Using a copper water pipe in place of a ground rod?
 

In the "How to drive the ground rods in" thread, Ralph Mowery wrote:

Dig out a hole about 4 or 5 inches in diameter and about that deep.
Fill it with water. Put the ground rod in the center of that hole and
push it down. Then pull it back slightly. Doing this several times you
should be able to get to get it down several inches with each cycle.
Keep doing this without stopping. If you get to about 3 or 4 feet put
the rod all the way out and fill the hole with water . Put the rod back
in the same hole and keep pushing and pulling it a few inches at a
time.

Good evening, Ralph.

That brought something else to mind... something I'm sure has been thought
of by greater minds than mine, and one or two of you have hinted at
something like it in these last few threads...

How about a 10-foot length of copper water pipe, connected to a garden
hose with an adapter fitting (as simple as a short length of another
garden hose, clamped to the pipe with radiator hose clamps). Run water
down the pipe and stick the pipe in the ground, pulling it up and pushing
it down so that the water helps drill the hole in a manner just like you
described. Keep it up until it has gone in as far as it will go, then (if
it hasn't gone in the whole 10 feet) cut it off and solder a copper cap on
the end.

You end up with a hollow pipe in the ground instead of a solid steel rod,
but everything I read about lightning strikes says that the vast majority
of the current flows in skin effect anyway.

I did something like this once in my backyard when I was about 9
years old, using our garden hose. I recall being amazed at how the hose
just kept going in, kept going in ... 'course then when I tried to pull it
out again it was a different story. My father was not happy. :-(

If a hollow water pipe isn't a good enough ground rod, how about drilling
the hole as described above using the water pipe, and then (if I can get
the pipe back out of the ground) beating the ground rod into the resulting
hole? Should go in pretty easy...

I know that by now everyone pretty much believes that a house's copper
water pipes don't make good grounds, but that's mostly because they aren't
connected very well to actual ground... in my house, the copper water
pipes go to the water pump which sucks the water out of the well via a
hard rubber hose... not very good for ground. The only connection to
ground we got (before I connected the copper pipes to the service ground)
was through the minerals in the water.

Using a copper water pipe in place of a ground rod?
 

On Sat, 14 Jul 2007 02:04:34 +0000, Owen Duffy wrote:

You will see articles on the net describing drilling a hole with a hose
and a peice of pipe. I have reservations about this, because it is no
longer a drive electrode. I have not seen this method used by commercial
applications and I suspect that if one was contracted to drive
electrodes, this would not be an acceptable method.

Good evening, Owen.

I am unsure what you mean by "it is no longer a drive electrode" and "I
suspect... this would not be an acceptable method".

Certainly the earth's grip on the ground rod will be much less tight this
way, but only for a little while... over time, won't the earth shift with
weather and rain and such, so that eventually (in days or weeks) it will
grip the ground rod sufficiently well?

Or am I missing your point? (No surprise there...) :-)

Using a copper water pipe in place of a ground rod?
 

On Sat, 14 Jul 2007 02:04:34 +0000, Owen Duffy wrote:

You will see articles on the net describing drilling a hole with a hose
and a peice of pipe.

Owen;

Can you please give me a hand finding those articles? I tried Google and
Yahoo with various combinations of things like "drill hole in ground with
water pipe" and "hole ground hose pipe" and am coming up empty.

Thanks...

Using a copper water pipe in place of a ground rod?
 

In article ,
"Rick (W-A-one-R-K-T)" wrote:

Can you please give me a hand finding those articles? I tried Google and
Yahoo with various combinations of things like "drill hole in ground with
water pipe" and "hole ground hose pipe" and am coming up empty.

Rick-

My recollection is the use of this method to sink a well pipe for a lawn
pump. Try this approach in your search.

Fred
K4DII

Using a copper water pipe in place of a ground rod?
 

"Rick (W-A-one-R-K-T)" wrote in
:


On Sat, 14 Jul 2007 02:04:34 +0000, Owen Duffy wrote:

You will see articles on the net describing drilling a hole with a
hose
and a peice of pipe. I have reservations about this, because it is no
longer a drive electrode. I have not seen this method used by
commercial
applications and I suspect that if one was contracted to drive
electrodes, this would not be an acceptable method.

Good evening, Owen.

Good morning Rick,


I am unsure what you mean by "it is no longer a drive electrode" and "I
suspect... this would not be an acceptable method".

Certainly the earth's grip on the ground rod will be much less tight
this
way, but only for a little while... over time, won't the earth shift
with
weather and rain and such, so that eventually (in days or weeks) it
will
grip the ground rod sufficiently well?

Or am I missing your point? (No surprise there...) :-)


I should have said it is no longer a driven electrode.

