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Discussion Starter #1
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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Mad Scientist
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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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Discussion Starter #3
Follow up question

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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Discussion Starter #4
Adding RV electric cord to calculation

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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Mad Scientist
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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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Sparky
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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.
 

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yeah, right
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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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A "Handy Husband"
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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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Scared Electrician
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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:laughing:
 
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Scared Electrician
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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:laughing:
 

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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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Licensed Electrical Cont.
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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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A "Handy Husband"
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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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Electromagician
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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:laughing:
Cowboy
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.
 

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Licensed Electrical Cont.
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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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A "Handy Husband"
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He says it is 100 feet from the panel.

"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."

So I assumed that it is remote from the building but I guess it could be a very large building.

Interesting issue though:
If the RV box is mounted on the outside of the building , no ground rod required. If you put it on a post a foot away from the building, a ground rod would be required:)
 
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Licensed Electrical Cont.
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I'm with rjniles. I think it is a safe assumption since it is 100' away.

If not then that is one big a** shop. :whistling2:
 

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Agreed, I think it's also detached - due to the distance comment and desire for conduit. But it could be a large workshop, metal out-building, farm building, etc. So thought I would point it out for completeness.
 

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Scared Electrician
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Cowboy
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.
Thank You
 
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