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Thread: class 1 division 2 boundaries

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    class 1 division 2 boundaries

    for slabbing purposes, if you have two hangars seperated by a metal frame wall is inside the wall considered part of the hazardous location?

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    That's an excellent question and, to my knowledge, there is no documented standard that covers it. I can only offer my opinion.

    A boundary is created relative to a potential gas or vapor source, and a physical barrier creates a "boundary" with respect to the source. Conceptually, the desire is for a boundary seal to minimize the migration of vapors and gases through a conduit from one location to another, so it is desirable to seal it where it penetrates a physical barrier. However, where the two locations are at the same relative air pressure, it is not generally necessary to use an explosionproof seal.

    Now, if Section 513.8 is what is under discussion, the wall is irrelevant since the slab's surface is what creates the boundary and underground wiring must comply with either 513.8 (A) or (B).
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

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    After rereading it, I note my previous post is with respect to Class I, Division 2 locations only.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

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    Rob, I felt the question and the answer were not in synch. At least, after the OP asked the question it raised one in my head. Basically is the space between the two sides of sheetrock a classified area with classified area on both sides? My first thought was yes, but then I thought if only one side was classified, then no. So my final answer is, I don't have a clue.


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    Quote Originally Posted by Strathead View Post
    Rob, I felt the question and the answer were not in synch. At least, after the OP asked the question it raised one in my head. Basically is the space between the two sides of sheetrock a classified area with classified area on both sides? My first thought was yes, but then I thought if only one side was classified, then no. So my final answer is, I don't have a clue.
    I think that is the right answer.

    Might vary from one jurisdiction to another to some extent. I think will at very least depend on what kind of finish is applied to the wall, and even if there is any openings in that wall, primarily doors or windows and how they are designed/arranged/maintained. Then there may be differences in division 1 vs division 2 as well as effects from any ventilation that may apply to an area. I guess OP says he has div 2 location and presumably unclassified on the other side of the wall.
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    Quote Originally Posted by kwired View Post
    I think that is the right answer.
    I guess OP says he has div 2 location and presumably unclassified on the other side of the wall.
    I think he was implying div 2 on each side of the wall and whether they are considered the same area or two separate areas with a boundary between.


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    Quote Originally Posted by Strathead View Post
    I think he was implying div 2 on each side of the wall and whether they are considered the same area or two separate areas with a boundary between.
    As I mentioned in my earliest response neither the NEC nor any other standard I know of deals specifically with two locations, while having the same "classification", are actually classified because of different sources or parameters. My opinion, that a physical barrier creates a 'boundary' with respect to Section 501.15(B)(2) and dealing with a conduit that crosses such a boundary, is based on my experience, my interpretation of Section 501.15 IN No.1, and how I would deal with the issue should it arise in a practical case.

    I also responded to "slabbing" mentioned in the OP which is the basic "hanger" issue of Section 513.8.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

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    Quote Originally Posted by Strathead View Post
    I think he was implying div 2 on each side of the wall and whether they are considered the same area or two separate areas with a boundary between.
    I see what you are saying now and I think he is asking if the space inside the dividing wall would be a classified area.

    My bet is many AHJ's will say yes, especially if there is classified area on each side, all depends on how well it is "suitably cut off from the hangar" as is mentioned in 513.3(B).

    If you wanted to bring say a PVC raceway out of the slab, here in the past it likely would be acceptable to encase it in 2 inches of concrete until you get above 18" (as long as you don't end up in other classified area above that 18").
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