection for
    specific applications and utilization equipment such as luminaires
    and appliances. This limited protection is in addition
    to the protection provided in the required branch circuit
    by the branch-circuit overcurrent protective device.
    Bob

  8. #8
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    Brandon, Manitoba, Canada
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    Voltage Drop

    Hello good people,

    I am a little late to this party, but the saying goes, "better late than never". I am writing from the perspective of someone who uses the Canadian Electrical Code - a close relative to the NEC - and from what I read and understand in the Code, the definition of a branch circuit (that portion of wiring between the final overcorrect protection and the utilization equipment) is explicitly connected to the allowable voltage drop across wiring (in the case of a branch circuit - no more than 3%; service to utilization equipment - 5%).
    I think this might be part of the situation you are thinking about.

    avoidingshocks



    I have been searching around to get an explanation why this is an issue with some inspectors wheres others have another opinion on where the branch circuit begins from the perspective of NEC and UL508A panels.
    The problem is when it comes to having several branch circuits breakers in series. Some inspectors point out that the branch circuits begins after the last branch circuit breaker due to the code says so.
    I do not understand why it is an issue to not begin at the first branch circuit breaker. There the branch begins and all circuit breakers after this branch circuit breaker is just additional protection for specific circuits within its branch.
    I have been speaking to two guys at UL and also been in contact with Intertek. As I understands it is an issue if you strict go by the wording in the code/standard.

    NFPA 70:
    Feeder. All circuit conductors between the service equipment,
    the source of a separately derived system, or other
    power supply source and the final branch-circuit overcurrent
    device.

    Why do I want to have two branch circuit breakers in-line.
    To get as quick as possible the branch circuit spacing per distances in UL508A §10.
    To protect the EMI filter for the panel.
    Power switch -> CB1 -> EMI -> CB(x) -> Motor controller
    After EMI filter there can be several CB's for several motor controllers.

    How do you build your panels to follow the feeder description in NFPA 70 or NFPA79?[/QUOTE]

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