I just put in Ufers in a perimeter foundation. According to code here
they need to be a 20' long rebar less the stub out and tied to the other
rebar (4 x #5 x 262' in my case). #4 (1/2") was used for the stub 20'
and I think it would take quite a strike to vaporize it. For my tower,
I welded rebar all around at two levels to the 6 x 1 1/8" anchor bolts,
mainly to keep them in place during the pour (K7LXC idea). That cage is
also wired to the structural cage, making a Ufer out of the concrete
tower base, which has about 250 sq ft of contact area with wet ground.
In a prior thread the concrete/wire damage issue was covered - what
should be avoided is short paths through the concrete between
conductors, think resistors. If the rebars are spaced then there is a
lot of concrete to handle the current = lower power density. Otherwise,
tie or tack weld them together (if the inspector allows that).
b.t.w. today my electrician told me the NEC now requires GFI's on ALL AC
outlets above uncovered concrete floors. A real $$ and maintenance
pain, but note the thinking about how conductive concrete really is.
Grant KZ1W
On 12/22/2011 5:11 PM, Cqtestk4xs@aol.com wrote:
> If that's the case, why do we use UFERS? Same concept. Just wondering.
>
> Bill K4XS
>
>
> In a message dated 12/23/2011 12:58:34 A.M. Greenwich Standard Time,
> wa8jxm@gmail.com writes:
>
>
> On Dec 22, 2011, at 2:18 PM, David Gilbert wrote:
>
>> I put up an An Wireless HD-70 tower and exothermically welded some
>> ground wires to the base section before it was embedded in the concrete,
>> figuring that down there (roughly four feet below the surface of the
>> concrete)
>
> Poor choice AFAIK. My understanding is that if the tower gets takes a
> heavy hit by lightning, the wire could vaporize and crack the concrete.
>
> Ken WA8JXM
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