Sizing grounding electrode conductor

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Transportation Guy

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Williamsburg,VA
We have a church we inherited from an unlicensed contractor. Cleaning up a huge mess. We have 3 service disconnects (200 amp) fed by 1 utility company transformer. (1 meter) Coming out of the transformer are 3-2" pipes and per plan we installed 4-3/0 cables. 3 hots and a neutral. I was planning on installing 1#4 bare copper per panel based on 250.66 but realize now that's not correct based on note 1. Please help.


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You can install a separate grounding electrode conductor from each disconnect as stated. Each would be sized per 250.66 for the conductor supplying the individual disconnect (assuming 3/0, then a #4 Cu except for the #6 exception for ground rods).
OR you can install one conductor to the electrodes based on the combined cir/mil of the service conductors (211,600 x 2 = 423,200 for a 1/0 GEC) (exceptions for ground rods & UFER)
If you use the single GEC you can connect it at the meter (if allowed), and common point ahead of the disconnects, or with a #4 tap from each disconnect. (example shown below ..not your conductor sizes))
grounding2disconnects2.jpg
 
If you elect to connect from each service panel to building steel independently with no common grounding electrode conductor, each panel will need a conductor to the steel.
 
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