Paul,
The portion of R56 that you quoted has more to do with individual or
building footings used as a UFER.
With the tower foundation I would assume that you will have substantial
rebar in it. If all that rebar is tied together that will make a good UFER
ground on its own. No need to run a wire inside and or up to the top. You
will already have the pier pin connected with J bolts in the concrete or
otherwise. Just make sure that the rebar in the foundation is tied to the J
bolts or whatever is supporting the pier pin. All auxiliary ground rods can
be bonded to the pier pin or J bolts or tower legs.
73
Gary K4FMX
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> Paul Christensen
> Sent: Thursday, July 14, 2016 9:48 PM
> To: towertalk@contesting.com
> Subject: [TowerTalk] Ufer Grounding
>
> 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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>
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