I dont make the decisions, I just find problems and offer solutions.
I guess the issue is the two welders in question have been rode hard and put away wet for many years. From what I understand the internal rectifiers/inverters are going bad and would need to be replaced. It's evidently causing HF bleedback on the ground bus. This could be done for roughly about the cost of a new machine.
They've since solved the problem by making those two welders the LAST two on the line so that they only get used when they are slammed and behind schedule. They say they haven't heard it in months now. Physically they are further away from the demarc now too.
Before that I was able to lessen the noise by grounding the other 3 unused pairs like KLD suggested. It then became a slight rumble in the background (that's not too bad when you are talking) versus a nice loud crackle like before. It was still noticeable but permissible by them when given the option of living with it or paying me to build shielding and run conduit and ground isolaters and such.
If I have a need for such a thing in the future i'll be more then glad to shoot you a PM over.
