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    Hazardous Location Boundary

    I have a situation in a C1D1 area (Headworks of a Wastewater Plant) that I need some help with.

    If a conduit is routed in the concrete floor slab and turns up in a classified area and an unclassified area a conduit seal should be placed as the conduit enters/leaves the classifed location before entering/leaving the concrete floor slab. And as I understand it no additional seal is needed at the unclassified location. Correct?

    Now what if a conduit is routed in the same concrete floor slab but both ends turn up the the same classified location. Should a conduit seal should be placed as the conduit enters/leaves the concrete slab?

    I guess it all boils down to where the Hazardous location boundary is located. If the concrete floor slab is considered to be part of the hazarodus location then any conduit traveling through it and into new areas would make those areas classified due to the possibility of transmission of hazarous materials.

    I tend to think of the concrete floor as not being part of the classified location but am having a hard time finding anything that can back me up. And if the concrete floor slab is not considered as being part of the classified location can PVC conduit be used. I see where PVC is allowed with 24" of cover and a 2" concrete envelope in a classified location (But I am assuming the floor slab is not a Classified location) but that only makes sense in areas like aircraft hangers where belowgrade is specifically noted to be C1D1. So can i use PVC conduit in the floor slab without violating code?

    Thanks for any and all help. If you need any additional information let me know. NFPA 820 was used to classify the location. Code in force is 2005 NEC but would appreciate knowing what current code dictates.

    #2
    xception.



    inException

    In order to use nonmetallic raceways I would want the full requirements of the Exception.



    Where the stub-ups for both ends of a raceway are in the same
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

    Comment


      #3
      I am curious once again about the PVC. The code you referenced (501.10.a.1.exception) is specific to C1D1 locations correct, and we both seem to agree that the classification boundary stops at the concrete floor slab so the slab is then covered under unclassified installations, so if I use conduit seals (to maintain the classified boundary) at the transition I can use pvc in the slab without having to adhere to the rules of the exception which are specific to pvc installed in an underground classified areas such as those found at aircraft hangers.

      Comment


        #4




        An Exception must always be interpreted in context of its primary rule; i.e., Section 501.10(A)(1)(a). In this case, this is an exception to where RMC or IMC mustnot specifically covered by those Articles.

        Unfortunately, how below grade or floor is classified becomes a judgment call. Ironically, a good case can be made for either unclassified or Division 1, but not Division 2. (Another part of the debate).

        "Bob"
        Robert B. Alexander, P.E.
        Answers based on 2017 NEC unless otherwise noted.

        Comment

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