I moved my Westinghouse "mig" machine to a new location with a nice new
electric box set up with a four prong plug 230 volt single phase outlet. I
had it wired for a three prong plug but that outlet went directly to the
panel. The schematic inside the machine shows L1 and L2 for the load but
that is it. I hooked the wire attached to the chassis to the ground
terminal. It is smaller in diameter than the other three wires but that
seemed to be the best choice as I figured 115 volt stuff would be using the
common and the chassis probably would be charged at times. Do you think I
made the right choice? The welder is on a non conducting cart and non
conducting wheels if it matters. I am pretty sure the ground and the common
are supposed to be attached at the main panel near the meter. However I
only see three big wires going toward the meter and other out buildings feed
off the big three wire cluster. Funny the new plug instructions uses the
same color wires as the three phase four conductor wires have. Just an
aside but is three phase now going to have five wires?
It's hard to figure out what you mean here.
But yes, in general, with a 4 wire 220V plug for a welder, L1, and L2 power
the welder, the common is not used (just cut it off, or insulate it with a
wire nut or tape), and the ground wire is used to ground the machine
Are you saying the machine did include a ground connection, or not? You say
the schematic only listed L1 and L2 but no ground for the box? That would
Yes that's right. The difference however is that the ground wires running
though the building should _never_ carry any current. The common will
carry current. This is important because if the ground were to carry a
current, the small resistance in the wire would cause a voltage drop, which
would put the chassis of all the grounded machines at a slightly different
voltage level - which could lead to someone getting a shock when they touch
two different machines, each at a slightly different ground level. Grounds
wires only work to keep everything at the same voltage level if there is no
current flowing through them.
Small leakage current is ok, but a large load like a welder running though
a ground wire would put it's case ground at a substantially different
voltage level and could cause people to be shocked.
Right. The ground in your main panel is the reference that all equipment
in your house is grounded to. You will see that it is also grounded to a
water pipe or ground rod to tie it to earth potential.
Thanks for the answer
I got the machine at a sealed bid sale surplus to the electric company at
least 10 years ago. The side which comes off easily has the schematic so
you can figure out the whole thing or just where to put the wires for 230 or
460. the third wire is attached to the chassis with an original type
connector I don't really remember if I installed a new chord or it had no
chord at all when I got it. The manual which I didn't get probably tells
where to attach the ground but there is no ground symbol on the schematic
which is about the size of three typewriter papers. Well I won't bet my
life someone else might find one on it.
I have worked with an electrician for a year or so so not totally clueless
about this stuff but we mostly worked on burglar/fire alarms and coaxial
stuff. A friend of mine insists that the ground should be big enough to
handle all the current the hot legs provide which isn't the case this new
box I am using has a four conductor wire going to it and the ground is
significantly smaller but still about the size of the wires I am using to
feed the welder. it is 200 amps at 60% and says 40 amps for the draw on
230. whether that means 40 amps at the 60% rating or 40 amps max I really
That's true for a neutral wire which much act as the return for the same
current a hot leg carries, but it's not true for a safety ground which
should carry no current under normal conditions. The safety ground can be
smaller and is specified by code as to what size it must be.
As someone else pointed out, older equipment might not have a separate
ground and neural even though it uses the neutral for a 120 V load. I
don't know what was typical in older welding machines and if you have a
machine which uses some 120 V current (like for a fan as someone
suggested), and if that load is attached to the chassis so you can't
separate the 120 V neutral load from the chassis, I'm not sure what is
considered "correct" in how it would be wired. I don't know if it would be
better to use the neutral or ground in that case.
However, it sounds like your unit has no neutral (or else it would be
obvious in the schematic) so it's not an issue.
BTW, if we are talking about a Miller or Lincoln, both those companies have
all their old manuals on line so you can download it and read it to find
out what they suggest.
That plate is the specific requirement per the electrical code. That's the
official "rated" current of the machine. The US electrical code has tables
for calculating wire size for welders based on that rating. Welders are
tricky in the codes becuase you can use smaller feed wires since they don't
draw their full load constantly. How much smaller you can get away is a
based on the tables from the code books and the information on that plate.
The % number is the duty cycle - not a percentage of full load in case you
didn't understand that. So it means the machine will draw 40 amps input
when you run it at 200 amps output. The 60% duty cycle means you can only
run it for 6 out of every 10 minutes at 200 amps - you have to let the
machine cool down for 4 minutes out of every 10. The rated current however
is typical not the max current the machine can put out. A Miller
Syncrowave 200 for example has a rated current of 150 amps, but looking at
the volt current curves, the machine can actually tops out at 300 amps
(which is not normal welding current but what happens when you short out
the welder when stick welding with the DIG turned all the way up). The
rated current however is typically the top of where the machine is expected
to be used under normal conditions.
The breaker or fuse they would recommend is typically a bit larger than the
rated current, like maybe a 50 amp fuse in your case.
What you actually need however to make it work is a function of what level
you run the machine at. If you never run it at it's full rated current, it
will draw less than the rated current and you can run it on a circuit with
a smaller breaker. So a machine like that might work fine on a 30 amp
circuit if you never run it over about 150 amps output for example.
A three phase connector with a separate neutral would require five wires.
Many three phase machines do not require a neutral and use an internal
transformer to furnish any small single phase loads such as lights or
convenience outlets. A totally separate ground connection is always
required, as far as I know.
The oldest ('60's) hobbyist/farm level 240 volt/180 to 225 amp) welders
were set up with factory cords with 2 hot and neutral (3 angle blades).
In the '70's they switched to 2 hots and a ground (2 straight blades and
a pin). In the '90's they switched yet again to 2 hots, neutral, and
ground (3 blades and a pin)
Neutral but no ground worked ok since the welders had little or no
current on the neutral leg (maybe the fan) so the neutral and ground
functions were pretty close to the same. (The NEC folks weren't very
happy!) The 2 hots with ground is a safe way to do it as long as there
is NO 120volt load in the box. Buzz box welders were OK as long as they
used 240 volt fans (I have one like that), MIG welders are a bit suspect
because they have both fans and control circuitry.
It sounds like you really need to look at your schematic to see which
system the welder is using. You want to hook the ground lead on the cord
to a convenient chassis part, the neutral should be hooked to it's spot
on the main power block or taped off if it is not used.
I would test the welder with a clamp on ammeter on the ground line. If
there is any current you need to have another look at things.
And the 3 phase question: yes full 3 phase with neutral and ground will
have 5 wires (black/red/blue/green/white). I just bought 70' of 10-5
service cord for a mobile unit. Copper prices are down, it was only $.92
Thanks for responding, it isn't a cheap buzz box thing it is a spool gun
machine I installed a relay to be able to use a normal (yes I even found a
Westinghouse one) wire feeder as well. I think it kind of is supposed to
be wired direct to something with a switch as there is no on off switch in
the welder. Though it doesn't seem to have a lot inside it must weigh
around 400 pounds. It seems to work well with dual shield wire. Never
tried self shielded wire. It works best if you preheat where you start
especially for aluminum. Not sure if the modern stuff is much different.
I could check with a volt meter but never felt any shock from it and I can
feel shocks pretty well especially if I have a metal fragment in my finger.
I was more thinking about the ground for purposes of a major failure where
something live connects to the chassis somehow.
The place where I installed this welder has one of those 70's two blades and
a pin like I got when I bought a red Lincoln 225 ac machine in the seventies
with the welder. This new plug is on a new box set up for plugging in a
large motorhome and has a nice switch/breaker and fatter/less wire back to
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