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Thread: Conduit seal offs and explosion proof boxes

  1. #1
    Join Date
    Jun 2003
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    5,618

    Conduit seal offs and explosion proof boxes

    Wastewater from a couple of toilet rooms runs into a sealed pit (or burried tank), which has pumps to pump the wastewater back out.

    From NFPA 820, I believe the inside of the pit should be a class 1 division 1 location. Does that sound right?

    Wiring from the pumps and float switches passes through conduits to a control panel. Since the pit is Cl 1 Div 1, I specified seal-offs in the conduit runs. Those are required, right?

    What does the contractor have to put inside the seal off's? Is duct seal sufficient, or is concrete required?

    The electrical contractor would like to add a splice box between the seal-offs and the pit. Does the box have to be explosion proof??

    Thanks in advance,
    Steve

  2. #2
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,013
    Quote Originally Posted by steve66 View Post
    Wastewater from a couple of toilet rooms runs into a sealed pit (or burried tank), which has pumps to pump the wastewater back out.

    From NFPA 820, I believe the inside of the pit should be a class 1 division 1 location. Does that sound right?

    Wiring from the pumps and float switches passes through conduits to a control panel. Since the pit is Cl 1 Div 1, I specified seal-offs in the conduit runs. Those are required, right?

    What does the contractor have to put inside the seal off's? Is duct seal sufficient, or is concrete required?

    The electrical contractor would like to add a splice box between the seal-offs and the pit. Does the box have to be explosion proof??

    Thanks in advance,
    Steve
    • The location is indeed Class I, Division 1. Have you documented it properly so you know where your boundaries are? [500.4(A)]
    • Seals will be needed at the boundaries [501.15(A)(4)] and possibly the pump motors and switches [501.15(A)(1)]
    • Seals must conform to 501.15(C).(NO duct seal)
    • The splice box must be explosionproof [501.10(A)(3)] and possibly sealed[501.15(A)(1)]

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