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Old 05-21-2011, 11:11 AM   #1
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50 amp RV outlet


New to site. You guys are awesome!

I'm installing a 50 amp-4 wire 120/240 volt RV outlet about 100' from the panel in my shop. I have two main questions.
1) Should the breaker for this outlet reside in the current panel or should it reside in a box with the outlet? What is the difference between the two locations other than convenience?
2) #6 or #4 wire? It is very expensive so I want safe but not more than is required. I plan to run it inside plastic electric conduit. Please avoid debating me about using conduit. My mind is made up.

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Old 05-21-2011, 11:26 AM   #2
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1) The breaker must be in the panel that feeds this outlet. The breaker must be located where the circuit originates, in order to protect the entire circuit.

2) #6 wire is fine.

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Old 05-21-2011, 02:21 PM   #3
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Thanks McSteve! I just returned from a local shop that sells electrical parts commercially. The guy there said I could use #8 all around. I am skeptical and told him so. He then said I could use #6 for the two hot legs and #8 for the ground and neutral.
My concern is that I read the following "The two 125V circuits are additive when you connect across the two hot legs. Therefore the neutral wire must carry the difference current between the two circuits." Does this mean that if one circuit is carrying a max load (RV A/C for instance) the neutral could be carrying 50 amps?

I don't think I am "connecting across the two hot legs" but not totally sure what this means. I am assuming it means when operating a 240 volt device??
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Old 05-21-2011, 02:23 PM   #4
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I forgot to ask something else. Do I have to figure the length of the RV's electrical cord in my calculation for determining wire size? This would make it a 125' run.
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Old 05-21-2011, 02:33 PM   #5
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I think #8 is good for 50A, but only if the all the connections have a 75C temperature rating. I could be mistaken. There's also voltage drop to consider with a 100-foot run. I did the math before I answered your first post, and I believe I figured that #6 would drop about 4-5 volts under a full 50A load, which is acceptable.

It seems it used to be a somewhat common practice to undersize the neutral on circuits like this, but I don't believe it to be legal. As for the ground wire, if this were a subpanel feeder, I think the ground could be #8 or maybe #10. But for a single circuit to an RV receptacle, I'm honestly not sure. Perhaps one of the pros can give a more definitive answer.
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Old 05-21-2011, 03:43 PM   #6
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50 amp RV outlet


The neutral could only carry 50A if you have L1 drawing 50a while L2 is drawing nothing.. They cancel each other out normally.


#6 Copper, or #4 Aluminum would be acceptable.

Last edited by Techy; 05-21-2011 at 03:47 PM.
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Old 05-21-2011, 03:47 PM   #7
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You might want to consider a subpanel out by the RV pad. Then you can set up for a 50A connection, 30A connection and a regular 20A duplex. Nice when people come to visit with smaller RV's or you want to do something out there with a power tool.
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Old 05-21-2011, 05:59 PM   #8
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The breaker is required to be in the sub-panel. But it is recommended by the RV manufacturers that you turn off the power before you plug in. Thus it is handy to have breaker on the power pole to disconnect instead of walking back to the sub-panel. The breaker at the power pole is a disconnect and can be any size equal to or larger than the sub-panel breaker.
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Old 05-22-2011, 01:37 AM   #9
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Quote:
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It seems it used to be a somewhat common practice to undersize the neutral on circuits like this, but I don't believe it to be legal.

This is INCORRECT. it is legal. and done for a very good reason. consider three loads in the RV: a TV 8amps on one leg, a light 1amp on the other and the AC 30amps(240v across both legs)- The two hot legs would feel 38 and 31 amps respectively and the neutral would only feel 7amps. thus it is quite a good practice and saves money. As if copper wires "feel" electricity
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Old 05-22-2011, 01:42 AM   #10
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But it is recommended by the RV manufacturers that you turn off the power before you plug in.
If you forget to turn off every thing in the RV and plug it in the plug would arc when connected as it tries to start all electrical demands in the RV. There are two ways (three) around this 1. make sure there are no connected loads 2. disconnect 3. stand back when plugging it in
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Old 05-22-2011, 08:27 AM   #11
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My thoughts:
  • Install a RV pedistal panel - 50A/30A/20A connections - $100-$150 for a surface mount unit.
  • #6 wire from the breaker panel to the RV pedistal panel.
  • 50A breaker in the main panel.
If you don't want the 30A/20A connections, then just the appropriate 50A recept and enclosure plus a disconnect switch - instead of the RV pedistal panel.
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Old 05-22-2011, 08:53 AM   #12
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IF the run is in conduit the whole way using THHN/THWN conductors, then #8 is borderline OK for the circuit conductors. #6 would give you a full load cushion.
IF there is ANY NM cable in the circuit then you must go with #6 cable.
A #10 ground is all that is required in either case.


I also like the idea of a small RV panel out there.
Something like this will have the two "standard" RV receptacles plus a standard GFI receptacle for convenience. Not bad at $165 either.
http://www.dale-electric.com/products/view/U5000-XL-75
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Old 05-22-2011, 09:42 AM   #13
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I also like the idea of a small RV panel out there.
Something like this will have the two "standard" RV receptacles plus a standard GFI receptacle for convenience. Not bad at $165 either.
http://www.dale-electric.com/products/view/U5000-XL-75

Does not this panel become a sub-panel and have to meet the grounding requirements? It looks like 3 breakers installed (1 double & 2 single pole) with 2 spaces spare.
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Old 05-22-2011, 09:53 AM   #14
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Originally Posted by Saturday Cowboy View Post
This is INCORRECT. it is legal. and done for a very good reason. consider three loads in the RV: a TV 8amps on one leg, a light 1amp on the other and the AC 30amps(240v across both legs)- The two hot legs would feel 38 and 31 amps respectively and the neutral would only feel 7amps. thus it is quite a good practice and saves money. As if copper wires "feel" electricity
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How do you feel about this?

551.73

(D) Feeder-Circuit Capacity.
Recreational vehicle site
feeder-circuit conductors shall have an ampacity not less
than the loads supplied and shall be rated not less than
30 amperes. The neutral conductors shall have an ampacity
not less than the ungrounded conductors.

Last edited by powerfactor; 05-22-2011 at 09:55 AM.
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Old 05-22-2011, 10:08 AM   #15
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Quote:
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Does not this panel become a sub-panel and have to meet the grounding requirements? It looks like 3 breakers installed (1 double & 2 single pole) with 2 spaces spare.
Yes. Sink a ground rod (not that it will do any good).

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