Larry, thanks for bringing the topic back around. I have to admit that the IBM stuff was somewhat going over my head. All the same, perhaps I am a better person for it (but don't count on it).
And thanks to everyone for their inputs. I get so much out of these discussions.
I have really vascillated between (1)going the three-wire route (taping the red to green - yes, it violates code, but in a residential setting there is little chance of confusing a subsequent electrician as long as I tape it at all junction points - and I believe if there is to be a "noise" problem, having the ground insulated can only help), or (2) sticking with 12-2 and the bare copper ground. One remaining hesitation I have with the second method is that I would really want to bring the ground all the way through the distribution panel and into the service disconnect enclosure, without any bonding in the distrib. panel. But to do this would likely subject this bare ground to at least minimal contact with the "grounded" enclosure of the distrib. panel. Did I lose anybody?
With all that said, there is one remaining factor that is strongly influencing my decision. And that is that before the client said anything about isolated ground, I had already fished 12-2 into the basement crawlspace, where I will splice it into a j-box before fishing it up to the panel. Now I know most of you will say, 'oh, well, if you've already gone that far, why not just finish it with 12-2?" Thing is, I was wondering if I should refish the wall with 12-3. As I write this I can already hear the bombarding of answers, so I guess I can say that I will finish the job with 12-2, tell my client a "dedicated ground" is as good, and be done with it. Sigh.
