[TR] help wiring a 240v welder US

greg at gelhar.com greg at gelhar.com
Sat Jul 28 19:43:50 MDT 2012


> 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?
>
>
>
> 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.
>
>
> Sujit
>
Your 125/250 volt, 30 amp, dryer outlet accepts only a three prong plug.
If it is the stadard Nema 10-30, it does not have a grounding terminal.
Dryers, because they contain devices that require 120 volts, are permitted
to be grounded using the neutral terminal. That accepts the "L" shaped
blade on the plug. The other two terminals have 240 volts between them.

You should not have two separate circuit breakers. The two breakers must
have a common trip lever. They supply the 240 volts. The 120 volts, for
the dryer, is available between EITHER circuit breaker and neutral.

If you choose, the outlet will operate your welder, but again there is no
true ground. The neutral is a GROUNDED (white) conductor, but by code, you
should have a GROUNDING (green) conductor.


Greg


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