Dear Dave,
I’m new to a 50-amp rig. I have a 30-amp plug in my garage that’s set up for my old pull-behind camper at 120v. I also have a 50-amp plug that is 220. Is this the proper plug for my 50-amp motorhome? My local RV guy says no, but the seller says it’s what is required with the proper 50-amp receptacle. Don’t know who to believe and I certainly don’t want to fry anything. Who is right? —Travis, 2004 Winnebago Adventurer 35U
Dear Travis,
Your RV guy is correct, and this can be a dangerous situation when someone wires a 50- amp plug for a welder or 220-volt power. It can even happen on a 30-amp plug that is wired to a dryer, as it is also 220 volts.
30-amp RV plug
On the 30-amp outlet, you have one hot leg that brings 120 volts and a ground and neutral. If you test this with a multi-meter it will read 120 volts between the hot and ground, 120 volts between the hot and neutral, and 0 between the ground and neutral. In a 3-prong residential dryer outlet, there is a Hot 1, Hot 2 and neutral, so it has 240 volts and can cause damage. Make sure whoever is installing the outlet, or if there is an existing one, knows that it should have these voltages. The dryer outlet would have an L-shaped neutral at the top while the RV 120-volt has a semi-round ground at the top and the neutral is a slot. However, someone can purchase the correct outlet but wire it wrong!
50-amp RV plug
A 50-amp RV outlet has a Hot 1 and Hot 2 that are both 120 volts/50 amps, plus a neutral and ground.
This is a little deceiving, as Hot 1 goes to one side of the distribution center and Hot 2 provides power to the other side, so it is never 240 volts but rather 120 volts/50 amps to each side. In this situation, you should find 120 volts between ground and Hot 1, Ground and Hot 2, Hot 1 and neutral, and Hot 2 and neutral. You should find 240 volts between Hot 1 and Hot 2 and nothing between ground and neutral.
You can have the 220-volt welding outlet rewired correctly. However, if the 30-amp worked for your travel trailer, it will be fine for your Winnebago with a 50-30 reducer. You just won’t have full power and need to conduct some energy management. You will not be able to run both roof air conditioners at the same time unless you have SoftStartRV. I would suggest a Southwire Surge Guard that will tell you the amp draw, voltage, and if it is wired correctly.
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I believe you mean 240v, not 220v. After researching whether it’s 110/220 or some other combination my research says that the standard power supply in North America is 120v AC and 240v AC for the past 50+ years with 208v being a separate and not necessarily compatible alternative used in industrial applications. I’m not an electrician, but…….
30 amp and 50 amp 240 volt receptacles DO NOT have a neutral, they have hot 1, hot 2 and ground.
Dave, I’m sorry, but I think you’re wrong here on the 50 amp. If it is a 4-prong NEMA 14-50R receptacle that fits an RV power cord, it should be wired identically to a campground outlet, shouldn’t it? What’s the other way to wire it? The 50amp receptacle should be absolutely useable unless someone did something non-standard.
You are correct. IF they wire it with Hot 1 and Hot 2 so there is no 240 line. I recently got a call from a friend that had an electrician wire a 50 amp outlet and it fried his distribution center. It is possible to wire it incorrectly and have issues. I called my electrician that is also an RVer and he has seen several DIY jobs that are not correct. A 50 amp RV outlet as has been stated here by others has a hot 1 and hot 2 providing 120-volt power to separate sides of the distribution strip, a ground, and a neutral.
But how would you even wire a 240 line to it? 240 is created by combining two 120v hots. I just don’t see how this happens unless it’s a 3-prong 240 outlet, in which case you’d have to build a weird adapter to plug into it. Obviously you should meter and check to make sure the outlet is wired correctly anytime you plug an RV into any receptacle, but your assertion that the RV guy was correct doesn’t really hold water. The seller was correct as long as it was wired properly. That receptacle should only and always have two 120v hot legs, one neutral, and one ground.
Well Dave, the other comments are interesting, because they are correct but may be confusing to non-electricity knowledgeable folks. Which also supports why you need an RV savvy electrician if adding outlets. I have both a 30 amp RV plug and 50 amp 230 vac welder outlet in my garage. Best and safest way to go!