Over a long time, it probably becomes equivalent, but in the first
instance, it is in less intimate contact with the ground.

It has been my experience with voltage operated ELCBs and loose earth
electrodes that they are unreliable and cause false tripping at quite low
leakage currents which I attributed to a variable resistance, and they
were usually fixed by driving a decent electrode.

You will find lots of discussion about the merit of boring a hole,
placing an electrode and filling it with bentonite or kitty litter or
some other enhancing material. Some hams assert that they water the
electrode (plain tap water or urine or both) as a conductivity enhancer,
I think that is more an excuse for consuming 807s.

If you read performance data for a driven electrode, it doesn't
necessarily apply to an electrode in a bored hole and then backfilled,
whether by slurry or compaction or whatever.

I am not saying they don't work when done in that way, but they are
different and quite likely to be poorer than driving the electrode.

For a multi mode RF / AC protective / Lighting ground, shallow buried
radials might be more effective than one or several driven electrodes
anyway. A driven electrode (or any vertical electrode) is not very useful
for RF.

Someone commented to the effect that a vertical electrode that hits rock
is a waste of time. That depends, the ground above the rock may be much
wetter than for the presence of the rock, it which case the shorter
electrode might reach more conductive earth and be good. However a short
electrode in dry sandy soil that strikes rock may be quite high
resistance and recourse to buried strip electrodes is warranted.

I drove an electrode at a holiday cottage at the coast (where it rains)
and it hit a serious rock shelf at 2.1m. The electrode measured very low
resistance at 1kHz, much lower resistance than I expected from a single
2.4m electrode in clay. I attribute that to the rock shelf serving to
drain ground water down the hill and presenting quite wet clay in the
region above the shelf.

Owen

Using a copper water pipe in place of a ground rod?
 

On Jul 14, 8:49 pm, Owen Duffy wrote:


For a multi mode RF / AC protective / Lighting ground, shallow buried
radials might be more effective than one or several driven electrodes
anyway. A driven electrode (or any vertical electrode) is not very useful
for RF.

I was considering this the other day... Seems to me, a good set of
radials on/in the ground are about the only system which could
cover all three jobs. Course, it would be kind of silly to use that
ground as the wiring safety ground, but it could work, as long
as the earth connection at the center of the radials is good.
I can't really think of any other systems that can provide a good
RF ground system, and lightning at the same time. Of course,
from the lightning end, it again assumes a good earth connection
at the center of the radials.
Some might be surprised that my ground rods are not very long
at all. And all are copper tubing, not rods..
My longest one is probably only about 4 ft long. But I have
several spaced around the mast, and tied together underground.
But all are pretty close to the mast. Not even close to being 8 ft..
More like 3 ft across...
That then also ties to the steel water pipe which is about 2-3 ft
away. So far, that ground seems good enough as far as a
lightning return. And I've had two strikes with me sitting here to
be able to say that. Seemed to be a good ground connection.
How can I tell? The sound..
A strike to my mast is very quiet. All you hear is an arc, which
sounds like a light bulb being thrown on the ground and breaking.
Course, you hear the overhead sonic boom, but that doesn't
count.. :/ That's not the real sound of the strike.
In comparison, a poor ground return will cause the strike to be
very loud, with a real loud "CRACK" to it. Then again, the
overhead sonic boom... :( Trees make for a noisy strike..
My ground outside is for lightning return only. Does nothing
else. I use no RF ground. All my antennas are complete.
If a certain antenna requires an RF ground, that will be provided
as part of the antenna design.
My safety ground is provided by the house wiring.
So my outside ground scheme is a one trick pony.. :/
MK

Using a copper water pipe in place of a ground rod?
 

On Sat, 14 Jul 2007 19:16:59 -0400, "Rick (W-A-one-R-K-T)" wrote:


In the "How to drive the ground rods in" thread, Ralph Mowery wrote:

Dig out a hole about 4 or 5 inches in diameter and about that deep.
Fill it with water. Put the ground rod in the center of that hole and
push it down. Then pull it back slightly. Doing this several times you
should be able to get to get it down several inches with each cycle.
Keep doing this without stopping. If you get to about 3 or 4 feet put
the rod all the way out and fill the hole with water . Put the rod back
in the same hole and keep pushing and pulling it a few inches at a
time.

Good evening, Ralph.

That brought something else to mind... something I'm sure has been thought
of by greater minds than mine, and one or two of you have hinted at
something like it in these last few threads...

