I lost my text book with all my electrical/power stuff. I should say stolen, but it wasn't quite that either. maybe locked out and then stuff disposed of.
One lab I worked in had the high leg delta, but it was unimportant to be then. When we moved the guys in charge couldn't specify power correctly, so for 240 equipment we has 208V now and for systems that required L1, L2, G and N; Neutral was missing.
Later, I found potentially 470 outlets that were bad from the manufacturer after the warranty was up. More like: expensive equipment got destroyed and I wanted to know why.
AND we were assured we would have a cooling loop. Well, they tried to force 90F water from a 12" main through a 1/4" tube, so that didn't work well. It was supposed to be 55 F clean water. SO, the new equipment got connected to filters and drains. Luckily the drains were installed.
To make an isolated pad, you pour the entire pad. Cut and dig out the isolated portion and then poor it.