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Ground Rod Diameter vs grounding performance question BobK207 09-17-2006
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Posted by Tom The Great on September 19, 2006, 11:50 am
On Tue, 19 Sep 2006 08:26:20 -0400, gfretwell@aol.com wrote:

>
>>but if the code wants 25 ohms max to earth but it lets you do two rods
>>& not test?????......where is the performance in that? It's an
>>assumption that it's probably "good enough" but it could be pretty
>>bad, couldn't it?
>
>I have been involved in this a few times. The thinking is that if 2
>rods will not get you 25 ohms 20 rods probably won't do much better.

Amen brother, this concept is so hard to get people to understand.

But once they understand, they start crying about GFCI's not working
then, and I have to shake my head and walk away. Unless I'm charging
by the hour, then I'll take all day to explain how GFCI's work, and
normal breaker overcurrent, and short circuit protection work with no
grounding electrode conductor. Oh with drawings too!

I love when people agree to pay me by the hour!

tom

>Where we did need performance (radio towers, toll booths etc) we went
>to extremes that a normal residential contractor wouldn't be able to
>and still have an affordable home.
>Early in the construction process the Ufer (concrete encased
>electrode) is probably the best. If you are grounded to the foundation
>of the building, at least you are safe in reference to the concrete
>floor in the garage or the tile in the ground floor bathroom

AppliancePartsPros.com, Inc.
Posted by Bob on September 17, 2006, 11:24 pm

BobK207 wrote:
> If a small diameter ground rod (1/2" or 5/8") doesn't give the 25 ohms
> (or less) to ground.....would a larger (3/4" or 1") diameter rod in the
> same soil do better?
>
> Is the soil the culprit or the soil / rod contact resistance? The
> larger diameter rod contacts more soil..better grounding behavior?
>
> cheers
> Bob

Having worked electronic facilities where the ground resistance has to
be less than 5 ohms, I've tried a lot of tricks to get the resistance
down. There is no sure-fire trick to the process, but rod diameter is
WAY down the list of possibilities. The number of rods (up to 12) and
the depth of the rods (sometimes 40ft) is the usual key, but if that
doesn't work try pouring 25lb of salt in a hole next to the rods and
water it good. Salt is a good conductor & decreases ground resistance.

Bob S.


Posted by hallerb@aol.com on September 18, 2006, 8:20 am


> Having worked electronic facilities where the ground resistance has to
> be less than 5 ohms, I've tried a lot of tricks to get the resistance
> down. There is no sure-fire trick to the process, but rod diameter is
> WAY down the list of possibilities. The number of rods (up to 12) and
> the depth of the rods (sometimes 40ft) is the usual key, but if that
> doesn't work try pouring 25lb of salt in a hole next to the rods and
> water it good. Salt is a good conductor & decreases ground resistance.
>
> Bob S.

use copper or stainless rod other wise the steel rod will disappear.t
like my old car did:(


Posted by Bob on September 19, 2006, 11:15 pm

hallerb@aol.com wrote:
> > Having worked electronic facilities where the ground resistance has to
> > be less than 5 ohms, I've tried a lot of tricks to get the resistance
> > down. There is no sure-fire trick to the process, but rod diameter is
> > WAY down the list of possibilities. The number of rods (up to 12) and
> > the depth of the rods (sometimes 40ft) is the usual key, but if that
> > doesn't work try pouring 25lb of salt in a hole next to the rods and
> > water it good. Salt is a good conductor & decreases ground resistance.
> >
> > Bob S.
>
> use copper or stainless rod other wise the steel rod will disappear.t
> like my old car did:(

Good point. All I used was copper coated steel. It's silly to go
through that much work and use cheap rods.


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