How about a 10-foot length of copper water pipe, connected to a garden
hose with an adapter fitting (as simple as a short length of another
garden hose, clamped to the pipe with radiator hose clamps). Run water
down the pipe and stick the pipe in the ground, pulling it up and pushing
it down so that the water helps drill the hole in a manner just like you
described. Keep it up until it has gone in as far as it will go, then (if
it hasn't gone in the whole 10 feet) cut it off and solder a copper cap on
the end.

You end up with a hollow pipe in the ground instead of a solid steel rod,
but everything I read about lightning strikes says that the vast majority
of the current flows in skin effect anyway.

I did something like this once in my backyard when I was about 9
years old, using our garden hose. I recall being amazed at how the hose
just kept going in, kept going in ... 'course then when I tried to pull it
out again it was a different story. My father was not happy. :-(

If a hollow water pipe isn't a good enough ground rod, how about drilling
the hole as described above using the water pipe, and then (if I can get
the pipe back out of the ground) beating the ground rod into the resulting
hole? Should go in pretty easy...

I know that by now everyone pretty much believes that a house's copper
water pipes don't make good grounds, but that's mostly because they aren't
connected very well to actual ground... in my house, the copper water
pipes go to the water pump which sucks the water out of the well via a
hard rubber hose... not very good for ground. The only connection to
ground we got (before I connected the copper pipes to the service ground)
was through the minerals in the water.
This topic has aroused my curiosity. As a grounding device, why would a solid rod be better than a hollow
pipe, except for the current carrying capabilitY?

Walt, W2DU

Using a copper water pipe in place of a ground rod?
 

On Sun, 15 Jul 2007 17:23:13 +0000, Walter Maxwell wrote:

This topic has aroused my curiosity. As a grounding device, why would a
solid rod be better than a hollow pipe, except for the current carrying
capability?

Good afternoon, Walt.

The thing is, the current carrying capability for transient events like
lightning strikes should be about the same for the same diameter pipe or
rod, since most of the current is carried in skin effect anyway.

Using a copper water pipe in place of a ground rod?
 

Walter Maxwell wrote:

big snip

This topic has aroused my curiosity. As a grounding device, why would a solid rod be better than a hollow
pipe, except for the current carrying capabilitY?

Walt, W2DU

I would expect that a driven, solid rod would be in more intimate contact
with the earth while a water drilled pipe would have lots of surface air
gaps, at least initially.

After some period of time the gaps would fill in in most dirt and I
wouldn't expect there to be any difference.

--
Jim Pennino

Remove .spam.sux to reply.

Using a copper water pipe in place of a ground rod?
 

"Walter Maxwell" wrote in message
...
This topic has aroused my curiosity. As a grounding device, why would a
solid rod be better than a hollow
pipe, except for the current carrying capabilitY?

Walt, W2DU

I doubt that there would be any real differance to start with. The pipes
are thin enough they would be hard to drive in the ground and after a while
they would rust out sooner.

Using a copper water pipe in place of a ground rod?
 

"Rick (W-A-one-R-K-T)" wrote in
:

On Sun, 15 Jul 2007 17:23:13 +0000, Walter Maxwell wrote:

This topic has aroused my curiosity. As a grounding device, why would a
solid rod be better than a hollow pipe, except for the current carrying
capability?

Good afternoon, Walt.

The thing is, the current carrying capability for transient events like
lightning strikes should be about the same for the same diameter pipe or
rod, since most of the current is carried in skin effect anyway.

I think that is flawed thinking.

A lighning down conductor needs to carry something like 20kA for 100ms, so
it needs to be substantial enough that it doesn't melt and remains in place
to protect against the next strike.

Owen

Using a copper water pipe in place of a ground rod?
 

I doubt that there would be any real difference to start with. The pipes
are thin enough they would be hard to drive in the ground and after a while
they would rust out sooner.
==================================================
Copper ....rusting ? ........... must be veeeery acidic soil
.....perhaps in the backyard of a chemical plant ?


Frank GM0CSZ / KN6WH

Using a copper water pipe in place of a ground rod?
 

"Rick (W-A-one-R-K-T)" wrote in message
.. .

How about a 10-foot length of copper water pipe, connected to a garden
hose with an adapter fitting (as simple as a short length of another
garden hose, clamped to the pipe with radiator hose clamps). Run water
down the pipe and stick the pipe in the ground, pulling it up and pushing
it down so that the water helps drill the hole in a manner just like you
described. Keep it up until it has gone in as far as it will go, then (if
it hasn't gone in the whole 10 feet) cut it off and solder a copper cap on
the end.

You end up with a hollow pipe in the ground instead of a solid steel rod,
but everything I read about lightning strikes says that the vast majority
of the current flows in skin effect anyway.


