Community Forums

Ray,IN · 05-08-2021, 10:14 PM

Persistant said: You can draw 30 amps 120 volts through a 120v/30a system. I add, and usually melt the plug.

To the OP, sounds like you have a good plan. Cover all windows with reflexTec insulation, use insulation in roof vents.

Fiesta48 · 05-09-2021, 06:28 AM

I can run my 3 A/Cs at one time on 50A. They only pull 8A each. Tempting to try on 30A.

Persistent · 05-09-2021, 07:51 AM

Quote:

Originally Posted by Ray,IN

Persistant said: You can draw 30 amps 120 volts through a 120v/30a system. I add, and usually melt the plug.

To the OP, sounds like you have a good plan. Cover all windows with reflexTec insulation, use insulation in roof vents.

If a 30 amp plug melts, it is most likely because the plug, socket, cord, or connectors are defective. A proper plug will carry its rated load indefinitely without causing fire, smoke, or other life threatening failure. Things tend to work better if sustained draw does not exceed 80% of rating, but catastrophic failure should not happen in any case.

Don't worry! Be happy! Circuit breakers will protect you and can easily be reset. Just don't do that again.

I wish you good luck and happy trails ahead!

SKP Kirk · 05-09-2021, 08:25 AM

Quote:

Originally Posted by bry899

Yes it is confusing,
I am not an electrician but the 30 amp service is 120 Volts
The 50 amp service is 240 volts or two 120 volt lines at 30 amp each

As one who is an electrician, the thing you have to understand is that the 30A or the 50A ratings are for the circuit breakers that supply the power cord. With a 30A RV cord there is 1 hot wire, 1 neutral wire, and 1 ground. Only the hot wire passes through the circuit breaker rated at 30A, 120V.

In 50A RV power cord there are 2 hot leads (L1 & L2), 1 neutral wire, and 1 ground. Each of the hot leads has a separate circuit breaker of 50A. In the 50A cord the connections are from what we call a center tap transformer with the neutral from the center and L1 at one end and L2 at the other. If you measure from L1 to L2 you will read 240V but from either L1 or L2 to the neutral you get 120V. Since the cord is rated based on the circuit breakers it is a 50A cord but it is actually a 120/240V cord, which means that you can get either voltage from it, depending on how you connect the load.

So for the RV world to be theoretically accurate there would be 30A-120V power cords and the other choice would be a 50A-120/240V cord. When operating in the 120V mode, as most RVs do, the number of amps is theoretically doubled because they basically come in L1 and leave through L2 and nothing passes through the neutral wire. At the power distribution box there are 2 separate bus bars, one for L1 & one for L2. The RV loads are connected between one bus bar and neutral, so they see 120V.

To get 100A of total power the loads must be exactly 50A on each side of the cord. In theory you could use 100A of power, but in a real world the loads will never be exactly the same on each side so it is more practical to think in terms of 80A of available power, but that is still much more than the 20A difference in circuit breaker/power cord ratings. In practical application is it very unusual for a 50A RV to overload the main or pedestal circuit breakers.

Mr_D · 05-09-2021, 08:40 AM

Quote:

Originally Posted by Gary RVRoamer

It's not an RV thing - your house electrical is rated the same way. The load center (electrical panel) is 240v, so a 50A or 100A panel can in fact provide twice as much amperage when split into separate 120v circuits.

Yes, it would be clearer if everybody stated watts rather than amps, but most of us learned amp numbers on fuses/breakers & outlets and are not easily retrained. Electricians and engineers know what they are talking about regardless, but amateurs get confused. It might also help to always state 30/120v vs 50A/240v to make the distinction more obvious, but everybody likes shorthand notations (like acronyms!).

Good points Gary!
As a retired engineer it is very frustrating to see some of the misconceptions posted on various websites. Some of which are dangerous to the users too!

twinboat · 05-09-2021, 09:11 AM

50 amp uses a two pole breaker.

I suppose you can call them seperate, but they are always linked together. 2 breakers in one.

billyb · 05-09-2021, 11:27 AM

In my unit, you can. Only draw 30 amps on one line and 20 amps on the second line, for a total of 50 amps.

Old-Biscuit · 05-09-2021, 11:28 AM

Arggggggggggggggggg!

Coarsegold · 05-09-2021, 11:36 AM

Electrical is really confusing, I would just get out of Tucson in the summer.

Nwcid · 05-09-2021, 11:41 AM

Quote:

Originally Posted by billyb

In my unit, you can. Only draw 30 amps on one line and 20 amps on the second line, for a total of 50 amps.

How is that even possible to wire?

So the main breaker in your RV has a 20 amp main and a 30 amp main breaker? Tied together? If not does you unit have 2 separate cords to plug in?

If you are using a 50 amp cord on your RV you have to have a 50 amp panel.

This will allow 50 amps on each side. Individual breakers control each circuit.

If you have a 30 amp (120v) unit you have a panel like this.

wolfe10 · 05-09-2021, 11:46 AM

Quote:

Originally Posted by billyb

In my unit, you can. Only draw 30 amps on one line and 20 amps on the second line, for a total of 50 amps.

OK, let's see a picture of your 120 VAC main breaker box with a 20 amp and 30 amp main breaker!

Guess anything could be made, but, 100% of the 50 amp RV's I have ever seen or worked on have TWO 50 AMP BREAKERS!

Should be fun.

153stars · 05-09-2021, 11:57 AM

To sum up your question plug it in in best location for you with window vent and comfort. If you run another item on same circuit like microwave , hair dryer either shut it off or try different outlet or run a 12 or 14 GA cord.
After it runs for say 30 minutes to an hour, see if outlet gets warm at all, in case its not in great condition like someone overheated it with an electric heater.

SKP Kirk · 05-09-2021, 01:49 PM

Quote:

Originally Posted by wolfe10

OK, let's see a picture of your 120 VAC main breaker box with a 20 amp and 30 amp main breaker!

Guess anything could be made, but, 100% of the 50 amp RV's I have ever seen or worked on have TWO 50 AMP BREAKERS!

It sounds like he is wired to use one of these devices, hard wired where his 50A plug used to be.

twinboat · 05-09-2021, 01:58 PM

Quote:

Originally Posted by SKP Kirk

It sounds like he is wired to use one of these devices, hard wired where his 50A plug used to be.

Not likely, that adaptor will trip a GFCI outlet as soon as as its plugged in.

With most campground 15/20 amp outlets protected by them, it would be tough to use.