ECN Forum Forums General Topics of the Trade General Discussion Area what is ground?

Update from Fl IAEI
Bryan Holland (City of North Port) suggests the rebar in concrete pilings would be a good ground. He also says the shore side disconnect should happen.

Greg:
I agree with Bryan (BPHGravity, I believe) with the rebar in the concrete pilings, if & when that construction is available. The structures we have on piers here are wooden pilings; the grounding of the services is made on 'shore' (terra firma), at the disconnect, with a GEC installed with the feeder to the structure.

I agree with the concrete piles (vertical ufer) in principle but may requires an engineer approval. A lot would have to do with how deep the piles are and the muck its buried in

Greg,

I know this might be a little off the topic, but Talking about the Grounding Electrode being encased in concrete that is used for services in new houses. I hear from people that the electrode might blow out a footing if it was to take a direct hit from a lightning strike. Now being that you are in the lightning state, have you or any friends ever seen or heard of an instance where lightning damaged a footing or electrode?

I have never actually heard of that happening. I bet the only way it could would be if the concrete itself was very dry and not particularly well grounded itself. Heat comes from high resistance. P=I2R

Actually I suspect the opposite. The damper the concrete, the lower the resistance. Lower resistance means more current. More current PLUS water means a greater chance of forming steam. More steam, greater probability of catastrophic failure.

Larry C

All of the current from a lightning strike is going to be there no matter what (it came through 5-10 miles of air). If you are jamming it through a high resistance you get a lot of heat. If it goes through a very low resistance path it dumps the energy into the ground.
If you look at the extremes you can look at an old dried out tree, that will literally explode or you can look at the copper conductors from an air terminal that shows no damage at all.

All that said, I have never heard of a properly made Ufer blowing up and we have a lot of lightning strikes here.

It's not uncommon to see such trees hiking or hunting either, some looking like they were split by a giant axe

yet there were those who had to deal with Mother Nature before the modern age of our trade

for instance, some of the bigger barns built had a beech ridge runner , and you may have seen some ash trees nearby

it was believed that beech repelled, and ash attracted lightning

~S~

I don't have alot of experience with lightning. I have been wrong many times in the past and I will be wrong in the future. I still think that it would be possible to have catastrophic failure in a concrete enclosed electrode, but I know of no cases were it has happened.

Lets submit it to Mythbusters.

When mythbusters did their lightning show they couldn't get any bad things to happen until they lifted the ground electrode conductor. When they had the whole house, and phone line, isolated, all sorts of bad things happened.
We had a lot of lightning experience in the computer biz and the real answer was always more grounding and bonding.