Copper clad steel rods are made precisely because the copper cladding on the
outside skin is what conducts the current anyhow. So it makes no difference
whether you utilize copper pipe or copper clad steek rods. To drive copper
pipe down I use a length of about 1 foot of aluminum tubing connected to a
garden hose (tubing fits in garden hose and is clamped tightly, Aluminum
tubing slides into copper pipe. The rubber hose goes up against the copper
tubing rather tightly to make a quasi seal, it'll be enough although some
little bit of spray from backpressure will come out. Turn on the faucet and
the copper pipe will very quickly begin to drive itself into the ground.
Enough slurried wet soil mix will compact around the pipe to make a good
earth ground contact but I usually let the hose saturate the ground area
around it for about a half hour after so the voids fill in.

Bill KC9CS
http://home1.gte.net/res0958z/

Using a copper water pipe in place of a ground rod?
 

On Jul 15, 1:47 pm, Owen Duffy wrote:


I think that is flawed thinking.

Dunno.. Not if the ground connection itself is good enough..

A lighning down conductor needs to carry something like 20kA for 100ms, so
it needs to be substantial enough that it doesn't melt and remains in place
to protect against the next strike.

A #10 wire can handle that job if the ground connection is up to par.
Course, most real down conductor will be flat copper strap.
The rod or tube in the ground is not the down conductor per say,
although I guess you could consider it the end of it..
As far as DC contact with earth, it's possible the tubing could be
slightly better, as it's got surface both on the outside, and the
inside..
But I imagine RF flowing along tubing would mostly flow on the
outside,
rather than inside. But maybe a bit of both.. Not sure..
Copper tubing itself can easily handle any lightning strike. Way
overkill actually. If you had a well grounded copper tube lightning
rod, and it was struck, all you would see on the tip would be a tiny
arc spot, which might even be unnoticable unless you were looking
for it. Even a lowly #10 wire will barely raise temp when struck as
long as the connection to ground is real good. Of course, if it isn't,
it may well vaporize into blobs of metal..
MK

Using a copper water pipe in place of a ground rod?
 

If you already have the copper pipe and you can get it in the ground I
doubt you will ever notice the difference.

I live on red clay in the Piedmont region of North Carolina. There are
times when I could push three feet of #3 rebar in the ground with one
hand. At this time of year I doubt I could drive it more than about 6
inches!

Two years ago I had a pro install lightning rods. They added two
galvanized 1/2 inch ground rods at diagonal corners of the house. They
then tied one of these to the power ground. They also tied one corner
to my tower with a massive clamp. A whole house surge protector was
installed at the power panel. I have since added a vertical antenna
(28 feet) with 35 radials 70 feet long.

I have not had a lightning strike since they did the install. I think
the charge bleeds off before it builds up to a serious level.

Before the install I was averaging about $500 a year in VCRs, TV sets,
Stereos, etc. The best advice I can offer is to use conventional
materials available in your area, meet code and keep your insurance
company satisfied.

BTW, I still unplug antennas and rotors when not in use!

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

Using a copper water pipe in place of a ground rod?
 

I have used hollow copper pipe for years.

I have one 10 foot copper clad steel ground rod which I used to drive the
pilot hole into the ground, then hauled it out using a car jack. I then put
a copper pipe in the hole. The copper pipe has 1/4 inch holes drilled
along its length for the bottom three feet.

I used 3 pipes and the copper clad rod as a system of four tied together
with #2 copper which is soldered to all four pipes.

At first the copper pipes are loosely set into the hole left by the
steel rod, but after a while the ground settles and they are firmly
implanted.

Every year I take a mixture of water and epsom salts and pour it
down the hollow pipes. I cannot see what is happening under the
ground, but I consider my ground system to be as good as can be
hoped for.

I have run a couple marconi's without radials using the system
and found their performance 'pleasing'. One was an 80m folded
marconi -- about 50 ft of it vertical, and the rest folded back
at about 45 degrees. It was a great performer and a chum of mine
to whom I gave the design has worked all continents and most
countries on it. The ground, of course, is the secret.

The system has been in place for 24 years. four years ago I jacked
one of the pipes out just to see about all these rumors of corrosion
but it was fully intact. I steel-wooled it, then put it back in and
resoldered it to the system.

The pipe was cheaper than the ground rod although that was quite a
while back. I say go for it!


Irv VE6BP

Using a copper water pipe in place of a ground rod?
 

Owen Duffy wrote:
"Rick (W-A-one-R-K-T)" wrote in
:


On Sun, 15 Jul 2007 17:23:13 +0000, Walter Maxwell wrote:


This topic has aroused my curiosity. As a grounding device, why would a
solid rod be better than a hollow pipe, except for the current carrying
capability?

