[TowerTalk] Fw: w7ekb & ground rods

[Jim Lux]

On 1/18/15 9:53 PM, Kelly Taylor wrote:
> It seems to me a valid question to ask on this thread: Do you gain anything
> by, for example, drilling a hole to get a ground rod deeper?
>
> If you think about it, the answer might not be so simple.
>
> The point of a ground rod is to maximize electrical contact with the ground.
> If you have to drill 48 inches of an eight-foot rod and don't employ some
> kind of conductive filler (concrete, bentonite, etc.) to bond the rod to the
> rock, how much better off are you than just putting in a 48-inch rod? Even
> if you do use bentonite, is rock a good connection?
>
> If that's the case, what would be wrong with cutting the eight-foot rod into
> two 48-inch rods and driving them 96 inches apart?
>
> The point of eight- or ten-foot ground rods is to get eight or ten feet of
> contact area, not necessarily to get eight or ten feet deep, yes?
>


Yes, and two short rods would work as well, if not better, than 1 big rod.

However, there is a potential depth related issue: soil moisture varies 
a lot in the first few feet, and in a lot of places, the chemical 
composition of the soil changes (top soil vs subsoil).  That's not 
really addressed in the building code, though.

For what it's worth, the reason the code expresses a preference for Ufer 
grounds(concrete encased grounding electrodes) is just this sort of 
problem.  A big block of concrete 20 feet long and a foot square is 
going to have a lot of contact area with the surrounding soil, in a lot 
of places, so local anomalies of dry or loosely compacted soil aren't 
going to be as big a problem.



> Just curious on all this.
>
> 73, kelly
> ve4xt
>
>
> On 1/18/15 10:04 PM, "Bill Aycock" <billaycock at mediacombb.net> wrote:
>
>>
>
> -----Original Message-----
> From: Bill Aycock
> Sent: Sunday, January 18, 2015
>> 7:23 PM
> To: Ken
> Subject: Re: [TowerTalk] w7ekb & ground rods
>
> Ken--
> I was once
>> told (Unofficially) by a power line guy that the length was more
> important
>> than depth, and a rod driven at an angle was often the only option
> when rock
>> was a problem.
> However, Mr. Murphy ruled against me and I only knew I had a
>> rock problem
> when I had only about 8" left to go.
> Bill--W4BSG
>
> -----Original
>> Message-----
> From: Ken
> Sent: Sunday, January 18, 2015 7:00 PM
> To:
>> maflynn at theflynn.org
> Cc: towertalk at contesting.com
> Subject: Re: [TowerTalk]
>> w7ekb & ground rods
>
> If I may ask, what¹s the ³appropriate tool² when you have
>> a rock layer 40²
> down?  i tried a hammer drill, waste of time.  I rented an
>> SDS-MAX hammer
> and I got one in all the way, four others only made it most of
>> the way.   So
> what is the recommendation?
>
> Ken WA8JXM
>
>> On Jan 18, 2015, at
>> 7:46 PM, Martin A Flynn <maflynn at theflynn.org> wrote:
>>
>> Ran this past one of
>> the code enforcement guys in the county. Surprising
>> response:
>>
>> "We make
>> you buy a UL listed panel board and breakers -  what makes you
>> think you
>> can build a grounding system that is equal to UL *and*  be able
>> to prove it
>> in court if there is a problem? Buy the listed rod(s) and
>> drive them with
>> the appropriate
>> tool"
>
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