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Thread: Lift Station Conduit Seal or Air gap

  1. #1
    Join Date
    Feb 2006
    Honesdale, Pa

    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
    Join Date
    Apr 2004
    Mission Viejo, CA
    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)
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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