Section 110.12 contains arguably the least understood and most commonly violated requirements in the NEC. For example, consider 110.12(A), which requires closing unused openings in equipment. If your facility already has this problem nailed, the odds are good you can find dozens of such violations in a tour of any facility picked at random.
You can't close these openings with duct tape or other flimsy material. The closure must provide protection substantially equivalent to that provided by the enclosure. Though the NEC doesn't explicitly state what kind of protection, it means protection from shock and arc flash. So use the standard enclosure plugs to close these openings.
Another "gray area" is the requirement that electrical equipment be "installed in a neat and workmanlike manner." While the NEC doesn't explicitly say the equipment must be maintained that way, common sense tells us there's no point in the NEC's installation requirement if you don't maintain that neatness.
But what does this mean? Although the NEC doesn't say (to understand why it doesn't digress into this area, read 90.1), it does refer the reader to the applicable ANSI/NECA standard. Your best bet is to obtain the standard and follow these three steps:
- Make your own checklist to use with PMs and repairs.
- Conduct training on methods and finish.
- Photograph examples of good workmanship; use for training.