I just bought one of those 50A sockets for my welder last year from home
depot. Sold as a range outlet. They still had the 3 wire cords for the range
there too. It is my understanding that the 3 wire circuit is still ok to use
for existing house wiring as there are still a lot of those circuits out
there but any new wiring must be 4 wire.
I just put in a new electric stove and a new 4 wire circuit for it. The new
stove has a jumper strap at its cord connection that is to be installed if
you use a 3 wire cord and not used for a 4 wire cord. The jumper straps
neutral and ground together for a 3 wire circuit.
The older stoves and dryers had only a 3 wire circuit in them and it was
intended that the neutral/ground be common.
The NEC had exceptions for these two appliances to their "separate ground
and neutral rule". But the stove or dryer using this exception had to be a
dedicated line back to the fuse box. Nothing else on that circuit but that
Those are the only two appliances that I can think of that you could use a
common ground/neutral on for 120/240 service. Everything else had to have
the ground and neutral separate. Now the new rules for new wiring must not
share ground/neutral on anything.
However the old welder that I have, 3 wire circuit, does have a 120 outlet
on it so for that it does use the ground as the neutral. It is from the late
50's early 60's. I don't know if it was compliant then or not.
> -----Original Message-----
> From: email@example.com [mailto:firstname.lastname@example.org] On
> Behalf Of Tom W8JI
> Sent: Monday, July 09, 2007 8:12 PM
> To: Jim Brown; Amps Amps
> Subject: Re: [Amps] Transformer question
> > However -- I have heard that there used to be some
> > exception for
> > certain heavy appliances. If that execption exists,
> > perhaps
> > someone could cite the specific paragraph.
> It's my understanding the exposed case of large appliances
> was never supposed to be tied to the neutral, but it became
> so commonly misused it appeared many places.
> They solved that problem in the mid-90's by mandating a four
> wire plug for anything that uses 120/240. As a matter of
> fact I tried to buy a 50A socket formerly common for
> electric ranges at Lowes or Home Depot (for a welder) a
> couple years ago and they told me I could no longer buy a
> three pole 50A socket.
> The important thing to remember for this discussion is while
> some old ranges used 120/240 and may have tied the case to
> the neutral, small appliances and devices using 15-30A plugs
> never tied the neutral to the case. The is absolutely no
> reason at all to do that in a Ham amplifier, and very few
> commercial amps I've seen have ever done that.
> 73 Tom
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