Sizing grounding electrode conductor

[Transportation Guy]

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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[augie47]

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))

 

[Transportation Guy]

Thanks. Do we hit the building steel 3 times if we go with the number 4? Or is 1 time sufficient?


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[augie47]

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.