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Thread: NEMA 12 for Class II Division 2 Group G

  1. #1
    Join Date
    Apr 2004
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    Cool NEMA 12 for Class II Division 2 Group G

    I cannot find any reliable source to come out and specifically say that NEMA 12 or NEMA 4 enclosures are suitable for use in Class II Division 2 Group G environments.

    I recognize that temperature limitation will always apply, however dust accumulations are not permitted in a Division 2 environment. If dust accumulations do occur, then it would be a Division 1 environment and that is not what I am asking about.

    Can anyone help me clarify this? I would like some document that I can reference in this case. I know that NEMA classifies NEMA 6, 4, and 12 as dust tight, but is that official enough for a AHJ?

  2. #2
    Join Date
    Aug 2004
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    Take a look at 500.8 (A) (3) and 502.115 (B) and 502.135(B).

    Dust accumulation is mostly about housekeeping and not about installed equipment.
    Bob

  3. #3
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    The NEMA reference should be good enough for an AHJ, but if it isn't the UL Whitebook Category Code (AALZ) ELECTRICAL EQUIPMENT FOR USE IN ORDINARY LOCATIONS states:
    A Type 3, 3S, 5, 12K, or 13 enclosure may be marked ‘‘Dusttight’’
    Note it is a general permissive, the mark may or may not be there but it is nevertheless permitted just for being one of the "Types."
    At one time NEMA 250 and UL 50 were virtually identical. They have departed recently with the UL recogniation of IEC equipment.
    Last edited by rbalex; 06-17-09 at 07:14 PM.
    "Bob"
    Robert B. Alexander, P.E.
    "I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)

  4. #4
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    Jul 2009
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    I would say no, NEMA 4/12 isnt classified for the area. NEMA 9 would seem to suite your needs.

  5. #5
    Join Date
    Dec 2003
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    126
    we use NEMA 4 enclosures in our class 2 div 2 areas.
    we either purge them or pressurize them.

    take a look at 500.7(d).

    regards,
    james

  6. #6
    Join Date
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    Quote Originally Posted by cndguy View Post
    I would say no, NEMA 4/12 isnt classified for the area. NEMA 9 would seem to suite your needs.
    If Article 502 calls for "Dusttight" such as it does in 502.10(A)(4) or 502.10(B)(4), then NEMA Types 3, 3S, 5, 12K, or 13 are adequate - even in Division 1 depending on the application and constuction details. Section 502.10(A)(4) identifies where more rigorous requirements may be necessary in Division 1.

    NEMA Type 9 is required where a "Dust-ignitionproof" enclosure is specified.
    Last edited by rbalex; 07-13-09 at 03:19 PM.
    "Bob"
    Robert B. Alexander, P.E.
    "I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)

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