Lightning protection [RE-wrenches]

[Travis Creswell, Ozark Solar]

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Sounds like a job for Tool Time Tim and his Binford 2000...  more power....

Good point. You've made me wonder.  Assuming that a major component of the
effectiveness of a ground system is how well it conducts to the surrounding
soil the one with the most surface are should be the most effective?  Right?
Of course, the conductivity of the surrounding soil maybe even more do with
effectiveness.  I really don't know.

Let's compare the surface area of cylinders and see what wins.  I just so
happen to know that formula off the top of my head.  You believe that, don't
you?  

(2 x pi x r x r) + (2 pi x r x h)  for those who might need to look it up

80' x 3/4" ground rod = 15.7 ft2

300' of bare 2/0 (I'm giving a generous OD of .75 to save the time of
looking it up) = 58.9 ft2

A 8' deep x 3' diameter cylinder = 89.5 ft2

I'm not sure why the bare 2/O didn't work.  Maybe it was close enough to the
surface in soil that dried out and lost conductivity.

The ground rod must get deep enough to be in very conductive soil.

Even though the bentonite clay technique gives the most surface area it
might still be too shallow to stay dry year round.  I know when it gets
really dry around here and the utilities actually water this style of
ground.  So maybe they are digging smaller diameter holes deeper.  This
isn't something they are doing at homes by the way.  This technique is for
their switch gear and sub stations so they can afford to get a pier truck
out.  Next time I talk to my substation designer buddy at the utility I'll
ask him.

Travis


-----Original Message-----
From: Darryl Thayer [mailto:daryl_solar at yahoo.com] 
Sent: Monday, July 25, 2005 8:09 PM
To: RE-wrenches at topica.com
Subject: RE: Lightning protection [RE-wrenches]



--- "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
wrote:
> How does one drive a ground rod 80'?   Must be very
sandy soil which
> explains the need for such
> a long ground rod.

Yes, I used a Bosch electric pavement breaker with a
ground rod driver attachment. 
> In trouble spots around here the utilities will
> auger a hole in the soil
> then pack it with bentonite (sp?) clay and drive the
> ground rod in that.
> Travis

That sounds like a good idea, however prior to driving
the 80 foot rods, I buried 300 feet of 2/0 bare wire
to no benifit.  
 

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