A big part of being qualified is the ability to recognize the hazard. Back in my day is was easy to look at a panel and see what control wiring was verses power wiring. The old NEMA stuff, it was easy to look at a panel and see the difference. With the new IEC stuff it?s more difficult. We recently purchased a machine from a European vendor. One of more experienced guys was poking around the control panel not realizing it had 480V wiring. The darn cabinet had a 480V to 24VDC power supply, go figure. The 480V contactor looked like a cheap control relay, the 3 phase breaker had the look of a DIN rail mounted breaker one would use for control. Here we had a guy that was experienced but clearly not qualified to be working on that machine. With all the above said, we did install some labels & physical barriers in the panel to protect folks from the majority of the 480 Volt stuff. This experience was a real eye opener for me; experience has nothing to do with qualifications. How do you teach someone to recognize a hazard exists? We are trying o get our guys to pull prints and look them over before they dive head long into a troubleshooting mode, know and understand what voltage levels are where. We are doing our best to put warning labels on all panels with mixed voltage. All it takes is for one panel to slip thru the cracks.