So based on the above discussion, what can we advise the OP about lightning protection for his ground mount array? Since the array is supported by wood posts (a fairly good insulator) then no connection to earth is made and no additional grounding (ie grounds rods) should be installed at the array. Thus we are treating the array just as we would an external generator and would not define it as a "structure" per NEC rules. A four wire connection to the house main service entrance is all that is needed. But if his AHJ requires him (as I think they will) to sink a ground rod or two at the array then he should bond the electrodes together underground between the array and the main service entrance using a separate thick copper conductor, as max2k recommends.
In the case of ground mounts that use metal pipes embedded in concrete a few feet in the earth, then a separate thick copper conductor would be bonded below ground from array structure to grounding electrode at the house in addition to the four wire connection. But IMO it depends on distance between the two structures. Then a risk/cost analysis is necessary. A four wire connection many hundreds of feet between the structures will have inherent resistance and thus force a side strike into the ground or reduce the step potential because of distance at either site without damaging the other. How risk adverse are you and how much money do you want to spend?
In all cases an EGC is necessary to protect people from faults in the equipment wherever located.
In the case of ground mounts that use metal pipes embedded in concrete a few feet in the earth, then a separate thick copper conductor would be bonded below ground from array structure to grounding electrode at the house in addition to the four wire connection. But IMO it depends on distance between the two structures. Then a risk/cost analysis is necessary. A four wire connection many hundreds of feet between the structures will have inherent resistance and thus force a side strike into the ground or reduce the step potential because of distance at either site without damaging the other. How risk adverse are you and how much money do you want to spend?
In all cases an EGC is necessary to protect people from faults in the equipment wherever located.
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