Grounding for Gable end bracket & mast.
 

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain. I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. What thickness and width should I
use in the earth between the two Grounding Electrode Systems. I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. On
one end that will be only six feet due to the proximity of the
property line. At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. To
compensate for the proximity to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. What is the best way to attach the copper strap to
the support masts and eve brackets themselves? Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. I
have no idea how that is usually done.
--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne
wrote:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.

Hi Tom,

Consult the NEC code for your area. I have never seen them specify
strap in any situation, and don't try your own interpretations of what
"continuous"or "direct" means.

73's
Richard Clark, KB7QHC

Grounding for Gable end bracket & mast.
 

Tom Horne wrote in news:e802f6fa-b0e1-471b-bf31-
:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be ...

In this part of the world, we have an Australian / New Zealand Standard
(our version if you like of ANSI, BS etc) which explains the rationale
behind lightning protection, a method of estimating the downcurrent for
protection design purposes and a process for designing down conductors.

Broadly, the scheme is that downconductors are designed to withstand a
few donwstrokes in quick succession without melting the down conductor.
If you work from a peak current of 20kA, it would lead to a down
conductor in copper of at least 25mm^2 which is about #2 to you folk.

I regularly see hams recommend much thinner down conductors, and can only
assume that there is not regulatory guidance or requirement, and I wonder
at the effectiveness of using #6 as often recommended, especially
aluminium as is often the case. Note that reducing conductor size is a
double whammy, you increase the resistance (so the power), and decrease
the mass that has to be heated to melting point, and so the energy
required.

But, firstly, you should determine if there are regulatory requirements,
such as NEC etc.

The question of equipotential bonding conductors ought be dealt with in
the same way, though that is not to imply that they will be the same
size.

Owen

Grounding for Gable end bracket & mast.
 

I don't remember the sources but I have concluded that the Grounding
wire should be no smaller than #6.

More than 8 feet of ground rod is of little consequence.

All ground rods should be tied together. Don't put your house between
two electrodes!

The ground rods are better directly under the structure that they are
protecting.

The system does not absorb massive high energy strikes. It starts
bleeding off the energy before the strike builds and thus minmiizes
the effect.

Home improvement stores sell #6 wire, ground rods and connectors.


On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne
wrote:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain. I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. What thickness and width should I
use in the earth between the two Grounding Electrode Systems. I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. On
one end that will be only six feet due to the proximity of the
property line. At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. To
compensate for the proximity to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. What is the best way to attach the copper strap to
the support masts and eve brackets themselves? Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. I
have no idea how that is usually done.
John Ferrell W8CCW

Grounding for Gable end bracket & mast.
 

On 7/13/2010 9:52 AM, John Ferrell wrote:
I don't remember the sources but I have concluded that the Grounding
wire should be no smaller than #6.

More than 8 feet of ground rod is of little consequence.

All ground rods should be tied together. Don't put your house between
two electrodes!

The ground rods are better directly under the structure that they are
protecting.

The system does not absorb massive high energy strikes. It starts
bleeding off the energy before the strike builds and thus minmiizes
the effect.


Exactly! May often see during an electrical disturbance little spikes
off the top point of a lightning rod doing its job.

I've been through many 'lightning events' in my day with the closest
direct strike to a neighbor's tree. Also a former wife in my old house
that was hit after she and new husband had cut all the leads to my
ground rods from high TV antennas.

Marv
W5MTV

Home improvement stores sell #6 wire, ground rods and connectors.

Grounding for Gable end bracket & mast.
 

Owen Duffy wrote in
:

....
But, firstly, you should determine if there are regulatory
requirements, such as NEC etc.

Is "NFPA 780: Standard for the Installation of Lightning Protection
Systems" a relevant standard in your jurisdiction?

Owen

Grounding for Gable end bracket & mast.
 

Owen Duffy wrote in news:Xns9DB5277B6263Bnonenowhere@
61.9.134.55:

....
Is "NFPA 780: Standard for the Installation of Lightning Protection
Systems" a relevant standard in your jurisdiction?

If it is applicable, it seems that for a Class 1 structure (less than 75'
in height???), the requirement for the main down conductor is 57,400
circular mils CSA if copper, that is about 29mm^2 or #2 conductor.

By contrast, #6 is 26,000 circular mils, has approximately twice the
resistance per unit length, half the mass per unit length, and somewhere
just less than 25% of the stroke current withstand of #2.

Owen

Grounding for Gable end bracket & mast.
 

In article
,
Tom Horne wrote:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain. I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. What thickness and width should I
use in the earth between the two Grounding Electrode Systems. I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. On
one end that will be only six feet due to the proximity of the
property line. At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. To
compensate for the proximity to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. What is the best way to attach the copper strap to
the support masts and eve brackets themselves? Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. I
have no idea how that is usually done.
--
Tom Horne, W3TDH

You seem to be confusing Lightning Ground, Electrical Ground, and RF
Ground, here, and they are basically three different things. If you
build a Lightning Ground, it may, or may not, be an effective Electrical
Ground. Neither of these will be of any use as an RF Ground, unless you
happen to live in a Salt Marsh. You see Copper Strap Grounds, mostly on
Wood, or Plastic Boats, (ships) used to extend the RF Ground, from the
SeaWater, to the Radio, or Antenna Tuner. Here the Strap becomes part of
the Antenna System, and they need to be engineered, so as to provide as
low of impedance connection, between the two as possible, over the
widest Frequency Range. Some work better than others. Some don't work at
all, and the only way the radio functions at all, is because of Good
Band Conditions.

--
Bruce in alaska
add path after fast to reply

Grounding for Gable end bracket & mast.
 

On Jul 13, 12:52*am, Richard Clark wrote:
On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne

wrote:
Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.

Hi Tom,

Consult the NEC code for your area. *I have never seen them specify
strap in any situation, and don't try your own interpretations of what
"continuous"or "direct" means.

73's
Richard Clark, KB7QHC

Richard
I will certainly make the installation code compliant. What I was
looking for help on was how to make it effective in avoiding damage
from lightning. I have read all of the applicable material from the
Polyphaser, NIST, and several other sites but what I was hoping to
elicit was specific guidance on what size strap to use for the down
conductors and what size to use for the ground ring so that they might
actually work rather than just comply with the code. I can certainly
add any regular wire conductor that would keep the electrical
inspectors happy since I already have 2/0 bare copper for the ground
ring; were only #2 is required and, the ridiculously undersized,
number ten that the code requires for down conductors in hand.

