Less than 10 ohms

[yellow77]

I am testing the resistance of an extension of the lightning protection with a clamp grounding tester. They tailed a single 4/0 from the ring to the top of a 20' of ground rod and the resistance is 20 ohms. To reach the minimum 10 ohms in the specs would you suggest creating a seperate loop for the rod or just add more to it.

 

[K8MHZ]

I am testing the resistance of an extension of the lightning protection with a clamp grounding tester. They tailed a single 4/0 from the ring to the top of a 20' of ground rod and the resistance is 20 ohms. To reach the minimum 10 ohms in the specs would you suggest creating a seperate loop for the rod or just add more to it.

Sounds like a job for PolyPhaser.

http://www.polyphaser.com/technical_notes.aspx

Read until your heart's content. It's a great source of info.

Short answer, a serviceable grounding electrode system. That is NOT the cheap answer, though.

The cheap answer would be to dump a 55 gallon drum of salt water around and on the ground rod and re-test.

For real though, this notes on the PolyPhaser site are excellent.

 

[K8MHZ]

Also, be sure the technique used to make such a measurement is correct.

This link is to a great book about grounding.

http://www.metercenter.com/biddle/GettingDownToEarth-MC.pdf

 

[chris kennedy]

Sounds like a job for PolyPhaser.

http://www.polyphaser.com/technical_notes.aspx

Nice link, thank you. (bookmarked)