GES

[mwm1752]

To the OP

The common grounding electrode conductor shall be sized in accordance with 250.66, based on the sum of the circular mil area of the largest ungrounded service-entrance conductor (s)

• of the largest ungrounded service-entrance conductor

We have sets of service disconnects (more than one enclosure) implying you have at least one set of service entrance conductors supplying each enclosure.

You can have more than one set of service entrance conductors supplying a single enclosure. In the example I gave disconnect one is feed with two sets of 200 Kcm conductor and defined as a single conductor base on the sum of the circular mil area 400 Kcm. Conductor.

If one of the single service disconnects s supplied by a 500 Kcm (two sets of 250Kcm) than the 400 Kcm (defined single conductor) is not the largest the 500 kcm would be the bases for the rule.

Edit If in your reading of the sentence you remove the word largest than you have a sum of circular mil area of the service entrance conductors

The common grounding electrode conductor shall be sized in accordance with 250.66, based on the sum of the circular mil area of the ungrounded service-entrance conductor (s)

David, your drawing shows 3 separate service laterals in which each would need a continuous electrode conductor each sized accordingly. I do not see where they are all tied together at the building in the drawing to make it a single lateral as per exhibit 250.27.

 

[david]

David, your drawing shows 3 separate service laterals in which each would need a continuous electrode conductor each sized accordingly. I do not see where they are all tied together at the building in the drawing to make it a single lateral as per exhibit 250.27.

The service disconnects are grouped at one location. you only need one continuous un-spliced grounding electrode conductor to the service disconnect supplied by the largest service entrance. You would tap the other two grounding electrodes to that one.

you could run three separate if you choice to