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2 "ground rod" questions (Thumper aka cable fault locator)

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2 "ground rod" questions (Thumper aka cable fault locator) Ignoramus31595 12-14-2006
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Posted by Ignoramus31595 on December 14, 2006, 11:10 pm


I have a particular device that I would like to test, which is called
a "thumper". It was made by associated research (model 8613) and is
comprised of two under-desk-refrigerator-sized pieces, about 600 lbs
total weight.

For those who do not know, a thumper is a device that delivers pulses
of high voltage (up to 25 kV DC in my case) and huge currents, usually
above 1000 joules energy, to a buried high voltage cable where an
insulation fault needs to be located to find out where to dig to
splice it. The lineman walks along the cable path until he feels
"thumps" under his feet from electrical discharges in the faulty
insulation.

There are warnings on my thumper that say in big letters that it must
be grounded to a ground rod. For obvious usual reasons. I do not want to
ground it to my house ground rod for safety reasons. So I went to Home
Depot and bought their 5/8" 10' "copper clad" ground rod.

What I would like is to achieve two goals with this:

First is to ground the thumper to test it.

The second is to use this rod later for lightning protection. My house
is on top of a modest hill and was already hit by lightning. See

http://igor.chudov.com/tmp/lightning/

So later on I could save some $$ on needing to install a ground rod
for that.

FIRST QUESTION

So, my thinking is, the second ground rod would go in the ground close
to the first rod, maybe 2-4 feet or so distance. It would be close to
where other electricals are located and would be in the area that
would be convenient for connecting to some lighting rod to be
installed in the future.

Is that a sensible plan in light of wanting to use that second rod for
the thumper?

SECOND QUESTION

How to drive this ground rod. I have a decent compressor and a cheap
"medium" air hammer. Would I be able to drive it in my clay soil? I
read somewhere a suggestion to dig a small hole and fill it with
water, which would then liquefy the soil under air hammer's
pounding. Is that really helpful? How to actually angage an air hammer
to a ground rod?

thanks

i

Posted by Jerry on December 15, 2006, 4:52 am


Ignoramus31595 wrote:
> I have a particular device that I would like to test, which is called
> a "thumper". It was made by associated research (model 8613) and is
> comprised of two under-desk-refrigerator-sized pieces, about 600 lbs
> total weight.
>
> For those who do not know, a thumper is a device that delivers pulses
> of high voltage (up to 25 kV DC in my case) and huge currents, usually
> above 1000 joules energy, to a buried high voltage cable where an
> insulation fault needs to be located to find out where to dig to
> splice it. The lineman walks along the cable path until he feels
> "thumps" under his feet from electrical discharges in the faulty
> insulation.
>
> There are warnings on my thumper that say in big letters that it must
> be grounded to a ground rod. For obvious usual reasons. I do not want to
> ground it to my house ground rod for safety reasons. So I went to Home
> Depot and bought their 5/8" 10' "copper clad" ground rod.
>
> What I would like is to achieve two goals with this:
>
> First is to ground the thumper to test it.
>
> The second is to use this rod later for lightning protection. My house
> is on top of a modest hill and was already hit by lightning. See
>
> http://igor.chudov.com/tmp/lightning/
>
> So later on I could save some $$ on needing to install a ground rod
> for that.
>
> FIRST QUESTION
>
> So, my thinking is, the second ground rod would go in the ground close
> to the first rod, maybe 2-4 feet or so distance. It would be close to
> where other electricals are located and would be in the area that
> would be convenient for connecting to some lighting rod to be
> installed in the future.
>
> Is that a sensible plan in light of wanting to use that second rod for
> the thumper?
>
> SECOND QUESTION
>
> How to drive this ground rod. I have a decent compressor and a cheap
> "medium" air hammer. Would I be able to drive it in my clay soil? I
> read somewhere a suggestion to dig a small hole and fill it with
> water, which would then liquefy the soil under air hammer's
> pounding. Is that really helpful? How to actually angage an air hammer
> to a ground rod?
>
> thanks
>
> i

On the first question:
Your existng ground rod is already provides lightning protection to
your electrical supply. If you are going to add a ground rod it should
be the length of the ground rod or 10 feet in your case from the
existing ground rod and they should be bonded together.
If you are going to install a lightning protection system this quite
another story. The NEC does not cover lightning protection systems but
has this to say:

250.106 Lightning Protection Systems. The lightning
protection system ground terminals shall be bonded to the
building or structure grounding electrode system.
FPN No. 1: See 250.60 for use of air terminals. For further
information, see NFPA 780-2004, Standard for the Installation
of Lightning Protection Systems, which contains detailed
information on grounding, bonding, and spacing from
lightning protection systems.
FPN No. 2: Metal raceways, enclosures, frames, and other
non-current-carrying metal parts of electric equipment installed
on a building equipped with a lightning protection
system may require bonding or spacing from the lightning
protection conductors in accordance with NFPA 780-2004,
Standard for the Installation of Lightning Protection Systems.
Separation from lightning protection conductors is
typically 1.8 m (6 ft) through air or 900 mm (3 ft) through
dense materials such as concrete, brick, or wood.