810.58 Grounding Conductors — Amateur Transmitting and Receiving
Stations.
Grounding conductors shall comply with 810.58(A) through (C).
(A) Other Sections. All grounding conductors for amateur transmitting
and receiving stations shall comply with 810.21(A) through (J).
(B) Size of Protective Grounding Conductor. The protective grounding
conductor for transmitting stations shall be as large as the lead-in
but not smaller than 10 AWG copper, bronze, or copper-clad steel.
(C) Size of Operating Grounding Conductor. The operating grounding
conductor for transmitting stations shall not be less than 14 AWG
copper or its equivalent.

810.21 Grounding Conductors — Receiving Stations.
Grounding conductors shall comply with 810.21(A) through (J).
(A) Material. The grounding conductor shall be of copper, aluminum,
copper-clad steel, bronze, or similar corrosion-resistant material.
Aluminum or copper-clad aluminum grounding conductors shall not be
used where in direct contact with masonry or the earth or where
subject to corrosive conditions. Where used outside, aluminum or
copper-clad aluminum shall not be installed within 450 mm (18 in.) of
the earth.
(B) Insulation. Insulation on grounding conductors shall not be
required.
(C) Supports. The grounding conductors shall be securely fastened in
place and shall be permitted to be directly attached to the surface
wired over without the use of insulating supports.
Exception: Where proper support cannot be provided, the size of the
grounding conductors shall be increased proportionately.
(D) Mechanical Protection. The grounding conductor shall be protected
where exposed to physical damage, or the size of the grounding
conductors shall be increased proportionately to compensate for the
lack of protection. Where the grounding conductor is run in a metal
raceway, both ends of the raceway shall be bonded to the grounding
conductor or to the same terminal or electrode to which the grounding
conductor is connected.
If metal enclosures such as steel conduit are used to enclose the
grounding conductor, bonding must be provided at both ends to ensure
an adequate low-impedance current path.
(E) Run in Straight Line. The grounding conductor for an antenna mast
or antenna discharge unit shall be run in as straight a line as
practicable from the mast or discharge unit to the grounding
electrode.
(F) Electrode. The grounding conductor shall be connected as
follows:
(1) To the nearest accessible location on the following:
a. The building or structure grounding electrode system as covered in
250.50
b. The grounded interior metal water piping systems, within 1.52 m (5
ft) from its point of entrance to the building, as covered in 250.52
See the commentary following 250.52(A)(1).
c. The power service accessible means external to the building, as
covered in 250.94
d. The metallic power service raceway
e. The service equipment enclosure, or
f. The grounding electrode conductor or the grounding electrode
conductor metal enclosures; or
(2) If the building or structure served has no grounding means, as
described in 810.21(F)(1), to any one of the individual electrodes
described in 250.52; or
(3) If the building or structure served has no grounding means, as
described in 810.21(F)(1) or (F)(2), to an effectively grounded metal
structure or to any of the individual electrodes described in 250.52.
(G) Inside or Outside Building. The grounding conductor shall be
permitted to be run either inside or outside the building.
(H) Size. The grounding conductor shall not be smaller than 10 AWG
copper, 8 AWG aluminum, or 17 AWG copper-clad steel or bronze.
(I) Common Ground. A single grounding conductor shall be permitted for
both protective and operating purposes.
(J) Bonding of Electrodes. A bonding jumper not smaller than 6 AWG
copper or equivalent shall be connected between the radio and
television equipment grounding electrode and the power grounding
electrode system at the building or structure served where separate
electrodes are used.

--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

On Jul 13, 2:18*am, Owen Duffy wrote:
Tom Horne wrote in news:e802f6fa-b0e1-471b-bf31-
:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be ...

In this part of the world, we have an Australian / New Zealand Standard
(our version if you like of ANSI, BS etc) which explains the rationale
behind lightning protection, a method of estimating the downcurrent for
protection design purposes and a process for designing down conductors.

Broadly, the scheme is that downconductors are designed to withstand a
few donwstrokes in quick succession without melting the down conductor.
If you work from a peak current of 20kA, it would lead to a down
conductor in copper of at least 25mm^2 which is about #2 to you folk.

I regularly see hams recommend much thinner down conductors, and can only
assume that there is not regulatory guidance or requirement, and I wonder
at the effectiveness of using #6 as often recommended, especially
aluminium as is often the case. Note that reducing conductor size is a
double whammy, you increase the resistance (so the power), and decrease
the mass that has to be heated to melting point, and so the energy
required.

But, firstly, you should determine if there are regulatory requirements,
such as NEC etc.

The question of equipotential bonding conductors ought be dealt with in
the same way, though that is not to imply that they will be the same
size.

Owen

Owen
Believe it or not the NEC only calls for number ten American Wire Gage
(AWG) or 5.261 (mm)2 for protective grounding conductors. Bonding
conductors between electrodes are only required to be number six AWG
or 13.30 (mm)2. So leaving aside the bad joke that is the NEC
requirements I'm trying to get some idea of what best practice might
be.
--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

On Jul 13, 10:52*am, John Ferrell wrote:
I don't remember the sources but I have concluded that the Grounding
wire should be no smaller than #6.

*More than 8 feet of ground rod is of little consequence.

All ground rods should be tied together. Don't put your house between
two electrodes!

The ground rods are better directly under the structure that they are
protecting.

The system does not absorb massive high energy strikes. It starts
bleeding off the energy before the strike builds and thus minmiizes
the effect.

Home improvement stores sell #6 wire, ground rods and connectors.

On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne



wrote:
Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain. *I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. *What thickness and width should I
use in the earth between the two Grounding Electrode Systems. *I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. *On
one end that will be only six feet due to the proximity of the
property line. *At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. *To
compensate for the proximity *to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. *I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. *What is the best way to attach the copper strap to
the support masts and eve brackets themselves? *Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. *I
have no idea how that is usually done.

John Ferrell W8CCW

John
Would you mind sharing what you base that advise on? Much of it
appears contrary to NIST guidance on protective grounding and current
industry practice.
--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

On Jul 13, 1:52*pm, Owen Duffy wrote:
Owen Duffy wrote :

...

But, firstly, you should determine if there are regulatory
requirements, such as NEC etc.

Is "NFPA 780: Standard for the Installation of Lightning Protection
Systems" a relevant standard in your jurisdiction?

