The problem is that strap can decay and degrade over time directly in some
types of earth AND As you have pointed out, connection to strap is problematic
at best unless it is also welded (brazed using silver bearing welding) The only
place I recommend strap is between the external grounding electrode system and
the building coax entrance panel. Harger http://www.harger.com/ makes a
special welded system to transition the strap to a copper bar and then it's cad
welded to the #2AWG bare tinned grounding system.
Most communications sites (cellular and public safety) use #2 AWG tinned
underground conductors that are exothermically welded together. Some Federal
Government installations may have specifications that require larger wire. But
over the years, solid tined wire has proven to be the best.
73
Jim W7RY
Motorola Solutions
From: Mat Eshpeter
Sent: Sunday, April 17, 2011 9:34 AM
To: w7ry@inbox.com ; towertalk@contesting.com
Subject: RE: [TowerTalk] grounding quesitons: Ufer, strap, exothermic welds
Jim - what about the inductance of wire? The reading I have done strongly
suggests that lightning is better handled with solid strap because of its low
inductance versus wire. Lightning is supposed to be broadbanded with most
energy centered around 1MHz so strap is supposed to be "king" for the purposes
of dissipating lightning.
73,
mat
> From: w7ry@inbox.com
> To: kk1c@live.com; towertalk@contesting.com
> Subject: Re: [TowerTalk] grounding quesitons: Ufer, strap, exothermic welds
> Date: Sun, 17 Apr 2011 07:58:27 -0700
>
> I would put some #2AWG tinned solid in the foundation and not rely on the
> rebar.
>
> I have used a clamp type unit to clamp the copper strap to the ground rod.
>
> If it's lightning your concerned with, I would not use strap. Stick with
> #2AWG tinned bare copper, copper clad rods and exothermic attachment.
>
> 73
> Jim W7RY
>
>
> --------------------------------------------------
> From: "Mat Eshpeter" <kk1c@live.com>
> Sent: Sunday, April 17, 2011 7:24 AM
> To: <towertalk@contesting.com>
> Subject: [TowerTalk] grounding quesitons: Ufer, strap, exothermic welds
>
> >
> > I am about to pour concrete for the base of my HDX589 tower. I am going to
> > go with a Ufer ground as well as the Polyphaser recommended eight 75'
> > radials with multiple ground rods (8' rods every 16'). Location is on top
> > of a 1600' ridge in WV and lightning is a very real concern. My QRZ web
> > page gives a feel for the location.
> >
> > To build the Ufer ground, I am thinking about connecting a single bare 2/0
> > stranded copper wire to the rebar. Questions:
> > 1) is one enough?
> > 2) how do I properly connect the copper to the rebar? Is exothermic weld
> > the only way? Any problem with dissimilar metals?
> > 3) how should the copper exit the base slab - above grade or below grade?
> >
> > Also, seems that copper strap is the preferred ground material for
> > connecting rods together. Will 0.032" thick strap have significantly
> > better longevity than 0.022" strap? I am refering to the strap sold by
> > Georgia Copper. Copper is expensive and I don't want to invest in copper
> > that won't add any value to my installation.
> >
> > Where can I find exothermic weld products to connect copper strap to 5/8"
> > copper clad ground rods? I am exhausted reading Harger, Erico, Terraweld
> > info, and can only find wire-to-ground rod products, no strap-to-rod
> > products.
> >
> > 73
> > Mat
> > KK1C
> >
> >
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> >
> >
> > -----
> > No virus found in this message.
> > Checked by AVG - www.avg.com
> > Version: 10.0.1321 / Virus Database: 1500/3578 - Release Date: 04/16/11
> >
--------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1321 / Virus Database: 1500/3579 - Release Date: 04/17/11
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|