Grounding both panels

Hi,
I have two 100A service panels. Panel 1 has a #6 copper wire running from it to a water pipe and believe it is the correct size based on the
NEC 250.122 because, the largest service wire is 200A at the meter to power the panels. Panel 2 doesn't have a ground so, can I connect a #8 wire (that I see listed as 100A under the NEC 250.122) from that panel to panel 1's grounding bus bar? or to panel 1's #6 wire?
Thank You.
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Are they two service panels, i.e., they both are fed from the meter directly? Or is one a subpanel for the other, i.e., one is fed from a breaker in the other?
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Matthew Beasley wrote:

Yes, they are both fed from the meter box directly. I have 200A a copper SE cable feeding the meter then, two 100A aluminum SE cables comming from the meter box feeding the panels. Also, the reason that they are separated is because they are apartments.
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snipped

the
Before you go off the deep end. Better check your building code, for compliance.
you need 4 wires, 2 hots a neutral and a ground for the subpanel, all grounding is done at the service location
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js5895 wrote:

I have a similar set up with two panels both are fed directly from the meter. One panel is in my house and the other panel goes to my shed.
The panel in my house is evidently connected to a water pipe. There is no ground rod outside the house. The electrician who installed the panel in my shed (60 feet away) drove a very long ground rod into the ground next to the shed.
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js5895 wrote:

The minimum size Grounding Electrode Conductor for your two hundred ampere service is #4 AWG copper. The panel closest to the metal underground water line should have a number four American Wire Gage Grounding Electrode Conductor run to the water line within five pipe feet of were that piping enters the building. The panel further away should have the number six copper conductor run from it to the nearest point on the number four GEC and connected with a split bolt. If the layout works out better then you can run the number four GEC to the neutral conductor at the service drop and connect it with a split bolt connector. If your power company will allow it you can also make that connection inside the meter can. When the GEC is attached prior to the reduction in gage of the service entry conductors you only need to run that one conductor to the grounding electrode system. If the water line is the only grounding electrode available on the premise then you must supplement it with another electrode. Driven rods are the easiest to install but they are also the least effective. In new structures a concrete encased electrode and or a ground ring is a much better choice.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
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Tom Horne, Electrician wrote:

Why a #6 for panel 2 and not a #8? Because I see under the aluminum column in table 250.66 that the GEC should be a #8 for a 100A #2 aluminum wire. Also, I thought table 250.122 would be used for the grounding tap and table 250.66 was used for conductors connected to a electrode, say, the #4 that is connected to my pipe.
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js5895 wrote:

The reason for using the number six is to avoid the requirement for physical protection. Number six is permitted without additional protection were not subject to severe physical damage. I should have made that clear. The conductor from the second panel is still a grounding electrode conductor so it is sized in accordance with 250.66. The language that permits the use of the tap is, after all, in table 250.66 Note 1.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
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Tom Horne, Electrician wrote:

Thank you for clarifying this, I appreciate it.
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