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I am planning an underground feeder to a barn. I am intending to direct bury instead of installing in conduit. I can find various cables (4 wire) that are rated for direct burial, but due to availability right now, I'm not finding the gauges of wires I want. I can find USE-2 wire in the correct sizes. In my reading of NEC, it seems that laying four individual wires in a trench is acceptable, but I can't find examples online of this being done. One other solution I've found is to install a URD 3 wire feeder and add a USE-2 wire in the trench for the 4th wire. Is that acceptable?

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    Definitely can't bury loose wires. Keep in mind that some of the cost of conduit is offset by easier trenching. Jan 17 at 22:06
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    @manassehkatz-Moving2Codidact I agree completely, you should post that as a answer. + Jan 17 at 22:09
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    What gauge of wire are you after for this, and why are you planning to direct bury it? Jan 17 at 23:47
  • COVID has caused a storm of novice DIY improvements, and novices love copper (or to be more precise have heard vaguely negative things about aluminum that they didn't really understand. So definitely look at aluminum if you're not... the subpanel lugs will be aluminum. Jan 18 at 2:07

2 Answers 2

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USE-2 is sold as cable, not wire, just to be clear on the terminology. It is made of stranded wires wrapped/sheathed in an impermeable cable.

I don't know of any wire types that are permitted under the NEC to bury directly in the ground (though I'm not an electrician, so I haven't ever hunted down every single option). USE and UF cable are the only types of electrical cable that I am aware of which may be directly buried; any others need to be in conduit of some kind.

I would strongly recommend you opt for PVC conduit. It is quite cheap and will allow you to fix change the wiring you have later on when you discover you want more/different power options out at your barn. Running conduit also means you don't have to dig as deeply into the ground to meet code (it requires 18 inches vs. 24 inches for direct-burial options), and will let you run THHN/THWN/XHHW wires rather than a cable, which are much easier to fish through conduit than cable such as UF or USE, even for fairly straight runs.

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    MH feeder also direct buries. If the distance isn't far, there's a strong case for Rigid Metal Conduit, only needs 6” of cover which means you can trench it with a garden trowel lol. Thread all the inline connections but use threadless couplers for the precise ones. Jan 18 at 2:08
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    +100 for the PVC conduit. You can never be sure that the cables you have is all you need, and with a PVC pipe and some empty space future you will thank you
    – Hobbamok
    Jan 18 at 8:55
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    Also, make sure you have a couple of pilot lines in the conduit. It's cheap and easy during installation and may greatly help in the future.
    – Mołot
    Jan 18 at 13:15
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    And, as cheap as conduit is (relative to trenching and to the price of the cable running through it), go big to accommodate potential future upgrades. Even if you don't upgrade it, mentioning it to a potential buyer might get a bit or a higher bid.
    – FreeMan
    Jan 18 at 17:17
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What's probably throwing you on USE-2 or URD is that, while they call it "cable", it doesn't have an outer sleeve (compare with, say, XHHW-2 or NM, which does). USE-2 is twisted so it forms a logical cable out of multiple wires. Similar wires by themselves would be sold as THWN-2, which requires conduit.

My suggestion would be to go buy 2-2-2-4 aluminum wire in USE-2 (direct burial). That's commonly used for housing applications and should be easily found (similar copper offerings are exceedingly rare or expensive of late). Otherwise, bury conduit as TylerH suggests.

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  • I think I found my answer elsewhere. So if anyone looks at this thread in the future: USE-2 wires ARE commonly available as individual wires and not just as cable, and it IS acceptable to install direct buried as individual wires. In addition, PVC conduit is not cheap now due to whatever. The conduit would cost an additional $800 for my project.
    – Seabornman
    Jan 18 at 14:34
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    @Seabornman are you 100% certain that the conduit plus individual wires (consider aluminum, not just copper) are more expensive than the USE-2 cable you're looking at? Include the added expense of the additional trenching depth required for direct burial over conduit, and the added expense of digging it back up to repair/replace it in the future if there is ever damage and/or your needs ever change.
    – FreeMan
    Jan 18 at 17:25
  • I own a backhoe. I can bury as deep as I want. 2" PVC conduit is $3/ft right now, 4 times what it was, and more than the cost of the wire. $800 for conduit isn't in the plan. As far as digging up in future to repair, that's not happening in my lifetime, so that's someone else's problem.
    – Seabornman
    Jan 18 at 18:15
  • @FreeMan Even 1-1/4" PVC is $2/ft now... it's a bit crazy. The supply chain is still reeling.
    – J...
    Jan 18 at 20:19
  • And buried USE-2 isn't really uncommon in neighborhoods with underground wiring
    – Machavity
    Jan 18 at 20:55

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