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Thread: Electrical Code, buried cable question

  1. #1
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    Question Electrical Code, buried cable question

    I have a couple electrical code problems that need to be fixed. One that is simple to ask about is this. I have a buried UF cable running from the house to a shed. The cable should have been run in conduit from the opening in the side of the house down into the ground at least 24-inches. Is there a product that can be used to properly protect this cable without cutting it, something that can be put over the cable, or wrapped around it?

    If you do good on this one, I have more complicated questions

    Thanks...

  2. #2
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    So you are saying the UF cable is perfectly visible and non-protected as it leaves your house and then enters the ground?

    I'm far from a code expert but could you buy some schedule 80 oversized, split it lengthwise, and then work it around the exposed cable? In fact, I'm sure you can do this but will it pass inspection? Could you simply box in the cable with plywood? Bolt a couple pieces of wood around the cable and then slip a simple plywood box around it, secure it to the wood, paint it to match the house?

    I know UF is solid and very stiff to work with but is disconnecting it a real bear?

    There is my shot.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  3. #3
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    Without cutting the cable - yeah ... disconnect it from the feeding panelboard, pull it out, slip a section of Schedule 80 conduit over it (appropriate size of course) and reconnect the cable to the panelboard.

    That meets your criteria of "properly protect this cable without cutting it", although that would be a bit of a nuisance to do.

    Chris' idea of boxing in the cable is an interesting one. I'd ask your local AHJ (Authority Having Jurisdiction) if that would be acceptable. One issue is that the wood would need to be buried 24" deep and that, to me, is like building a critter highway for termites.

    = = = = = = = = = = = = = =

    The sleeving to protect the UF only needs to go 18" below grade - not 24". The code section is 300.5(D)(1).
    Last edited by Rob Russell; 02-21-2008 at 8:16 AM. Reason: Correct information

  4. #4
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    Ah, I neglected to consider the 2' of burial depth. Plastic is termite proof! Pressure-treated could be used...or that plastic/milk-jug "wood" as well.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  5. #5
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    Quote Originally Posted by Chris Padilla View Post
    Ah, I neglected to consider the 2' of burial depth. Plastic is termite proof! Pressure-treated could be used...or that plastic/milk-jug "wood" as well.
    Wouldn't termites just crawl up whatever is buried and keep on going until they hit munchable stuff? They build tunnels up concrete. We put the metal flashing termite shields on our addition to keep them from getting to the wood.

  6. #6
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    I am no exterminator, Rob! LOL...I don't even play one on TV!! I guess it all depends on the type of siding on your house and any exposed wood you might have that they could build a tunnel to, I suppose. I heard some termites have wings, too, and can fly up to exposed wood on second/third stories!
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  7. #7
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    Thanks for trying...

    Many times the easiest way is just to go ahead and do it right. The only two options I could come up with were, as Chris suggested, try to split a condolet and piece of pvc conduit and work it in there or pull the wire back and properly install the pvc and condolet, as Rob was saying. I don't believe anything not made for the purpose, i.e. wood, would be viewed as acceptable.

    If I can find a couple inches of slack anywhere between the panel and the wire outside, I guess I'll go ahead and try to re-run it.

    Anyone know if a sub panel is needed in an out building? By needed, I mean needed by code? I was running a 40 amp line to the shed with a sub panel. The sub panel is improperly wired. It has only 3 conductors instead of 4. I figure I can 'fix it' by simply making the shed run on 110v only from a 20 amp breaker in the main panel and make the sub panel into just a junction box (no breakers) That would reduce the available power out there to lights and a couple outlets but I think it would meet code. The sub panel would no longer be a sub panel per se, just a big junction box.

    Any thoughts?

    Regards...

  8. #8
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    At least here in the Bay Area, I can say for sure that a sub-panel is NOT NECESSARILY needed when feeding a line from say your house panel to say, a shed that you want some electricity in. I've done this and it was fine. I tapped off a 15-A circuit and put two outlets and a light in one of my sheds...no problem.

    I have NO CLUE if you can simply turn a breaker box into a juntion box but if you gut it enough so it has no chance (or is difficult) to be turned back into a breaker box, it seems to me it would be okay.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  9. #9
    You can use a three-wire feed if there aren't any other metal pathways between the buildings (water line, cable tv, phone, etc). If there are any other metal pathways (or you intend to install them) then a four wire feed including hot, hot, neutral, and ground is required. You'll need a driven ground for a subpanel on an accessory building. If your area has adopted the 2008 NEC, a four wire feed would be required.
    Last edited by Ernie Starnes; 02-20-2008 at 1:46 PM.

  10. #10

    chedule # 40 Conduit

    I recently ran 200 feet of # 2, four wire underground from my home to my new workshop. Since this is an extremely rocky area, its necessary to use conduit around e- wire to prevent eventual degrading of the insulation around your underground cable. I used schedule # 40 conduit from Lowes ($3.18 for a 10 foot section) and lay the cable/conduit at 24" depth. You have to use UL rated (Underground rated) cable even if its sealed inside conduit. I had to cross a gravel driveway so I elected to use galvanized 1 1/2" conduit where the conduit would be subjected to vehicle traffic. Seal the joints between sections after installation and use wire lubricant to put the cable inside the conduit. .Extra expense but well worth the extra cost.

  11. #11
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    If you have enough slack, can you add a waterproof junction box at the house? You could cut the wire, add your conduit, and reconnect inside the box. If not, ask if an oversized pipe cut in half length wise, slipped around the pipe, and then held together with pipe clamps would be code.
    As far as termites, I'd think that they could also tunnel inside the pipe too, but maybe the mud for their tunnels won't stick to the PVC pipe? Jim.
    Last edited by Jim O'Dell; 02-20-2008 at 7:43 PM. Reason: spelling
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  12. #12
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    Bill
    You may want to check out this product as it would allow you to encase the wire without removing it. This doesn't solve your problem of the condulet but with a fine saw and super glue hmmmmm.http://www.conduitrepair.com/ Hope this helps
    Dave

  13. #13
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    Honestly I would just dig the trench and run the cable through conduit like it should be. Splitting a conduit will only allow water to leak in lay against it anyway.

    Conduit keeps accidental cutting when digging, but around here it keeps the moles from chomping into it!

    Anyway, I suspect it would be cheaper to use regular pvc conduit rather than buying something special to go around it. PVC conduit is only $1.50 or so for 10 feet around here.
    One good turn deserves another

  14. #14
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    call your local inspector and ask what the local requirements are. he works for the government which is almost like he works for you.

  15. #15
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    Split conduit

    Yes they do make split conduit.

    http://www.innerduct.com/products/split_pvc.php

    Residential direct buried is 18".

    It's only 12" if it's 120v or less, 20amp max. with GFCI protection.

    The UF cable only needs protection down to 18" below grade. I would see if you can find enough slack in the cable and use the correct fittings to do it right.

    Rob D.

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