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Thread: Underground conduit and pull-box questions

  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.

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    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

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    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.

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    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.

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    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.

  7. #7
    DIY Junior Member charp's Avatar
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    Googling results in all kinds of random images, not many that are helpful! I talked to a commercial electrician today so now I know what to do. I had to locate the existing underground conduit which I eventually found with a digging bar, the resulting crack in the 2" ABS conduit produced a 6" mini geyser. Is it a good idea to run a drain to daylight and/or spray some expanding foam into the end of the conduit that will go under the house to the panel?
    Last edited by charp; 10-03-2011 at 08:24 PM.

  8. #8
    Electrician ActionDave's Avatar
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    I would not run a drain. I would make a weep hole in the lowest section.

    Spray foam does not hurt, but as has been said you will never have a water proof conduit.

  9. #9
    Electrical Contractor/Instructor jwelectric's Avatar
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    Never and I repeat never use spray foam in conduit use Duck Seal only.

    There is no such thing as ABS concuit.

    Edited to add

    Anything you put around electrical conductors or cables must be listed for the purpose or application. I have seen caulking installed in conduit supplying walk-in coolers that destroyed the insulation on the conductors resulting in a fault situation.
    Last edited by jwelectric; 10-04-2011 at 10:41 AM.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Condenstion comes from moist air being "chilled". IF there is NOT air movement in the conduit, there can be NO condensation. I have installed MANY conduits which did NOT fill with water. And since ONLY "W" rated conductors are "wet", the wires in a "flooded conduit" would have to be THWN or similar.
    Last edited by hj; 10-04-2011 at 03:40 PM.
    Licensed residential and commercial plumber

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    Living in the desert is different than situations where the water table is near the surface.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    DIY Junior Member charp's Avatar
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    "There is no such thing as ABS concuit"

    All I know is that the plastic conduit is black. I guess it could be poly pipe? It was installed in the late 1970s. Also, the ground is in it's own smaller diameter black conduit.

    Is there a minimum depth for the service conductor inside the "Christy" box?
    Last edited by charp; 10-04-2011 at 07:21 PM.

  13. #13
    Electrical Contractor/Instructor jwelectric's Avatar
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    There is not now nor has there ever been ABS (black) conduit. The grounding conductor is required to be installed in the same raceway as the ungrounded conductors.

    If you are doing all this because there is a split in the black pipe, don’t waste your time and money. Leave it alone.

  14. #14
    Electrical Contractor Jim Port's Avatar
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    The black ABS pipe was for plumbing, not for use as an electrical conduit.

  15. #15
    General Engineering Contractor ballvalve's Avatar
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    When some clown puts wires in an abs pipe it becomes conduit.

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