Owen

Owen
It is relevant as a consensus standard but it is not adopted as local
or State law. Do you have a link to a copy that can be read online?
--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

On Jul 13, 2:29*pm, Bruce in alaska wrote:
In article
,
*Tom Horne wrote:



Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain. *I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. *What thickness and width should I
use in the earth between the two Grounding Electrode Systems. *I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. *On
one end that will be only six feet due to the proximity of the
property line. *At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. *To
compensate for the proximity *to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. *I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. *What is the best way to attach the copper strap to
the support masts and eve brackets themselves? *Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. *I
have no idea how that is usually done.
--
Tom Horne, W3TDH

You seem to be confusing Lightning Ground, Electrical Ground, and RF
Ground, here, and they are basically three different things. If you
build a Lightning Ground, it may, or may not, be an effective Electrical
Ground. Neither of these will be of any use as an RF Ground, unless you
happen to live in a Salt Marsh. You see Copper Strap Grounds, mostly on
Wood, or Plastic Boats, (ships) used to extend the RF Ground, from the
SeaWater, to the Radio, or Antenna Tuner. Here the Strap becomes part of
the Antenna System, and they need to be engineered, so as to provide as
low of impedance connection, between the two as possible, over the
widest Frequency Range. Some work better than others. Some don't work at
all, and the only way the radio functions at all, is because of Good
Band Conditions.

--
Bruce in alaska
add path after fast to reply

Bruce
I don't know were your getting the idea that I'm confusing the purpose
of the grounding when I specifically asked about lightning protective
down conductors. The other places that I have seen copper strap
grounds is on the Polyphaser web site. Polyphaser is one of the most
respected names in lightning protection for radio installations in the
United States. Let me be clear that since I'm using balanced antennas
I have no pressing need for an RF ground. Lightning grounding is what
I'm interested in and I'm looking for someone with actual field
experience of best practice.
--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

On Jul 13, 2:18*am, Owen Duffy wrote:
Tom Horne wrote in news:e802f6fa-b0e1-471b-bf31-
:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be ...

In this part of the world, we have an Australian / New Zealand Standard
(our version if you like of ANSI, BS etc) which explains the rationale
behind lightning protection, a method of estimating the downcurrent for
protection design purposes and a process for designing down conductors.

Broadly, the scheme is that downconductors are designed to withstand a
few donwstrokes in quick succession without melting the down conductor.
If you work from a peak current of 20kA, it would lead to a down
conductor in copper of at least 25mm^2 which is about #2 to you folk.

I regularly see hams recommend much thinner down conductors, and can only
assume that there is not regulatory guidance or requirement, and I wonder
at the effectiveness of using #6 as often recommended, especially
aluminium as is often the case. Note that reducing conductor size is a
double whammy, you increase the resistance (so the power), and decrease
the mass that has to be heated to melting point, and so the energy
required.

But, firstly, you should determine if there are regulatory requirements,
such as NEC etc.

The question of equipotential bonding conductors ought be dealt with in
the same way, though that is not to imply that they will be the same
size.

Owen

Owen
The NEC only requires 5.261 (mm)2 for the protective down conductor
and 13.30 (mm)2 for the bonding conductor between electrodes. Since
those sizes are at best a bad joke I was hoping to elicit best
practice advise on what size the conductors should actually be as well
as advise on how to accomplish the bonding of the interior single
point grounding buss bar to the exterior grounding conductors and
Grounding Electrode System.
--
Tom Horne, W3TDH

Grounding for Gable end bracket & mast.
 

Tom Horne wrote in
:

....
Is "NFPA 780: Standard for the Installation of Lightning Protection
Systems" a relevant standard in your jurisdiction?

Owen

Owen
It is relevant as a consensus standard but it is not adopted as local
or State law. Do you have a link to a copy that can be read online?

Ok, well the question is whether you give it importance, or stay with NEC.
I think it turns out that you have a copy, read it and make you own mind
up.

If it was me, I wouldn't waste the money on an inadequate protection
scheme.

Owen

Grounding for Gable end bracket & mast.
 

On Thu, 15 Jul 2010 18:32:02 -0700 (PDT), Tom Horne
wrote:

Richard
I will certainly make the installation code compliant. What I was
looking for help on was how to make it effective in avoiding damage
from lightning.

Hi Tom,

Then that is the end of it. ...but I see more writing below....

I have read all of the applicable material from the
Polyphaser, NIST, and several other sites but what I was hoping to
elicit was specific guidance on what size strap to use for the down
conductors and what size to use for the ground ring so that they might
actually work rather than just comply with the code.

This borders on regret - for what, I haven't a clue.

I can certainly
add any regular wire conductor that would keep the electrical
inspectors happy since I already have 2/0 bare copper for the ground
ring; were only #2 is required and, the ridiculously undersized,
number ten that the code requires for down conductors in hand.

This is not a beauty contest for the diversion of inspectors.

Forgive my not continuing to quote you further as I see that it
NOWHERE employs strap in its description of conductors.

Here is a clue. Call up your insurance agent that provides coverage
for your house against lightning strike. Ask him if your policy would
be honored if your home did not conform to code. Ask him how many
claims had been made for lightning damage to homes that did conform to
code.

73's
Richard Clark, KB7QHC

Grounding for Gable end bracket & mast.
 

On Tue, 13 Jul 2010 10:52:14 -0400, John Ferrell
wrote:

I don't remember the sources but I have concluded that the Grounding
wire should be no smaller than #6.

#6 is a minimum required by code here in the Midland MI area. As it's
a minimum, I would not use anything less than #2 Copper.

More than 8 feet of ground rod is of little consequence.

That depends on your soil conditions. Here I'd probably agree as the
soil is usually quite moist and just a couple feet down is just plain
wet.

However a string of ground rods tied together can be quite effective.

All ground rods should be tied together. Don't put your house between
two electrodes!

I'd put a circle of them around the house, all tied together every
16', but due to the garage and driveway, that is not possible.

The ground rods are better directly under the structure that they are
protecting.

I have a 100' 45G 10' from the NW corner of the garage. Tied into it
is a grounding system consisting of 32 or 33 8' ground rods connected
together with over 600 feet of bare #2.

This system consists of a ground rod about a foot outside the concrete
bare in like with each tower leg. The cable is clamped to each tower
leg and comes off in a curve to the ground rod and is extended out in
a straight line at least 80' with additional ground rods every 16'
(give or take a tad) This system also ties into the house electrical
ground. There is an additional run that goes directly from the ground
rod at the base of the 45G to the 25G on the West end of the shop.
From there it goes on around the shop to the mast holding the 144/440
vertical and around the south side to enter the shop to provide
grounding for the station and computers. This also ties the shop
ground (which is on a different electrical feed) to the house ground.


The system does not absorb massive high energy strikes. It starts
bleeding off the energy before the strike builds and thus minmiizes
the effect.

Mine has taken at least 17 direct hits that have been visually
verified. All that energy had to go some where.

