This tells me that with the receptacles themselves, the green ground terminal is not electrically connected to the metal piece that is used to screw the receptacles into the boxes. Is that what you have in mind?
Not me..............
I do not understand what you are describing here. What do you mean by ?spliced?? Are you saying that a wire will be connected from the green ground terminal of one receptacle to the green ground terminal of another receptacle, and perhaps from there to the green ground terminals of other receptacles, and that this wire will then be routed to the water meter?
If that is the situation under discussion, then I agree that this violates 250.146(D). The green ground terminals of two or more of this type receptacle can be connected to each other, but the wire must be run with the circuit conductors back to the service?s (or separately derived system?s) ground bar.
here's the post....
Ugh - I really didn't want to be making any updates in this thread, but the GC's electrician subcontractor was at the site today doing some other stuff. I asked him again about the IG setup, and his reply was kind of troubling.
He actually *is* going to run the insulated ground conductors from the 3-prong receptacles to a dedicated ground #6 ground cable, which will be completely isolated from anything inside the panel. This ground cable will run to our water main entry, which is acceptable as a ground electrode under Canadian code. The "normal" main ground conductor is also connected at this point.
I'm still getting my head around all the issues related to residential grounding, but I'm pretty sure this is wrong. It seems to be gospel (in US code, anyway) that the ground conductor and neutral *must* be bonded inside the service panel to provide a low resistance (and physically protected) return path for current in the event of a ground fault.
I have a copy of the Canadian code version applicable in Quebec from the library, and will try to find the section where this is covered - could also call the city building department. They don't generally do inspections, but could probably answer the question and point to correct portion of code.
I'm also pretty sure this is useless in preventing the kind of ground loops that are problematic in audio. As I understand it:
- AC wiring around the house emits time-varying magnetic fields
- Faraday's law says that a voltage (emf) will be induced in any closed loop, proportional to the time-rate-of-change of the magnetic flux (basically the intensity of the magnetic field added up over the area of the loop)
- the building ground conductor, grounded receptacles, and shield conductors in audio cables can form such a loop
- the current around the loop will be the induced voltage divided by the total resistance in the loop
- voltage differences between different points in the loop depend on how resistances are distributed around the circuit
Whether the ground conductors of my receptacles are connected directly to the water main, or to a bus in the panel that is in turn connected to that water main, a loop is a loop and the above points should still apply. I can see how it would help to break the loop with an isolation transformer, or reduce the area of the loop like John Brandt suggests, but don't see any benefit to fancy grounding schemes like this...
The discussion was in French (which I speak ok, but am at a disadvantage in debates like this) and he was just kind of blathering on about "the frequencies put out by the equipment" and "this is how it's done for commercial printers". I will tell him to quit with the isolated ground BS, but would like to give an informed and convincing explanation why it's BS (and possibly dangerous) so as to hopefully avoid paying for it.
