Sunday, December 4, 2022

# Can I use a welder outlet for 50-amp RV power?

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[Click images to enlarge.]

Dear Mike,
I’m having some trouble figuring out the difference between my 50-amp RV fifth wheel plug and a 50-amp welder plug. I want to wire up a 50-amp outlet for my RV but have been told by my electrician that my RV is not 240 volts. I understand that each leg on the 50-amp outlet is 120 volts, but why don’t they consider this a 240-volt RV? I’m trying to explain this all to my electrician, but he seems confused. Thanks in advance and hope you can help me out. —David

Dear David,
Here’s a graphic of how the electrical system of your RV is wired. Even though you have 240 volts between Hot 1 and Hot 2, virtually everything in your RV needs only 120 volts to operate. That’s right, the air conditioner(s), microwave, converter/charger, television set, hair dryer and everything else all need 120 volts (in the United States, at least). A neutral connection is needed to carry the balance current back to the center-tap of the power company’s transformer. Without a neutral the 240 volts won’t divide evenly into 120 and 120 volts, but instead will vary wildly depending upon the load on each leg. And the only way to get this to work properly is have a neutral connection in the plug itself. The standard RV plug, a NEMA 14-50 shown on the right, is indeed a 4-wire plug with 2-hots, a neutral, plus a ground wire.

On the other hand, a NEMA 6-50 (pictured on the left), which is the standard welding plug you’re proposing to use, does NOT have a neutral conductor, only 2 hots and a ground. So there’s no way to divide the 240 volts into 120 + 120 volts. Some of the confusion is that 50-amp RV shore power should REALLY be called a 100-amp service since it does supply 50 + 50 amps, which equals up to 100 amps of current draw at 120 volts. NEVER plug your RV shore power cordset into any outlet without a neutral. Very bad things will happen.

Also, be sure to test any outlets installed by an electrician BEFORE you plug your expensive RV into it. I have dozens of emails on file from homeowners and confused electricians who didn’t understand RV wiring and did many thousands of dollars’ worth of damage in seconds. Don’t make me put you in that file…

Here’s a reminder of how 50-amp pedestal outlets need to be wired. Don’t make an expensive mistake even if your electrician says he knows how to wire up your new pedestal. Test any new outlet with a voltmeter BEFORE plugging your RV into it.

As always, all of my graphs and pictures can be downloaded in full size to read or print out simply by clicking on them.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

##RVT848

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Marcus
5 months ago

Mike, Thanks for the article. Very helpful.

And there is another detail in the circuit that confuses me. The RV 50A twist locks only have three pins, while the other end (NEMA 14-50) has 4 pins (Ground, 110 Hot, 110 Hot, neutral) Where is the safety ground conductor on the twist lock 50A connection? Is it the little metal plate on the outside? Where is the neutral?
Do you have a diagram of that connector?

Jen
1 year ago

Can I use my welders 50amp extension cord as an extension cord for my rv that has a 30amp cord if I use a dog bone adapter from the rv cord to the welder cord then another dog bone adapter from the other end of my welders cord to plug it into the 14-50r outlet would that be safe or what do you suggest I do

Bryan Watts
3 years ago

Mike I have 50 amp welder receptacle and we just purchased an rv with 30 amp service is there anything I can do to utilize this outlet to power the rv. I believe I know the answer.

Mike Sokol
4 years ago

Patrick, much as I would like to I really can’t go into that much troubleshooting detail in a newsletter. And there’s only so many reader questions I can answer on a weekly basis. The reason why I can’t get to everyone immediately is that I’m now receiving over 200 emails and comments every week asking me questions about RV electrical systems. Some of these questions are general, which I try to answer in the comments section. Some of them are wide reaching teaching opportunities, which I turn into weekly articles and draw up the graphics to explain. However, I get at least a dozen questions a week just like yours that are specific troubleshooting questions.

Sadly, most of the manufacturers can’t or won’t help you figure this out, and most RV technicians aren’t qualified to troubleshoot this sort of problem. However, I am highly qualified for this type of troubleshooting and do it all the time, which is why my consulting rate to businesses and manufacturers is \$250/hour (no kidding). However, I do charge a discounted technician rate of \$125/hour for non-business consumers like yourself. Now if this sounds like a lot of money for a guy on a phone, it’s right in line with any good diesel mechanic, and I can assure you that I have way more specialized training and troubleshooting knowledge than most mechanics out there, that is unless they’re full-blown mechanical engineers who actually design diesel engines. BTW: Those guys are REALLY smart.

So what this means for you (and the other dozen or so readers who will ask me to troubleshoot their RV electrical systems this week) is that I can’t answer and help everyone for free or I would go broke trying. I’ll answer as many questions as I can in this newsletter, especially if they’re universal or a big safety issue that should be immediately addressed. But if you want me to take time away from my regular \$250/hr consulting gig, then I’ve got to charge you at least \$125 per hour. Sorry, but I can’t do specific troubleshooting for free.

PATRICK PETERMAN
4 years ago

FIREST OFF,THANKS FOR THE TIMELY RESPONSE; AS FOR YOUR FEE I REALLY DO UNDERSTAND; AND IN THE SCHEME OF THINGS YOUR FEE IS REASONABLE; I DO HAVE A” PRO” COMING OUT TO CHECK THE SYSTEM ; I WOULD LOVE TO GET BACK TO YOU AFTER WE HAVE “GIVEN IT OUR ALL” !! I AM NOT LAZY OR CHEAP- I HAVING LITTLE KNOWLEDGE OF ELECTRICTY IN GENERAL REALLY HAVE TO RELY ON THOSE WHO POSSESS THE KNOWLEDGE AND EXPERIENCE; MIKE, I WILL LET YOU KNOW HOW WE MADE OUT OR”DIDN,T”!! GOD BLESS, PATRICK.P WE RVER,S NEED YOU MICHAEL !!

PATRICK PETERMAN
4 years ago

MY QUESTION WAS RELATED TO A -POOR PERFORMING LOW VOLTAGE OUTPUT OUTLET- NOT THE QUESTION ABOUT THE WELDER??? PATRICK.PETERMAN

PATRICK PETERMAN
4 years ago

I HAVE A 2003 HOLIDAY RAMBLER- THERE IS A DEDICATED 15AMP 125V SCD OUTLET( SELF CONTAINED DEVICE INSIDE AN UPPER CABINET! I HAVE VERY LITTLE POWER COMING TO THE OUTLET THE ROMEX IS STANDARD 12 -2- WITH A GROUND; MY MUUTI-METER READS THE OUTPUT AT 2.27-2.58- THATS ALL THERE IS I HAVE CHECKED ALL THE BREAKERS- THEY ARE ALL IN THE 221 + SIDE I JUST DON,T UNDERSTAND WHY THIS COULD BE?? ALL THE OTHER OUTLETS SEEM TO FUNCTION AS THEY SHOULD; I CALLED MONACO AND THEY WERE OF LITTLKE HELP’CALL AN ELECTRICIAN” WELL I TRIED THAT TO “NO LUCK!! IS IT POSSIBLE I HAVE A WIRE CONNECTION IN THE BAY AREA(THATS WHERE THE LOOM RUNS INTO AND ABOUT 5 DIFFERENT WIRE ARE CONNECTED ALL YELLOW WIRES WITH ONE WHITE WIRE- WRONG WIRE CONNECTION?? ANY AND ALL ADVISE APPRECIATED,THANKS YOU I AM ENJOYING YOUR BOOK TRYING TO LEARN AS I GO,PATRICK.P