The bleeding off theory has been pretty well discussed and discarded
on the tower talk reflector. Read up on the Polyphaser site. They have
some good information. Those lightning balls or porcupines have
proven ineffective. The major work for lightning rods and ground
systems is to divert the lightning away from the interior of buildings
and process control systems in Industry.


Home improvement stores sell #6 wire, ground rods and connectors.

Read the new NEC code for tower and antenna grounding. There is a
reason I went with #2.


On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne
wrote:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.

I agree with the #2 recommendation. OTOH there is nothing that will
protect an installation from the big atypical Positive lightning, or
super strikes. That's the stuff that blows holes in airplanes.

I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. What thickness and width should I
use in the earth between the two Grounding Electrode Systems. I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. On
one end that will be only six feet due to the proximity of the
property line. At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. To
compensate for the proximity to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. What is the best way to attach the copper strap to
the support masts and eve brackets themselves? Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. I
have no idea how that is usually done.

The Polyphaser site has a tutorial on grounding tower legs and coax
shields. this would be applicable to connecting to the 1" pipe.
Use lots on NoAlox between the strap and pipe.

73

Roger (K8RI)

John Ferrell W8CCW

Grounding for Gable end bracket & mast.
 

On Thu, 15 Jul 2010 18:54:08 -0700 (PDT), Tom Horne
wrote:

On Jul 13, 10:52*am, John Ferrell wrote:
I don't remember the sources but I have concluded that the Grounding
wire should be no smaller than #6.

*More than 8 feet of ground rod is of little consequence.

All ground rods should be tied together. Don't put your house between
two electrodes!

The ground rods are better directly under the structure that they are
protecting.

The system does not absorb massive high energy strikes. It starts
bleeding off the energy before the strike builds and thus minmiizes
the effect.

Home improvement stores sell #6 wire, ground rods and connectors.


John Ferrell W8CCW

John
Would you mind sharing what you base that advise on? Much of it
appears contrary to NIST guidance on protective grounding and current
industry practice.

Parts come from the code books,
some from experience and
some from observation.

The #6 wire is out of the code book. Reason and observation leads to
the conclusion that whatever you use there is the possibility of a
lightning strike that can vaporize it. That also supports the notion
that the charge must be bled off over time (seconds?) rather than
shunted to ground instantaneously. In a moment of lapsed judgment I
installed a ground rod for an invisible dog fence on the opposite side
of the house from the electric service ground. I also allowed the
TV-Internet cable ground a few feet away. Lightning strikes carbonize
cable coax connectors. Dog fence controller factory repair is $40 per
event. After much consideration I ran a #6 wire between the power
service ground and the rods for the dog fence and cable ground rods.
Much thought was given to this because that route involved putting a
conductive path along the floor joists just beneath my bed! I
considered the fact that copper plumbing is routinely routed without
concern wherever it is needed. No more service calls to the cable
company, no more repairs needed for the dog fence controller!

I have concluded that if more than 8 foot ground rods were required
for effect or code, the supply houses would be selling them. I cannot
argue with redundancy though. THERE IS A POTENTIAL PROBLEM WITH GROUND
RODS THAT ARE NOT BONDED WITH AT LEAST #6 WIRE! Common sense dictates
that protective system be continuously bled to a common level rather
than allowed to build up a differential charge.

My observations have led me to the notion that the frail little #6
wire does not provide the path for a direct strike. It only suggest a
route for the strike. A straight direct route is more likely to be
followed to ground than a longer twisted route. Lightning is a "boss
force". It can and will ionize its own path in a seemingly whimsical
manner. A spin-off cable loop has been popular for antenna entry
points for many years. This is one of those considerations that may
not do anything but it cannot hurt either!

Whatever you do it must:
Meet code, follow the law
Satisfy the Insurance company, don't give them room to wiggle out of a
claim!
Enhance safety
Protect your property.

In spite of all the precautions and preparations that you take you can
only reduce your exposure to the natural forces in life! My dog Shadow
(a black Labrador Retriever) endorses this by retreating to the Master
Bathroom during storm conditions. Midnight, (Shadows Cat) concurs by
hiding in the basement workshop under those same conditions. I
disconnect all ham radio antennas.

At this time I seem to have my problems at bay... but I also have
professionally installed lightning rods on the house.

John Ferrell W8CCW

Grounding for Gable end bracket & mast.
 

On Fri, 16 Jul 2010 02:37:18 -0400, Roger
wrote:

On Tue, 13 Jul 2010 10:52:14 -0400, John Ferrell
wrote:

I don't remember the sources but I have concluded that the Grounding
wire should be no smaller than #6.

#6 is a minimum required by code here in the Midland MI area. As it's
a minimum, I would not use anything less than #2 Copper.

More than 8 feet of ground rod is of little consequence.

That depends on your soil conditions. Here I'd probably agree as the
soil is usually quite moist and just a couple feet down is just plain
wet.

However a string of ground rods tied together can be quite effective.

All ground rods should be tied together. Don't put your house between
two electrodes!

I'd put a circle of them around the house, all tied together every
16', but due to the garage and driveway, that is not possible.

The ground rods are better directly under the structure that they are
protecting.

I have a 100' 45G 10' from the NW corner of the garage. Tied into it
is a grounding system consisting of 32 or 33 8' ground rods connected
together with over 600 feet of bare #2.

This system consists of a ground rod about a foot outside the concrete
bare in like with each tower leg. The cable is clamped to each tower
leg and comes off in a curve to the ground rod and is extended out in
a straight line at least 80' with additional ground rods every 16'
(give or take a tad) This system also ties into the house electrical
ground. There is an additional run that goes directly from the ground
rod at the base of the 45G to the 25G on the West end of the shop.
From there it goes on around the shop to the mast holding the 144/440
vertical and around the south side to enter the shop to provide
grounding for the station and computers. This also ties the shop
ground (which is on a different electrical feed) to the house ground.


The system does not absorb massive high energy strikes. It starts
bleeding off the energy before the strike builds and thus minmiizes
the effect.

Mine has taken at least 17 direct hits that have been visually
verified. All that energy had to go some where.

The bleeding off theory has been pretty well discussed and discarded
on the tower talk reflector. Read up on the Polyphaser site. They have
some good information. Those lightning balls or porcupines have
proven ineffective. The major work for lightning rods and ground
systems is to divert the lightning away from the interior of buildings
and process control systems in Industry.


Home improvement stores sell #6 wire, ground rods and connectors.

Read the new NEC code for tower and antenna grounding. There is a
reason I went with #2.


On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne
wrote:

Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.

I agree with the #2 recommendation. OTOH there is nothing that will
protect an installation from the big atypical Positive lightning, or
super strikes. That's the stuff that blows holes in airplanes.

