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Thread: Class I, Division I Seal-Off Controversy

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  1. #1
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    Class I, Division I Seal-Off Controversy

    I need your help as soon as possible.
    We have a dilemma at our current job site with installation of seal-off’s in a gas production facility at our present job site. The situation is that it is common practice to install a short within 18", a run from the seal-off, to a GUAC conduit body, on to a hazard rated union, and on to an instrument; in all, does not exceed the 18 inch maximum requirement as per NEC Art. 501.15(A)(1)(2) and 501.15(A)(3) See attached picture.
    With understanding that in NEC Art. 501.15(A)(3) first states that two or more enclosures basically have to have a seal-off within 18" of each other of not more than 36" in a conduit run and goes on to state "or run of conduit shall be considered sufficient if the seal is located not more than 450 mm (18 in) from the enclosure." Until now, our past customers in the Class I, Division I environment, ruled this installation acceptable and within guidelines.
    The reasoning on this is so that if the instrument needs to be replaced, that you can access conductors from the GUAC without damaging them. In addition, the instrument could be easily replaced without shortened or damaging branch circuit conductors, prevent possible seal-off damage and make termination readily accessible. Unfortunately, although this installation is common practice here in the gas and oil fields, the customer wages different to say that this installation is not legal.
    Please advise.
    Regards, Scooter Hoffman
    Name:  Class1_Div1 Seal-Off Controversy IMG951746.jpg
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  2. #2
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    read carefully what the last paragraph of 501.15 (A) (2) says.
    Bob

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    These are not intrinsically safe circuits?

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    Violation if a seal is required, adding the extra volume of guac adds more to the possible explosion pressure on that seal. Its like going over 18". 501.15(A)(1) last paragraph after (1)&(2)

    Also, that liquidtight isn't legal, if c1d1 like you say

  5. #5
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    Prior to the 2017 code, conduit bodies of the same trade size as the conduit were permitted between the enclosure that requires sealing and the seal fitting.
    2014 501.15(A)(1) ... Only explosionproof unions, couplings, reducers, elbows, capped elbows, and conduit bodies similar to L, T, and Cross types that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosionproof enclosure.
    That permission to install conduit bodies between the enclosure and the seal was removed in the 2017 edition of the code.
    2017 501.15(A)(1) ...Only explosionproof unions, couplings, reducers, elbows, and capped elbows that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosionproof enclosure.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

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    Thanks for clarifying

    Thanks for your support. I have read several forums relating to this issue and like the other fella's noticed in the 2017 that 'conduit bodies' was omitted compared to 2014 and not sure if it was intentional or error. It is what it is and thanks. Scooter

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