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Thread: And another 2008 question

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  1. #1
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    And another 2008 question

    Does a metal raceway that penetrates a rooftop vertically and enters directly into the bottom of a disconnect (cutout box) have to comply with the ampacity adjustment rules of (new) section 310.15(B)(2)(c)? If yes, is there any way around derating the conductors?
    Ryan Jackson, Salt Lake City
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  2. #2
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    Quote Originally Posted by ryan_618
    Does a metal raceway that penetrates a rooftop vertically and enters directly into the bottom of a disconnect (cutout box) have to comply with the ampacity adjustment rules of (new) section 310.15(B)(2)(c)? If yes, is there any way around derating the conductors?
    After a quick peak at the change, here is my take.

    Yes, the raceway penetrating the roof and installed in a vertical position will require derating - "installed in conduits exposed to direct sunlight ON or ABOVE rooftops."


    Notice this says CONDUITS and EXPOSED TO DIRECT SUNLIGHT

    I would think they were very specific in this wording.
    If so, then raceways may not be the proper term, but conduits which include...RMC, IMC and RNC. I wonder, by the wording they chose, if they meant to not include EMT-electrical metallic TUBING ?
    What about a trough (wireway) installed in rooftop locations?
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  3. #3
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    Quote Originally Posted by Pierre C Belarge
    I wonder, by the wording they chose, if they meant to not include EMT-electrical metallic TUBING ?
    What about a trough (wireway) installed in rooftop locations?
    You might want to re-read 100~ Raceway
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    An error on your part does not constitute an emergency on my part.8-)


  4. #4
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    Conduits are raceways, but not all raceways are conduits...
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  5. #5
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    Maybe I oughta read your question again

    I see what you mean...CONDUITS is the question, not RACEWAYS
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    An error on your part does not constitute an emergency on my part.8-)


  6. #6
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    Quote Originally Posted by Pierre C Belarge
    if they meant to not include EMT-electrical metallic TUBING ?
    What about a trough (wireway) installed in rooftop locations?
    I cannot imagine why EMT would be excluded from this derating. I would assume that the derating has to do with the heat that is produced from the rooftops thus incresing the ambient temp.

    I would guess that masts for services would also be affected.

  7. #7
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    What about the part that says "bottom of conduit". Does that mean it only applies to horizontal raceways?
    Ryan Jackson, Salt Lake City
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  8. #8
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    Ryan
    I read the wording out of the analysis book. I do not see where it says the "bottom" of the conduit. It the wording different in the actual code book?
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  9. #9
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    I don't have my code book here, but I am pretty sure that the table is measured to the "bottom" of the conduit.
    Ryan Jackson, Salt Lake City
    Inspector, Instructor

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