mksj , some very good points.
I see NEC as a guideline for design in my OEM equipment and not a rule book unless my product will see an Inspector ( house or building type jobs ). When that is the case you need a licensed electrician, not someone like me. TUV, UL and the such add to the mix as well.
I got a pdf copy of the 1897 NEC if you are interested.
http://www.linghunt.com/101Spearfishing/Spearfishing101RefManuals.html#NEC
Mike Holt is a great source of info as well.
EC & M is one of my favorite spots current events on this topic.
http://www.ecmweb.com/
To add to the mix the OSHA regulations make designing pretty tough. Poorly written technical regulations by lawyers and other inside the beltway types.
Go read section
1910.333 which has some pretty good stuff, and my favorite
1910.147 for Lock out / Tag Out.
I can walk into any company and shut you down for not being 100% compliance with this document.
PHA documents and the such is the kinda stuff an inspector will want to a see if they are giving you an exam. Do diligence is very important. I've had outside independent inspectors review some of my equipment and was told it was not in "complete" compliance. That said I was also told it was one of the safest designs he had ever seen. You can't win is the point for a design that is actually safe and in check with laws and regulations.
I went to a paid OSHA class once through the local jr college, It was a joke for me, but boss sent me with a couple techs and our companies hygienist. The instructor couldn't answer my tough nosed questions on the gray areas, I keep them to a minimum and did more of it in 1 on 1 chat. Class was for general introduction for Industrial Hygienist types to check off a box for knowledge base.
I'm a huge fan of LOTO. The biggest flaw in any LOTO program is "real" education of the end users. Designing to protect electricians and technicians is one of my main concerns. This ties me back to floating neutrals and commons that tweaks me big time.
TUV and European compliance certificates has been a tough bar to jump for me. EM noise emissions in general. What was interesting is their lack of LOTO requirements.
One of my favorite accidents to illustrate LOTO safety. The Fortuna, CA tree debarker (1992). Watch the FARGO movie (1996) and the brush shredder for a visual.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=170718944