Good afternoon, Walt.

The thing is, the current carrying capability for transient events like
lightning strikes should be about the same for the same diameter pipe or
rod, since most of the current is carried in skin effect anyway.


I think that is flawed thinking.

A lighning down conductor needs to carry something like 20kA for 100ms, so
it needs to be substantial enough that it doesn't melt and remains in place
to protect against the next strike.

Owen

The fusing/melting current for 1/2" copper pipe is probably well above
20kA, even for 100ms pulses. A more interesting potential failure mode
might be from the mechanical forces due to the magnetic field. (see,
e.g., quarter shrinking or can-crushing)

Using a copper water pipe in place of a ground rod?
 

Jim Lux wrote in
:

Owen Duffy wrote:
"Rick (W-A-one-R-K-T)" wrote in
:


On Sun, 15 Jul 2007 17:23:13 +0000, Walter Maxwell wrote:


This topic has aroused my curiosity. As a grounding device, why
would a solid rod be better than a hollow pipe, except for the
current carrying capability?

Good afternoon, Walt.

The thing is, the current carrying capability for transient events
like lightning strikes should be about the same for the same diameter
pipe or rod, since most of the current is carried in skin effect
anyway.


I think that is flawed thinking.

A lighning down conductor needs to carry something like 20kA for
100ms, so it needs to be substantial enough that it doesn't melt and
remains in place to protect against the next strike.

Owen

The fusing/melting current for 1/2" copper pipe is probably well above
20kA, even for 100ms pulses. A more interesting potential failure mode
might be from the mechanical forces due to the magnetic field. (see,
e.g., quarter shrinking or can-crushing)


Hi Jim,

I note the "probably" in your comment, and the "dunno" in N5MK's
response.

The uncertainty in my statement is over the exact lightning scenario,
they vary, and the circuit response (ie current waveshape, amplitude,
duration, ringing etc) depend on the specific excitation and circuit
elements (parameters of the down conductor, nature of the earth system,
ground, environment etc).

As far as supposition as to the fusing current for conductors, that is
determinable for a given scenario. I have at hand the Protective Earthing
Code of Practice published by the Electricity Authority of NSW June 1975
and it shows that a 35mm^2 copper conductor has a fault current withstand
of 20kA for 100ms. (I have considered implementing the underlying
formulas in an online calculator.)

N5MK stated "A #10 wire can handle that job". If he is talking copper, I
understand that #10 means 2.5mm diameter, or ~5mm^2, or less than 15% of
the recommended conductor csa for the stated scenario. I am not familiar
with your water pipe sizes. If it were, say, a half inch diameter #19, it
has a CSA of around 35mm^2, so the #10 wire should melt before the pipe
electrode, thus protecting the pipe electrode from failure. Yes,
mechanical forces are also relevant to lightning conductors, but my
comment was about the fusing current.

In this part of the world there is an Australian Standard (AS1768)
relating to lightning protection, there may be a similar standard or
"code" in other jurisdictions, and they would not be a bad place to start
in understanding lightning protection and designing a protection scheme.

Another source of information is to walk around a mobile phone base
station and look at the earthing system from the outside. It is even more
enlightning (no pun) to look inside. These things withstand lightning
events quite well. Are they over engineered? Probably not, they do suffer
damage from time to time.

It is my view that there is a significant risk that an inadequate
lightning protection scheme may be much worse than doing nothing.

Owen

Using a copper water pipe in place of a ground rod?
 

Owen

The fusing/melting current for 1/2" copper pipe is probably well above
20kA, even for 100ms pulses. A more interesting potential failure mode
might be from the mechanical forces due to the magnetic field. (see,
e.g., quarter shrinking or can-crushing)



Hi Jim,

I note the "probably" in your comment, and the "dunno" in N5MK's
response.
That's because I was lazy and didn't want to actually compute it. I've
put multi tens of kA pulses through 1/4" copper pipe, but they're not
100ms long.



The uncertainty in my statement is over the exact lightning scenario,
they vary, and the circuit response (ie current waveshape, amplitude,
duration, ringing etc) depend on the specific excitation and circuit
elements (parameters of the down conductor, nature of the earth system,
ground, environment etc).

One could certainly use the standard double exponential approximations..
either a 2/50 waveform for a strike or the longer surge impulse (I can't
remember the exact rise/fall times for the surge..)



As far as supposition as to the fusing current for conductors, that is
determinable for a given scenario. I have at hand the Protective Earthing
Code of Practice published by the Electricity Authority of NSW June 1975
and it shows that a 35mm^2 copper conductor has a fault current withstand
of 20kA for 100ms. (I have considered implementing the underlying
formulas in an online calculator.)

