On 11/12/12 1:30 PM, Mat Eshpeter wrote:
I am finally getting around to putting up my 60' AN Wireless tower on top of a
rocky ridge in WV. I rented a Hilti demo hammer and got about 1/3 of my rods in
to the ground at least 4' -- but the majority are only 2 or 3 feet deep because
of the rocks/ledges. I don't think I have much of a choice other than to cut
the rods off and drive the remnants into the ground field and exothermically
weld my 20 gauge copper strap to all of these shallow rods.
Other than paying big money for a well drilling rig to drill some deep 6" holes
and filling them with bentonite (which may not be possible given the slope of the
land and the fact that I now have 8 trenches running 75' out from the tower pad) do
I have any other practical alternatives?
It's all about contact area... Ufer grounds work well because a 20 foot
wire in a chunk of concrete has a huge contact area (a footing 20 feet
long and 1x1 foot is 80 square feet, right?)
Rods are used because it's cheap to drive a rod (some places) compared
to, say, trenching and laying a AWG 2 ring around the building.
There's also a ton of places where rods don't work very well (which is
why the electrical code doesn't let you use a single rod as the sole
grounding method these days...)
Rods are traditional, but the physics says that they don't work very
well (except maybe in perpetually rainy places with good conductive
soil, like Germany and England.. where all those traditions originated?)
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