High Frequency Welding Machine Additional Ground

[johnnycarcinogen]

I have an Everlast Welding machine that uses high frequency generator to start the arc for TIG welding. The owner's manual instructs to run a 14 awg or larger wire from the lug on the back of the machine to a separate electrode in the earth to "bleed off" excess high frequency current otherwise it could "back feed" through panel, into grid, etc. etc... After watching your videos I was wondering what the code says about this ?

Thanks a bunch. cheers.

 

[GoldDigger]

The building wiring system was not designed to present a low wire network impedance at frequencies significantly higher than 60Hz, although good wiring practices will minimize the effect of inductive components.
NEC does not address whether or not a local earth electrode is a good idea, but I think it would allow the extra rod as a "supplemental" electrode not subject to the full set of wiring and bonding rules for the primary GES. The one thing that the NEC does not support is connecting the safety ground of the machine (metal case, fault current return, etc.) to a local electrode and then not also connecting that same point to the circuit EGC.
Unfortunately your average residential or commercial electrician is probably not well equipped to give you guidance on this either.

 

[infinity]

I agree with Goldie according to the NEC you can use the electrode if they want it. My guess is that it won't do much. Auxiliary electrodes are covered in 250.54.

 

[FionaZuppa]

HF on TIG is not only when starting

That Everlast has adjustable HF overlay in both AC and DC welding.

more than likely its not "HF current", its HF noise. tying the frame into earth helps to couple that HF (whatever is on the frame of the welder) away from the electrical wires.

 

[MTW]

Many large machines like CNC plasma tables, require a supplemental electrode, for high frequency dissipation, before it gets into the distribution system.

High frequency has a skin effect, and travels on the outer surfaces of the conductor. The more surface area the better, straps are better than wires. But are hard to attach to a rod with a clamp.

MTW

 

[FionaZuppa]

Many large machines like CNC plasma tables, require a supplemental electrode, for high frequency dissipation, before it gets into the distribution system.

High frequency has a skin effect, and travels on the outer surfaces of the conductor. The more surface area the better, straps are better than wires. But are hard to attach to a rod with a clamp.

MTW

not really sure skin effect is a worry for TIG overlay Hz. starting Hz is audible. welding overlay is also fairly low.