On Wed, 19 May 2010 07:25:55 -0400, Joe wrote
the following:

On Tue, 18 May 2010 07:35:38 -0700, Larry Jaques
wrote:

On Tue, 18 May 2010 07:02:33 -0400, Joe wrote
the following:

On Mon, 17 May 2010 12:03:27 -0400, "Michael A. Terrell"
wrote:

I suppose you have lightning rods on your workbench and a piece of
antistatic mat on your roof.

As a matter of fact, I do have a (single) lightning rod on my
workbench. A few weeks ago, I found a really cool antique twisted
copper rod at the flea market. It was six feet tall, had a
multicolored glass sphere about 4 inches diameter, in addition to a
clear spool-shaped glass piece. The forked tip elements were curved
inwards toward each other. I never have been able to justify paying
the price dealers get for those old rods, but when he said "Five
bucks", I just about tripped over other shoppers to give him the
money. It now is lying on the workbench while I try to figure out how
and where I will mount it.

Cool. I'd never seen one until you mentioned it. Here's a
hand-crafted one: http://www.metalhands.com/lightningrod.htm

Sweet. That is a really imaginative design - sorta steampunk in fact.

Right, imaginative in a pushy way, just like steampunk.


Thanks for the link. I will try to get a picture or two of mine and
post them somewhere (got a good photo sharing site?). I've seen lots

http://en.wikipedia.org/wiki/List_of...aring_websites


of 2 or 3 foot lightning rods, but this is the only one I've seen that
is so tall. The cable that was used to connect the rods to the ground
was often a thing of beauty as well. There is a good example in a park
near Wilmington, DE that protects a beautiful oak tree; it is a very
thick braided copper cable that divides off to follow each major limb.
The park formerly was the private garden of one of the DuPont women,
so she had the werewithal to provide the care that such a specimen
deserved.

I hope you have lots of pics of that one. I'd love to see it.


I don't have an antistatic mat on my roof, however; since both my
house and my garage roofs are metal, it would be somewhat redundant.

It's properly grounded?

Nah.

Cool. Have someone _else_ post pics (both of the building and of your
charred body) after the next cumulonimbic display day, OK?

--
The great thing about getting older is that
you don't lose all the other ages you've been.
-- Madeleine L'Engle

Joe wrote:

On Tue, 18 May 2010 08:45:12 -0400, "Michael A. Terrell"
wrote:


Joe wrote:

On Mon, 17 May 2010 12:03:27 -0400, "Michael A. Terrell"
wrote:


Joe wrote:

On Sat, 15 May 2010 20:39:41 -0400, "Michael A. Terrell"
wrote:


Don Foreman wrote:

On Fri, 14 May 2010 02:02:50 -0400, "Michael A. Terrell"
wrote:


jk wrote:

"Michael A. Terrell" wrote:



BS. There are no fish or sharks swimming in Florida's air. OTOH,
ESD isn't a big problem here.

Oh???? Isn't that where one of the nation's top lightning research
centers is?


Woooooooooooooooooosh! ESD isn't lightning.

But lightning is ESD, sure enough. BIG ESD.


How often have you had lighting hit your workbench and leave
lecetronics working, but damaged?

Magnitude notwithstanding, lightning IS an electrostatic discharge.


And the sun is a flashlight?

Not quite; the sun is a big fusion reactor, although, come to think of
it, both give off light by incandescence (assuming the flashlight is
the old style).


Other than scale, they are both portable lights with a limited life
span.


I suppose you have lightning rods on your workbench and a piece of
antistatic mat on your roof.

As a matter of fact, I do have a (single) lightning rod on my
workbench.


And? It won't prevent ESD (Electro Static Damage) to elctronics on
your bench.

But that issue wasn't part of your original reply to me.


Then you assumed that ESD meant 'Electro Static Discharge' instead of
'Electro Static Damage'


A few weeks ago, I found a really cool antique twisted
copper rod at the flea market. It was six feet tall, had a
multicolored glass sphere about 4 inches diameter, in addition to a
clear spool-shaped glass piece. The forked tip elements were curved
inwards toward each other. I never have been able to justify paying
the price dealers get for those old rods, but when he said "Five
bucks", I just about tripped over other shoppers to give him the
money. It now is lying on the workbench while I try to figure out how
and where I will mount it.

