50amp RV wiring question

Shortbus · Apr 18, 2015

I had someone at work ask if ever wired temporary power outlet at home for rv and what is needed. I told them I did for parents and asked if they had 30 or 50 amp - they didn't know so I drew the receptacles and asked which looks like your plug. It was the 50 amp so told them I used 14-50r receptacle, 4 gauge 3 conductor with ground as it was a decent run from main, 240v 50a dpst breaker, ran in conduit and used a waterproof (resistant) box. They tell me I'm crazy the rv is 110v and that won't work. I said yes it uses 110v and that's how I wired it so can use everything in RV.

So enough story and to the question... Is there something special I don't know about the 50a for rv and if so why does the way I wired theirs work fine for my parents if it's wrong? I've always thought that it works just like a house - L1 for one circuit L2 for the other with common neutral.

John Galbreath Jr. · Apr 18, 2015

It is a 240 volt plug. But the RV uses two 120 legs of 50 amp power, or a total of a 100 amp 120 volt service.

See attached.

I have a real good RV electrical tutorial PDF but it is too large to post here. If you want it, just email me at [email protected] and I'll send it to you (and others interested).

Shortbus · Apr 18, 2015

I'll send you an email for the file. I keep getting a can't open file error on my phone for the attachment.

So the 240v breaker is correct.

John Galbreath Jr. · Apr 18, 2015

Shortbus said:
I'll send you an email for the file. I keep getting a can't open file error on my phone for the attachment.

So the 240v breaker is correct.

I'll send both, they are PDFs.

vidio1 · Apr 18, 2015

Ya know, I've been camping for several years now and never stopped to question why campers don't use 220v.

Shortbus · Apr 18, 2015

JohnG said:
I'll send both, they are PDFs.

Thanks John I was able to open those. So I'll give him this for his install. Anyway this confirms the rv is just like a house with 240v input 120v each leg.

poolman · Apr 20, 2015

vidio1 said:
Ya know, I've been camping for several years now and never stopped to question why campers don't use 220v.

My camper uses 220v or 110. I can't run the furnace without 220 but everything else works

John Galbreath Jr. · Apr 20, 2015

poolman said:
My camper uses 220v or 110. I can't run the furnace without 220 but everything else works

That is very unusual. I have never seen an RV that uses 240volts. Many use two legs of 50 amp 120 volt power, for a total of 100 amp 120 volt service. The plug is a 240 plug, but each leg in separate inside the RV. I have never seen one that the L1 and L2 connect to make 240 volts, even in the largest units, like Provost.

poolman · Apr 20, 2015

I'm sure your correct, I've never looked in the box since I bought it. I'll electrical savi but I've never wired a camper but I do know the blower on the heat will not work unless I'm plugged in to 220? :dunno:

LandSpeeder · Apr 20, 2015

poolman said:
I'm sure your correct, I've never looked in the box since I bought it. I'll electrical savi but I've never wired a camper but I do know the blower on the heat will not work unless I'm plugged in to 220?

Where are you plugging in to 220? Not at any RV park or rec area I've seen. Those are 120V 50/30AMP outlets. I lived in my pusher for months before I understood the plug. And it may have been John's PDF's that helped me understand it. I was SURE I could plug in to dryer outlet at anyone's house... I was WRONG. Unless you've specifically installed a 30AMP or 50AMP outlet at your house, then just use an adapter and find a circuit in your house that uses 20AMP breakers and use one of those outlets with a HEAVY gauge cord.

Even living in this unit... it confused the shite outta me the first year. Still may be.

Caver Dave · Apr 21, 2015

For the record...

220VAC "Single Phase" *IS* 2 separate 110VAC circuits or "hot legs"

It's the same thing that feeds most houses... regardless if the house or trailer circuits use the combined 220VAC (Stove/Oven/HVAC) or the individual 110VAC legs (receptacles/lights) doesn't matter, it's still 220VAC at the panel

Shortbus · Apr 21, 2015

Caver Dave said:
For the record...

