TIG high frequency trips GFIs in shop... WHY!!???

The GFI will be less likely to nusance trip if each outlet has it's own GFI.

Battery powered radio don't need GFI.

James,

Obviously electrical interference from the high-freq start is getting into the GFI device. GFI's have toroid coils in them with the two wires (hot and neutral) passing through them. If all of the current that goes out the hot doesn't come back on the neutral it senses this imbalance which can be as small as 0.005A, amplifies it and fires the trip circuitry within a few milliseconds.

You can see it wouldn't take too much interference to upset this device. Obviously removing the GFI would cure the problem but first check to see if the supply wire for the welder runs near the wires for that particular circuit; if so, move them apart if you can. Also, look inside the panel if you feel comfortable doing so and once again see if the welder's wires (both hot and neutral and perhaps even the safety ground) runs close to that circuit. If say the breakers for the circuits are close together consider relocating one of them in the panel. If this doesn't work and a GFI is needed on that circuit, I would try a different one; it may be less sensitive to extraneous electrical noise.

Wires that run parallel to each other can have considerable coupling for high-frequencies.

Hope this helps,

Billh

It sounds from your description that the GFI breaker is in the breaker box near the breaker for the welder. I would try replacing the GFI in the breaker box with a standard breaker and install one of those outlet combined with GFI at the first outlet served by that circuit. The outlet combined wih GFI can be wired so that all the outlets after it are also GFI protected. A combined outlet and GFI breaker will only cost about $7 or $8.

Dan