convert 220 v plug to 50amp rv plug

Robin'n'Marian wrote:
We will talk to our electrician about converting the receptacle in the garage and see if it is possible, he will know if it can be done, if our wiring codes, etc are the same as yours in the US. I know that a lot of things are the same, but not everything.
Thanks for the help, it sounds like we will have to wire in the receptacle.

Good luck, and it's not a big or difficult job as your electrician will probably tell you. It's just got to be done right. Happy Camping!

We will talk to our electrician about converting the receptacle in the garage and see if it is possible, he will know if it can be done, if our wiring codes, etc are the same as yours in the US. I know that a lot of things are the same, but not everything.
Thanks for the help, it sounds like we will have to wire in the receptacle.

NEC article 250.130 (C) allows a separate ground wire to be used when replacing receptacles. Ground conductor must in some way get connected back to the electrical service ground connection.

wa8yxm wrote:
IF all 3 wires in a 3 wire outlet are the same size, a 4th wire (Safety ground) can often be added fairly easily. Not code, but still safe.

Why do you say running a separate ground is "Not code?" I recall looking this up once and IIRC, a separate ground can be run according to code. There were some limitations, requiring it to be run with the existing 3 wire, wire gauge requirements, etc., but I'm pretty sure there was a provision in the NEC allowing it. I considered it at one time. No one should proceed on my comment, it's just my recollection, but it's worth checking up on.

ktmrfs wrote:

One BIG issue is that as you point out, the neutral
in these old 3 wire systems (and some 4 wire as well)neutral was often NOT the same gauge, it was smaller.

That was, in fact, the primary purpose for my post..

IF all 3 wires in a 3 wire outlet are the same size, a 4th wire (Safety ground) can often be added fairly easily. Not code, but still safe.

But if the neutral is reduced size.. There is no safe way save running brand new cable.

I see many things done that are less than safe.. This thread covers a bunch of them.

Now, to the O/P (Since the guy I'm replying to clearly understands this)

here is what happens in a 120/240 system and why the neutral needs to be the same size (or larger) than the hots.

The advantage to the dual voltage system is this.

Let's assume there is 0.25 ohm resistance in each leg between your appliances and the transformer.. That means that at 10 amps you are loosing 5 volts 2.5 volts each way.

So 120 volts is now 115 volts.

But you turn on the other A/C, and "Balance" the legs.

now that 115 volts magically becomes 117.5 There is no longer any "Return current" the neutral (it is being used a 2nd time and returning through the other hot).

BUT.. What happens if everything you have turned on (one A/C, the Microwave, and perhaps some other stuff) is all on the same leg?

now you are pulling 30,40,50 amps all of it running through 1 leg and the neutral.. IF the wires are all the same size, NO problem (Save the voltage drop is greater)

If the neutral is smaller... .. Well the Fire Department still makes house calls.

enblethen wrote:
In the US and some parts of Canada, the elctrical code changed dryers and range receptacles to four wire. Both dryers and range circuits after about 1988 has four wires.
Look closely at the receptacle for number of openings. It should have four on later installations.
It is not only look at but must be tested for proper wiring.
You should not attempt to make an adapter. The receptacle must have a neutral and a ground

Agreed, and that's how my dryer receptacle was wired (luckily 4 wire) I pulled the hot, neutral, and ground off of it to wire my 30A RV outlet on the other side of the wall, opposite the dryer receptacle. We didn't have an electric dryer so the receptacle was not being used.

ktmrfs wrote:

wa8yxm wrote:
Ok, I will answer, Dryer outlets come in two flavors and one of them can be wired two different ways.

The two flavors are 3 and 4 wire

Now if it's a 3 wire the answer on converting ins likely NO, you will really need to pull new 4-wire feed line to do it properly and safely.

If it's a 4 wire then you need to look at the wires.

There are 4 wires, One white, and either a black and a red, or two blacks, and a bare or green.

Forget the bare/green for the momnent.

Are the black, red and white wires ALL THE SAME SIZE.

If so, then you can convert.

yes, the 110/220V appliance wiring is a real can o worms!!

A wide variety of NEC code changes over the years has really made it a quagmire IMHO.

The "3 wire" dryer plug systems still have two 120V legs and a neutral, just like 3 wire ovens and stoves of the same era. The motor and controls run off one leg at 120V. The heating element across the two legs for 240V.

There is also a neutral/"ground", but in "days of old" around WWII, NEC allowed neutral and ground to be tied together at the appliance plug. Ergo, no seperate ground available, and therfore no seperate ground back to the panel. (Or that's what the folklore is anyway) Was comon and per NEC code at least through the 80's in the US for dryers, ovens, stoves etc.

So, a 3 wire may or may not be adaptable. Is it really a 3 wire or a 4 wire? with ground in the box, but not at the outlet.

