[TowerTalk] Grounding base slab and pier tower bases

[Nick Pair]

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 6".
  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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