Why two ground rods

[tom baker]

This was in general electrical and I will post here
"Drive two and go home" its 2 due to diminishing returns
2 rods decreases resistance by 60%
2 rods decreases resistance by 40%
Adding electrodes in parallel decreases resistance
This is from AEMC. I do not know the source of the orginal information, likely some test years ago when the 25 ohms was adopted

 

[Fred B]

This was in general electrical and I will post here
"Drive two and go home" its 2 due to diminishing returns
2 rods decreases resistance by 60%
2 rods decreases resistance by 40%
Adding electrodes in parallel decreases resistance
This is from AEMC. I do not know the source of the orginal information, likely some test years ago when the 25 ohms was adopted
View attachment 2558615

That's 3 rods 40%

 

[wwhitney]

And it should be "2 rod decreases resistance to 60%, 3 rods decreases it to 40%."

Of if you like "2 rods decreases resistance by 40%, 3 rods by 60%."

Cheers, Wayne

 

[petersonra]

Personally, I am pretty much convinced one rod does as much good as two, or ten for that matter, in most situations.

 

[tom baker]

Personally, I am pretty much convinced one rod does as much good as two, or ten for that matter, in most situations.

Probabaly, for for our AHJs, GRs are always checked
With more ufer grounds, in 10 years we will have explain what a ground rod is.