Don, In addition to the things I sent you, I'll pass this along. Article 250 regarding separately derived services says it's ok to connect X0 to the water pipe. I've had a problem with this technique for a good long time. In the mid 80's, my company had a lot of work in one of our large malls in the DC area, and the local AHJ required the use of the water pipe over the use of the bldg steel. The bldg steel had been prepped well in this case, every other one having a ground rod driven and cadwelded to it. (That is the job that actually got me in the middle of the 'discussion' I told you about). I was talking to a plumber one day, and just happened to ask him what the jumper cables were in his tool bucket for. His reply got me drawing a good many little schematics. They were beginning to 'jump' any pipe they took apart for any reason, to make a connection to a new store, maintenance, or whatever, because the pipe was 'energized'. I actually followed him to a joint they were putting in, and witnessed as he jumpered the pipe with the cables, THEN, and only then, cut the pipe. When it got finished draining down, I asked him to move and pulled one end of the cable off the pipe, coming off and going on, there was a sizable arc. I did not have an amprobe nearby and failed to take measurements, something I always regret, but don't forget, I was in business and merely followed (usually) the AHJ's orders.
This is definitely a case that would have been MUCH safer going only to the properly grounded bldg steel. I teach it that way for that reason. I don't know if anyone has been injured (above what we all take as a normal unreported shock), but always worried about the wet (from draining lines), plumbers standing on aluminum ladders.
Yes, before you ask, I did make a quick drawing and 'discussed' it with the AHJ. I was promptly told to mind my own business. I had already taken this group to the State level on several decisions (and won
) and decided to just back off, probably shouldn't have.
I might add, this bunch forced contractors to build an 1 1/2" layer of drywall around the house transformers in the hallways for fire protection. Yes, completely enclosed. I don't know how many transformers had to burn up before they changed that decision, or if they ever did. Put that one on the Fire Marshall.