50 Amp Usage Question

[JimBollman]

I occasionally have friends visit and stay in their camper. I have installed a 35 amp RV box by the back driveway. I also have a 4 wire 20 amp 220 outlet by my carport for an emergency generator which also acts as two 110v circuits with an adapter which is how I normally use it.

I have never owned an RV with 50 amp service so the question is if you had the choice of plugging into 220v 20 amp or 110v 30 amp, which would better serve your needs? I plan to pick up an adapter for the 220v 20 amp if it would be better for a visiting RV if it would be used. I figure they would have an adapter for the 30 amp since it is a standard RV outlet.

[CA_Traveler]

OP Your adapter will not work with a GFCI plug. The code requires that outside GFCI plugs be GFCI protected.

[CA_Traveler]

dodge guy wrote:
Look at the wiring of a 50A RV outlet. It is not 240V! Now you can wire in 240 after the panel in the RV. But coming in, no it’s 2 120V 50A circuits. Just adding up the voltage does not make it 240!

Dodge guy that is incorrect.

It's a 120/240V 50A 4 wire circuit. The very same circuit used in virtually every house in the US except they are 100A or more.

Granted very few 50A RVs have 240V appliances but some do.

[ScottG]

dodge guy wrote:

ScottG wrote:

dodge guy wrote:
Well first off you can’t use a 220V circuit on a 50A RV!
Second higher amps is always the better way to go.
But since you’re wiring everything, why not just run a couple 50A RV services with a 30A RV outlet.

Every 50A RV has 240VAC coming into it but it's then separated into two 120VAC circuits.

Look at the wiring of a 50A RV outlet. It is not 240V! Now you can wire in 240 after the panel in the RV. But coming in, no it’s 2 120V 50A circuits. Just adding up the voltage does not make it 240!

I'm sorry but you just don't understand what this circuit is. It's simply a 240VAC range outlet. It does measure 240 across in your RV's panel and yes, adding up two 120VAC circuits that are on opposite sides of a split phase does give you 240V.
Maybe we're just getting stuck in semantics here..

[dodge_guy]

ScottG wrote:

dodge guy wrote:
Well first off you can’t use a 220V circuit on a 50A RV!
Second higher amps is always the better way to go.
But since you’re wiring everything, why not just run a couple 50A RV services with a 30A RV outlet.

Every 50A RV has 240VAC coming into it but it's then separated into two 120VAC circuits.

Look at the wiring of a 50A RV outlet. It is not 240V! Now you can wire in 240 after the panel in the RV. But coming in, no it’s 2 120V 50A circuits. Just adding up the voltage does not make it 240!

[ScottG]

dodge guy wrote:
Well first off you can’t use a 220V circuit on a 50A RV!
Second higher amps is always the better way to go.
But since you’re wiring everything, why not just run a couple 50A RV services with a 30A RV outlet.

Every 50A RV has 240VAC coming into it but it's then separated into two 120VAC circuits.

[BB_TX]

JimBollman wrote:
Thanks to those that answered my question. Sounds like even though the total watts available on the 20amp 220v outlet is higher, the option to the RV to use up to 30 amps selectively would be better. I didn't know how the 30amp to 50amp adapter was wired that makes sense.
........

I tend to agree with the 30 amp being the better option even though the dual 20 amp has the potential for more total power. And it would depend on the individual RV. An AC will run fine from a 20 amp circuit. But depending on how an individual RV is wired, there may be other commonly used higher amp devices on that same hot leg and cause a 20 amp breaker to trip where it would be fine on the 30 amp. Whereas the other 20 amp hot leg might be only lightly used due to the devices wired to it.

[JimBollman]

Thanks to those that answered my question. Sounds like even though the total watts available on the 20amp 220v outlet is higher, the option to the RV to use up to 30 amps selectively would be better. I didn't know how the 30amp to 50amp adapter was wired that makes sense.

As far as why I don't just put in a 50 amp service, access to my place is questionable to all but the smallest of 50amp RVs so probably would never be used. Accept for the 30amp RV box I already had everything else I needed to put in the the 30amp service.

