electrican sent 240v to my rv.

calamus wrote:
The amp rating of the wire should never be less than that of the circuit breaker that is used.

Sorry, but this is not true. The Code allows a breaker to be a larger rating than the wire if it supplies a motor load only. For motors only, the wire gets sized for the running current and the breaker gets increased to handle the inrush/starting current.

In an RV, it can have #14 ga. wire and a 20 amp breaker, otherwise the AC unit would trip the breaker from the momentary inrush current.

There is no point in oversizing conductors if not required because copper is just too expensive to waste.

That's one reason I always check a socket with my DVM before ever plugging my RV in. I've encountered some bad boo-boo's in a few RV parks, the worse one in a KOA in Kingman, AZ. Fortunately one of the employees was able to fix it immediately. I've also recently been using my new Surge Guard as a test instrument before plugging in. Better to take a little time checking things out before incurring a disaster such as you encountered.

Yes there are cases where you could use a 3 wire 240 volt but I have not seen any residential wiring done other than a well (and that is rare) with 240v 3 wire they have not done it for years now.

I see it every day. I have two of the 3 wire 240 outlets in my residential outbuilding, less than 10 years old. They are part of the original electrical system, permitted and inspected of course. One is for an air compressor, another for a heater.

Three wire 240 is common and current NEC for residential and commercial applications like AC (yes they still come with three terminal plugs) and many other modern devices such as those I listed. It is used where 120 or a neutral is not needed.
Brand new, modern devices such as these still use the perfectly safe NEMA 6-30 because they don't need a neutral, 120 leg or ground fault protection.

This is for a CAMPER, Yes there are cases where you could use a 3 wire 240 volt but I have not seen any residential wiring done other than a well (and that is rare) with 240v 3 wire they have not done it for years now. And what would you do with the netural 120' down in the water? IF you had a 2 wire pump ( which has 3 wires hot hot ground) and you only have 4 wire well wire you combine them or dont hook one up at all, on the well and the panel. Like I said you dont screw this up if the outlet has 3 wires I cant see how you could make that mistake these days. That means he did not even bother to look at the outlet. Almost every welder /generator every piece of equipment now has 4 wires if its 240 volt. Read below.


Wire for 220 Circuits

The wire requirements for 220 volt circuits are pretty much the same as for any other circuit - it must be of the proper type for the place that it is being used, it must have sufficient volt - amp capacity, and it must have the correct number of conductors. Proper color coding would also be nice, but isn't a big deal because the exposed lengths of the conductors (in the main panel and in the terminal device) can be colored with paint, tape, or permanent marker. If you are wiring for a dryer, range, or any other 220-110 combo appliance you must use a four conductor wire with an insulated neutral and a separate ground such as X-3-WG. If you are wiring for straight 220 equipment such as a water heater then you can use a three conductor wire such as X-2-WG. The amp rating of the wire should never be less than that of the circuit breaker that is used. You can find a handy wire application / amp rating chart on this page.

Note: You can no longer install 3 wire range or dryer circuits - you must install 4 wire systems for ranges and dryers. If you already have a 3 wire range or dryer then don't worry, your old appliance can be made compatible with a 4 wire system by installing a 4 wire pigtail on it. Then when you buy a new appliance it will plug right in to your new 4 wire system.

calamus wrote:

ScottG wrote:

calamus wrote:
There should of been a 4th wire if it was 240v.

There's a 30A 240V outlet that only has three conductors that is common for use with welders and compressors. That's probably how he wired it.

even a 30A 240v will have 4 wires hot hot netural ground. If you have seen one I would like to see a link the only time I have seen where you use the 3 wire system for 240 volt is in a two wire submersible well pump it only has a hot hot ground coming off the pump so you would combine the netural and ground or just run 3 wires. Like I said this is a major screw up. If it was done at a home then and 3 wires were used I just can see someone with any know how could do this. You would know that as you hooked up in the panel when you didnt have a netural and or a ground wire??? This guy was an idiot.and should lose his/her license but Im guessing he doesnt have one.

No, not all have 4 wires. The three wire outlets are common for compressors, welders, larger window AC's and some dryers. They are wired with Hot, Hot, Ground.
Google is your friend: NEMA 6-30R

Oh and you were wrong if you combined the neutral and ground at the well pump. They are only connected together back at the main panel.

Things are improving.. Used to see a new thread like this just about every week, Now I can go months without seeing one.

I always advise folks who think to ask to have a 50 amp outlet put in, not a 30,, Two reasons,

The minor reason: You might wish to upgrade some day, Very easy to upgrade from 50 to 50 or from 50 with a 30 amp breaker to 50.

The REAL reason: See original post.

I have heard, over the years (about 10) I've been here many rumors of parks where the 50 amp outlet was wired wrong, SAFE but wrong with the same leg feeding both sides of the outlet (Well it is not the safest but thankfully the RV makers use wire a bit heavier than absolutly needed so the odds of a disaster go down should that happen)

I have heard of exactly ONE case where a 50 amp outlet had a polarity reversal and sent 240 volts into the RV (And that was about a week ago). (And in an RV park).. But threads like this. Very common.

Damage list: Anything that easts 120 volts possibly including but not limited to:
Radios
Televisions
Sat receivers
DVR/DVD/BlueRAY/VCR/CD players
Some TV antennas (Doubtful but there are a couple)
Converter
Control board on Fridge
Energy Management systems if any.
Microwave
And if you have anything plugged in like a coffee pot
Heat elements in fridge and water heater.
Some air conditioners, epically if running

Would be on my list, basically ANYTHING that uses 120vac power.

ScottG wrote:

calamus wrote:
There should of been a 4th wire if it was 240v.

There's a 30A 240V outlet that only has three conductors that is common for use with welders and compressors. That's probably how he wired it.

even a 30A 240v will have 4 wires hot hot netural ground. If you have seen one I would like to see a link the only time I have seen where you use the 3 wire system for 240 volt is in a two wire submersible well pump it only has a hot hot ground coming off the pump so you would combine the netural and ground or just run 3 wires. Like I said this is a major screw up. If it was done at a home then and 3 wires were used I just can see someone with any know how could do this. You would know that as you hooked up in the panel when you didnt have a netural and or a ground wire??? This guy was an idiot.and should lose his/her license but Im guessing he doesnt have one.

The inlaws' fridge worked on propane after a similar thing, but would not work on electric, either 120 or 12V. Needed a new fridge.

Also needed to replace a fair bit of wiring in the RV.

I've read lots of posts on here over the years like this. The one common thing that comes up is that the electrician was a lic. professional. I don't remember ever reading about a home owner making the same mistake although I'm sure it happens.
It's probably just a case of a pro making assumptions.