Brothers' Son in law is coming to visit the lake cabin. He is borrowing a camper and I have to provide power to it by next weekend. I don't know if he needs 120 or 240 volts but I do know it is 30 amps. I think that I can park him within 100 feet of the fuse panel but am confused about the plug shapes for the outlets. I went up to the local RV store but they were closed for Independence Day. However I did take a photo of a camper's power in plug thingy.
What do I need to feed his camper? I have space for a Eaton CH (Cutler Hammer) style 30 amp 120 volt circuit breaker or 240 if needed.
I have a 100' 12ga 3 wire plus ground if I could provide power with only 20 amps, otherwise I will need $175 100 feet of 10 gauge wire. I assume the biggest power draw will be the air conditioning and maybe if I can keep them from to cooking, 20 amp would be enough. 
Random camper on the RV lot.
Goggle 30RV extension cord. That will show you what he will have on the end of his 120v/30A cord.
If that unit is 50 amps it is probably a two A/C unit. If they don't use the second A/C or the microwave they could run easily on 30 amps. 12 Gauge wire won't do it. 10 Gauge would for 30A. It will need a 220v circuit because the RV divides the 220v into two 110v legs. So if you provide only 110v half of the stuff in the RV won't power up. Then you only need 10 gauge from your 30A breaker to their 30A cord. Build an extension cord from your panel to a 30A female outlet and you are good to go. Do it all the time. In your case you don't need to convert from 50 to 30. easy peasy.
Of course the side of my shop has a 50A outlet... then folks visiting with 30A units need the 30A to 50A converter... many already have them on board. Rental unit usallly don't have all those extra adapters.
In reply to Purple Frog :
The nice thing is that he asked for 30A. Which is only 120v/30a.
you are correct! My bad. Still 10 gauge needed. Might still get a little warm at 100 feet.
SV reX
MegaDork
7/4/24 10:20 p.m.
RVs are not 240V. They are 120V. Even when they are 50A.
Thanks guys. I only have 100 amps to start with so we will have to ration electricity usage, turn the water heaters off when the oven is running and such.
In reply to VolvoHeretic :
If they don't use microwave you probably could get away with 20 A. The A/C will get close to 20A only when it starts. I have run a 50A big RV on a 110V 15A circuit overnight on occasion. Most new units have LED lighting that lessens the load.
SV reX said:
RVs are not 240V. They are 120V. Even when they are 50A.
You're correct, much like a dryer isn't 240... even though it's 240.
The RV doesn't have any 240v appliances, but it's easier to supply two 120v legs to get the juice instead of trying to get 50A at 120v through a conductor.
Fortunately, you just need a 10-ga supply hooked to a single pole 30A breaker. Alphadriver has you on the right track.
This is of interest to me. After my house burned I am going to have it rewired and add a recepticle next to the garage to plug my motorhome into. It's an old Dodge with a 20 amp system but since this is being done from scratch is there any advantage to wiring it for 50 amps even though only a 20 amp motorhome is being plugged in. Since this is a permanent plug, I may upgrade the motorhome or even replace it with a different one someday so I am thinking long term here.
I am also looking at RV microwaves. Do they draw fewer amps that regualar microwaves. Can you buy a smaller microwave that uses fewer amps.
In reply to Snowdoggie (Forum Supporter) :
The big question to wire for capability, sure. But 50a is double wired. When at home, I have never once come close to using full rated power, but we don't camp at home, too. If you are sure, sure, sure you will never, ever use the power, you can get converters from 20a up to at least a 30a plug (we have one for home). I'd wager 50a exists, too.
One thing to consider, this new, high output, outlet can be used for other things, too. Like a welder. I have my camper plugged into my welder outlet.
In reply to alfadriver :
I could see using a welder next to the garage.
SV reX
MegaDork
7/5/24 9:23 p.m.
In reply to VolvoHeretic :
There's some stuff in the thread that is electrically incorrect, but the answer you've got for your question is correct. Your visitor needs a 30A 120V outlet. His camper will run on a single 20A circuit, but not with the AC. You can't run the 30A circuit on 12 ga wire. You need 10 ga.
One other thing... it's highly likely your 100A service will be fine feeding the 30A circuit (because it is based on load, and it is highly unlikely you will ever pull more than 100A at one time).
50A RV outlets are 240V, but RVs never are. The 50A plug is identical to the feed coming into a home. It is 2 separate 120V hot legs and a neutral. In your home, those 2 legs can be combined to deliver 240V. The RV panel does not allow combining the 2 legs- they are kept separate in 2 separate 120V legs. The reason they are wired as 240V at the plug is to insure that the 2 separate legs are opposite phase from each other. The 2 120V legs share a neutral. If you tried to bring 50A in on a single 120V circuit it wouldn't work- 1/2 the panel would be electrically out of phase.
A 30A RV can be plugged into a 50A plug with an adapter. A 50A RV can't be plugged into a 30A plug- there isn't a 2nd hot leg, so half of the panel would be out of phase.
The RV doesn't "split" the 240V. It just never combines the 2 legs at all (unlike your house, which does).
Curtis: not sure what you meant about dryers not being 240V. As far as I know, the motors and heating elements are wired for 240V, not 120V. They don't work in RVs.
As an opinion, I find it bad that RV ac systems need the 30a service. I'm running a unit in my trailer right now that uses less than 10a. And I know of better ones out there.
And the one rental we had that had a roof mounted ac system sucked really bad.
But that isn't important to the question.
The A/C doesn't require 30A. Maybe it starts at ~13A, runs at less than 10A. But, if you are trying to run everything in the unit (lights, A/C, microwave, etc.) at the same time you need 30A.
In reply to Purple Frog :
Mine does not surge past 10a. So.
Fwiw our 26' RV came with an adaptor to plug the 30A RV lead into a 15A outlet. I run it through a standard orange extension cord into the garage & am able to run the A/C without any problems.
SV reX
MegaDork
7/6/24 9:45 a.m.
In reply to alfadriver :
No.
Because the two hot legs will be 180 degrees out of phase with each other they are actually able to provide 50 amps of 120VAC per leg.
I don't think any RV would ever pull that much, but that's how they are wired.
Its also what makes an RV plug useful as a power source for a welder. 😊
In reply to SV reX :
Every dryer I've serviced used one 120v leg for the heater and one 120v for the motor/controls. I haven't repaired more than 6 or 8, but it's been true every time I tore into one.
SV reX
MegaDork
7/7/24 6:25 p.m.
In reply to Curtis73 (Forum Supporter) :
Huh. Seems odd.
I wonder why none of them ever have convenience outlets...
And older ones don't have a neutral. Just 2 hot legs and a ground....
In reply to Curtis73 (Forum Supporter) :
I'm at about the same number of repairs - maybe a bit older machines.
120VAC motors / 240 heating elements.
(Will still turn, but not heat, is a indication of bad wireing. )
In reply to SV reX :
I always assumed it was easier than leg-jacking because the heating element doesn't need a ton of wattage for the small space.