On your second question about driving the ground rod. I have driven
many without pouring the water. I have used a sledge hammer, a pipe
driver, and an electric jack hammer equipped with a special hollow bit
that goes over the top of the ground rod supplied by the local rental
company.

About your thumper vibrating the earth - never heard of this before.
The one's I used required a sensor attached to head phones.


Posted by DAC on December 15, 2006, 8:12 am


Don't know about the first...the second...

if you use the water method...you don't need anything other than a
sledge to drive it home the last foot or so. Just put the rod in the
depression and start move it up and down...add water as needed. The
rod will push it's own way though the soil.

best of luck...

DAC



On Dec 14, 10:10 pm, Ignoramus31595
> I have a particular device that I would like to test, which is called
> a "thumper". It was made by associated research (model 8613) and is
> comprised of two under-desk-refrigerator-sized pieces, about 600 lbs
> total weight.
>
> For those who do not know, a thumper is a device that delivers pulses
> of high voltage (up to 25 kV DC in my case) and huge currents, usually
> above 1000 joules energy, to a buried high voltage cable where an
> insulation fault needs to be located to find out where to dig to
> splice it. The lineman walks along the cable path until he feels
> "thumps" under his feet from electrical discharges in the faulty
> insulation.
>
> There are warnings on my thumper that say in big letters that it must
> be grounded to a ground rod. For obvious usual reasons. I do not want to
> ground it to my house ground rod for safety reasons. So I went to Home
> Depot and bought their 5/8" 10' "copper clad" ground rod.
>
> What I would like is to achieve two goals with this:
>
> First is to ground the thumper to test it.
>
> The second is to use this rod later for lightning protection. My house
> is on top of a modest hill and was already hit by lightning. See
>
> http://igor.chudov.com/tmp/lightning/
>
> So later on I could save some $$ on needing to install a ground rod
> for that.
>
> FIRST QUESTION
>
> So, my thinking is, the second ground rod would go in the ground close
> to the first rod, maybe 2-4 feet or so distance. It would be close to
> where other electricals are located and would be in the area that
> would be convenient for connecting to some lighting rod to be
> installed in the future.
>
> Is that a sensible plan in light of wanting to use that second rod for
> the thumper?
>
> SECOND QUESTION
>
> How to drive this ground rod. I have a decent compressor and a cheap
> "medium" air hammer. Would I be able to drive it in my clay soil? I
> read somewhere a suggestion to dig a small hole and fill it with
> water, which would then liquefy the soil under air hammer's
> pounding. Is that really helpful? How to actually angage an air hammer
> to a ground rod?
>
> thanks
>
> i


Posted by EXT on December 15, 2006, 4:10 pm


Don't know what type of soil you are used to working with, but the heavy
hard-pan type of clay we have in this area would have no effect on easing a
ground rod into the soil. I installed 2 10 foot rods with a 10 pound sledge
and at the half way point I was getting 1/16 of an inch per hit, that meant
the last 5 feet required 16 hits per inch or 960 hits or more to get the rod
into the soil, no wonder I was exhausted after driving only one rod.


