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I need to run a 50 amp circuit (120/240V) from a shed to a travel trailer that is permanently in place.

The previous trailer had 30 amp 120V service running underground to a mounted/covered outlet under the trailer and then the standard trailer cable/plug into that.

The run is ~50 ft. Running the 30 amp 120V service was fairly straightforward (big box hardware stores have the right wired for burying). But when I start looking at 50 amp things get less straightforward (to me).

I'm assuming from a brief googling of big box stores have not resulted in any results for #6 non-conduit buriable wire. So this leads me to believe that I need to run it in conduit, but then I get concerned about heat (this may be an incorrect understanding).

We only occupy the travel trailer 2 - 3 days a week for May/Jun/Jul/Aug/Sept. Most of the days are spent outside and the AC & oven will rarely be used. (I understand that you should plan for the largest load not smallest).

Can I run 50 amp (120/240V) underground? Do I need to ground the chassis of the trailer to a 8ft grounding rod? Should I use #4 instead of #6 to reduce the heat concern?

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Both Lowes, and Home Depot advertise 6/3 UF cable, though Lowes seems to only sell it by the foot. Are you asking how to run the cable, or where you can buy it? –  Tester101 Oct 1 '13 at 14:31
    
At $4 per foot, you won't want to buy a lot of extra "just in case". Measure carefully at least three times. –  wallyk Oct 1 '13 at 16:05
    
Thank you all. It is so obvious on their pages now. Not sure how I missed it. $4/foot is crazy, but I understand why. Thanks much. –  Wayne Arthurton Oct 1 '13 at 16:10
    
Aluminum is usually far cheaper than copper. –  Jay Bazuzi Oct 2 '13 at 20:45
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If you go through the trouble of digging a trench for this new wire, bury several conduits instead of burying wire directly. You can then use them for a fresh water line, a sewer line out of a macerator, an additional circuit, telephone, ethernet, compressed air, etc. –  Jay Bazuzi Oct 2 '13 at 20:47
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1 Answer 1

up vote 10 down vote accepted

Cable

The cable you're looking for is Type UF, or Underground Feeder cable.

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It can be purchased at big orange, and big blue, by the foot. It's available in 6/2, 6/2 with ground, 6/3, and 6/3 with ground, and is rated for direct burial.

Attachment to Service

There is one temporary, and two permanent ways to supply power to a park trailer.

Temporary

Power-Supply Cord

You'll want to use a NEMA 14-50 receptacle, and 4 wire cord with NEMA 14-50 plug to connect the trailer to the service. The trailer's electrical grounding will be through the service plug, so only the distribution panel will have to be grounded.

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Permanent

Mast Weatherhead

You can use four continuously insulated, color-coded feeder conductors strung from a mast to a weatherhead as a permanent feeder.

enter image description here

Raceway

A metal raceway, rigid nonmetallic conduit, or liquidtight flexible nonmetallic conduit, from the disconnecting means to a junction box on the underside of the trailer can serve as a pathway to run permanently attached feeders.

enter image description here

NEC

For reference, park trailers are covered in article 552 of the National Electrical Code.

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Thank you. It is so obvious on their pages now. Not sure how I missed it. $4/foot is crazy, but I understand why. Thanks much. –  Wayne Arthurton Oct 1 '13 at 16:10
    
If the cable is buried does it need to also be in conduit? –  The Evil Greebo Oct 1 '13 at 16:21
    
@TheEvilGreebo No. –  Tester101 Oct 1 '13 at 16:23
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@TheEvilGreebo If you need more questions answered, please deposit another $0.25. –  Tester101 Oct 1 '13 at 16:25
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When you run it underground, it's a good idea to also bury a marker several inches above it (often a red poly tape that says something like "CAUTION: Buried electric line below"). This helps prevent anyone who is digging from hitting it. You also need to use conduit above the minimum burial depth including when it's above ground. –  gregmac Oct 1 '13 at 21:22
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