[TowerTalk] [Bulk] Re: Tower grounding connections and foundation

[Grant Saviers]

Re TIA-222-G:

I would like to be enlightened why  #00 wire is needed to attach to two 
ground rods which are likely several ohms resistance to the "remote 
earth"?  Especially when #6 was ok in the last rev of the standard and 
when from an I^2*R and fusing current it would do the job.

Further, it is a bit of a mystery why Ufer grounding is not included 
when it is the NEC & military standard for structures containing 
munitions, explosives, etc.  This forum has opined extensively about why 
Ufer's beat ground rods.

Is there any science and engineering behind the new rev G requirements 
and documented failures of towers installed to the old standard?

Or is this "standards polishing" by parties with a beneficial interest?  
I've been there, seen it happen.

Then there is the "default" - 10 ohms - maybe one ground rod and 18 
gauge wire?  Hilarious!

Grant KZ1W

On 8/7/2015 16:10 PM, JVarney wrote:
> Patrick Greenlee wrote: >>So would circling the Ufers be redundant?<<
>
> =====
>
> I won't give you advice on what to do but I will share with you what the
> TIA-222-G code says about grounding.  Generally TIA-222-G is the governing
> code, not NEC.*
>
> Per TIA-222-G, "Protective Grounding":  The default configuration for a
> self-supporting tower is a star ground consisting of 6 ground rods arranged
> symmetrically around the tower base with each rod separated a minimum of 20
> feet apart from its neighbor, with at least one #00 wire connecting each
> tower leg, each to two of the rods.  If the default grounding system is not
> installed then the tower owner has the option to install an alternate
> system that provides no more than 10 ohms resistance to "remote earth."
>
> Ufer grounds are not recognized by TIA-222-G; they seem to imply the
> opposite because the purpose of the grounding system is to "limit damage to
> the structure or foundation."
>
> The TIA-222-G grounding requirements is a tough standard to amateurs to
> meet, it's expensive and big! I think it's clear the TIA committee's
> philosophy is to provide multiple low resistance paths throughout a large
> volume of earth away from the tower as a way of dissipating lightning and
> static charges. If I was putting in a large tower with an Ufer, I would
> supplement the Ufer and mimic the TIA-222 design as best I could with big
> conductors connected to each leg and multiple ground rods well away from
> the tower.
>
> 73 Jim K6OK
>
> * If the tower is immediately adjacent to a house then NEC and TIA codes
> conflict with each other. Assuming the tower is well away from any
> structure, TIA would apply.
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