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Thread: Lift Station Conduit Seal or Air gap

  1. #1
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    Lift Station Conduit Seal or Air gap

    I've seen lift stations with conduit seals installed at the boundary of a C1D1 area and lift stations without seals using a 24in air gap before connecting to a enclosure. I'm thinking the C1D1 ends at the conduit leaving the station boundary(grade) and the air gap creates a unclassified area outside of 24in.

    My question is where does the documentation allowing for a air gap come from and what authority allows this type of installation in place of NEC requirements for seal placement in classified areas. I've seen jobs engineered both ways but only have the NEC to reference on my responsibilities as a contractor.

    Any thoughts would be appreciated. Thanks

  2. #2
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    If the source of one end of the conduit run is in Division 1, Section 501.15(A)(4) requires a boundary seal - period. The Exceptions, such as they are, are for a few rare cases where both ends are in unclassified locations and the raceway is unbroken OR where they are describing the permitted location of the seal for an underground installation but an "air gap" is never permitted.

    If the source is in Division 2 and it terminates in an unclassified location, Section 501.15(B), Exception No 2 has some rather detailed and convoluted provisions for an "air gap". (I'm rather embarrassed to admit that I proposed part of the original version of that Exception to the API for support)
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
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    air gap

    Would this application Meet 501.15 (B) (2) ex 2.? This is a typical installation that is mainly for maintenance reasons. Some applications have a cored hole in the top of the pump station, with the cords running in free air to a termination cabinet. This would eliminate the need for a seal leaving the C1D1 being we don't have a raceway. I think at this point the area is reclassified C1D2 allowing for this application.

    I just don't know if it meets code, but I see this all the time and I've installed this design.
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  4. #4
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    Quote Originally Posted by Al Pike View Post
    ...
    This would eliminate the need for a seal leaving the C1D1 being we don't have a raceway.
    ...
    Not quite - you just moved your problem from Section 501.15 (sealing) to Section 501.10 (wiring methods); i.e., what recognized Class I, Division 1 wiring method are you using? IMPORTANT: Section 501.10(A)(2) does NOT apply since the flexible wiring is for convenience rather than necessity.

    Your diagram doesn't clearly indicate the various location boundaries. Oddly enough, the apparent success of this type installation may (ONLY may) warrant reviewing the area classification(s). See NFPA 496 (2017 Edition) Section 5.6.4 for example.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #5
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    Quote Originally Posted by rbalex View Post
    Not quite - you just moved your problem from Section 501.15 (sealing) to Section 501.10 (wiring methods); i.e., what recognized Class I, Division 1 wiring method are you using?
    The cords are the only C1D1 wiring. I don't see where cords are approved in 501.10, but I'm not sure if the cords are a wiring method being they're part of the pump apparatus and have to terminate somewhere.

    The wireway is out of the classification and the conduits from the wireway pass through the C1D2 unbroken.

    I feel the area above the pump station needs reclassification to proceed with this type of install.
    Last edited by rbalex; 11-07-17 at 09:02 AM. Reason: Cleaned up the “Quote”

  6. #6
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    Quote Originally Posted by Al Pike View Post
    The cords are the only C1D1 wiring. I don't see where cords are approved in 501.10, but I'm not sure if the cords are a wiring method being they're part of the pump apparatus and have to terminate somewhere.

    The wireway is out of the classification and the conduits from the wireway pass through the C1D2 unbroken.

    I feel the area above the pump station needs reclassification to proceed with this type of install.
    I’m sorry, but so far you haven’t described a Code compliant installation. Whether the cords are part of the pump assembly or not they still need to be in a raceway unless they can be shown to be compliant with Sections 501.10(A)(2) and 501.140. Then they would still need to be sealed in accordance with Section 501.15(D).

    Section 501.15(B)(2) Exception 2 only applies to a Division 2/unclassified boundary; you still have a Division 1/Division 2 boundary unless you can figure out how to validly reclassify the Division 1 location.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #7
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    are the pump mfr, float mfg cables sunlight and weather resistant?

  8. #8
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    Quote Originally Posted by drktmplr12 View Post
    are the pump mfr, float mfg cables sunlight and weather resistant?
    Assuming the cables are sunlight and weather resistant, how would that make the installation as described so far Code compliant?
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  9. #9
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    Quote Originally Posted by rbalex View Post
    Assuming the cables are sunlight and weather resistant, how would that make the installation as described so far Code compliant?
    op seems to have disappeared. i was getting at-if those aren't/can't be listed as such you would be in violation no matter how you fly the cables. the question of classification boundaries still exists.

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