I don't have an antistatic mat on my roof, however; since both my
house and my garage roofs are metal, it would be somewhat redundant.


Are those roof panels bonded & grounded? If not, you will have a
real mess if lightning strikes.

Yeahbut, you didn't explicitly stipulate grounding in your reply, and
I make no claims as to the effectiveness of the metal roof in any
other sense than how well it works at shielding my buildings from
cumulonimbus discharge. g


It is never a shield 'from cumulonimbus discharge'. It is, however a
safety issue. Grin all you want. A bonded and grounded roof can mean
the difference in a minor problem, or a major fire.



--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Michael A. Terrell wrote:
Joe wrote:

Yeahbut, you didn't explicitly stipulate grounding in your reply, and
I make no claims as to the effectiveness of the metal roof in any
other sense than how well it works at shielding my buildings from
cumulonimbus discharge. g


It is never a shield 'from cumulonimbus discharge'. It is, however a
safety issue. Grin all you want. A bonded and grounded roof can mean
the difference in a minor problem, or a major fire.

If it lets the 'cumulonimbus discharge' in, its time to get up there
with a tube of mastic! ;-)



--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:

IanM wrote:

Michael A. Terrell wrote:
Joe wrote:

Yeahbut, you didn't explicitly stipulate grounding in your reply, and
I make no claims as to the effectiveness of the metal roof in any
other sense than how well it works at shielding my buildings from
cumulonimbus discharge. g


It is never a shield 'from cumulonimbus discharge'. It is, however a
safety issue. Grin all you want. A bonded and grounded roof can mean
the difference in a minor problem, or a major fire.

If it lets the 'cumulonimbus discharge' in, its time to get up there
with a tube of mastic! ;-)


More likely it'll be time for a bulldozer to clear the site, for a nw
building.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

On Wed, 19 May 2010 14:57:02 -0400, "Michael A. Terrell"
wrote:


Joe wrote:




And? It won't prevent ESD (Electro Static Damage) to elctronics on
your bench.

But that issue wasn't part of your original reply to me.


Then you assumed that ESD meant 'Electro Static Discharge' instead of
'Electro Static Damage'

Well, this is getting overly long, but I gotta say...

I spent 4 years as the electronics tech for the EMC/ESD Lab at 2
different facilities for NCR. EMC stood for Electromagnetic
Compatability and ESD stood for Electrostatic Discharge. Those were
the terms in the 1970s and early 1980s, used by everyone with whom I
came in contact, including the guys involved in the military's TEMPEST
program. Maybe the initials have changed in meaning over the years,
but back then, when everything was being driven by the FCC part 15,
subpart J rules, those were the terms we used.




Are those roof panels bonded & grounded? If not, you will have a
real mess if lightning strikes.

Yeahbut, you didn't explicitly stipulate grounding in your reply, and
I make no claims as to the effectiveness of the metal roof in any
other sense than how well it works at shielding my buildings from
cumulonimbus discharge. g


It is never a shield 'from cumulonimbus discharge'. It is, however a
safety issue. Grin all you want. A bonded and grounded roof can mean
the difference in a minor problem, or a major fire.

Cumulonimbus clouds shed a lot of moisture - we call it precipitation.
My roof is an effective shield from that discharge. My general apathy
is my effective shield towards pedantic humorless replies. Please
lighten up a bit.

Joe

On Wed, 19 May 2010 06:29:31 -0700, Larry Jaques
wrote:

On Wed, 19 May 2010 07:25:55 -0400, Joe wrote
the following:

On Tue, 18 May 2010 07:35:38 -0700, Larry Jaques
wrote:

On Tue, 18 May 2010 07:02:33 -0400, Joe wrote
the following:

On Mon, 17 May 2010 12:03:27 -0400, "Michael A. Terrell"
wrote:

I suppose you have lightning rods on your workbench and a piece of
antistatic mat on your roof.

