in our new house, there's a 30 amp RV outlet with an attached standard GFCI outlet on the side powered by a 20 amp breaker. The RV box has been cracked open and the GFCI receptacle is dangling off the side, wires rubbed open. Obviously, it's now off at the panel and I plan on replacing it.

While doing so, I'd like to run a wire back out of the replacement RV box and 20 feet over to a large, currently unwired shed. From what I can tell, I can run bare UF-B wiring at only 12 inches deep, assuming it's <= 20 amp (true), no more than 120 volt (true), and GFCI protected(more on that below). The last part is what I'm not sure of. The panel does not have a GFCI breaker and I'm not sure how it would be possible to introduce GFCI protection on the line to the shed. So that's my question - is it possible to have GFCI protection at the box for the replacement outlet, with the replacement RV receptable, AND INCLUDE GFCI on the line going to the shed?

I would like to be safe and run it 18 inches and in some PVC conduit. I've read various things about condensation, etc, but I can't find anything explicit forbidding this, just that THWN-2 is usually used instead.


  • Is there a reason you want to put bare UF in here? A conduit to the shed would give you far more flexibility in the future... Apr 10, 2018 at 0:02
  • I've closed the box up now, but if I recall it was standard 10/2 wire from the panel directly to the existing. I'm not an electrician and I was trying to stick to the items I'm familiar with. Likewise my local big box only had THWN-2 in large and expensive rolls, so I thought to keep it simple.
    – James F
    Apr 10, 2018 at 0:23
  • Is the RV line 120V (TT30 or NEMA 5-20)? Also stop buying from big-box and find a proper electrical supply. Big-box has convenient hours and a well lit parking lot, but they cost dearly in bad advice and are overpriced on most items. They know they gotcha, since you have no earthly idea where else to go! Apr 10, 2018 at 4:14

1 Answer 1


That's kind of a Code mess. The biggest problem is that your receptacle size must match your breaker size, with an exception that allows 15A or 20A receptacles on 20A circuits (due to a design exception in UL standards which require 15A receptacles to be rated internally for 20A).

So you have a 30A TT30(?) RV socket on a 20A breaker. Can't do that.

What you can do is whistles dixie get an adapter cable from TT30 receptacle to NEMA 5-20 plug, and fit a 5-20 receptacle (5-20 is the usual receptacle, with an extra little sideslot on the neutral.)

Now it's possible your electrician ran two separate cables, a #10 for the TT30 and a #12 or 14 for the GFCI. In that case nevermind.

Also if you have a NEMA L14-30 connector (twist lock) instead of a TT30, everything in this answer is out the window.

Feeding GFCI protection downline

Every GFCI+receptacle combo device has a pair of terminals called LOAD, that you normally do not use (or rather, should not use unless you intend to do the following). If you connect hot+neutral to that LOAD pair, and continue it to another outlet point, that outlet is also protected by the GFCI. (grounds you just continue through, GFCIs don't use ground for anything.)

So you can continue off the LOAD terminals of that GFCI+receptacle device, on to the shed. That meets the GFCI requirement.

If you place the NEMA 5-20 outdoor receptacle downline of the GFCI, that will also inherit GFCI protection to the RV. They also make 5-20 GFCIs so you can kill 2 birds with 1 stone.

I'm a big, big fan of putting GFCI devices not outdoors. I would site the GFCI+receptacle combo somewhere in the dry, then feed the outdoor receptacles, RV, shed, etc. off its LOAD terminals.

You cannot feed a 30A receptacle from a 15/20A GFCI. Adapter cables are not part of the house or RV, so are not subject to NEC rules.

Rigid only goes 6" deep but is expensive

"Rigid steel conduit" is magic conduit that only needs 6" of cover, whether it's GFCI or not. It involves a little bit of threaded pipe fitting, so you may need a trip or two to the building supply to have threads cut unless you have a friend with a Ridgid (no relation). Rigid is pretty expensive so it's best if it's not far. Cable in conduit isn't illegal, just really hard to pull. Better to use THWN-2 wires in conduit. Menards won't sell you by the foot, some others will and your friendly neighborhood electrical supply will certainly be happy to, and if you diagram out what you're doing, they'll give you correct advice.

  • This is a great response, thank you! I agree, there's probably a code mess in there - this house is a nightmare of wiring and water problems. I will do some more investigation and may end up removing the RV 30 amp outlet entirely, because I'm almost positive it's standard 30 amp box on a 20 amp line, but I will research more. I will also fit a GFCI breaker at the panel I think, but until then, I will use your GFCI chain option. Thanks again, I will continue to read/ask around at a local shop.
    – James F
    Apr 10, 2018 at 12:41

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