Reno:
Yes, 250 is confusing, no doubt. Mike has some good references. Over the years, wacky EE layouts/specs drove me (EC) and the inspectors up many a wall.
One memorable job consisted of a 20' ground electrode augered into mother earth, and backfilled with 'Montana Clay'. It was a 2" diameter heavy wall copper pipe, filled with some exotic salts' (Thinking 'Lyncole') 4/0 tail, cadwelded to more 4/0, then to a grd buss, cadwelded to a 1/4" copper plate. Plate covered the floor (wall to wall) of a clean room cell for some really deep electronics tool.
The inspector came in.....stared....shook his head....laughed....and wrote a red sticker! He had no clue why, but failed it on 'principal'. Long story short...plans were approved as installed, he came back...I explained...he laughed.. I showed him where the 'system' was bonded to the bldg steel, got a white sticker.
Lets see if anyone jumps in
Got to head home, may be back later
