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Electrical Code - USA Commercial or Residential 1999 / 2002 / 2005 versions - for UNITED STATES

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  #1   IP: 70.139.49.104
Old May 29th, 2009, 07:49 PM
aggiehobbie aggiehobbie is offline
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Default Wiring for a Travel Trailer

I just recently found this site, and the expertise and help is great. So I have my first question...

I am getting ready to place a travel trailer on some property and need to get pwer to it. Therefore would like your suggestions on how to wire this up, here are the details:
* I have a 200amp box (Square D) on the power pole that I will be hooking into.
* Need to run wire from the circuit breaker box to where the trailer will be, whic is approx. 125 feet away. Need to put the wire underground.
* Would like to put a pole near the trailer where I terminate the wire and place a sub-panel or plug.
* The trailer has is typical with a 30amp plug

Questions:
1. What type breaker should I use in the main 200 amp box?
2. What type of wire should I run from the box to the trailer (undergound), should I direct bury or run conduit?
3. Should I put a sub-panel or just have the femail plug receptical on a pole next to the trailer?
4. Any other guidance or advice?

Thanks.
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  #2   IP: 76.22.81.239
Old May 29th, 2009, 08:16 PM
suemarkp suemarkp is offline
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Two choices. Do you want to wire for this trailer, or a possibly a larger one with a 50A plug (like a motorhome has).

For this trailer, you need a single pole 30A breaker in your panel. The best way to feed it is in PVC conduit buried at least 18" down. Then pull individual wires at least #10 copper (black, white, and green). But because of the distance, I'd consider pulling #8 copper wire (for all 3). If this costs too much, consider burying 8-2 UF cable at 24" down. The stubs in and out of the dirt will need to be in PVC conduit to protect it from damage (probably 1" diameter).

If you want to be prepared for a 50A motorhome, then put a double pole 50A breaker in the panel. Then run #6 in red, black, and white, and a #8 green in a 1" PVC conduit. You could choose to run 6-3 UF cable instead buried at 24" with 1.25" conduit stubs.

Both of the above setups should use the appropriate weatherproof receptacle box. If you want a "normal" 120V 20A receptacle near these trailer receptacles, then run at least what I said for the 50A circuit but put a small outdoor panel there instead. Then, a double pole 50A would go in it for the motorhome outlet, and/or a single 30A for the current trailer outlet. Then put in a single pole 20A breaker for the regular power outlet (and this receptacle must be a GFCI). This would also be best if you upsized the wire from the main panel to the trailer subpanel to #4 copper wire (all black, but put white tape on the ends of the neutral and red or blue on one of the phase wires). I'd then put a 60A or 70A double pole breaker in the main panel to feed this trailer subpanel.
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  #3   IP: 70.139.49.104
Old May 30th, 2009, 07:00 PM
aggiehobbie aggiehobbie is offline
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Mark,
Thank you for the guidance. On the 8-2 UF suggestion, should this actually be a 8-3 UF cable? I will not be upgrading to a motor home, the plan in a year or so is to build a small cabin/house. I like the idea of a larger circuit to run some other items, but will need to look at if I can justify the extra costs. I re-verified the total length today, and it looks like it is closer to 200 ft. If I stick with the 30amp circuit, is the 8 -2 (or 3?) UF cable still acceptable?

Thanks,
David
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  #4   IP: 76.22.81.239
Old May 30th, 2009, 11:51 PM
suemarkp suemarkp is offline
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A 30A trailer circuit is 120V. A 120V circuit needs 2 wires (typically black and white). You'll also need a green or bare grounding wire. So even though there are 3 wires in the jacket, this would be called 8-2 with ground.

