Size of grounding electrode conductor and main bonding jumper

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marcs11

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We have a 3 Phase 120/208 320 amp meter socket. With (2) 3/0 cu conductors per phase. Feeding (2) 200 amp Main breaker Panels. (1) conductor from each phase terminating at each of the 200 amp Main breakers. Technically NOT a parallel connection because only one side of the conductors are terminated at the same point. Would the size be based on the largest Ungrounded conductor 250-66 and 255-102 (c)(1) in this case 3/0. Requiring (2) # 4 cu OR treat the installation like a parallel connection requiring (1) 1/0

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A main bonding jumper or grounding electrode connected at the meter socket itself would be based on the size of the service conductors supply that meter socket/ Bonding jumpers in you individual 200 amp panels would be based on the 3/0 feeding each panel.
If you run separate grounding electrode conductors from each panel, those would be bases on the 3/0. If you elect to run a single GEC and tap onto it from the panels, the single GEC would be sized on the sum of the CM of the 3/0s
 
Thank you The local utility co will not allow any grounding conductors in the meter. The utility will be pulling their own conductors from the street to the meter most likely 250 MCM AL. So all the connections will be in the panels. We have (1) # 6 cu going to two ground rods and (1) # 4 cu to our UFER ground. I suggested to run both to each Main breaker panel. The Main bonding jumper from the grounded conductor to the can # 4??
 
I will likely use the "grounding electrode conductor taps" provision to run a tap from each GEC to each panel. As far as the MBJ, isnt that a screw provided with the panels? IF you made your own, yes it would be #4.
 
Sounds like you have it covered. Keep in mind if your GEC originates in the service equipment, each enclosure must have a GEC connection. Details are found at 250.64(D)
 
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