commercal service bonding two 200 amp services from a 400 amp meter with two sets of 3/0 cu to each panel no bonding allowed in meter can, do I tie both net together with a 1/0 cu from water pipe and a # 6 from ground rod and a #4 to each panel in the wireway and bond there or one #4 from the water pipe and one #6 from the rod to each panel.
The easiest way would be to loop a GEC, based on the conductors feeding the panels (250.66) down from one to the water pipe, through the clamp and up to the other. You can size to each panel. The other option is to run a GEC sized to the SE conductors (250.66) up towards the panels and splice the appropriate GEC from the panel to that.
You can't splice the GEC but you can splice a GEC "tap. Clear as mud huh? That is why I said the easiest way is to loop one #4 or #2 through the pipe clamp and then you will not get a fight ... unless they actually want to size it to the SE conductors per 250.66
The GEC is limited to the rating of the electrode. A rod is #6, A Ufer #4 and a water pipe, the full size called for in 250.66
Another quibble I have with the artwork is that it appears to show a GEC that is larger than the service 'hot.'
Again, you're never required to have a BEC larger than the 'hot.'
I'm not sure you're required to have the GEC 'land' in every panel (or disconnect). As I see it, 1 meter = 1 GEC, land it in whichever panel is convenient.
No? I'm thinking of the meter bank at the apartment building across the street .... 12 meters, one GEC landing in one place.
Using Holt's explanation (ground rod for lightning / static only), I see the issue also as one grounding electrode for each building. I don't see the pictured 'tap' as accomplishing anything at all.
As for lite bulb's second question ....
TWO sets of 3/0? A parallel feed? Well, that's a different way to do it ....
First, I'm uncomfortable feeding the panels without having a disconnect first.
I'd run 500's to a trough above the panels (as in the drawing), and tap off then with 3/0's for each panel (using NSI's).
Could you run your GEC taps up into that trough, splice them together and run the GEC from the trough to your electrodes? I don't see why not- assuming the trough remains accessible (not sealed by the PoCo).
The easiest way is to land the full sized 250.66 GEC in the meter/CT can and be done with it. Some PoCos may not allow that but it is the preferred method here. You use an RNC nipple to get through the wall to the service disconnect with 3 (or 4 for 3p) wires and hit the bus with the MBJ. That satisfies the inspectors who don't want a parallel neutral path although, on the line side of the MBJ, I am not sure that matters.
A agree as soon as NFPA allows "taps" the idea of an unspliced GEC flies out the window.