I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. What thickness and width should I
use in the earth between the two Grounding Electrode Systems. I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. On
one end that will be only six feet due to the proximity of the
property line. At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. To
compensate for the proximity to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. What is the best way to attach the copper strap to
the support masts and eve brackets themselves? Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. I
have no idea how that is usually done.

The Polyphaser site has a tutorial on grounding tower legs and coax
shields. this would be applicable to connecting to the 1" pipe.
Use lots on NoAlox between the strap and pipe.

73

Roger (K8RI)

John Ferrell W8CCW

Roger, I like your response better than mine.

It sounds to me like you have the ultimate solution. I arrived at my
operating point one step at a time and I quit working on the problem
when I quit having problems!

I have a non-Ham friend that lives a couple of miles down the ridge
from me that continues to have lightning related problems that may
benefit from your advice. I will pass along the Wisdom.

Thank you!
John Ferrell W8CCW

Grounding for Gable end bracket & mast.
 

On Jul 15, 9:18*pm, Tom Horne wrote:


Owen
The NEC only requires 5.261 (mm)2 for the protective down conductor
and 13.30 (mm)2 for the bonding conductor between electrodes. *Since
those sizes are at best a bad joke I was hoping to elicit best
practice advise on what size the conductors should actually be as well
as advise on how to accomplish the bonding of the interior single
point grounding buss bar to the exterior grounding conductors and
Grounding Electrode System.
--
Tom Horne, W3TDH

It's not that bad a joke.. If the ground connection is good, #10
is plenty thick enough. In fact, it would barely get warm if it
took a strike. Of course, if the connection to ground is bad,
it will be toast. But so would a lot of heavier gauges also..
The connection to ground is the critical factor in such a case.
But I would still follow what the local code says.
The main reason I'm making this post is only to clarify that
under proper conditions, #10 is plenty thick enough to safely
route the strike to ground with no damage to the wire.

Grounding for Gable end bracket & mast.
 

Tom Horne wrote:
On Jul 13, 12:52 am, Richard Clark wrote:
On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne

wrote:
Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.
Hi Tom,

Consult the NEC code for your area. I have never seen them specify
strap in any situation, and don't try your own interpretations of what
"continuous"or "direct" means.

73's
Richard Clark, KB7QHC

Richard
I will certainly make the installation code compliant. What I was
looking for help on was how to make it effective in avoiding damage
from lightning. I have read all of the applicable material from the
Polyphaser, NIST, and several other sites but what I was hoping to
elicit was specific guidance on what size strap to use for the down
conductors and what size to use for the ground ring so that they might
actually work rather than just comply with the code. I can certainly
add any regular wire conductor that would keep the electrical
inspectors happy since I already have 2/0 bare copper for the ground
ring; were only #2 is required and, the ridiculously undersized,
number ten that the code requires for down conductors in hand.


Hmmm you say "ridicuously undersized"..

Why?

have you studied the fusing current of AWG 10?
Have you compared the inductance of various sizes?

Do you know *why* the code only requires AWG 10?

The code requirements are based on actual science, engineering, and test
data, so if the code requires AWG 10, it's probably for a fairly good
reason.

Note that they allow bronze and copper clad steel as well as solid
copper, so clearly, DC resistance isn't what they're worried about.

(hint.. think of mechanical reasons)

Note, especially, that the NEC (NFPA 70) grounding/bonding requirements
are NOT for lightning protection. (that's in NFPA 780, not NFPA 70)

Grounding for Gable end bracket & mast.
 

Tom Horne wrote:

Owen
Believe it or not the NEC only calls for number ten American Wire Gage
(AWG) or 5.261 (mm)2 for protective grounding conductors. Bonding
conductors between electrodes are only required to be number six AWG
or 13.30 (mm)2. So leaving aside the bad joke that is the NEC
requirements I'm trying to get some idea of what best practice might
be.


Tom is a bit confused here about the purpose of NEC vs NFPA 780..

The bonding requirements in the NEC are designed to keep the building
from burning down in the event of an accidental fault to an energized
conductor. The basic requirement is that it carry enough fault current
for long enough to trip the overcurrent protection device on the
energized conductor.

It's not for lightning protection, per se. (although NEC bonding will,
incidentally, provide some degree of protection against induced transients)

I'd also note that AWG 10 wire is more than sufficient to carry a 50kA
pulse for the 20 microseconds or so that a lightning stroke lasts
without melting.
Using the Onderdonk equation, you can calculate that a AWG16 copper wire
will carry about 90kA for a 20 microsecond pulse. AWG10 should be able
to carry 4 times that much. AWG6, 10 times, because it scales with cross
sectional area.

Having only really paid attention to this recently, I noticed that in
Rome (a place with a fair number of thunderstorms), they use fairly
small down conductors (AWG 10 or 6, just by eye), and similar for 7
story tall wooden pagodas in Nara, Japan (another place with lots of
thunderstorms).

I'm not quite sure where the fashion for 2/0 grounding conductors comes
from (maybe Phelps-Dodge has a representative on the NFPA 780 review
committee?grin)

Grounding for Gable end bracket & mast.
 

Tom Horne wrote:
On Jul 13, 1:52 pm, Owen Duffy wrote:
Owen Duffy wrote :

...

But, firstly, you should determine if there are regulatory
requirements, such as NEC etc.
Is "NFPA 780: Standard for the Installation of Lightning Protection
Systems" a relevant standard in your jurisdiction?

Owen

Owen
It is relevant as a consensus standard but it is not adopted as local
or State law. Do you have a link to a copy that can be read online?


NFPA 780, like NFPA 70, is a copyrighted document *sold* by NFPA.
However, there *are* online copies of various provenance and age around.
http://www.atmo.arizona.edu/students...A_780_2004.pdf

Unfortunately, the bare code doesn't tell you much about the "why" for
various code provisions, so if you're thinking of going "off code" for
one reason or another, you don't have a lot of information to tell you
whether it's a good idea.

There's also some interesting seeming inconsistencies.. NFPA 780
requires a minimum length of a ground rod of 8 feet (4.13.2.1) but also
requires that they extend vertically not less than 10 feet into the
earth (4.13.2.3(A))) The figure makes it clear.. the top of an 8 foot
rod is 2 feet below the surface of the soil.

NFPA 780 says 29 square millimeters for main conductors (6 mm in
diameter or a strip that is 1.3mm thick x 22.3 mm wide).. That's AWG 6
roughly.


There's also a great site by Carl Malamud: publicresource.org that has
all the California Building Codes (including an older rev of the NEC)
although it doesn't have NFPA 780 on it, as far as I know.

Grounding for Gable end bracket & mast.
 

