Ground bonding two main breaker panels

[DrSparks]

So normally I use a meter bank with integral main breakers for a multi-family residence. however in this case I have a two family dwelling and the owner provided a Milbank twin meter socket with no disconnects. he also provided to main breaker panels 100 amp. normally I run the grounding electrode conductors for the water main and ground rods to the meter socket enclosure where it is bonded to the neutral bus bar. in this case I will need to find the grounding electrode conductors to the neutral bar in each main breaker panel. my question is can I run one grounding electrode conductor to the first panel from the water main and the ground rods that being number 4 gauge copperand then jump from the first panel to the second panel with 4 gauge copper. or will I need to run a separate grounding electrode conductor from each panel to the ground rods in the water main bus having two separate conductors and two sets of clamps on each ground rod and the water main.

 

[DrSparks]

Seriously? You guys are slacking today

 

[roger]

So normally I use a meter bank with integral main breakers for a multi-family residence. however in this case I have a two family dwelling and the owner provided a Milbank twin meter socket with no disconnects. he also provided to main breaker panels 100 amp. normally I run the grounding electrode conductors for the water main and ground rods to the meter socket enclosure where it is bonded to the neutral bus bar.

As far as the NEC is concerned all you have to do is bond the neutral in the two gang meter socket

in this case I will need to find the grounding electrode conductors to the neutral bar in each main breaker panel. my question is can I run one grounding electrode conductor to the first panel from the water main and the ground rods that being number 4 gauge copperand then jump from the first panel to the second panel with 4 gauge copper.

That would work

or will I need to run a separate grounding electrode conductor from each panel to the ground rods in the water main bus having two separate conductors and two sets of clamps on each ground rod and the water main.

Code wise you can but, the problem with this is, you have now created a loop for neutral current to flow like shown in the illustration below. Just imagine your two gang meter socket in place of the single gang.

Roger