Re: [TowerTalk] Re: Floating Ground Steel Building?

[doc <kd4e@verizon.net>]

> > As I understand the UFER system either the rebar is extended
> > beneath the slab well down into the soil or a second metal mat
> > is laid beneath the slab -- I don't recall the UFER ground depending
> > only on the marginal conductivity of moist concrete.
> Nope.. UFER grounds (aka "concrete encased grounding electrode) are just 
> a wire embedded in the concrete, or a suitably bonded rebar cage.
> Recall, though 
> that the NEC is concerned about not burning down the house or causing 
> physical damage, not blasting your delicate electronics.  The latter 
> reason may inspire you to put in a somewhat lower resistance (or, more 
> important, lower inductance) path, to limit the peak voltages.
> This is why GOOD connections (tight clamps, exothermic welding) are 
> needed. You do not want an arc forming

So the standard slab rebar "should" manage whatever discharge comes to 
it (indirectly) off the roof and walls into the channel bolts embedded 
in the concrete?

And, so long as the entry-point grounding system is done correctly I
"should" be OK?

Would adding some ground rods exothermically tied to the metal channel 
at the base of the metal walls be a) worthless, b) of marginal value,
c) good insurance, or d) counterproductive?

One other concern.

I had originally been told that the outer and inner layers of the
steel panels were electrically isolated from one another -- this
I just discovered is not true.

Although the outer and inner steel on the roof panels are separated by 
6" of fireproof foam and the wall panels by 4" and attachments from the 
roof to the slab require and through-connects (bolts, etc), the wall 
sections do sit on a metal channel that joins the outer and inner
layers electrically.  Sigh.

That established, were the building to take a significant lightning 
charge and I were to be touching the inner metal skin with one hand
and grounded somehow via hands or feet, would I risk becoming part
of the ground path?

Thanks! & 73, doc kd4e
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