Preece or Onderdonk?
(http://home.earthlink.net/~jimlux/hv/fuses.htm

N5MK stated "A #10 wire can handle that job". If he is talking copper, I
understand that #10 means 2.5mm diameter, or ~5mm^2, or less than 15% of
the recommended conductor csa for the stated scenario.


Preece equation gives fusing current for AWG10 (2.5mm diameter, as you
say) as 316 amps, but that's sort of for a steady state.

Onderdonk's equation, plugging in 100 ms for the melt time, gives 4.7kA,
which I can believe. I've blown up a lot of AWG10 wire with those sorts
of currents in a quarter shrinker. Partly melting, partly mechanical
stresses in that application.

The purpose of the National Electrical Code (National, here, referring
chauvinistically to the U.S.) required AWG 6 (diam 0.15 inches, 3.8 mm)
bonding wire for grounds is NOT to carry the lightning current (which it
wouldn't, in most cases) but to carry fault currents from things like
shorts from line to grounding conductor, which are usually in the
hundreds of amps range. Say an energized power line falls down and hits
the antenna. You want the antenna's grounding conductor to carry the
likely fault current and not go open, and carry enough current to trip
any overcurrent protective devices.

Lightning protection is usually things like 2/0 (0.364 inch diameter,
9.25 mm), which has a fusing current (viz Onderdonk) of 65kA.

I am not familiar
with your water pipe sizes. If it were, say, a half inch diameter #19, it
has a CSA of around 35mm^2, so the #10 wire should melt before the pipe
electrode, thus protecting the pipe electrode from failure. Yes,
mechanical forces are also relevant to lightning conductors, but my
comment was about the fusing current.

35 mm^2 would have a fusing current of around 30-35 kA.

1/2" Copper pipe is 0.625" od and 0.545" id (very close to 1mm wall)
so, has about 47 mm^2 area.


In this part of the world there is an Australian Standard (AS1768)
relating to lightning protection, there may be a similar standard or
"code" in other jurisdictions, and they would not be a bad place to start
in understanding lightning protection and designing a protection scheme.

Another source of information is to walk around a mobile phone base
station and look at the earthing system from the outside. It is even more
enlightning (no pun) to look inside. These things withstand lightning
events quite well. Are they over engineered? Probably not, they do suffer
damage from time to time.

It is my view that there is a significant risk that an inadequate
lightning protection scheme may be much worse than doing nothing.

I would agree..



Owen

Using a copper water pipe in place of a ground rod?
 

On Mon, 16 Jul 2007 21:26:16 +0000, Owen Duffy wrote:

It is my view that there is a significant risk that an inadequate
lightning protection scheme may be much worse than doing nothing.

Owen, certainly optimal is better than sub-optimal, but I don't understand
why sub-optimal can be worse than nothing at all. So far you have been
exceedingly helpful and I have learned a lot. Can you explain why
something isn't necessarily better, and in fact can be much worse, than
nothing?

Using a copper water pipe in place of a ground rod?
 

....

Jim, a lot of interesting stuff with which I generally agree.

The approach that my reference took to rating the conductor for a
lightning discharge includes a safety factor (as you might expect), and
so will rate the conductor at lower I^2*t than finding the conditions to
melt the wire. In real life, you would want the conductor to withstand a
second strike or fault soon after, and you would want to allow some
tolerance for other variables, hence the safety factor. The approach is
to find the I^2*t that raises the conductor one third of the way from
ambient (323K) to melting point. The calculator you used might assume
resistivity is at 0°C , ambient is 0°C, and the material is raised to
melting point with no heat loss, and that would give a fusing current
close to double of the approach that I used.

BTW, we have half inch copper water pipe over here (we still do but it
has a nominal metric size) and it is half in od... whereas half inch
galvanised steel pipe is half inch nominal bore... actually about 5/8"
id. Don't you like consistency in the same field!

Some years ago I did extensive modelling of a double exponential
excitation of structures and facilities (not lightning, faster than
lightning) and it was interesting how much the circuit configuration
affected the transformation of the excitation waveform to structure
current, including ringing. The same software could run a lightning
scenario, but that wasn't the main goal of the analysis so my experience
with the lightning scenario is more limited. So, as I said, the nature of
the current waveform is the big uncertainty and so measures are usually
quite conservative to cover that uncertainty.


Owen

Using a copper water pipe in place of a ground rod?
 

"Rick (W-A-one-R-K-T)" wrote in
:

On Mon, 16 Jul 2007 21:26:16 +0000, Owen Duffy wrote:

It is my view that there is a significant risk that an inadequate
lightning protection scheme may be much worse than doing nothing.