Tom Horne wrote:


Owen
The NEC only requires 5.261 (mm)2 for the protective down conductor
and 13.30 (mm)2 for the bonding conductor between electrodes. Since
those sizes are at best a bad joke

Perhaps you could explain why you think it's a bad joke? Do you think a
13 square mm conductor couldn't carry the strike current? (it can)

Or, perhaps, you're thinking that there are some other design criteria
that might push one towards a larger conductor (mechanical strength in
the face of icing and storms might be one).

Grounding for Gable end bracket & mast.
 

On 7/19/2010 10:54 AM, Jim Lux wrote:
Tom Horne wrote:
On Jul 13, 12:52 am, Richard Clark wrote:
On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne

wrote:
Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.
Hi Tom,

Consult the NEC code for your area. I have never seen them specify
strap in any situation, and don't try your own interpretations of what
"continuous"or "direct" means.

73's
Richard Clark, KB7QHC

Richard
I will certainly make the installation code compliant. What I was
looking for help on was how to make it effective in avoiding damage
from lightning. I have read all of the applicable material from the
Polyphaser, NIST, and several other sites but what I was hoping to
elicit was specific guidance on what size strap to use for the down
conductors and what size to use for the ground ring so that they might
actually work rather than just comply with the code. I can certainly
add any regular wire conductor that would keep the electrical
inspectors happy since I already have 2/0 bare copper for the ground
ring; were only #2 is required and, the ridiculously undersized,
number ten that the code requires for down conductors in hand.


Hmmm you say "ridicuously undersized"..

Why?

have you studied the fusing current of AWG 10?
Have you compared the inductance of various sizes?

Do you know *why* the code only requires AWG 10?

The code requirements are based on actual science, engineering, and test
data, so if the code requires AWG 10, it's probably for a fairly good
reason.

Note that they allow bronze and copper clad steel as well as solid
copper, so clearly, DC resistance isn't what they're worried about.

(hint.. think of mechanical reasons)

Note, especially, that the NEC (NFPA 70) grounding/bonding requirements
are NOT for lightning protection. (that's in NFPA 780, not NFPA 70)


IIRC the purpose is to primarily drain off the static charges so the
gnd-cloud potential difference is minimized. A direct strike will
usually just melt whole house wiring, etc. etc.

Marv

Grounding for Gable end bracket & mast.
 

I have concluded that if more than 8 foot ground rods were required
for effect or code, the supply houses would be selling them. I cannot
argue with redundancy though. THERE IS A POTENTIAL PROBLEM WITH GROUND
RODS THAT ARE NOT BONDED WITH AT LEAST #6 WIRE! Common sense dictates
that protective system be continuously bled to a common level rather
than allowed to build up a differential charge.


This is actually a big problem.. counterfeit rods with UL markings on
them, and rods that are too small in diameter or too short to meet NEC
requirements.

Electrical Supply places (not the home improvement stores) have had 10
foot rods for a long time.

The NEC has required 8 feet *in the ground* for years and years (at
least 20, I think), so the only way to do that with an 8 foot rod is to
do your exothermic bond to the rod and completely bury it.

The home improvement stores don't like to stock longer rods because most
of the buyers are not "code-aware" and buy on price (hey, an 8 foot rod
is cheaper than a 10 foot rod, I'll use that). Besides, for new
construction in a lot of places, a rod isn't an acceptable primary
grounding means anyway.

And we won't even get into the grounding/bonding practices of satellite
dish and Cable TV installers. There's a great website out there with
pictures of truly lame installations.

Grounding for Gable end bracket & mast.
 

IIRC the purpose is to primarily drain off the static charges so the
gnd-cloud potential difference is minimized. A direct strike will
usually just melt whole house wiring, etc. etc.

Not true.

The cloud has SO MUCH charge you don't stand a chance of bleeding it off.

Direct strikes are typically around 20 kA, and can be as high as 100kA.
Both can be adequately carried by the usual AWG6 wire, because the
current pulse only lasts a few microseconds.

Grounding for Gable end bracket & mast.
 

On Jul 13, 12:21*am, Tom Horne wrote:
Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain. *I have a a
mount for an antenna at one gable end and a mount for a weather
station sensor array at the other. *What thickness and width should I
use in the earth between the two Grounding Electrode Systems. *I will
drive five eighths inch copper rods, each eight feet long as far out
from the foundation as I can get them or eight feet were possible. *On
one end that will be only six feet due to the proximity of the
property line. *At all of the other rod locations I will be able to
keep them at least eight feet from any underground obstructions. *To
compensate for the proximity *to the foundation wall to the first rod
I will use rod couplers and drive it to hard rock or sixteen feet
whichever comes first. *I'm guessing that in keeping the remaining
rods at least eight feet out from the foundation and sixteen feet
apart that I will only have four rods total in a ring around the back
side of the house. *What is the best way to attach the copper strap to
the support masts and eve brackets themselves? *Do you know of
anything that will make a good connection to the one inch galvanized
iron pipes that I'm using for support masts?

Can you recommend a technique for bonding the interior grounding buss
at the operating position to the exterior vertical copper strap. *I
have no idea how that is usually done.
--
Tom Horne, W3TDH

If you want something beyond code typically we use 00 braided copper
at work for lightning protection on towers. NEC and Polyphaser
recommendations usually work pretty good

Jimmie

Grounding for Gable end bracket & mast.
 

Jim Higgins wrote:
On Mon, 19 Jul 2010 09:23:53 -0700, Jim Lux
wrote:

Tom Horne wrote:

Owen
The NEC only requires 5.261 (mm)2 for the protective down conductor
and 13.30 (mm)2 for the bonding conductor between electrodes. Since
those sizes are at best a bad joke
Perhaps you could explain why you think it's a bad joke? Do you think a
13 square mm conductor couldn't carry the strike current? (it can)

Or, perhaps, you're thinking that there are some other design criteria
that might push one towards a larger conductor (mechanical strength in
the face of icing and storms might be one).

Maybe E=IR has something to do with wanting a larger conductor. The
voltage between the strike point and true ground is going to be the 20
- 100 kA of the strike times the resistance of the down conductor from
the strike point to true ground. With a smaller conductor,
fewer/shorter ground rods, or other conditions that raise the
resistance of the path to ground that voltage will be higher and if
high enough the strike will seek additional paths to ground by arcing
to nearby objects closer to ground potential.


Resistance isn't actually a big deal here. It's all about inductance on
that microsecond rise time pulse. And there's not much difference in
inductance between a AWG 6 and 2/0 (it's very weakly dependent on
diameter and strongly dependent on length.. 1 microhenry/meter is a good
estimate, pretty much independent of diameter)

The other problem is that for fast transients, skin effect means that
the AC resistance goes more as the diameter than as the cross sectional
area (hollow tubes work just as well as solid conductors).

