Grounding Issues??

[Electric]

I got an odd issue happing at a shop that I basically re-wired. Installed 200amp load center down from a new metered main panel.
The guys who own the shop call and tell me the tig welder (A big *** Lincoln stationary 100amp 240volt, switch in AC position) when in use makes the mig strike an arc (wire is touching the work table) (Nobody is touching the migs handle)

Im stumped on this one. All my grounds are good (correct size and all on same buss bar)
Im thinking the ground clamp on tig might be the problem or maybe the tig itself be the issue.
The shop had some serious electrical load balancing issues with an under sized load center. That needed a fan blowing on it so the breakers wouldn’t trip as fast. Might’ve damaged the welder?
Has anyone had this or a similar problem before?

Oh the work table has a 2” flat stock running across the floor from tig grounding electrode and it’s welded to leg of table.

[G-ManBart]

Just another example of why calling the work clamp a ground clamp makes things confusing.

[danielplace]

So if tig is welded with the mig torch starts welding by itself ? Actual high amperage welding arc. Or are we talking about a tiny little arc that does melt anything ?

Is the work clamp of the mig also clamped to the table when this occurs.

Is high Frequency on when it occurs ? If you weld with out high freq does it still happen ?

[Electric]

The wire of the mig slowly heats up, turns red and starts to disappear. You know almost the same way when mig welding and you try to strike an arc in an area that has some continuity with work clamp.
Yes work clamp from mig is clamped to table which in turn is attached to tig machine.
Yes, high frequency. It kind of try’s to do the same thing but just sparks a tad when mig wire comes in contact with work table or work clamp.

[danielplace]

Is this something that has just started happening and they have been working like this a while fine or maybe you haven't noticed till now ?

Check the grounding from table to tig. Sounds like maybe the connection in that return is possibly compromised. Hard to think of any other way it would choose to do anything to any other return path available. Can you cable the tig all the way to the table for a test maybe.

[Lis2323]

Just another example of why calling the work clamp a ground clamp makes things confusing.

Agreed. But if the title was "Working Issues" we may have unfairly assumed the OP was lazy and unmotivated.


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[whtbaron]

I'm not an electrician so I'm not sure if this is your issue, but I had a ground/work electrode burn off internally in my Forney AC buzz box once while I was welding metal pens in a hog barn. The welder would still weld, but was obviously grounding through the green/bare ground in the electrical wiring of the barn... which was very unfortunate for the pigs that touched the pens. I suspect you may have an issue with that welder... is there another one you can plug in at the site to see what happens?

[G-ManBart]

Agreed. But if the title was "Working Issues" we may have unfairly assumed the OP was lazy and unmotivated.

LOL...true, although he does talk about ground and neutral at the panel, so the headline might still work.

[ccawgc]

First safety (green wire) ground and the neutral buss bar are to be connected together only in the first panel. after that the neutral and ground must be kept separate going out to sub panels. green and white wires.
That said most welders do not use the neutral unless they run on 115 volts.
If you read the owner's manual installation instructions you will find the TIG welder needs a ground stake right next to the welder and connected to the case and any other metal object near buy. this will keep the HF from traveling into other equipment. Some electrical code frown on second ground rods but this rod is not for electrical safety. It is for radio frequency noise caused by the HF arc starter.
It may be that if the mig welder is power on and just setting there. When the tig fires off the HF it may cause the electronics in the mig welder to turn on just a little.
Try turning off the HF and scratch start an arc. if the mig welder stays off. you have HF getting into the control circuits of the mig welder.
can also try leaving mig welder plugged in but powered off. try TIG welding inAC with HF on. see if the wire sparks and gets hot. I think a proper grounding plan will fix your problem. IF the Lincoln manual is not clear enough. go to millerwelds.com and down load any syncrowave owner's manual. Find the HF ground sheets.
They have very good drawing on how to control HF and keep it out of other equipment. I have one customer that in order to keep the HF from their Lincoln TIG
they had to drive the ground rod and then also run a number 8 bare copper wire up the wall and out to the middle of the repair shop. they were knocking PLC controllers off line in the next room every time they tried to weld.