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Re: [TowerTalk] Grounding base slab and pier tower bases

To: JC Smith <>,
Subject: Re: [TowerTalk] Grounding base slab and pier tower bases
From: Nick Pair <>
Date: Mon, 3 Jul 2006 11:13:46 -0700 (PDT)
List-post: <>
The mention of buried tower section in slab was to infer that lightning going 
down this steel doesn't cause exploding bases either. One more myth busting to 
exploding base myth.
  The extra ring outside of base would be overkill but does no harm so go for 
it. It would still be in the discharge volume of the encased electrodes.
  Are your shack rods connected to your house electrical ground system. NEC 
requires this. It's one of the most overlooked things hams do. The other one is 
running ground wires through metallic tubing or even a hole in metal. This 
forms a choke for current flow and will limit ground fault or lightning 
current. This can be prevented by grounding each end to conduit or metal plate 
on one side. If you want to choke lightning current on outside of coax just run 
singly in a horizontal conduit for 20 feet or more.
  Happy 4th,
  Nick WB7PEK

JC Smith <> wrote:

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        Jim, Nick, and All,
  Thanks again for the advice.  Good point, I will flatten and ss bolt all 
ground pipe connections? no solder.
  Obviously the tower is grounded to the slab by the bottom section being 
encased in it so I will just be creating parallel paths to ground.  How about 
installing a Ufer ground down at the bottom of the foundation (in the 9x9 pad) 
AND installing the ?ring? of copper pipe all around the outside of the pier 
when we backfill (with bentonite added? it?s cheap)?
  It?s probably overkill, especially considering that my present tower is not 
grounded other than by the base bolts, but it?s cheap and easy to do at this 
point so why not?  While I?m at it I think I?ll add another ground rod for the 
shack.  It has two now but one of them is approaching 20 years of age.
  Unfortunately, no more tower progress until after the holiday.  I had to 
spend yesterday (and today) working on a house we are selling.
  I hope you all have a great Independence Day holiday!
  73 ? JC, K0HPS
  -----Original Message-----
From: Nick Pair []
Sent: Sunday, July 02, 2006 11:26 PM
Subject: RE: [TowerTalk] Grounding base slab and pier tower bases
  Hello JC,
  I would still encase the cu pipe in the concrete for several reasons. First 
the concrete enhances the contact area between the conductor and the soil. 
Second it isolates the cu from the soil which contains sulpher. The sulpher 
will bond to the cu making copper sulfate which will lower the surface 
conductivity. Third no soil enhancement needed. Try to keep undisturbed soil 
next to concrete pour anyway, for best load bearing ability, which your 
foundation size was based on.
  Nix on the solder for underground and ground conductors in general. The NEC 
doesn't allow it. Another consideration is the fact that its introducing 
dissimilar metals to a acidic environment. For your use a flattened, bolted, 
stainless hardware connection would suffice anywhere you need to splice or 
attach. Try to avoid splices if you can.
  All cell site towers are grounded to the rebar and to everything that can 
conduct in a 50 foot radius around them. The only cravat is they don't rely on 
the rebar soley to carry the current to ground grid. I've never heard of one 
falling after a strike or even multiple strikes. After all the base stub or 
bolts are in the concrete too as a parallel path and they present no problems. 
The radius is the only was to go. As large as you can and in no case less than 
  Concrete is such a good conductor that a large ( hundred square foot or 
better ) metal sheet (16 Gage min.) laid directly on clean concrete is used for 
grounding at 911 com centers in existing building basements where access to 
grid and rebar is limited or too great a distance away.
  I've done quite a few cell sites for different cell companies with different 
contractors and different inspecting jurisdictions. The engineering spec's were 
pretty much similar and of course NEC always the same. Feel free to bounce any 
questions or ideas off me on this subject.
If you lived in a more lightning prone area I'd recommend a lightning discharge 
device for the tower top. They do a good job of keeping the tower potential 
below where a leader arc can be created preventing a strike from occurring to 
the tower and a radius equal to the height around it.
  Nick WB7PEK
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