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
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