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Thread: wireways and 310.15

  1. #1
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    wireways and 310.15

    I was studying/going through the 376 article (Metal wireways) and 376.22(b) is about conductor ampacity adjustment factors. If there are more than 30 CCC in the wireway then the ampacity factors of 310.15(b)(3)(a) apply.

    Can the exception of 310.15(a)(2) apply to the wireway CCC ampacity factors? (10' 10% rule)

    Thanks
    Edward
    Education is a progressive discovery of our ignorance.


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    Quote Originally Posted by edward View Post
    I was studying/going through the 376 article (Metal wireways) and 376.22(b) is about conductor ampacity adjustment factors. If there are more than 30 CCC in the wireway then the ampacity factors of 310.15(b)(3)(a) apply.

    Can the exception of 310.15(a)(2) apply to the wireway CCC ampacity factors? (10' 10% rule)

    Thanks
    yes and yes.

    You need to look at each conductor individually when determing 10'/10% though. You may have some in the wireway you can apply the rule to and some you can't.

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    Quote Originally Posted by kwired View Post
    yes and yes.

    You need to look at each conductor individually when determing 10'/10% though. You may have some in the wireway you can apply the rule to and some you can't.

    Edward
    Education is a progressive discovery of our ignorance.


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    So when the conductors in the wireway are 10' or shorter the ampacity adjustment is irrelevant.
    Edward
    Education is a progressive discovery of our ignorance.


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    Quote Originally Posted by edward View Post
    So when the conductors in the wireway are 10' or shorter the ampacity adjustment is irrelevant.

    No because in general the 10'/10% rule still needs to factor in the entire conductor length.

    Although the code is not very clear IMO the 10'/10% rule does not apply to wireways.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by infinity View Post
    No because in general the 10'/10% rule still needs to factor in the entire conductor length.

    Although the code is not very clear IMO the 10'/10% rule does not apply to wireways.
    What do you mean "the entire conductor length"? You mean the conductor length that is in the wireway or the length of the circuit?
    Edward
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    Quote Originally Posted by edward View Post
    What do you mean "the entire conductor length"? You mean the conductor length that is in the wireway or the length of the circuit?
    "Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length figured at the higher ampacity, whichever is less"

    This is concerning individual circuit ampacity selection, more then 30 in the wireway still requires adjustment, but you need to look at each conductor individually to see what adjustment that conductor needs. Just because you have a 35 or 40 percent adjustment factor doesn't necessarily mean every conductor in the raceway/wireway will need increased in size.

    If the circuit length is less then 100 feet then this exception doesn't allow you to use the conductors at the higher ampacity in a 10 foot length in a wireway. If a circuit is over 100 feet long you can use the higher ampacity up to 10 feet, but another circuit in the same wireway may not have a length of 100 feet, if it were only 60 feet long you can only apply the higher ampacity to 6 feet of the conductors, if only running six feet through the wireway then exiting, you could apply the exception there though.

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