"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"
No idea, but Erico sells many forms of Cadweld shots that are designed to
bond coper wire with rebar. Anyone know the answer? Is there a special
form of rebar that can only be used with an exothermic weld?
Paul, W9AC
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Dick
Blumenstein
Sent: Friday, July 15, 2016 11:59 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Ufer Grounding
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.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk