Since so many of you seem to be backyard camping this summer, or possibly setting up your RV for a COVID-19 medical staff to shelter in place in the RV, I’m getting all kinds of emails about plugging an RV into a 30-amp dryer or even an electric welder outlet. So I’m updating an earlier article about the dangers of miswiring an RV TT-30 outlet with 2-pole 240 volts instead of the correct 1-pole 120 volts.
Thank you for bringing the miswiring issue to light. I have been a licensed journeyman electrician for over ten years, but when a customer asked me to install an outside 30-amp outlet for his RV in the driveway, I accidentally wired it up for 240 volts, NOT 120 volts. That was a costly mistake on my part since it destroyed a lot of the RV appliances and electrical system. Yes, I paid for the RV repairs, but I hated to write that check. More folks need to understand that RV electricity does not follow the norm for house wiring. —Adam
I get emails like this every week from an electrician or homeowner who’s made this same costly miswiring mistake. An RV 30-amp plug is NOT wired for 240 volts like the home dryer plug it resembles. The first time I saw one of these TT-30 plugs on an RV I also assumed it was 240 volts, until I looked at the plug closely and saw it was listed for 120 volts. That was the hint I needed to avoid making an expensive mistake as well.
Below is what a 30-amp/120-volt RV outlet looks like compared to a 30-amp/240-volt dryer outlet. See why residential electricians can easily be confused because of the similar size and shape?
And here’s how 50 and 30-amp RV pedestal outlets are supposed to be wired.
Using welder outlets for your RV (Don’t do it!)
Note that a 240-volt NEMA 6-50 receptacle, which is the standard welding outlet many are proposing to use to power their RV, DOES NOT have a neutral conductor, only 2 hots and a ground. So if you want to hook it up to a 50-amp RV outlet there is no neutral conductor and no safe way to divide the 240 volts into 120 + 120 volts.
Remember, you can’t use the ground wire as a neutral as that’s a serious code violation and very dangerous because it’s not sized to carry full load current. So if the ground wire you’re using as a neutral were to open up (a real possibility) then that 240 volts could divide to 200 volts on the one leg and 40 volts on the other leg. And that will destroy half of your RV wiring (likely the expensive half).
Also, it would be disastrous to attempt to rewire this same welder outlet with a 30-amp RV outlet since the incoming power is 2-pole 240-volts, not 1-pole 120-volts. Doing so will destroy most of your RV’s electrical system in a few seconds. While it’s possible to rewire the circuit breaker in the panel to single-pole, and color code the existing wiring run, this is something you should have an electrician do since lethal voltages are involved.
So if you’re going to have a 30-amp RV outlet wired up for your RV when it’s parked at home, be sure to show this article to your electrician before he makes a costly mistake. Plus, it’s really a good idea for you to measure every new or unknown RV outlet for correct voltage BEFORE you plug in your expensive RV. Avoid that costly and time-consuming mistake.
And that’s also a great reason to purchase something like a Southwire Surge Guard 34931 for your RV. This is cheap insurance since it won’t let a 240-volt wiring mistake reach your RV’s electrical system.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. 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.