Sal M. Onella wrote:
Dave Lemper wrote in message
...
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE



Here's a snippet from the state of Washington's website that quotes the NEC:

NEC 250-52 (c)(3) (1999 edition) requires that ground rods "be driven to a
depth of not less than 8 feet
(2.44m) except that, where rock bottom is encountered, the electrode shall
be driven at an oblique angle
not to exceed 45 degrees from the vertical or shall be buried in a trench
that is at least 2½ ft. (762mm)
deep."

The requirement is that the rod be driven to a depth of 8 feet. If the rod
cannot be driven then there is a
choice of either driving it at a 45-degree angle or laying it in a trench
that is not less than 2½ feet deep.

http://www.lni.wa.gov/tradeslicensin...ts/elc0210.pdf.

I browsed some newer discussions and found nothing newer to be at variance
with the quoted material. The current NEC is $75 if snippets won't do ya'.

http://www.nfpa.org/itemDetail.asp?c...RL=Pub licati
ons/

You need 25 ohms maximum rersistance (three-point method) to say you have a
good ground.



or, do what most jurisdictions now require, and build yourself a
concrete encased grounding electrode (Ufer ground)... no minimum depth,
per se.

Jim Lux wrote:
Sal M. Onella wrote:
Dave Lemper wrote in message
...
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE



Here's a snippet from the state of Washington's website that quotes
the NEC:

NEC 250-52 (c)(3) (1999 edition) requires that ground rods "be driven
to a
depth of not less than 8 feet
(2.44m) except that, where rock bottom is encountered, the electrode
shall
be driven at an oblique angle
not to exceed 45 degrees from the vertical or shall be buried in a trench
that is at least 2½ ft. (762mm)
deep."

The requirement is that the rod be driven to a depth of 8 feet. If the
rod
cannot be driven then there is a
choice of either driving it at a 45-degree angle or laying it in a trench
that is not less than 2½ feet deep.

http://www.lni.wa.gov/tradeslicensin...ts/elc0210.pdf.


I browsed some newer discussions and found nothing newer to be at
variance
with the quoted material. The current NEC is $75 if snippets won't do
ya'.

http://www.nfpa.org/itemDetail.asp?c...RL=Pub licati

ons/

You need 25 ohms maximum rersistance (three-point method) to say you
have a
good ground.



or, do what most jurisdictions now require, and build yourself a
concrete encased grounding electrode (Ufer ground)... no minimum depth,
per se.


The minimum depth is provided by the building code. Since the footer
must be below the frost line the resultant Ufer Ground is also below the
frost line. If it's not it will be ineffective.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

Earlier, someone wrote:
Renting a back hoe is out.

I just skim-read that as "Renting a black hole is out"... well, why not?


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

In article ,
Ian White GM3SEK wrote:

Earlier, someone wrote:
Renting a back hoe is out.

I just skim-read that as "Renting a black hole is out"... well, why not?

Getting your cash deposit back is hell, in those cases. It's as if
the rental agency dropped it down... well, you get the idea.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

The minimum depth is provided by the building code. Since the footer
must be below the frost line the resultant Ufer Ground is also below the
frost line. If it's not it will be ineffective.


To split hairs a bit, you can build a Ufer ground that isn't a
structural footer, and so, may not be subject to the frost line rules.

Jim Lux wrote:

...
To split hairs a bit, you can build a Ufer ground that isn't a
structural footer, and so, may not be subject to the frost line rules.


In California, in the central valleys, the question is simply, "What
frost-line? 8-)

Regards,
JS

Jim Lux wrote:

The minimum depth is provided by the building code. Since the footer
must be below the frost line the resultant Ufer Ground is also below
the frost line. If it's not it will be ineffective.


To split hairs a bit, you can build a Ufer ground that isn't a
structural footer, and so, may not be subject to the frost line rules.


Yes Jim he can. But if he does will frost heaves likely destroy it.
When I was younger I spent a lot of time building duct banks and they
were always built with the base of the bank below the frost line so that
the formation of ice in the soil during a hard winter would not destroy
them. Remember that even a ground ring composed of straight wire is
buried a minimum of thirty inches deep. The objective in constructing
grounding electrodes is to get them down below the permanent moisture
level well into the so called water table.

I know that the subject area is Texas and the strata he's dealing with
is quite hard but he didn't seem to be asking how to install what looks
like an electrode but rather what will function as an electrode.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

On Sat, 23 Aug 2008 10:58:19 -0500, Dave Lemper wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE


I have a Glen Martin ground rod driver (fashioned after a fence post
driver) that worked fine in Houston. In San Antonio, it only drives a
rod about one foot down, then muck... I ended up just driving a short
rod, mainly used as a connection post, and then I extended several
long, buried wires out from it.

bob
k5qwg

I got a better ground than using a stake by doing something a little
unorthodox.

I buried an old channel 6 yagi antenna in under six inches of earth. It
made a pretty good ground. It was a lot better than a stake.

Michael


Dave Lemper wrote:
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE

Dave Lemper wrote in :

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE


Dave,

If you truly cannot drive an electrode vertically, then you will need to
consider drilling for horizontal electrodes in trenches chased into the
rock. Drilling creates another problem, backfilling for conductivity.

Electrodes in dry rock might not be very effective.

I have had success in driving electrodes into moderately shaly ground,
and even very dry clay isn't too difficult. Pointed 19mm copper clad
steel rods or stainless steel rods are a lot easier to drive into hard
stuff than smaller sizes.

The following article shows some of the equipment that I have used
sucessfully, and likely to be more successful than using an ordinary
hammer. Machine driving does not mushroom then end of the electrode near
as much as hand hammering.

http://www.vk1od.net/post/driver.htm

Owen