So, the net effect is that you need to design for several things:
1) the wire not melting..
2) The wire not breaking from mechanical impact (ladders hitting it,
lawnmowers, etc.
3) The wire not breaking under electromagnetic forces (this is why you
don't want loops and why NFPA 780 says 8" bend radius.. while a 1
microsecond pulse at 10kA won't melt a AWG 10 wire, if it's in a loop,
it will destroy it from EM forces)

You'll see heavier conductors where they have to be able to move (say on
a gate or actuated device), not only for mechanical life, but also
because the flexible wire is more subject to destruction by EM forces.

Side flash is a consideration, but usually accommodated by making sure
your downleads are far from potential victim circuits.

Grounding for Gable end bracket & mast.
 

On Jul 19, 1:03*pm, Jim Higgins wrote:
On Mon, 19 Jul 2010 09:23:53 -0700, Jim Lux
wrote:

Tom Horne wrote:

Owen
The NEC only requires 5.261 (mm)2 for the protective down conductor
and 13.30 (mm)2 for the bonding conductor between electrodes. *Since
those sizes are at best a bad joke

Perhaps you could explain why you think it's a bad joke? *Do you think a
13 square mm conductor couldn't carry the strike current? (it can)

Or, perhaps, you're thinking that there are some other design criteria
that might push one towards a larger conductor (mechanical strength in
the face of icing and storms might be one).

Maybe E=IR has something to do with wanting a larger conductor. *The
voltage between the strike point and true ground is going to be the 20
- 100 kA of the strike times the resistance of the down conductor from
the strike point to true ground. *With a smaller conductor,
fewer/shorter ground rods, or other conditions that raise the
resistance of the path to ground that voltage will be higher and if
high enough the strike will seek additional paths to ground by arcing
to nearby objects closer to ground potential.

That's why I tie everything together. In my case, the ground rods
are minimal.. Just a few copper tubes pounded into the ground
around the base of the mast. None are too deep. But I consider
the ground adequate for the purpose, and it seems to be, being
as I've taken strikes on that mast with no damage to anything.
But I tie that ground into the electrical ground, and also the
plumbing, which I clamp to just a few feet away from the base
of the mast. If all grounds are at the same appx potential, and
the connection to ground is up to par as far as resistance, you
shouldn't see flashing over to other objects. I've never had that
problem here so far. In fact, the connection to ground seems
good enough that strikes to that mast are fairly silent and
only make an electrical arc sound which sounds like throwing
a light bulb onto the ground.
On the other hand, a strike to a poorly grounded object with
high resistance is hugely loud.. Say when it strikes the tree
in the front yard.. It's like a 12 gauge going off. And this
sound is separate from the sonic boom of the strike as
it travels through the air. The sonic boom will come from
overhead and is not local like the actual strike noise at the
object being struck.

Grounding for Gable end bracket & mast.
 

Jim Lux wrote in
:
....
The other problem is that for fast transients, skin effect means that
the AC resistance goes more as the diameter than as the cross
sectional area (hollow tubes work just as well as solid conductors).

The problem is that while we might characterise the raw excitation caused
by lightning, and use assumptions about the shape, rise and fall times
and peak field strength, the response of circuits (such as those that
include the down conductor) is quite different, and it is unsafe to
assume in the general case that skin effect is fully effective for all or
even most of the energy spectrum.

Perhaps that is why some of these standards tend to treat the conductor
as having a resistance equal to that implied by just the conductivity (or
resistivity) and CSA. It might be conservative, but then standards tend
to be so.

Having seen the results of fairly detailed EM modelling of EMP and
lightning excitation of major infrastructure, and the effects of some
small changes to the model, I wonder a bit about the effectiveness of
some measures... but over engineering probably saves the day in a lot of
cases.

The real danger with lightning protection is that a half baked approach
my give the implementor some comfort, but actually increase the risk of
adverse outcome.

The most thorough and consistent practice I have seen is that employed
here in mobile phone base stations. Sure, they are occasionally damaged
by lightning, but the vast majority of lightning incidents do not cause
permanent damage.

Owen

Grounding for Gable end bracket & mast.
 

On 7/19/2010 6:54 PM, Owen Duffy wrote:
The real danger with lightning protection is that a half baked approach
my give the implementor some comfort, but actually increase the risk of
adverse outcome.

The most thorough and consistent practice I have seen is that employed
here in mobile phone base stations. Sure, they are occasionally damaged
by lightning, but the vast majority of lightning incidents do not cause
permanent damage.

Owen

The biggest problem with lightning protection in my area is that the
local power company leaves the ground lines coiled up at the bottom of
the poles. On about half the poles I've checked.

When they put the new transformer in across the street from my house the
crew said they would be back to put in the ground rod. Nope. So I
called a friend that si a troubleshooter for the power company about 2
months later and told him about it. "Yup, I'll get somebody right
over." No joy 4 years later.

I lost $1500 dollars worth of gear last year because the only decent
ground was connected to my radio. And every bit of current that came
into the house on the power line exited that direction.

The power companies are likely the worst culprits from my perspective.
I have installed more grounds at my house than the rest of the street
has. Probably not all to spec, but safer than what wasn't here before.

I also discovered the dictionary definition of replacement cost is not
the same one the insurance industry uses. Big surprise.

tom
K0TAR

Grounding for Gable end bracket & mast.
 

On 7/19/2010 8:06 PM, tom wrote:
On 7/19/2010 6:54 PM, Owen Duffy wrote:
The real danger with lightning protection is that a half baked approach
my give the implementor some comfort, but actually increase the risk of
adverse outcome.

The most thorough and consistent practice I have seen is that employed
here in mobile phone base stations. Sure, they are occasionally damaged
by lightning, but the vast majority of lightning incidents do not cause
permanent damage.

Owen

The biggest problem with lightning protection in my area is that the
local power company leaves the ground lines coiled up at the bottom of
the poles. On about half the poles I've checked.

When they put the new transformer in across the street from my house the
crew said they would be back to put in the ground rod. Nope. So I called
a friend that si a troubleshooter for the power company about 2 months
later and told him about it. "Yup, I'll get somebody right over." No joy
4 years later.

I lost $1500 dollars worth of gear last year because the only decent
ground was connected to my radio. And every bit of current that came
into the house on the power line exited that direction.

The power companies are likely the worst culprits from my perspective. I
have installed more grounds at my house than the rest of the street has.
Probably not all to spec, but safer than what wasn't here before.

