One more welder wiring question.

I'd say the $10 would be a real good investment, if you don't want a real electrician involved.

--->Paul

Maybe I can help. The reason multiple grounds are not a good idea (not allowed by National Electric Code) is that there can be a potential difference (voltage) between them. This sets you up to get a shock when you get between two "grounded" objects.

As for only connecting grounds to neutrals in the service panel - the neutral is grounded at the service equipment to limit stray voltages (above nominal voltage) in the local system. To explain why grounds shouldn't be tied together anyplace other than the service, I need to refute a common fallacy. We've all heard that "electricity follows the path of least resistance". Electricity follows all paths of conductance. Current flow will be inversely proportional to the resistance in each path. If you have a ground wire, which is tied to the neutral at the service, and it is also tied to the neutral at another point remote from the service, these two wires will form a parallel circuit. Normal circuit current will flow on the ground wire, which is always a bad, for a number of reasons. This is "foundational" and should be understood before doing any electrical work (above 12 volts, that is). I hope this helps.