Owen, certainly optimal is better than sub-optimal, but I don't
understand why sub-optimal can be worse than nothing at all. So far
you have been exceedingly helpful and I have learned a lot. Can you
explain why something isn't necessarily better, and in fact can be
much worse, than nothing?



Rick,

I guess to some extent it goes to the meaning of do nothing.

If you did not install a lightning protection system, but only connected
antennas at a time of low risk, then you might be much better off than
trusing an inadequate protection scheme.

It does reach a point where the disconnect strategy is not convenient /
practical / effective, so you are faced with performing a risk assessment
and designing a solution to mitigate the high risk factor risks. (Risk
factor considers the likelihood of an outcome and the severity of an
outcome.)

Owen

Using a copper water pipe in place of a ground rod?
 

Jim Lux wrote in
:

The purpose of the National Electrical Code (National, here, referring
chauvinistically to the U.S.) required AWG 6 (diam 0.15 inches, 3.8
mm) bonding wire for grounds is NOT to carry the lightning current
(which it wouldn't, in most cases) but to carry fault currents from
things like shorts from line to grounding conductor, which are usually
in the hundreds of amps range. Say an energized power line falls down
and hits the antenna. You want the antenna's grounding conductor to
carry the likely fault current and not go open, and carry enough
current to trip any overcurrent protective devices.

I meant to comment:

I think that it is common in electricity distribution level networks,
that they are designed to hold fault current to about 20 times the
maximum working current.

In this part of the world, a single phase 240 home probably has a 80A
rated service, and fault current would usually be not worse than than
about 1600A, so the specified 6mm^2 earthing conductor and 4mm^2 bonding
conductor should withstand that current for 100ms until the protective
device operates. (4mm^2 withstands 3200A for 0.1s with a safety factor of
3.)

You probably know the numbers for your own distribution network practice,
they may be of interest to readers.

So you raise a good point, that if your tower falls onto power lines, it
would be good if your earth system could withstand the likely fault
current to take out the protection on the power lines and leave the tower
un-energised. In this part of the world with LV distribution, the
protection is probably a 500A HRC fuse with a fault current level of 10
+kA. It may be much lower for you if power lines are HV where the fault
current level should be a good deal lower.

Owen

Using a copper water pipe in place of a ground rod?
 

Owen Duffy wrote in
:
protective device operates. (4mm^2 withstands 3200A for 0.1s with a
safety factor of 3.)

That should read:


protective device operates. (4mm^2 withstands 2400A for 0.1s with a
safety factor of 3.)

Using a copper water pipe in place of a ground rod?
 

On Tue, 17 Jul 2007 03:29:55 +0000, Owen Duffy wrote:

If you did not install a lightning protection system, but only connected
antennas at a time of low risk, then you might be much better off than
trusting an inadequate protection scheme.

Ah, I see your point.

My main objective in all this is keeping the house from burning down. I
have a very low level of confidence that ANYTHING I do will prevent the
radio from receiving damage if the tower gets a direct lightning hit
while the antenna is connected to the radio. So, I'll continue to
disconnect antennas, ground feedlines, etc. when a storm is near or we're
going to be away for a while.

Maybe I'll get lucky and end up with a ground system that will protect
everything so I can continue to merrily yak or tap away during the worst
thunderstorm, but I'll be satisfied if I can just be confident that any
hit on the tower will go to ground and not to the house. If I have to
replace lengths of coax after a hit, I can live with that.

We aren't exactly in a high-occurrence area, here. In 22 years of living
here we have only had one lightning hit on our property, which hit (and
utterly destroyed) a tree in our backyard, damaged my Internet router,
tripped the main house circuit breaker, and blew out the timer and display
on the microwave oven. The tower was 10 feet shorter then and wasn't hit.
Now the tower is 10 feet taller AND will have a 25-foot-high VHF antenna
and mast on it, so it's time to do something to improve protection.

Using a copper water pipe in place of a ground rod?
 

I use 4 foot to 8 foot long, half inch dia., copper pipe put into the
ground with the use of a water hose clamped to the top of the pipe and
a pump - this hydraulically drills the pipe into the soil... They are
laid out in a grid around the towers and along the back side of the
shack with 16 feet separation... They are all interconnected with bare
copper #2 gauge, stranded ground wire (mostly) which is slit into the
ground an inch or so to keep it away from the mower blades... All of
this creates a large area of metal in contact with the soil..

All of this agonizing over contact of hydraulically driven pipe versus
pounded stakes, etc., etc., amounts to counting the number of angels
dancing on the head of a pin... Just get in as many ground pipes/
stakes as you can on 16 foot centers, interconnect them in a grid with
bare wire slit into the soil, run heavy gauge wire from the stake just
outside of wall of the house/shack to the buss bar behind the radio,
and be happy...

