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Thread: 501.10(B)(1) Terminated with Listed Fittings

  1. #11
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    Quote Originally Posted by fifty60 View Post
    I am not able to find where THHN wiring is allowed inside a junction box in a CID2 location. I k now that 501.10(B)(4) says that boxes and fittings are not required to be explosion proof, but that does not seem to provide the justification of general purpose enclosures with THHN wiring..
    Let’s take this from a different perspective. How do you know you can use THHN in any enclosure in an ordinary location?
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  2. #12
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    To clarify I am talking about a sub-panel enclosure on a piece of industrial equipment. Article 300 of NFPA 70 2017 explicitly states that "the provisions of this article are not intended to apply to the conductors that form an integral part of equipment...". So to justify the use of THHN or MTW wiring on my sub-panel, I know I would not be able to use NFPA 70.

    So that would lead me to the normative standards. I know UL508 does not apply in hazardous areas, so I would turn to NFPA 79. 12.3.1 of NFPA 79 2007 (only edition I have handy) lists MTW and THHN as acceptable insulation types. So the normative standard NFPA 79 is how I would justify using THHN or MTW wiring on my sub panel in a non- hazardous area.

    So how would I tie this back to being able to using THHN or MTW on a sub-panel within a Hoffman Enclosure in a CID2 area? Still not seeing it within Articles 500 or 501...
    Time is of the essence, and I am low on essence. ~ Graham Hill

  3. #13
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    501.10 is referencing "Wiring Methods" I am originally taking this to also include wire types themselves. But now I am starting to realize that wiring methods refers to actually running the wire/cabling from point A to Point B outside of an electrical enclosure. It is listing the types of conduits you can use, or it is listing the cable types you can use if you are not using one of the approved conduit types. It is not explicitly restricting the types of wiring you can use inside of enclosures.

    501.20 is referring to Conductor Insulations in CID1 and CID2, and references situations where condensed vapors or liquids may collect on wiring. In that circumstance, the insulation shall be of a type identified for us under such conditions... This however, is not explicitly referring to inside of enclosures identified for CID2.

    Since wire types are not explicitly referenced in 500 or 501 for CID2, I would base my reasoning for using MTW or THHN off of 500.8(A)(3) and 500.8(B)(1). Does this seem correct?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  4. #14
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    I donno; sounds pretty flimsy to me. How do you know NFPA 79 is normative? It isn’t listed in NEC Annex A nor OHSA’s list of Appropriate Test Standards. Why should an AHJ buy in under Section 500.8(A)(3)? Since you now have taken it out of the NEC’s Scope, what has Section 500.8(B)(1) got to do with it anyway?

    Since you appeared to want an explicit statement for THHN in Post #11, I was where you found such a statement for THHN for any Type of enclosure.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #15
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    Well I don't think there is anywhere that explicitly says you can use THHN or MTW inside a gp enclosure in a CID2 area. So would the reasoning then be that it is not explicitly prohibited? The wiring methods dictated by the standard would not apply once we are inside of the enclosure, so at that point, it would fall under the overall suitability of identified equipment criteria from 500.8.A...
    Time is of the essence, and I am low on essence. ~ Graham Hill

  6. #16
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    Quote Originally Posted by fifty60 View Post
    Well I don't think there is anywhere that explicitly says you can use THHN or MTW inside a gp enclosure in a CID2 area. So would the reasoning then be that it is not explicitly prohibited? The wiring methods dictated by the standard would not apply once we are inside of the enclosure, so at that point, it would fall under the overall suitability of identified equipment criteria from 500.8.A...
    How would you know THHN or MTW is suitable in any Type enclosure in an ordinary location? It can be pieced together from several Sections, but it ain’t explicit anywhere else either.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #17
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    Would it be reasonable and acceptable to say that 501.10(B)(4) is saying that Boxes and Fittings that meet the requirements of 501.10(B)(4) are themselves accepted wiring methods? And that inside the enclosure you can use normal wiring practices just like in 501.10(B)(1) where you can imply that normal wiring practices can be used inside rigid metal conduit without threaded fittings?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  8. #18
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    Quote Originally Posted by fifty60 View Post
    Would it be reasonable and acceptable to say that 501.10(B)(4) is saying that Boxes and Fittings that meet the requirements of 501.10(B)(4) are themselves accepted wiring methods? And that inside the enclosure you can use normal wiring practices just like in 501.10(B)(1) where you can imply that normal wiring practices can be used inside rigid metal conduit without threaded fittings?
    Yes, Boxes and fittings fall under Section 501.10 Wiring methods.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  9. #19
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    wouldn't that kind of fall back to 110.2, AHJ approving the conductors? if nowhere is calling it out one way or another. it's probably not a wet location or any type of degrading atmosphere(uv) right (inside the enclosure).

  10. #20
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    Quote Originally Posted by Wire-Smith View Post
    wouldn't that kind of fall back to 110.2, AHJ approving the conductors? if nowhere is calling it out one way or another. it's probably not a wet location or any type of degrading atmosphere(uv) right (inside the enclosure).
    Sure, why not for those incapable of making cognitive leaps - let the AHJ tell you how to do everything.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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