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Thread: Seal location

  1. #1
    Join Date
    Feb 2006
    Location
    Honesdale, Pa
    Posts
    54

    Seal location

    A Client wants me to install conduits from a C1D1 wet well encased in concrete to above grade. Once it leaves grade we have 2ft exposed with a union to connect the conduit to an explosion proof enclosure. The seals are to be installed after the enclosure before it routes to the control panel.

    501.15(A)(4) 4) Class I, Division 1 Boundary. A conduit seal shall be required in each conduit run leaving a Division 1 location. The sealing fitting shall be permitted to be installed on either side of the boundary within 3.05 m (10 ft) of the boundary, and it shall be designed and installed to minimize the amount of gas or vapor within the portion of the conduit installed in the Division 1 location that can be communicated beyond the seal. The conduit run between the conduit seal and the point at which the conduit leaves the Division 1 location shall contain no union, coupling, box, or other fitting except for a listed explosion proof reducer installed at the conduit seal.

    Am I reading this wrong? I cant find a exception allowing this installation. I've voiced my concerns and was informed that all of their pump stations are done this way.

    Thanks for all replies.

  2. #2
    Join Date
    Sep 2016
    Location
    Longmont, CO
    Posts
    167
    Quote Originally Posted by Al Pike View Post
    A Client wants me to install conduits from a C1D1 wet well encased in concrete to above grade. Once it leaves grade we have 2ft exposed with a union to connect the conduit to an explosion proof enclosure. The seals are to be installed after the enclosure before it routes to the control panel.

    501.15(A)(4) 4) Class I, Division 1 Boundary. A conduit seal shall be required in each conduit run leaving a Division 1 location. The sealing fitting shall be permitted to be installed on either side of the boundary within 3.05 m (10 ft) of the boundary, and it shall be designed and installed to minimize the amount of gas or vapor within the portion of the conduit installed in the Division 1 location that can be communicated beyond the seal. The conduit run between the conduit seal and the point at which the conduit leaves the Division 1 location shall contain no union, coupling, box, or other fitting except for a listed explosion proof reducer installed at the conduit seal.

    Am I reading this wrong? I cant find a exception allowing this installation. I've voiced my concerns and was informed that all of their pump stations are done this way.

    Thanks for all replies.
    What is the classification above grade? Assuming it is CID2 or unclassified, the seal off would need to be the first fitting above grade, other than an RB. You are reading it correctly as far as I know.

  3. #3
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    15,578
    why is the box XP?
    Bob

  4. #4
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,878
    Usually, when someone else has "taken up the gauntlet" and given a good response I try not to interfere. So, to make it clear, I endorse the two previous responses.

    Jim1959 correctly says nothing should be between the seal and the boundary except possibly an explosionproof reducer. petersonra correctly asks why is the box explosionproof.

    Basically nothing in your description, including, "We've always done it this way", makes the installation Code compliant. So far, they may have just been lucky OR they have been wasting a great deal of money on an unnecessary explosionproof enclosure.

    The opening sentence of Section 501.15, IN No. 1 gives the basic purpose of sealing:

    Seals are provided in conduit and cable systems to minimize the passage of gases and vapors and prevent the passage of flames from one portion of the electrical installation to another through the conduit.
    What you described doesn't do that. Threaded connections can and do "leak" (regularly by design). The installation you describe gives an excellent path for "the passage of gases and vapors ... from one portion of the electrical installation to another through the conduit." In this particular description, a flame path is not too serious since it sounds like the installation will contain it - BUT, unless the surrounding installation is at least Class I, Division 2 there is a distinct possibility that material from the Division 1 location could be ignited by equipment external to the installation.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #5
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
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    4,878
    Sorry I just noted PA is on the 2008 NEC. In that case, the reference should be to FPN No. 1; the content is the same.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  6. #6
    Join Date
    Feb 2006
    Location
    Honesdale, Pa
    Posts
    54
    Thanks for the replies. I don't know why it was designed this way or how the existing pump stations passed inspections but I'm only concerned about our work. I intend to install the seals before the $3k useless enclosure and call it a day.

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