Ground Rod Proximity

[brian john]

I see quite a few post, one rod two rods.

What really is the big deal with today's hammer drills drive two rods and be done with it.

Had a job where the contractor wanted to test his two rods seems they were more than 6 feet apart and the AHJ would not accept the install.

I tried to explain to them that 6 feet is a minimum and most likely makes the tow rods less effective and rod electrodes will have better performance at greater distances. When I quoted the guy to test he decided to drive a 3rd electrode 6 feet from one of the original. Not sure if the AHJ allowed him to use all 3 driven electrodes.

 

[Dennis Alwon]

I think the difference between a CEE in a slab and a footer is the contact the footer has with the earth. The footer is always below grade and surrounded by soil where a slab is only on the surface.

I would think a CEE in a slab would not be code compliant but possibly still better than 2 ground rods-- I don't know.

Also the slabs, at least in a residence, around here don't have rebar but have a small metal mesh and sometimes a fiber mesh that holds the concrete together.

In the footers the rebar is driven down into the earth and then tied to horizontal runs of rebar.

I am sure in different areas the construction is different.