[TowerTalk] Ground Rods in rocky soil

[Jim Lux]

At 05:37 PM 1/21/2007, Gary Schafer wrote:


> >
> > So, your piers probably have rebar in them.. if they are tied to the
> > bolts?  Actually, interestingly, for a Ufer type ground, all the
> > metal doesn't have to be connected.
>
>Not a good idea. You don't want the possibility of an arc inside the
>concrete by not having a solid connection between metal parts.

So you might think at first, but apparently there is a wealth of test 
data that shows it works just fine (at least for DC, 60 Hz, and 
lightning impulses).  I suspect there are some practical limits (I've 
not got a copy of the paper with the testing yet).. You couldn't 
expect to shove a 6" long bolt into the footing and have it work.


There were a series of tests done with Ufer type grounds using 
lightning impulse simulators, etc. a few decades ago.  I have a 
reference to a paper by Fagan and Lee from 1970, but I don't know if 
that's the one that has the testing procedures and data.


Jim, W6RMK