[TowerTalk] Ground Rod Myths?

[Brian Amos]

Thanks for the advice.  I think my best course will be to test the
soil conductivity.  The only time we have lightening here is during
the summer storms; the soil is usually damp from the sprinklers all
summer so it's probably better with no concrete.  Does anyone know the
conductivity of concrete offhand? I guess I could always ask google,
although it probably depends on the aggregate.  Local aggregate has a
pretty high iron content and I expect would conduct fairly well,
unless the paste is a good insulator.

Brian
KF7OVD

On Thu, Apr 24, 2014 at 10:10 PM, Mike Fahmie via TowerTalk
<towertalk at contesting.com> wrote:
> It all depends on the conductivity of the concrete versus the local soil.
>
> Ufer grounds excel in soils with poor conductivity (dry sand is an extreme case), but it makes no sense to wrap your ground rod in a material that has poorer conductivity than the soil surrounding it.  Concrete can be a much better conductor than poor earth but worse than earth with good conductivity.
>
> I chose the Ufer path because my 'soil' is dry hardpan that resisted ground rod drivers and I felt that the large contact area of the concrete would makeup for the soils poor conductivity.
>
> -Mike-
> WA6ZTY
>
>
>
>>________________________________
>> From: Roger (K8RI) on TT <K8RI-on-TowerTalk at tm.net>
>>To: towertalk at contesting.com
>>Sent: Thursday, April 24, 2014 8:14 PM
>>Subject: Re: [TowerTalk] Ground Rod Myths?
>>
>>
>>On 4/24/2014 1:36 PM, Brian Amos wrote:
>>> I have the equipment to drill a 6 inch hole through just about
>>> anything, what if I placed my grounding rods in concrete or grout?
>>
>>I would think it wouldn't hurt.  It might act as a small UFER ground.
>>increasing the contact area of 20 inches Vs 1.9 inches or almost 11
>>times the area of the single ground rod.
>>
>>How well that'd hold true? I don't know.
>>
>>73
>>'
>>Roger (K8RI)
>>
>>
>>
>>> Would that help or hurt the grounding?  I do have a ground resistance
>>> meter I use for work for providing soil resistance values for
>>> grounding communication towers and equipment so I could test it I
>>> suppose, but I usually like to know what I'm getting myself into.  I
>>> have seen them drive a steel lathe (about 3/4 inch in diameter) into
>>> slightly weathered bedrock with a post pounder on a bobcat.  The
>>> cobbles and boulders just cause it to move a bit to the right or left.
>>>   Of course the commercial towers I do the foundation design for
>>> usually have a grounding grid surrounding them.  I am tempted to see
>>> if one of the tower engineers will design my grounding system with a
>>> similar system, they tend to suffer little if any damage from
>>> lightening, and being on mountain tops I am sure they are struck quite
>>> often.
>>>
>>> Brian
>>> KF7OVD
>>>
>>
>>
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