> Don't know about the first...the second...
>
> if you use the water method...you don't need anything other than a
> sledge to drive it home the last foot or so. Just put the rod in the
> depression and start move it up and down...add water as needed. The
> rod will push it's own way though the soil.
>
> best of luck...
>
> DAC
>
>
>
> On Dec 14, 10:10 pm, Ignoramus31595
>> I have a particular device that I would like to test, which is called
>> a "thumper". It was made by associated research (model 8613) and is
>> comprised of two under-desk-refrigerator-sized pieces, about 600 lbs
>> total weight.
>>
>> For those who do not know, a thumper is a device that delivers pulses
>> of high voltage (up to 25 kV DC in my case) and huge currents, usually
>> above 1000 joules energy, to a buried high voltage cable where an
>> insulation fault needs to be located to find out where to dig to
>> splice it. The lineman walks along the cable path until he feels
>> "thumps" under his feet from electrical discharges in the faulty
>> insulation.
>>
>> There are warnings on my thumper that say in big letters that it must
>> be grounded to a ground rod. For obvious usual reasons. I do not want to
>> ground it to my house ground rod for safety reasons. So I went to Home
>> Depot and bought their 5/8" 10' "copper clad" ground rod.
>>
>> What I would like is to achieve two goals with this:
>>
>> First is to ground the thumper to test it.
>>
>> The second is to use this rod later for lightning protection. My house
>> is on top of a modest hill and was already hit by lightning. See
>>
>> http://igor.chudov.com/tmp/lightning/
>>
>> So later on I could save some $$ on needing to install a ground rod
>> for that.
>>
>> FIRST QUESTION
>>
>> So, my thinking is, the second ground rod would go in the ground close
>> to the first rod, maybe 2-4 feet or so distance. It would be close to
>> where other electricals are located and would be in the area that
>> would be convenient for connecting to some lighting rod to be
>> installed in the future.
>>
>> Is that a sensible plan in light of wanting to use that second rod for
>> the thumper?
>>
>> SECOND QUESTION
>>
>> How to drive this ground rod. I have a decent compressor and a cheap
>> "medium" air hammer. Would I be able to drive it in my clay soil? I
>> read somewhere a suggestion to dig a small hole and fill it with
>> water, which would then liquefy the soil under air hammer's
>> pounding. Is that really helpful? How to actually angage an air hammer
>> to a ground rod?
>>
>> thanks
>>
>> i
>



Posted by DAC on December 18, 2006, 7:52 am


Oh Man, I feel for ya!

I was really fortunate. This last pair the about 6 feet down the clay
had an unusual amount of sand, the rod basically jumped into the
ground...couldn't believe it. 2 rods in about 5 minutes.

Hang in there!

DAC


EXT wrote:
> Don't know what type of soil you are used to working with, but the heavy
> hard-pan type of clay we have in this area would have no effect on easing a
> ground rod into the soil. I installed 2 10 foot rods with a 10 pound sledge
> and at the half way point I was getting 1/16 of an inch per hit, that meant
> the last 5 feet required 16 hits per inch or 960 hits or more to get the rod
> into the soil, no wonder I was exhausted after driving only one rod.
>
>
> > Don't know about the first...the second...
> >
> > if you use the water method...you don't need anything other than a
> > sledge to drive it home the last foot or so. Just put the rod in the
> > depression and start move it up and down...add water as needed. The
> > rod will push it's own way though the soil.
> >
> > best of luck...
> >
> > DAC
> >
> >
> >
> > On Dec 14, 10:10 pm, Ignoramus31595
> >> I have a particular device that I would like to test, which is called
> >> a "thumper". It was made by associated research (model 8613) and is
> >> comprised of two under-desk-refrigerator-sized pieces, about 600 lbs
> >> total weight.
> >>
> >> For those who do not know, a thumper is a device that delivers pulses
> >> of high voltage (up to 25 kV DC in my case) and huge currents, usually
> >> above 1000 joules energy, to a buried high voltage cable where an
> >> insulation fault needs to be located to find out where to dig to
> >> splice it. The lineman walks along the cable path until he feels
> >> "thumps" under his feet from electrical discharges in the faulty
> >> insulation.
> >>
> >> There are warnings on my thumper that say in big letters that it must
> >> be grounded to a ground rod. For obvious usual reasons. I do not want to
> >> ground it to my house ground rod for safety reasons. So I went to Home
> >> Depot and bought their 5/8" 10' "copper clad" ground rod.
> >>
> >> What I would like is to achieve two goals with this:
> >>
> >> First is to ground the thumper to test it.
> >>
> >> The second is to use this rod later for lightning protection. My house
> >> is on top of a modest hill and was already hit by lightning. See
> >>
> >> http://igor.chudov.com/tmp/lightning/
> >>
> >> So later on I could save some $$ on needing to install a ground rod
> >> for that.
> >>
> >> FIRST QUESTION
> >>
> >> So, my thinking is, the second ground rod would go in the ground close
> >> to the first rod, maybe 2-4 feet or so distance. It would be close to
> >> where other electricals are located and would be in the area that
> >> would be convenient for connecting to some lighting rod to be
> >> installed in the future.
> >>
> >> Is that a sensible plan in light of wanting to use that second rod for
> >> the thumper?
> >>
> >> SECOND QUESTION
> >>
> >> How to drive this ground rod. I have a decent compressor and a cheap
> >> "medium" air hammer. Would I be able to drive it in my clay soil? I
> >> read somewhere a suggestion to dig a small hole and fill it with
> >> water, which would then liquefy the soil under air hammer's
> >> pounding. Is that really helpful? How to actually angage an air hammer
> >> to a ground rod?
> >>
> >> thanks
> >>
> >> i
> >


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