I also competely isolate the radios and amps when they are not in
use...

denny / k8do

Using a copper water pipe in place of a ground rod?
 

Owen Duffy wrote:
...

Jim, a lot of interesting stuff with which I generally agree.

The approach that my reference took to rating the conductor for a
lightning discharge includes a safety factor (as you might expect), and
so will rate the conductor at lower I^2*t than finding the conditions to
melt the wire. In real life, you would want the conductor to withstand a
second strike or fault soon after, and you would want to allow some
tolerance for other variables, hence the safety factor. The approach is
to find the I^2*t that raises the conductor one third of the way from
ambient (323K) to melting point. The calculator you used might assume
resistivity is at 0°C , ambient is 0°C, and the material is raised to
melting point with no heat loss, and that would give a fusing current
close to double of the approach that I used.

BTW, we have half inch copper water pipe over here (we still do but it
has a nominal metric size) and it is half in od... whereas half inch
galvanised steel pipe is half inch nominal bore... actually about 5/8"
id. Don't you like consistency in the same field!
But they're not the same field.. the stuff made of copper is actually
"tubing" and the stuff made of steel is "pipe", and historically,
they've been measured differently.

Tubing is usually soldered/sweated/brazed into fittings with a
receptacle, so the OD is important, because even with different wall
thicknesses, the fittings are all the same.

Pipe is based on something else (King John's toe diameter or something)

Some years ago I did extensive modelling of a double exponential
excitation of structures and facilities (not lightning, faster than
lightning) and it was interesting how much the circuit configuration
affected the transformation of the excitation waveform to structure
current, including ringing. The same software could run a lightning
scenario, but that wasn't the main goal of the analysis so my experience
with the lightning scenario is more limited. So, as I said, the nature of
the current waveform is the big uncertainty and so measures are usually
quite conservative to cover that uncertainty.

There's some fascinating papers out there that use NEC to model response
to a nearby lightning stroke (a much more common occurance than a direct
hit). It's actually quite involved, since they model the traveling
impulse of the stroke.


Owen

Using a copper water pipe in place of a ground rod?
 

On Tue, 17 Jul 2007 04:48:48 -0700, Denny wrote:

I use 4 foot to 8 foot long, half inch dia., copper pipe put into the
ground with the use of a water hose clamped to the top of the pipe and
a pump - this hydraulically drills the pipe into the soil... They are
laid out in a grid around the towers and along the back side of the
shack with 16 feet separation... They are all interconnected with bare
copper #2 gauge, stranded ground wire (mostly) which is slit into the
ground an inch or so to keep it away from the mower blades... All of
this creates a large area of metal in contact with the soil..

All of this agonizing over contact of hydraulically driven pipe versus
pounded stakes, etc., etc., amounts to counting the number of angels
dancing on the head of a pin... Just get in as many ground pipes/
stakes as you can on 16 foot centers, interconnect them in a grid with
bare wire slit into the soil, run heavy gauge wire from the stake just
outside of wall of the house/shack to the buss bar behind the radio,
and be happy...

Like Denny I have a lot of ground rods (32 or 33) in a network
CadWelded (TM) to over 600 feet of bare #2 copper wire that ties into
the station forming a single point ground or as near to it as I can
get. The coax shields are grounded at the top and bottom of the tower
as well as to a ground plate where they enter the house.

I also competely isolate the radios and amps when they are not in
use...

Unlike him I rarely disconnect anything for several reasons. The
first is the stuff is just too difficult to get to. The second is, I'm
lazy and although I could disconcert the station when not in use it
takes a good 10 to 15 minutes to get things hooked back up. Typically
I want to turn it on, listen, and then operate if the bands are open
or shut down if not. In addition, nature threw me a curve a bit over 3
months ago making it very difficult for me to get into places like
behind the rigs to disconnect things although I hope to be able to get
back in there and up the tower again before long.
One other thing and it may be, and probably is due to luck, but with
an average of three verified direct hits on the tower per year I've
had no damage to any rig since finishing up the ground system.

Roger (K8RI)

denny / k8do

Using a copper water pipe in place of a ground rod?
 

Denny wrote:

All of this agonizing over contact of hydraulically driven pipe versus
pounded stakes, etc., etc., amounts to counting the number of angels
dancing on the head of a pin

Amen Brother!



-73 de Mike KB3EIA -

Using a copper water pipe in place of a ground rod?
 

We had a near by lightning strike last night... All my radios and
antennas survived... My son's Dish Network receiver did not... He's
quite bummed out...

denny