One BIG issue is that as you point out, the neutral
in these old 3 wire systems (and some 4 wire as well)neutral was often NOT the same guage, it was smaller. The heater element, which was the 30, or 50A draw is across the two hot legs, so no current flows in the neutral from that load. The motor and control circuit doesn't draw near as much current, so in these old systems any neutral or ground wire was often a smaller guage.

I think it was sometime in the late 80s' early 90's that NEC code changed and now requires a 4 wire system (two hot legs, neutral and ground) for dryers, ovens, stoves for new construction or remodel.

You'll have 240V across the two hot legs, 120v from either leg to neutral, and a ground. Same as the configuration of a 50A RV. But for an RV the neutral must be the same size wire as either hot leg. RV's have lots of 120V stuff and often little or no 240V stuff, so current flow is from each 120V hot leg to the load and back through the neutral to the panel. depending on the load balance in the trailer between the two hot legs, you could end up with anywhere from 0 to 50A in the neutral leg.

And to add to the mess, often the 3 wire setup was aluminum wire, which requires special recepticals that are rated for connection to aluminum wire.

Don't know if Aluminum is still common or allowed on the 4 wire dryer, oven, stove or not. But if that's what you have on a 4 wire system, make sure you use the proper receptical.

When we remodeled and I switched the dryer, stove, oven to 4 wire copper.

so.... IMHO unless you really know wiring, best left to an electrician.

Good advice and reading. Don't let just any electrician work on your trailer I've heard some bad stories. Rvs are a little different. Sometimes there not use to them.

wa8yxm wrote:
Ok, I will answer, Dryer outlets come in two flavors and one of them can be wired two different ways.

The two flavors are 3 and 4 wire

Now if it's a 3 wire the answer on converting ins likely NO, you will really need to pull new 4-wire feed line to do it properly and safely.

If it's a 4 wire then you need to look at the wires.

There are 4 wires, One white, and either a black and a red, or two blacks, and a bare or green.

Forget the bare/green for the momnent.

Are the black, red and white wires ALL THE SAME SIZE.

If so, then you can convert.

yes, the 110/220V appliance wiring is a real can o worms!!

A wide variety of NEC code changes over the years has really made it a quagmire IMHO.

The "3 wire" dryer plug systems still have two 120V legs and a neutral, just like 3 wire ovens and stoves of the same era. The motor and controls run off one leg at 120V. The heating element across the two legs for 240V.

There is also a neutral/"ground", but in "days of old" around WWII, NEC allowed neutral and ground to be tied together at the appliance plug. Ergo, no seperate ground available, and therfore no seperate ground back to the panel. (Or that's what the folklore is anyway) Was comon and per NEC code at least through the 80's in the US for dryers, ovens, stoves etc.

So, a 3 wire may or may not be adaptable. Is it really a 3 wire or a 4 wire? with ground in the box, but not at the outlet.

One BIG issue is that as you point out, the neutral
in these old 3 wire systems (and some 4 wire as well)neutral was often NOT the same guage, it was smaller. The heater element, which was the 30, or 50A draw is across the two hot legs, so no current flows in the neutral from that load. The motor and control circuit doesn't draw near as much current, so in these old systems any neutral or ground wire was often a smaller guage.

I think it was sometime in the late 80s' early 90's that NEC code changed and now requires a 4 wire system (two hot legs, neutral and ground) for dryers, ovens, stoves for new construction or remodel.

You'll have 240V across the two hot legs, 120v from either leg to neutral, and a ground. Same as the configuration of a 50A RV. But for an RV the neutral must be the same size wire as either hot leg. RV's have lots of 120V stuff and often little or no 240V stuff, so current flow is from each 120V hot leg to the load and back through the neutral to the panel. depending on the load balance in the trailer between the two hot legs, you could end up with anywhere from 0 to 50A in the neutral leg.

And to add to the mess, often the 3 wire setup was aluminum wire, which requires special recepticals that are rated for connection to aluminum wire.

Don't know if Aluminum is still common or allowed on the 4 wire dryer, oven, stove or not. But if that's what you have on a 4 wire system, make sure you use the proper receptical.

When we remodeled and I switched the dryer, stove, oven to 4 wire copper.

so.... IMHO unless you really know wiring, best left to an electrician.

RV 50A info......good read & pictures LINK

Ok, I will answer, Dryer outlets come in two flavors and one of them can be wired two different ways.

The two flavors are 3 and 4 wire

Now if it's a 3 wire the answer on converting ins likely NO, you will really need to pull new 4-wire feed line to do it properly and safely.

If it's a 4 wire then you need to look at the wires.

There are 4 wires, One white, and either a black and a red, or two blacks, and a bare or green.

Forget the bare/green for the momnent.

Are the black, red and white wires ALL THE SAME SIZE.

If so, then you can convert.