On 22 Sep 2009 23:19:40 GMT, Ed
wrote:

QUESTION: Are aluminum ground systems becoming common? Are they
reliable, even after absorbing some heavy strikes? Any other comments?
Ed K7AAT on the Oregon Coast

I've never seen any that use aluminum wire. Everything I've seen and
what little I've done was copper wire for both mountain top and home
grounding.

The National Fire Protection Association (NFPA) has guidelines such
things. See NFPA 780 "Standard For Installation Of Lightning
Protection Systems 2004". It describes protection for people,
building, and property from lightning damage.
http://www.atmo.arizona.edu/students/courselinks/spring07/atmo589/articles/NFPA_780_2004.pdf
1.1MByte PDF. Several sections mention aluminum use.

Googling merrily...

http://everything2.com/title/aluminum+wire
The only problem you have to consider is that you cannot
allow the wire to enter the structure because exploding
aluminum can cause a fire.

http://electrical.about.com/od/electricalsafety/a/lightningprotectionlightningrods.htm
The underground connection to the lightning protection system must
be made with copper wire because underground connections should not
be made with aluminum wire. Aluminum wire will corrode when placed
in the ground. The National Electrical Code requires the aluminum
wire connection be at least 18 inches above the ground [NEC Section
250.64(A)] with a bi-metal splice. This connects to an eight-foot
copper ground rod at least two feet from th home's exterior wall.
There must be a minimum of two ground rods installed to the system
on opposite ends of the home, with one near the service entrance
ground rod so it can be bonded to this ground rod. This ensures
that there is a common ground between all ground rods. This should
make the connecting copper wire length between the ground rod and
aluminum cable approximately four feet long. Place the ground rods
diagonally on either end of the house, not exceeding 100 feet
between the two ground rods. If this distance is exceeded,
additional ground rods must be added to ensure proper grounding.

http://www.glenmartin.com/catalog/lightning.htm
They use copper wire, but the lightning rod points are aluminum.

http://www.lightningrodparts.com/faq.html
(13) Will Aluminum Wire/Cable and Rods work as well as Copper?
It should as long as the installation rules are followed.
Certainly Copper is a better conductor than aluminum but
the Aluminum cable is larger than the copper therefore making
up for aluminum's lesser conductivity.

(24) BASIC INSTALLATION DETAILS:
No Structure shall have less than 2 ground rods (Aluminum wire
should not be underground)

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sep 24, 1:56*pm, Ed wrote:
* *Below is good information, *but only applies to electrical systems'
grounding... not commercial radio vault lightning ground systems. *Also,
the aluminum system I came across certainly had crimp or other mechanical
bonding methods which avoids the connection issues discussed in the NEC.

* *I have no control or great concern on this, but was surprised to see
aluminum for my first time. *I just wondered if it was common.

* *Ed * K7AAT

.

The National Electric Code has some fairly specific requirements for
how grounding system connections must be made. *Soldering is not
permitted, as the high temperatures which can occur at such
connections during a lighting strike can blow the soldered connection
apart. *Strong mechanical connections, or welding (e.g. "CadWeld"
thermite-type welding) is required.

I just ran across the following:

*http://www.homeinspector.org/resourc...lectrical-Grou
* nding.pdf

It indicates that the NEC forbids the use of aluminum conductors for
grounding "where in direct contact with masonry or earth. *Aluminum
conductors require 18 inches of clearance from earth." *(NEC
paragraphs 250-91a and 250-92a are cited).

There's also a note on the citation: *"ATJ note: *we have field
reports of complete failure of uninsulated bare aluminum grounding
conductor wire when it was not properly protected from corrosion - for
example where left touching a masonry foundation wall."

It sounds to me as using aluminum wire as a lightning ground system
is a poor idea.

The only time in my life that I saw aluminum corrosion was when I
spotted aluminum tubing sticking out of the ground at the house. It
just made a pile of aluminum dust!
I have no idea how a ground plane would work if the aluminum opened up
in time in different places, so sticking with copper seems the best
way to go. If I had a problem with radiation my mind would be pointing
at the aluminum every time so why the hassle?
You never know what state your ground is in these days because the
builders spread building garbage aound before they spread the grass !
Now we have acid rain to think about.

Ed wrote:
I am only interested in the long term reliability of an aluminum ground
system in comparison to the more common copper system. This is for
lightning suppression only, I am not addressing RF issues. I am wondering
if aluminum can handle the potential surge currents that copper can... and
how well does its ground conductivity work when buried, when compared to
copper.

Ed K7AAT

If you're talking lightning, you're talking RF!

73, Roger

If you're talking lightning, you're talking RF!

73, Roger


Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed




..

"Ed" wrote in message
. 192.196...


If you're talking lightning, you're talking RF!

73, Roger


Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed


A lightning bolt is a transient so its current must be composed of
components having a wide range frequencies. Consequently lightning
conductors need small self-inductance as well as small resistance to work
properly.

Chris

"Ed" wrote in message
. 192.196...


If you're talking lightning, you're talking RF!

73, Roger


Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?

lightning has MANY frequencies from DC to many MHz.

Ed wrote:
Lightning is DC. How could it be " RF " if it has no
"frequency" ?

Fourier analysis of pulsed DC?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Ed wrote:

Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed

If you're not convinced after reading the responses, turn on your radio
the next time a lightning storm is anywhere nearby -- or for that
matter, anywhere within skip propagation range. Then explain how it is
your radio is hearing DC.

Roy Lewallen, W7EL

Roy Lewallen wrote in
:

Ed wrote:

Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed

If you're not convinced after reading the responses, turn on your radio
the next time a lightning storm is anywhere nearby -- or for that
matter, anywhere within skip propagation range. Then explain how it is
your radio is hearing DC.

Roy Lewallen, W7EL


Indeed Roy, rather than argue that lightning doesn't contain AC
components, one could more cogently argue that it is *not* DC.

It is evident that many hams treat lighting as DC in the design of their
lightning protection system (eg small conductor diameter, sharp bends,
loops, u-turns etc in down conductors), but if you pick up the simplest
models for analysing a lightning down conductor, they treat it as excited
by a double ramp current, and the down conductor as an inducance.

Such a model is not a DC model.

Owen

In article ,
Owen Duffy wrote:

Roy Lewallen wrote in
:

Ed wrote:

Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed

If you're not convinced after reading the responses, turn on your radio
the next time a lightning storm is anywhere nearby -- or for that
matter, anywhere within skip propagation range. Then explain how it is
your radio is hearing DC.

Roy Lewallen, W7EL


Indeed Roy, rather than argue that lightning doesn't contain AC
components, one could more cogently argue that it is *not* DC.

It is evident that many hams treat lighting as DC in the design of their
lightning protection system (eg small conductor diameter, sharp bends,
loops, u-turns etc in down conductors), but if you pick up the simplest
models for analysing a lightning down conductor, they treat it as excited
by a double ramp current, and the down conductor as an inducance.

Such a model is not a DC model.

Owen

Lightning is pulsed dc. The pulse can be examined by fourier analysis,
as every sophomore electrical engineering student knows, revealing that
the lightning pulse is made up of a superposition of ac waves of many
frequencies.

One can get away with explaining some things about lightning using
simple dc analysis but most of the interesting stuff requires ac
analysis.

And then there is the business of a nearby lightning strike raising the
voltage of ground lines so that during the strike; they are no longer at
ground potential. This requires ac analysis with impedances rather than
resistances.