I also discovered the dictionary definition of replacement cost is not
the same one the insurance industry uses. Big surprise.

tom
K0TAR

Methinks you need a professional engineer and good lawyer?

Marv
W5MTV

Grounding for Gable end bracket & mast.
 

On 7/19/2010 9:31 PM, MTV wrote:
On 7/19/2010 8:06 PM, tom wrote:
On 7/19/2010 6:54 PM, Owen Duffy wrote:
The real danger with lightning protection is that a half baked approach
my give the implementor some comfort, but actually increase the risk of
adverse outcome.

The most thorough and consistent practice I have seen is that employed
here in mobile phone base stations. Sure, they are occasionally damaged
by lightning, but the vast majority of lightning incidents do not cause
permanent damage.

Owen

The biggest problem with lightning protection in my area is that the
local power company leaves the ground lines coiled up at the bottom of
the poles. On about half the poles I've checked.

When they put the new transformer in across the street from my house the
crew said they would be back to put in the ground rod. Nope. So I called
a friend that si a troubleshooter for the power company about 2 months
later and told him about it. "Yup, I'll get somebody right over." No joy
4 years later.

I lost $1500 dollars worth of gear last year because the only decent
ground was connected to my radio. And every bit of current that came
into the house on the power line exited that direction.

The power companies are likely the worst culprits from my perspective. I
have installed more grounds at my house than the rest of the street has.
Probably not all to spec, but safer than what wasn't here before.

I also discovered the dictionary definition of replacement cost is not
the same one the insurance industry uses. Big surprise.

tom
K0TAR

Methinks you need a professional engineer and good lawyer?

Marv
W5MTV

To deal with a monopoly? Approved by federal, state and local
government? Of both corrupt colors?

You are a comedian.

tom
K0TAR

Grounding for Gable end bracket & mast.
 

On 7/20/2010 11:24 AM, Jim Higgins wrote:
On Mon, 19 Jul 2010 21:40:04 -0500, wrote:

On 7/19/2010 9:31 PM, MTV wrote:
On 7/19/2010 8:06 PM, tom wrote:

I lost $1500 dollars worth of gear last year because the only decent
ground was connected to my radio. And every bit of current that came
into the house on the power line exited that direction.

Methinks you need a professional engineer and good lawyer?

Marv
W5MTV

To deal with a monopoly? Approved by federal, state and local
government? Of both corrupt colors?

You are a comedian.

tom
K0TAR


The value to the consumer of his state Public Utilities Commission
varies by state, but in those states where the PUC is good, the
utilities crap themselves when the PUC contacts them about something
like this. Maybe give it a try.


Minnesota is very similar to Illinois, and seems to be about as corrupt
in the way that only long entrenched Democrat machines can be. They're
just much nicer and friendlier about it. Which is a great disguise in
most cases, and helps the news crews put a positive spin on all the
nonsense that happens here.

I think I'll forego the pleasure of dealing with any state level
bureaucracies, thanks.

But thanks for the advice, I do appreciate it.

tom
K0TAR

Grounding for Gable end bracket & mast.
 

"Jim Lux" wrote
...


IIRC the purpose is to primarily drain off the static charges so the
gnd-cloud potential difference is minimized. A direct strike will usually
just melt whole house wiring, etc. etc.

Not true.

The cloud has SO MUCH charge you don't stand a chance of bleeding it off.

Each cloud has a charge and the all is flowing to the ground. But only 20%
as the direct stroke.

The rule is simple. A mast with the polished ball on the tip attract the
direct stroke (polished ball do not dissipate).
A mast with many sharp spikes dissipate the static charge and eliminate the
direct strike.

Direct strikes are typically around 20 kA, and can be as high as 100kA.
Both can be adequately carried by the usual AWG6 wire, because the current
pulse only lasts a few microseconds.

It is the oscillating current which has a canal in the air. It is not
obliged to flow only in the wire.
S*

Grounding for Gable end bracket & mast.
 

On Jul 23, 8:48*am, "Szczepan Bialek" wrote:
*"Jim Lux" ...



IIRC the purpose is to primarily drain off the static charges so the
gnd-cloud potential difference is minimized. A direct strike will usually
just melt whole house wiring, etc. etc.

Not true.

The cloud has SO MUCH charge you don't stand a chance of bleeding it off.

Each cloud has a charge and the all is flowing to the ground. But only 20%
as the direct stroke.

The rule is simple. A mast with the polished ball on the tip attract the
direct stroke (polished ball do not dissipate).
A mast with many sharp spikes dissipate the static charge and eliminate the
direct strike.

wrong, sharp spikes are designed to start an upward streamer that
connects the downward leader to the lightning rod. that is why they
have a sharp point, to reach the breakdown field gradient before
anything else around them.



Direct strikes are typically around 20 kA, and can be as high as 100kA.
Both can be adequately carried by the usual AWG6 wire, because the current
pulse only lasts a few microseconds.

It is the oscillating current which has a canal in the air. It is not
obliged to flow only in the wire.
S*

normally they don't oscillate, it is a mono-polarity pulse.

Grounding for Gable end bracket & mast.
 

On Jul 23, 3:48*am, "Szczepan Bialek" wrote:


The rule is simple. A mast with the polished ball on the tip attract the
direct stroke (polished ball do not dissipate).
A mast with many sharp spikes dissipate the static charge and eliminate the
direct strike.

A mast with a ball is less likely to attract a strike. That is why
they are
used on flag poles, etc.. They don't stream near as well as a sharp
point. They can still be struck though if nothing more attractive
is around as far as streamers.
A pointed mast streams much easier and will be much more
effective as a lightning rod.
A mast with a lot of spikes is wishful thinking. You can not bleed
off the charge fast enough to eliminate strikes. It's like whizzing
in a whirlwind.
You can not eliminate a direct strike by bleeding off the charge.
You can only offer it a better and easier streaming target than
whatever you do not want struck. And the sharper and more
pointy an object, the better it streams. When is the last time
you saw a lightning rod with a polished ball on top?
They don't sell them, as they would be fairly useless.

Grounding for Gable end bracket & mast.
 

Grounding for Gable end bracket & mast.
 

On 7/23/2010 4:23 PM, Jim Lux wrote:

If the ball is wet, especially with distinct droplets, then you can get
corona forming much earlier. The electrostatic forces tend to make the
droplets fly off.


Non-rhetorical question(s).

I must be missing something then. Why don't I see corona on the tips of
leaves at the tops of my trees? Trees are pretty conductive when
hundreds of kilovolts are involved.

Or my antenna masts for that matter, 'cause they are grounded, too.

tom
K0TAR