On 12/23/2011 2:03 AM, Grant Saviers wrote:
> 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.
What we did (at the suggestion of the inspector) was to use a GFI for
the first outlet. All subsequent outlets on that circuit fed through
that sensor.
This gave us the equivalent of a circuit with a GFI without having to
spend the big bucks for a GFI breaker, yet the entire circuit is
protected via GFI.
I hope they still allow that.
73
Roger (K8RI)
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