480sparky said:
Why would the plumbing need to be bonded? Bonding is intentionally creating a ground path. If it's copper or galvanized pipe thoughout, there's going to be a path to ground, even if it occurs at the pipe coming in from the street. A structure with all-metal piping is bound to be grounded, whether effective )or intentional) or not.
The purpose of a GFCI is to detect imbalance of current, on the basis that there is a possibility of that current leaking through a person, and they need to be saved. For the current to flow
through a person, the current has to go somewhere, Kirchoff's law applies. In any normal installation, there is a neutral / ground bond somewhere, and that will provide the path necessary for the leaking current to flow.
480sparky said:
I don't understand what you mean by 'two hots and no neutral".
In SDS with no bond anywhere to ground, there is no neutral, just two wires, which are both normally called hots. With this sort of system you can hold one hot, and not get a shock, as there is no path through ground for current to flow. A GFCI would not trip in this situation.
mivey said:
All you need is a second circuit that is faulted to the plumbing. No ground bond needed.
I was very specific to say "single fault": There are many double fault situations where there is danger, including the situation that you suggest. This does not remove the illustrative purpose of the single fault situation.