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Thread: Clarification of tap rule

  1. #1
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    Clarification of tap rule

    I'm having a hard time understanding the requirements when feeding a motor from a jbox,disconnect or vfd to a motor to size the wire.How is tap rule applied?Any help would be appreciated. Thanks

  2. #2
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    How long is the wire from the point your splicing to the load served?

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  3. #3
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    There are more circumstances involved in sizing conductors for motors is it a.
    Branch circut?
    Feeder?

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  4. #4
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    There are no tap rules involved for a single motor on the load side of the motor branch circuit overcurrent protective devices.
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

  5. #5
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    Quote Originally Posted by nickelec View Post
    There are more circumstances involved in sizing conductors for motors is it a.
    Branch circut?
    Feeder?

    Sent from my SM-G950U using Tapatalk
    How would serving a motor be a feeder?

  6. #6
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    You never seen a feeder feeding an OCPD serving multiple motors?

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  7. #7
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    Quote Originally Posted by Mightymite47 View Post
    I'm having a hard time understanding the requirements when feeding a motor from a jbox,disconnect or vfd to a motor to size the wire.How is tap rule applied?Any help would be appreciated. Thanks
    These are sized the same as the motor circuit conductors.


  8. #8
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    Quote Originally Posted by Mightymite47 View Post
    I'm having a hard time understanding the requirements when feeding a motor from a jbox,disconnect or vfd to a motor to size the wire.How is tap rule applied?Any help would be appreciated. Thanks
    Tap rule would be a situation where you "tap" from a feeder and end up in an overcurrent device to protect the branch circuit on the load side of that device.

    Say you ran a 100 amp feeder across the plant to an area where you had a group of motors. Near those motors you maybe place a gutter or splice box and make taps to that 100 amp feeder to several 30 amp fused disconnects each to supply a motor circuit of 30 amps or less.

    Tap rule covers any conductor between the feeder and each overcurrent device that has lesser ampacity then the feeder.

    See 240.21(B)

  9. #9
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    Quote Originally Posted by kwired View Post
    Tap rule would be a situation where you "tap" from a feeder and end up in an overcurrent device to protect the branch circuit on the load side of that device.

    Say you ran a 100 amp feeder across the plant to an area where you had a group of motors. Near those motors you maybe place a gutter or splice box and make taps to that 100 amp feeder to several 30 amp fused disconnects each to supply a motor circuit of 30 amps or less.

    Tap rule covers any conductor between the feeder and each overcurrent device that has lesser ampacity then the feeder.

    See 240.21(B)
    More specifically, IMHO, it covers any situation where a conductor (other than a service conductor) is protected at its rated ampacity only at the downstream end rather than at the upstream end.

  10. #10
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    Quote Originally Posted by GoldDigger View Post
    More specifically, IMHO, it covers any situation where a conductor (other than a service conductor) is protected at its rated ampacity only at the downstream end rather than at the upstream end.
    Yes.

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