lligetfa wrote:I don't wish to drag this off topic but the NEC required minimum for service ground is intended to draw enough current on a ground fault to throw your average 15A breaker but there is no actual test to verify intent. In some cases the resistance on the service ground added to the resistance on the circuit under fault might not actually trip a breaker. Remember that the code intent is not to protect sensitive electronic equipment but rather to save lives and buildings.
Also, code requirement for bonding is #6 wire, not that puny bare copper in your 12/2 feed.
I have always suggested when bonding service ground rods to tower ground rods to use #2
As you said those standards are not intended to make sure there is not more than 5 Ohms of ground potential to protect sensitive equipment.
But I still say in his application do not worry about bonding the service and tower grounds as they as so far apart, simply do not use the service ground and only use the tower grounding system as his electrical earth ground.
I do this at many of my sites and it stopped my problems. I was not the genius that came up with this I happen to be located on a cell tower owned by an electrical service company and they were providing me AC power from 200+ feet away and I was bonding the 12-2 ground wire to my ground bus in my box bonded to the tower ground system. Their service grounds at their shop were poor and the ground current was flowing across that 200+ feet of small copper trying to get to the GOOD ground halo ring the cellular companies put in. That 12-2 wire ground wire heated up and caught fire. THey came out and told me how stupid I was and explained why I did not want to use their ground just use their Hot and Neutral and use the tower Earth ground as my Electrical Earth ground and problems went away.
So that is an example how Ground Current can cause damage, in this case it was trying to push so much ground current across that 200' of cable that it heated up the ground wire so hot it caught the wire on fire. Luckily it tripped their breaker in their shop and the wire fire was nowhere near anything else that burned so no 3 alarm fire ensured.