With the length actually closer to 200', then you need to upsize to at least #6 copper. Because of the length and upsizing though, you also need to upside the grounding wire and unfortunately romex and UF cables don't upsize the grounds in #8 and #6 sizes. Another twist is if you want a second circuit along with the trailer circuit, then you can easily get that with one more wire (e.g. 8-3 instead of 8-2). If you're willing to limit yourself to 20A outlets, then 8-2 or 8-3 could work for that distance. Many trailers will work on 20A circuits if you're careful about running the airconditioning -- can't use it with anything else large like a microwave or electric water heater. A 30A plug to 20A receptacle adapter can be found at any trailer store.

So the best solution here is 1" PVC conduit with four #6 copper wires -- black, red, white, and green. Install a single pole 30A and a single pole 20A breaker in the main panel (put the black on the 20A breaker, and the red on the 30A breaker -- if the wires are too fat, put a #10 pigtail on the red and a #12 pigtail on the black). Put the white neutral and green ground on their appropriate busses (could be the same bus if a main panel).

At the post for the outlets, install the 30A and 20A side by side. Install a white #10 and #12 pigtail onto the white #6 with a wire nut. Install a green #10 and #12 pigtail onto the green #6 with a wire nut. Put a black or red #10 wire pigtail onto the #6 wire going to the 30A breaker. Put a #12 black wire pigtail onto the #6 going to the 20A breaker. Now run all the #10 pigtails to the 30A RV outlet and all the #12 pigtails to a 120V GFCI receptacle. You may also need an additional #10 green pigtail to bond the metal enclosure(s) and any metal conduits.

An 8-2 or 8-3 UF cable solution will most likely be OK, but isn't technically legal because the ground is too small.
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Last edited by suemarkp : May 30th, 2009 at 11:56 PM.
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  #5   IP: 70.139.49.104
Old May 31st, 2009, 08:01 PM
aggiehobbie aggiehobbie is offline
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Mark,
Thanks for your recommendation, very clear, will look at upgrading to the larger wire.

David
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  #6   IP: 70.139.49.104
Old June 20th, 2009, 04:26 PM
aggiehobbie aggiehobbie is offline
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Mark,
Follow-up question, I now have my RV trailer set and the distance is 150ft for the wire. So per your suggestion I am planning to run 3 #8 wires in a 1" conduit. My new question, do I have to run THWN wire, or can I use THHN? The reason I am asking is that I am having a harder time finding the THWN wire.

David
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  #7   IP: 64.83.195.10
Old June 20th, 2009, 06:58 PM
junkcollector junkcollector is offline
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I'm not Mark, but

You need to use THWN, it shouldn't be hard at all to find. Almost all wire that you can buy that is rated THHN is also dual rated THHN / THWN. A home center like home depot or such should have what you are looking for. Look what it says on the sheath.

The reason THHN cannot be used underground is it is not listed for wet locations. (That is what the W is for, as in Wet)

Good luck
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  #8   IP: 76.22.81.239
Old June 20th, 2009, 07:16 PM
suemarkp suemarkp is offline
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You also have to use the correct color wires when sized #6 and smaller. So I take it you want only one 30A receptacle installed. This would require black, white, and green #8 copper.

Carefully look at the wire you're buying. All THHN I've seen is also marked THWN and MTW. So just because the sign says THHN, it may be OK. What matters is what is stamped one the wire. You do need THWN for anything in an outside conduit.
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  #9   IP: 99.147.66.141
Old June 20th, 2009, 07:26 PM
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Harbormaster Harbormaster is offline
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Good info guys....except for the conduit size! If you're going to dig a ditch and bury conduit....may as well run a 2" for the feed to the house and at least (2) 1" conduits for land line and cable! PVC is cheap....get all you can in the ground before you cover the ditch! You can pull #4 (100 amp) feeders in a 2" conduit easily!
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  #10   IP: 70.139.49.104
Old June 20th, 2009, 07:35 PM
aggiehobbie aggiehobbie is offline
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Thanks guys, went back to the store and you were right, it is stamped on the wires as both THHN and THWN. So I am all fixed up...

Thank you!
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