[TR] help wiring a 240v welder US

[Dave1massey at cs.com]

In a message dated 7/28/2012 7:17:26 PM Central Daylight Time, 
triumphstag at gmail.com writes: 
> I have a old style 240v dryer outlet. (three pronged socket and not 4)
> What I was told is that one leg is 110v from one circuit breaker and
> another leg is 110 from another breaker.. Is the center third leg ground?
> Why are there two 110v lines from separate breakers? Why not one line
> taken form the circuit breaker and then split?

The answer is, as always: it depends.  It depends on how it was wired up.  
Never assume in a situation like this.  Codes vary from state to state and 
they change over time.

While it is true you will measure 110V from each leg to center it will vary 
as to where the center leg is connected.  In some cases it will be 
connected to neutral and in other cases it will be wired to earth ground.  Although 
these two points are bonded together at some point and, in theory, are at 
the same potential (zwro volts) their purposes are quite different.  One is a 
current carrying conductor and the other is there to save your life.  

> 
> 
> 
> On the welder plug, one pin/leg is narrower than the other. Why is this?
> And does it mater.
> 
> How do I connect this welder plug. The welder is 30 amp and the dry socket
> should be sufficient I've been told.

Since you are using an outlet designed for a single phase 220 volt load for 
a welder which is a single phase 220 volt load it should work as intended.  
There should be no problems with this setup.  My generic warning above is 
for those who would consider using this circuit to power a couple of 110V 
devices.  Don't do that without checking it out further.  Or find an 
electrician or someone like him.  (sorry for the Firesign reference)

Like brakes, your life is at stake, this is no place for shortcuts.

Stay safe.

Dave