[dodge_guy]

Well first off you can’t use a 220V circuit on a 50A RV!
Second higher amps is always the better way to go.
But since you’re wiring everything, why not just run a couple 50A RV services with a 30A RV outlet.

[wa8yxm]

I have used two 20 amp circuits to power my RV, I had to exercise limited energy management (leave water heater and fridge on GAS only. turn off an AC if I used elewctric Kitchen stuff) but that would be my choice.

However I will warn.. If you "Back feed" an outlet with a generator during power fail that is very very very very very dangerous.. Have a proper transfer switch installed so that the loads (Selected loads as well) are, at your choice, powered by Mains or Generator.

Leave one seldom needed light on the MAINS only. turn it on during power fail and when it glows.. Switch back to mains.

And yes. that is exactly how I did it.

[valhalla360]

larry cad wrote:

JimBollman wrote:


I have never owned an RV with 50 amp service so the question is if you had the choice of plugging into 220v 20 amp or 110v 30 amp, which would better serve your needs?

The simple answer to your STATED QUESTION which seems to be being ignored is that the 30 amp circuit will be able to supply 3600 watts to the camper, while the 240v, 20 amp circuit will be capable of supplying 4800 watts to the camper.

It's theoretically 4800w available.

Since the OP has implied a jury rigged electrical system, running air/con off a 20amp circuit might be marginal, in which case running off the 30amp might work better.

[larry_cad]

JimBollman wrote:


I have never owned an RV with 50 amp service so the question is if you had the choice of plugging into 220v 20 amp or 110v 30 amp, which would better serve your needs?

The simple answer to your STATED QUESTION which seems to be being ignored is that the 30 amp circuit will be able to supply 3600 watts to the camper, while the 240v, 20 amp circuit will be capable of supplying 4800 watts to the camper.

The remaining answers above are precautions to insure you don't wire either of the circuits incorrectly which would cause damage to your electrical equipment in the camper.

[ScottG]

Jim, the 30/50 dog-bone adapter joins the two sides of the 120/240 together in the trailer so the entire 50A circuit in the RV is alive.

[JimBollman]

Wasn't really asking for advice on wiring, I can handle that. I asked how a 50 amp RV setup distributes their power use. I know they sometimes plug into 30 amp outlets at campgrounds, does half the camper not have power? I assume if you have more than one AC unit that you can only use one if you're plugged into 30 amp service.

For those worried about my generator use, the previous owner had it wired to back feed, I wanted outlets and put in full 4 wire service to a 4 wire outlet that I could plug a commercially available adapter into to get two 120v circuits for use outside. I used this approach rather than putting in a couple of duplex outlets because it is mounted in a stone veneer wall and didn't want to get into masonry work just to change the use and I could mount the 4 prong outlet in the accesting box. I figured in the future if I wanted to connect a generator I could add a transfer switch.

So unless you can answer what I asked, don't bother posting.

[Beverley_Ken]

I'm a bit confused about the 4 wire receptacle. Is it wired to allow your generator to supply power to the house, input to the house or does it supply power out for other uses, generator? It can't do both. If it does feed the house from the generator, it would have to have a fool proof manual or automatic transfer switch to prevent your generator from backfeeding the neighbourhood and potential harming the lineman fixing the problem on the pole.
If it is wired correctly for 220, one leg on each side different phase of your panel, there would be 20 amp available on each leg, depends on the RV how much on each leg could be operated on 20 amps.

I would say, just just use the 30 amp receptacle that you have installed and let them use the 30/50.

Ken

[enblethen]

You must be careful about two independent 120 volt circuits. They must be on opposite side of the 120/240 power source or you have the potential of frying the neutral.
Wire to the electrical panel should be a minimum of #10 for proper operation. Breaker should be a double pole 30 amp. This should handle everything thin in a 50 amp rig.
Depending on how your location is constructed and location of the electrical panel to the rig, best would be to wire it complete for a 50 amp 120/240 circuit with 50 amp breaker and proper RV 50 amp receptacle.