3 point grounding system

[102 Inspector]

Have a project that the plans call for a 3 point ground rod system. I have never seen this referenced before and have questions. The project is wood frame with a concrete encased electrode provided and will have a 1 1/2" copper water line. What am I missing that would require a 3 point ground rod system. Are they indicating they want 3- 5/8" ground rods connected together? There is nothing about any ohms requirement. Any comments on what is intended. Thanks

 

[luckylerado]

Mabey they mean a triad??

"3 point" in the context of grounding usually would mean fall of potential test in my experience.

 

[roger]

For some reason some designers think there is something magical about three rods in a triad, but the fact is, it's just a waste of money.

Roger

 

[big john]

If you have an Ufer then your effective electrode is already the entire surface-area of the building footing. Adding three little rods on top of that ain't gonna do nuthin.

But yes, they got a grounding-voodoo spec from somewhere that says if you sink three electrodes in the shape of a mystical pyramid then this appeases the Almighty Diety of Grounding and he will favor their facility with reduced transient voltage.

So do it and get paid.

 

[J.P.]

Oh nooo! I usually put my three ground rods in a straight line.





Engineers are odd beast for sure. I had a spec for three ground rods with #2 wire, plus a CEE with #2 wire, and my building steel bond, gas and water bond. All spec'ed #2. 400A service.

Whatever... I'll do whats on the prints as long as it isn't unsafe.

 

[roger]

I had a spec for three ground rods with #2 wire, plus a CEE with #2 wire, and my building steel bond, gas and water bond. All spec'ed #2. 400A service.

Whatever... I'll do whats on the prints as long as it isn't unsafe.

I have an ongoing project with over 70 rods cadwelded to 4/0 :blink:.

Roger

 

[Tony S]

Three point fall of potential testing

http://www.fluke.com/fluke/inen/solutions/earthground/fall-of-potential

 

[roger]

Three point fall of potential testing

http://www.fluke.com/fluke/inen/solutions/earthground/fall-of-potential

Tony, that is not the subject matter of this thread.

Roger

 

[Tony S]

OK I should have quoted this first.

Mabey they mean a triad??

"3 point" in the context of grounding usually would mean fall of potential test in my experience.

Multi-point earthing is common the world over.

One particular job needed 10 off 30Ft rods to get to a value accepted by UK’s M&Q regulations (mines and quarries not BS7671). M&Q is statute law, there is no option other than comply.
Not fun in a quarry when you’re on bedrock before you start.

The testing was by fall of potential.

 

[iwire]

One particular job needed 10 off 30Ft rods to get to a value accepted by UK’s M&Q regulations

So other than complying with the local requirement what did this voodoo accomplish in regards to a safer installation?