As a matter of fact, I do have a (single) lightning rod on my
workbench. A few weeks ago, I found a really cool antique twisted
copper rod at the flea market. It was six feet tall, had a
multicolored glass sphere about 4 inches diameter, in addition to a
clear spool-shaped glass piece. The forked tip elements were curved
inwards toward each other. I never have been able to justify paying
the price dealers get for those old rods, but when he said "Five
bucks", I just about tripped over other shoppers to give him the
money. It now is lying on the workbench while I try to figure out how
and where I will mount it.

Cool. I'd never seen one until you mentioned it. Here's a
hand-crafted one: http://www.metalhands.com/lightningrod.htm

Sweet. That is a really imaginative design - sorta steampunk in fact.

Right, imaginative in a pushy way, just like steampunk.


Thanks for the link. I will try to get a picture or two of mine and
post them somewhere (got a good photo sharing site?). I've seen lots

http://en.wikipedia.org/wiki/List_of...aring_websites

Thanks


of 2 or 3 foot lightning rods, but this is the only one I've seen that
is so tall. The cable that was used to connect the rods to the ground
was often a thing of beauty as well. There is a good example in a park
near Wilmington, DE that protects a beautiful oak tree; it is a very
thick braided copper cable that divides off to follow each major limb.
The park formerly was the private garden of one of the DuPont women,
so she had the werewithal to provide the care that such a specimen
deserved.

I hope you have lots of pics of that one. I'd love to see it.

I'll get some shots this weekend; it can't rain forever, can it?


I don't have an antistatic mat on my roof, however; since both my
house and my garage roofs are metal, it would be somewhat redundant.

It's properly grounded?

Nah.

Cool. Have someone _else_ post pics (both of the building and of your
charred body) after the next cumulonimbic display day, OK?


OK, both you and Mike (Michael?) have posted rather dire commentary
about the lack of grounding on metal roofs. That has made me wonder if
there are any real guidelines for such. Metal roofs (here I'm
referring to galvanized steel types, from standing-seam to v-crimp and
the more modern variations, applied to wood-frame structures) have
been around for at least a century. I question that they would be more
prone to attracting strikes than any other roof covering, but I
readily admit that I've not looked very deeply into the issue.

Bonding and grounding would be a significant and problematic matter,
though. The burst of current from a lightning strike would require an
assload of bonding points, as I doubt that the roof itself would be
sufficient to drain away all the juice from the point of the discharge
to a single cable (no matter how thick the cable might be). Another
problem with most lightning rod schemes is that ground (soil)
conductivity is not always good enough to conduct the full current of
the discharge from any single point, so there is a lot of ancillary
discharge through all sorts of unplanned pathways (viz, lots of your
house structure). A direct strike on any house would necessitate a
distributed grounding "grid" to carry away the current before it could
do real damage. That's a lot more bucks than most people are willing
to spend.

The military used to (still does?) protect sensitive areas, such as
ammo dumps, by erecting a tall, well-grounded tower nearby. There is a
cone of protection (don't remember the angle) that extends around such
a structure.

There is also the matter of whether it is best to ground a high point
on a house if there are other tall objects nearby. "Well, I was going
to go to that tree, but the spike on the top of that house looks so
much more attractive to me; I think I'll hit it" (Apologies for
anthropomorphizing an electrical discharge.)

Anyway, I'd like to hear thoughts on the matter of grounding a metal
roof (on a wood frame building) as opposed to treatment of other types
of roofing material. Lightning protection is a very interesting,
complex, and poorly understood subject. Maybe a separate thread?

Joe

In article ,
Joe wrote:

[snip]


OK, both you and Mike (Michael?) have posted rather dire commentary
about the lack of grounding on metal roofs. That has made me wonder if
there are any real guidelines for such. Metal roofs (here I'm
referring to galvanized steel types, from standing-seam to v-crimp and
the more modern variations, applied to wood-frame structures) have
been around for at least a century. I question that they would be more
prone to attracting strikes than any other roof covering, but I
readily admit that I've not looked very deeply into the issue.

Metal roofs are no more a problem than metal plumbing, like the drain stack vent
that must protrude above the roof ridgeline. Or a TV antenna attached to the
chimney.


