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Thread: Underground conduit and pull-box questions

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  1. #1
    DIY Junior Member charp's Avatar
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    Default Underground conduit and pull-box questions

    Can the service conductors, neutral and ground be run in the same conduit?
    What is the minimum radius for bends in 3" conduit with 4/0 aluminum service conductor?
    Any pictures or diagram of a pull-box? What keeps the conduits from filling with water? How close to the lid are the conductors?

    Thanks

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    All conductors of the same circuit must be in the same conduit. There is no way to keep water out of conduit either underground or on the surface. Google underground boxes and you will find there are thousands of them.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    quote; There is no way to keep water out of conduit either underground or on the surface.

    Really? You mean it is IMPOSSIBLE? Then all those sealing methods used to do it are useless? Seems like people have been doing a lot of wasted effort in that case. Or maybe you are not fastening the pipes together tightly. IF you purchase your elbows, they will have the proper radius, however you can also get longer radius bends if you wish to have an easier time with the pull and have the space.
    Last edited by hj; 10-03-2011 at 06:15 AM.
    Licensed residential and commercial plumber

  4. #4
    Nuclear Engineer nukeman's Avatar
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    I think jw is talking about condensation and that conduit is considered a "wet location" and the wiring used needs to be rated as such.

  5. #5
    Electrical Contractor/Instructor jwelectric's Avatar
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    Typical question from a plumber and I have one that most plumbers hesitate when asked. Are plumbing pipes designed to keep water in or out?

    No pipe weather plumbing or electrical will keep water out. Seals are installed to slow the mitigation of gases not water in an electrical system. I seal one end or the other for a pipe entering an underground installation to keep methane from entering the enclosure not to keep water out where pipe is installed with direct burial conductors.
    Sealing compound is used when going from a cold to hot environment to keep condensation down. We don’t use check valves and flow meters in electrical wiring.

  6. #6
    General Engineering Contractor ballvalve's Avatar
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    Most conduit I cut into is water filled. I have run pump wires INSIDE the drop pipe.

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