convert 220 v plug to 50amp rv plug

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.