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Thread: Water Treatment Building in Class-1, Div-2, Grp-D area

  1. #1
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    Water Treatment Building in Class-1, Div-2, Grp-D area

    Hello... I have a water treatment building that is being located in a classified area, there are no classification hazards in the building, but being that it’s in a classified area would all equipment and electrical instations in the building need to be Class-1, Div-2, Grp-D or greater? It’s a sheet metal building, to provider weather protection for equipment only and is not pressurized or have AC. Any help with this would be appreciated .... Pete GH

  2. #2
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    Simply dropping an enclosure in a Classified location generally results in the interior taking on the same classification as the surroundings as if it weren't an enclosed space.

    You have eliminated pressurization which is one acceptable protection technique. There are other options; see Section 500.7.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
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    Quote Originally Posted by rbalex View Post
    Simply dropping an enclosure in a Classified location generally results in the interior taking on the same classification as the surroundings as if it weren't an enclosed space.
    Which means no boundary and therefore no need for boundary seals associated with the building, at least, correct?

  4. #4
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    Quote Originally Posted by GoldDigger View Post
    Which means no boundary and therefore no need for boundary seals associated with the building, at least, correct?
    At the very most actually. However, unless one of the protection techniques in Section 500.7 is employed, the interior is Class I, Division 2 and the wiring and equipment must be suitable [Section 500.8(A)]. Saving a few seals is no big deal, especially when they don't need to be explosionproof.
    Last edited by rbalex; 12-02-17 at 05:20 PM.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #5
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    Quote Originally Posted by rbalex View Post
    At the very most actually. However, unless one of the protection techniques in Section 500.7 is employed, the interior is Class I, Division 2 and the wiring and equipment must be suitable [Section 500.8(A)]. Saving a few seals is no big deal, especially when they don't need to be explosionproof.
    True, but looking at the picture from a different perspective, if you were going to place the equipment there anyway, putting an enclosure around it does not make things any worse.

  6. #6
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    Quote Originally Posted by GoldDigger View Post
    True, but looking at the picture from a different perspective, if you were going to place the equipment there anyway, putting an enclosure around it does not make things any worse.
    Depending on how the enclosure "breaths" it may make no difference; however, in many cases, especially with wide temperature or other atmospheric swings, process materials can and often do condense in small enclosures and concentrate in "dead air" spaces in large enclosures. This is one of the prime dangers in Division 2. The OP's best option is proper forced ventilation. This may take a bit of HVAC expertise to determine there are no "dead air" spaces.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #7
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    Got it!

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