[TowerTalk] Ufer Grounding

[Dick Blumenstein]

Hi Paul-

I thought that one is NOT supposed to ever weld to the rebar, unless the 
rebar is spec'd for welding, which most are not; that all grounding wire 
should be clamped to the rebar and then when the wire leaves the area of 
the tower base, you should/could cad weld it to the ground rod system.  
Am I wrong here? (I'm about to build a concrete tower base with a 5' x 
5' x 8' deep hole and a lot of rebar).

Dick, K0CAT

============================


Paul Christensen wrote on 7/14/2016 10:48 PM:
> It's looking more probable that the remote Internet site built last year by
> N4CC and myself will require a complete move about a half-mile down the
> road.  Assuming this is the case, I want to pay particular attention this
> time to Ufer grounding of the two tower bases.  These are large Pirod
> self-supporting towers with substantial concrete piers.  The relevant
> portion of Motorola's R56 standard is copied and pasted below.  The soil in
> this area is very sandy and at the current site, we ended up having to drive
> down a total of four 24 ft. rods to get adequately low earthing resistance.
> That was a rough day of work even with a hammer drill.
>
> My thought is to "spiral wind" solid #2 AWG wire, beginning the bottom rebar
> layer.  Cadweld it at the start point, and then periodically Cadweld at
> random points where the wire crosses other rebar sections.  The wire would
> exit at the top of the pier using a small-diameter PVC pipe as shown in one
> of the R56 diagrams.  As the wire nears the top, possibly it could branch
> out into two additional directions for bonding to the tower base and
> perimeter ring.
>
> Any issues with this plan?
>
> Paul, W9AC
>
> Motorola R56 Ufer Guidelines:
>
> . Concrete-encased electrodes shall be encased by at least 51 mm (2 in.) of
> concrete, located within
> and near the bottom of a concrete foundation or footing that is in direct
> contact with the earth.
>
> . Concrete-encased electrodes shall be at least 6.1 m (20 ft.) of bare
> copper conductor not smaller
> than 25 mm2 csa (#4 AWG) or at least 6.1 m (20 ft.) of one or more bare or
> zinc galvanized or other
> conductive coated steel reinforcing bars or rods at least 12.7 mm (0.5 in.)
> in diameter.
>
> . Concrete-encased electrodes shall be bonded to any other grounding
> electrode system at the site.
> See "Common Grounding (Earthing)" on page 4-5.
>
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