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Thread: Classification of conduit sleeve leaving CID1 wet well.

  1. #1
    Join Date
    Apr 2017
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    Seattle, WA, USA
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    Classification of conduit sleeve leaving CID1 wet well.

    I have a project where we are using flexible cord sealed at the termination of a submersible pump in a CID1 wastewater wet well and routed to a pump control panel via a conduit sleeve. The flexible cord is listed and installed per NEC 501.10(A)(2) and 501.140.

    My question regards the classification of the area around the above ground conduit sleeve stub-up. There is no conduit seal-fitting installed, only duct seal. If the wet well is classified as CID1 per NFPA 820, with NFPA 820 - Figure A.4.2(c) used as a reference, would this stub up be treated like a vent (3' div 1 radius, 5' div 2 radius) or a hatch (3' wide x 18" high div 2 classification)

    I appreciate any help, or direction to additional reference material!

    Thanks,

    C

  2. #2
    Join Date
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    There may be some question about the “necessity” of using a flexible cord connection which permits the application of Section 501.10(A)(2) in the first place. This is especially true for using it over the entire run of the cord.

    However, assuming that it has in fact passed AHJ muster, my inclination would be to treat the sleeve as a vent especially if any other electrical equipment beside the cord is within the 3’, Division 1 envelope.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
    Join Date
    Jun 2013
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    Sounds like a vent to me. Is the wet well outside? What access is provided to pull the pump?

  4. #4
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    Apr 2017
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    Bob,
    Thank you for the reply. My initial inclination would also be to treat it as a vent, if for no other reason than to be conservative.

    I have attached a photo of an example of a pump panel providing service to a CID2 wet well. The discussion in the office is whether a similar installation could be considered for a CID1 wet well. My concern was if the conduit was considered to be analogous to a 'vent', then the panel itself would need to be 5' above the conduit to be outside the classified area. If it was considered analogous to the 'hatch', then the panel would be okay as long as it was 18" above the conduit.

    So my real question is what makes the classification of the area around the vent different than the area around the hatch? If we routed the cable into a manhole/handhole below the panel instead of using conduit, and then up to the panel - would that make a difference?

    Thanks again!


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  5. #5
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    I've not heard of a "NECA and API approved air gap"

    Where can I find this language?

  6. #6
    Join Date
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    Quote Originally Posted by WittCR View Post
    ...So my real question is what makes the classification of the area around the vent different than the area around the hatch? If we routed the cable into a manhole/handhole below the panel instead of using conduit, and then up to the panel - would that make a difference?...
    In this case I won't do all your homework, but, if you dig deep enough into the various standards, you will find much of the basis for classifying locations is based on the consensus experience of the Technical Committee involved rather than specific testing or rigorous analysis. This is especially true for specific types of installation. Each of the Standards will mention this somewhere in the body of the text. For example, NFPA 497, Section 5.7

    With respect to vents versus hatches, there is something of a Bernoulli effect anticipated and the vent is more likely to "draw" volatiles from the Division 1 location.

    I was also curious about the source of "NECA and API approved air gap". I know API (I served on all their hazardous location Tech Committees for 15 years) doesn't have one although it may be surmised from several diagrams. NECA may have one - I don't know.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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