On 8/8/15 2:33 PM, N3AE wrote:
Concerning lightning damage to a concrete foundation .... ran across the
example in the link below. In this case a concrete guy anchor was damaged. But
looking at the pictures, this might have been caused by moisture entry due to
surface cracking with the lightning strike just finishing it off as the current
pulse turned the moisture into steam. Hard to say.
and this quote covers why "commercial" installations (where labor is a
big cost) are different than "ham" installations (where labor is often
free); "the conductors are really a small portion of the overall cost
of the job"...
"Deep-driven rods in combination with heavy copper cabling have proven
to be an effective, reliable and durable solution. And don’t skimp on
the copper. Use large conductors, not ‘Code Minimum’ sizes. The
conductors are really a small portion of the overall cost of the job.
“Install ring grounds and radials if there’s room, and bond all
connections properly. In a major lightning strike, you’re potentially
dealing with tens of thousands to hundreds of thousands of amps. Copper
is cheap insurance compared with the equipment damage that could occur
if the system is inadequate. In the case of the KPTH-KMEG tower, another
strong hit might have led to very expensive repairs … or worse.”
I think the real question is if a lightning strike can cause internal damage to
a tower concrete foundation that you can not easily detect.
N3AE
http://www.copper.org/applications/electrical/pq/casestudy/a6137/a6137.html
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