Electrical – run a 50 amp circuit underground

electricalundergroundwiring

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?

Best Answer

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.

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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.

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NEC

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