On 4/17/11 1:55 PM, Robert Harmon wrote:
> Wow, did I hit a nerve ? Didn't mean to stir up deep rooted
> feelings on this subject.
> Lets take one thing at a time. Our local building code does not specify
> connecting the tower to the rebar cage. It is also not required in the
> Uniform Building Code or the NEC.
NEC wouldn't require it, although it does require grounding the antenna
itself and any supporting structure (mast for a dish, for instance).
NFPA 780 (lightning protection) probably does require it, but around
here (low lightning southern California) the building departments don't
care much about NFPA 780.. your insurance company might.
> In building department inspections I have seen three separate instances of
> cracked concrete tower footings caused by lightning strikes. Two common
> denominators in each of these was the lack of tower grounding to a ground
> and a required building permit was not attained (which would have prevented
You're sort of implying that the footing wasn't built properly (i.e.
your comment about building permits)
In those cases, how did the lightning current get into the concrete? the
hold down bolts? Was the top of the footing well above grade level, etc.
so that water couldn't pool around the bolt?
There's a picture out there on the web of a ski-lift tower footing with
lightning spalling, and it's used as an example of bad installation and
design. The water pooled around the bolts, which started to corrode,
forming a gap between bolt and concrete, which does create a problem for
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