Yes, please, don't mess with your wiring. We have had actual cases where "electricians" thought they knew better than what we have on the machines and have changed the wires, and in so doing broke the switch or created some other issue in the machine. Customers called telling us how we don't have things wired properly and the electrician insisted he change the wire in the machine, and then somehow broke something inside. Yes, then the customers expected us to warranty the unit and parts. The NEC HAS a special section for wiring welders which fully explains it. BUT apparently many certified electricians never got that far, since its in section 630.