Bonding and grounding would be a significant and problematic matter,
though. The burst of current from a lightning strike would require an
assload of bonding points, as I doubt that the roof itself would be
sufficient to drain away all the juice from the point of the discharge
to a single cable (no matter how thick the cable might be). Another
problem with most lightning rod schemes is that ground (soil)
conductivity is not always good enough to conduct the full current of
the discharge from any single point, so there is a lot of ancillary
discharge through all sorts of unplanned pathways (viz, lots of your
house structure). A direct strike on any house would necessitate a
distributed grounding "grid" to carry away the current before it could
do real damage. That's a lot more bucks than most people are willing
to spend.

The military used to (still does?) protect sensitive areas, such as
ammo dumps, by erecting a tall, well-grounded tower nearby. There is a
cone of protection (don't remember the angle) that extends around such
a structure.

The top of the tower is called an air terminal. Tall thin metal poles are often
used. Such poles are usually seen in electric power switchyards in substations.

The half-angle of the cone is 45 degrees. In other words, the protection
footprint is a circle on the ground of radius equal to the tower height.


There is also the matter of whether it is best to ground a high point
on a house if there are other tall objects nearby. "Well, I was going
to go to that tree, but the spike on the top of that house looks so
much more attractive to me; I think I'll hit it" (Apologies for
anthropomorphizing an electrical discharge.)

Anyway, I'd like to hear thoughts on the matter of grounding a metal
roof (on a wood frame building) as opposed to treatment of other types
of roofing material. Lightning protection is a very interesting,
complex, and poorly understood subject. Maybe a separate thread?

All of this is well understood. There is a MIL Standard (I don't recall the
number, but it's publicly available) that is widely used for figuring out how
best to protect structures from lightning.

Joe Gwinn

Joe wrote:

On Wed, 19 May 2010 14:57:02 -0400, "Michael A. Terrell"
wrote:


Joe wrote:




And? It won't prevent ESD (Electro Static Damage) to elctronics on
your bench.

But that issue wasn't part of your original reply to me.


Then you assumed that ESD meant 'Electro Static Discharge' instead of
'Electro Static Damage'

Well, this is getting overly long, but I gotta say...

I spent 4 years as the electronics tech for the EMC/ESD Lab at 2
different facilities for NCR. EMC stood for Electromagnetic
Compatability and ESD stood for Electrostatic Discharge. Those were
the terms in the 1970s and early 1980s, used by everyone with whom I
came in contact, including the guys involved in the military's TEMPEST
program. Maybe the initials have changed in meaning over the years,
but back then, when everything was being driven by the FCC part 15,
subpart J rules, those were the terms we used.


'Electro Static Damage' was used in electronics manufacturing in the
'90s and early part of this millennium. failed parts are damaged by
multiple causes. Electro static is just one, but it was controllable in
a proper work environment. Conductive mats, wrist straps, heel grounds
and properly grounded soldering irons. A continuous audit of these
systems brought 'Electro Static Damage' down to an acceptable level, of
near zero.



Are those roof panels bonded & grounded? If not, you will have a
real mess if lightning strikes.

Yeahbut, you didn't explicitly stipulate grounding in your reply, and
I make no claims as to the effectiveness of the metal roof in any
other sense than how well it works at shielding my buildings from
cumulonimbus discharge. g


It is never a shield 'from cumulonimbus discharge'. It is, however a
safety issue. Grin all you want. A bonded and grounded roof can mean
the difference in a minor problem, or a major fire.

Cumulonimbus clouds shed a lot of moisture - we call it precipitation.
My roof is an effective shield from that discharge. My general apathy
is my effective shield towards pedantic humorless replies. Please
lighten up a bit.


Have you ever seen what happens when lightning strikes an ungrounded
roof? If you are in the wrong spot between it and ground, the discharge
continues through your body. In that case, you might as well be
outdoors, naked and holding a metal rod as high as you can.

A properly grounded metal framed & grounded building can still be
damaged. One was an office area. The strike magnetized the entire
skeleton of the building, making all their color video monitors
unusable.


I consider death rather humorless.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

On May 22, 11:28*am, Joseph Gwinn wrote:
I
All of this is well understood. *There is a MIL Standard (I don't recall the
number, but it's publicly available) that is widely used for figuring out how
best to protect structures from lightning.

Joe Gwinn

I think it is Mil-hdbk- 419a that you can't remember . I also think
they revised the method used to calculate the lightning protection
from a grounded pole.

Dan