Monday, January 17, 2022


RVelectricity™ – A tale of two welder outlets, and what can go wrong

Dear Mike,
I had a terrible situation that may be an important lesson to teach your RVelectricity™ readers.

My wife and I drove our Newmar Ventana from Clovis. California, to Aurora, Colorado, to a reunion with 4 fellow U.S. Army Vietnam Combat Soldiers in July. Upon arriving to my friend’s home, he replaced a 220 welding outlet plug to a 30-amp plug, so I could plug in to run our RV electric. Having a 50-amp service, I used a 50-amp to 30-amp dogbone adapter and plugged in. Not realizing that was dangerous it blew out the controller, where the electric comes into our motorhome, pumping in about 100 amps too much electricity!

I obtained a new power box for $140 and a mobile RV electric tech responded and took out the ruined box and components, and  installed the new one for $200. The nice Technician told us we could have had so much more damage to electrical boards, and wiring, in our motorhome and we were lucky that did not occur due to that overload!

I purchased an internal EMS/surge protector, and am having that installed to hopefully avoid future electrical problems!

I did not know the welding outlet was something not to use for RV electric, but sure learned the hard way!!!😊 —Brian “Doc” Burry

Dear Doc,
Thanks for your note. Yup, there are a lot of residential electricians and DIYers who still don’t understand that a 30-amp RV outlet is wired as single-pole/120 volts. So they put in a new outlet wired as 2-pole/240 volts. By using a 30-amp to 50-amp dogbone adapter you injected 240 volts into both legs of your 50-amp shore power connection.

You were very lucky to get away with that little amount of damage. Usually it costs 10 times as much to fix that kind of mistake. —Mike

And from my RVelectricity Facebook group…

Dear Mike,

Okay, a different problem with a welding outlet, but still dangerous for an RV. In this case it’s possible that this outlet was an old welding receptacle that was modernized with a 50-amp NEMA 14-50 receptacle for an RV. Or possibly it’s a new 14-50 outlet installed with a 60-amp breaker for a Tesla home charger, neither of which required a neutral conductor. The only way to know for sure is to turn off the power and get a look inside of the receptacle itself. Please find someone qualified to do this for you if you’re not trained in wiring safety.

While a welder or Tesla home charger doesn’t require a neutral to operate safely, plugging your 50-amp RV shore power cord into this kind of connection won’t allow the 240/120-volt split-phase service to divide evenly into 120/120 volts, with dire consequences.

Why are outlets so confusing?

Take a look at this NEMA chart below for the plethora of possible outlets in the USA alone. Unless an electrician is familiar with these various types, and knows how to meter the service properly, it’s easy to get confused. That’s why I get emails like this every week. That’s another reason why I always recommend a good EMS/Advanced Surge Protector that will shut off power to your RV if it’s plugged into a miswired outlet that could damage your electrical system.

Now you can see why you should hire a licensed electrician to hook up any RV outlets, and make sure they meter it properly. Never plug your RV into any newly installed outlet without carefully metering it yourself first. Here’s what to look for…

Yup, wiring can get a bit confusing in the USA. It’s actually much simpler in the UK, as they have fewer receptacle possibilities.

Let’s play safe out there (especially in the USA)….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity™ and No~Shock~Zone™ articles, seminars and videos, please click the I Like Mike Campaign.



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4 months ago

What would happen if I used a 30A 240V Dryer connection and rewired the pigtail I plug into it without the neutral so I only have one leg, then jumping the ground and neutral on the other end of the pigtail that plugs into the trailer?

Last edited 4 months ago by Jim
Mike Sokol
4 months ago
Reply to  Jim

That will work as long as you properly re-mark the wires and be sure that it’s connected to a single-pole breaker.

Jeff Arthur
4 months ago

Did the same 6 years ago. Changed a welder outlet to rv 50 amp outlet & changed breaker from 60 amp to 50 .
wired just like Mikes diagram.
If a 50 amp outlet would have been installed “correctly “ to start with this could have been avoided. It was the 30 amp outlet wired 240 that caused the problem ( best guess)
Nothing wrong with changing a welder circuit to rv 50 amp outlet & 50 amp breaker!

Henry Mackenroth
4 months ago

Given that I can buy a 15 amp residential GFI outlet tester for a few dollars, why couldn’t a manufacturer make a similar device to test the 20/30 and 50 amp RV outlets? You could just plug it in and get real time results in a GO – NO GO fashion.

4 months ago

You can use the 15 amp tester to test a 30 amp outlet if you utilize a 30A to 15A converter, the puck style is simple enough.

4 months ago

Interesting chart. Especially since it doesn’t show the TT-30 configuration anywhere!? Looks like the 50a RV plug might be a 14-50R but I’m wondering… What’s up, Mike?

John Goodell
4 months ago

Quick question: So plugging in and testing with my expensive Southwire Surge Guard Portable 50A ‎34950, or an entry level portable surge protector is the correct procedure? It won’t damage my Surge Guard 34950? Or do I have to get out the voltage meter?