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Thread: 501.10(A)(3) 501.15(A)(1) Factory Sealed PB Control Stations - Class I, Division 1

  1. #1
    Join Date
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    501.10(A)(3) 501.15(A)(1) Factory Sealed PB Control Stations - Class I, Division 1

    Art 501.10(A)(3) states "All boxes and fittings shall be approved for Class I, Division 1"
    To me, this means Nema 7 construction or equivalent.

    Art 501.15(A)(1) Exception states basically conduit seals shall not be required entering enclosures where the switch, CB, fuse etc, is enclosed within a factory sealed explosionproof chamber located within the enclosure.

    Therefore as long as the enclosure is explosionproof (e.g. Nema 7) in this case, a start-stop pushbutton control station, and contains has a factory sealed contact block, a conduit seal is NOT required.

    Please confirm.

  2. #2
    Join Date
    Apr 2004
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    Mission Viejo, CA
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    Your conclusion is correct, but you should review the definition of approved in Article 100. There are other protection techniques in Section 500.7 that are suitable [Section 500.8(A)] for Division 1 but are not necessarily explosionproof.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
    Join Date
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    Maryland
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    Quote Originally Posted by rbalex View Post
    Your conclusion is correct, but you should review the definition of approved in Article 100. There are other protection techniques in Section 500.7 that are suitable [Section 500.8(A)] for Division 1 but are not necessarily explosionproof.

    Will do, thanks Bob!

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