230 volt plugs

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?


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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 chassis.

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 be odd.

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.

Reply to
Curt Welch

Or, you can pull in that common, take a tap off one hot line, and put a breaker and 110volt outlet on the front panel of your welder, so you can plug in grinders and worklights and such.

Reply to
Stuart Wheaton

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.

Ddon Young

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Don Young

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 don't know.

thanks again.

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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 questi> I moved my Westinghouse "mig" machine to a new location with a nice new

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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 the meter.


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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.

Reply to
Curt Welch

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