50 amp wiring question

A 30A plug does not have 240V it is 120V only hence it cannot supply 240V to your RV. On your extension cord new 50A female connector connect gnd to gnd, neutral to neutral and 30A hot to BOTH 50A hots in the plug. This is how a 30/50A adapter is wired.

However consider: If the extension cord doesn't have the standard 30A female RV plug install one and buy a 30/50 adapter. Another option is buy a 50A extension cord and adapter, yes more expensive and heavy but allows for connecting to a 50A pedestal when it's to far from the RV. I occasionally run into this as there is absolutely no standard pedestal placement including even located on the passenger side.

pianotuna wrote:


On a fifty amp--I do recommend a top of the line energy management system that may detect an open neutral.

Why "top of the line"? Why not just use the same AC outlet ground tester we use on 30 amp circuits? We are still just testing for open ground or neutral.

https://www.amazon.com/Electrical-Receptacle-Outlet-Ground-Tester/dp/B0012DHVQ0

Let me rephrase my OP. I fully understand AC split phase wiring of the 50 amp supply. I guess I don't understand how combing L1 and L2 in the dogbone adapter supplies 120 volts. Seems like it would produce 240 volts.

I'm asking this because instead of buying a 50 to 30 amp dogbone adapter, I want to take an old 30 amp extension cord and modify the trailer end with a 50 amp female plug, in essence build a 25' adapter.

There is a very good YouTube video that explains in simple language the difference between 30 and 50 amp service. I refer back to it often: Click here.

I don't understand how it works, all I know is, the 50 amp service, the electric cord, and the trailer all work together to balance the 50 amps.

Manage your available electric Amperage usage, either 30 or 50 and let technology do what it is supposed to do, and just enjoy camping!

However, here's the formulaa used in the video.

120 volts X 30 amps = 3600 watts (I suppose that equal 2 electric 1500 watt space heaters, with 600 watts to spare).

120 volts X 50 amps = 6000 watts X 2 = 12000 watts (I suppose that equal 8 electric 1500 watt space heaters with zero watts to spare).

Good video. Watch it, it will help you understand.

Pretty hard to balance intermittent loads.

You may find dual air conditioning units have one on each leg.

It may be that the microwave is on one leg and the roof air on the other.

On a fifty amp--I do recommend a top of the line energy management system that may detect an open neutral.

Yes the 50A plug is 4 wire 3 pole and absolutely no concern about balancing loads. The 30/50 adapter works as you expect, your just limited to 30A total by the pedestal CB.

The 2 50A legs are combined (connected/shorted) in the adapter and NOT in the RV. When you plug into a 50A pedestal plug w/o the adapter you have 120/240V to the trailer panel with its dual 50A CB.

You can either Google up a 50a wiring diagram or someone will be along shortly to provide one.