220VAC "Single Phase" *IS* 2 separate 110VAC circuits or "hot legs"

It's the same thing that feeds most houses... regardless if the house or trailer circuits use the combined 220VAC (Stove/Oven/HVAC) or the individual 110VAC legs (receptacles/lights) doesn't matter, it's still 220VAC at the panel

Yes. This is right.

I've done some more research, as the guy still wasn't satisfied with the PDF. While the majority of all motor homes only use 120V, I found that some large and higher end units do use 240v. Mainly range and/or large heating cooling units. Many of those have a smaller 110V unit as well for parks without 50A service.

LandSpeeder said:
Where are you plugging in to 220? Not at any RV park or rec area I've seen. Those are 120V 50/30AMP outlets. I lived in my pusher for months before I understood the plug. And it may have been John's PDF's that helped me understand it. I was SURE I could plug in to dryer outlet at anyone's house... I was WRONG. Unless you've specifically installed a 30AMP or 50AMP outlet at your house, then just use an adapter and find a circuit in your house that uses 20AMP breakers and use one of those outlets with a HEAVY gauge cord.

Even living in this unit... it confused the shite outta me the first year. Still may be.

If you have plugged into a 50A at any park that didn't have 240V across the x-y (L1 and L2) you should NEVER use more than 50A total in the rv. You'll start a fire quick unless the neutral has some 00 or so wire, I doubt if the park went cheap and wired x-y on same leg they'd spend the extra for larger gauge wire on the neutral. If it's wired correctly you'll have 240V between legs otherwise you'll have 0V between legs. Yes most RVs only have 120V appliances but you need two separate legs for 100A. That way with balanced load on each leg you have almost zero current on the neutral vs 100A if only one leg was used.

Caver Dave · Apr 21, 2015

poolman said:
but I do know the blower on the heat will not work unless I'm plugged in to 220?

Saw this at my brothers place a few weeks back when he said that "everything (FL fixtures/AC/wall receptacles) would work, but not the exterior quartz worklights"...

The issue there is usually an adapter from the 50A trailer-side plug to something other than a 50A receptacle.
In his case, the adapter went from the 50A plug down to 20A 120VAC... it *ONLY* transfers power (120VAC) to one of the prongs (either X or Y) on the plug, so only the trailer circuits on that pole worked.

In the case of the furnace & blower not working... the blower was one the UN-energized prong of the plug/pole in the breaker box. Plugging into the 50A receptacle energizes BOTH (X & Y) prongs, allowing both the furnace & blower to work ;D

poolman · Apr 21, 2015

That's the way understand it. Surly there not wired any different than my home? But maybe I'm a dumb as and it is? :dunno:

LandSpeeder · Apr 21, 2015

Only units I've seen messed up are the ones that an unknowing person got a hold to and wired it up like a typical electrician would wire it. Seen a few, and some folks on this forum use these units so I'll be quiet.
Same scenario with a guy recently out here at a park I stay at a lot: He bought a very common brand motor-house. Apparently thought he was going to put a 220V dryer in it. Needless to say, I saw him pulling the dyer out a few weeks later. He said he thought maybe he would just be able to run an extension cord to the outside pole since the pole has a 220V outlet... He was referring to the 50AMP receptacle. SMH.

If your RV is built under Recreation Vehicle Industry Association Code (RVIA Code) then it will be 120V

http://www.hrvc.com/console/files/Understanding%20Your%20RVs%20110v%20Electrical%20System.pdf

LandSpeeder · Apr 21, 2015

Shortbus said:
I've done some more research, as the guy still wasn't satisfied with the PDF. While the majority of all motor homes only use 120V, I found that some large and higher end units do use 240v. Mainly range and/or large heating cooling units. Many of those have a smaller 110V unit as well for parks without 50A service.

Do you mind sharing your findings? I've seen the best come through, Newell and Prevost... ($2M units) they use the standard 50AMP plugs and outlets. Curious what brand you found.

Edit: Hell, the two I mentioned are the two that DO have 240V heating systems. LOL! And apparently thumb their nose RVIA Code. LOL! BUT... They also have 120V heat available too apparently. Doesn't surprise me, as these coaches seem to have ADSL (automatic **** suckers).. Waderlodge is the third high end unit that 240V heat systems are in.