On 1/1/13 8:21 PM, K8RI wrote:
On 12/30/2012 2:14 PM, ve4xt@mymts.net wrote:
Another repetition of the exploding base myth.
If concrete is so explosive, and such a poor conductor, why is it
often used to assist with rod-earth connections?
As well, the very existence of the Ufer ground pretty much debunks the
exploding base mythology.
The NWS even has video showing what could be construed as the exploding
base and it is no myth, BUT we need to be able to separate cause from
hearsay.
Can you provide a URL or something? I tried googling "NWS concrete
damage lightning" etc and couldn't turn something up.
I did find a LOT of pictures of concrete damaged by lightning, but none
of them were a Ufer ground.. More things like a sidewalk hit by
lightning, or a concrete block wall with a big crack.
I have seen pictures of concrete blown apart from lightning strikes and
some of those were from the NWS so I believe them. However in those
cases we need to ask WHY did the concrete either blow apart, or crack so
badly it had to be replaced.
Yes.. the ones I saw were not a Ufer style ground.
In the course of my googling, I also learned about Bruce McCain or Max
Mccomb (I saw both versions of the name), who was an electrical
contractor responsible for grounding ski-lift towers in the Sierra
Nevada. His success with the Ufer ground led to his advocating it for
the NEC.
Of course, this is hearsay so far.. haven't found the original info.
Just "did you know about x..." kind of stuff in a forum or website.
One common thread in all the discussions I've read where spalling did
occur was that either
a) it wasn't a grounding system issue.. it was somewhere else in the
structure
b) where it was a grounding system, everyone concerned thought that
nothing would have done any better than the Ufer ground, and probably worse.
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