Service grounding and lightning protection

[Aidan]

How far does the service ground rod need to be from the lightning protection ground rod and am I correct in saying that for the service which is 200 amps a second ground rod is not necessary if resistance is less than 25 ohms and is this resistance tested on just the rod or both rod and cable back to panel

 

[petersonra]

How far does the service ground rod need to be from the lightning protection ground rod and am I correct in saying that for the service which is 200 amps a second ground rod is not necessary if resistance is less than 25 ohms and is this resistance tested on just the rod or both rod and cable back to panel

I don't recall that the code has any such requirements. 250.106 refers you to NFPA 780-2014. maybe there is something there.

Incidentally 250.60 prohibits the use of the LPS grounding electrodes from being used as structure grounding electrodes even though they are required to be bonded together.

I think that you will find that the cost of testing to make sure the earth resistance is less than 25 Ohms will far exceed the cost of a second ground rod.