Hi All,
I have been asked to fit a lightning conductor to a friends house extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.

"DKSanders" wrote in message
...
Hi All,
I have been asked to fit a lightning conductor to a friends house
extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.



DON'T, please get advice

Thanks James, but I was hoping this request would result in said advice. If
not then I'll follow the sentiment of your reply, thanks again.
"James Salisbury" wrote in message
...

"DKSanders" wrote in message
...
Hi All,
I have been asked to fit a lightning conductor to a friends house
extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get
the
conductor from, do you have to use copper 'tape' like you see coming
down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.



DON'T, please get advice

"DKSanders" wrote in message
...

Thanks James, but I was hoping this request would result in said advice.
If
not then I'll follow the sentiment of your reply, thanks again.

Lightning conductors can 'ask' for a strike
where none would have occured.
KiloAmps can flow !.
'Step potential' can occur..i.e. you could
electrocute passers by if your earth plate/rods
are ineffective.

On Fri, 24 Oct 2003 22:46:34 +0000 (UTC), "DKSanders"
wrote:

I have been asked to fit a lightning conductor to a friends house extension

_DON'T_ !

You have to design these systems (it's not hard, but it's more complex
than you might think). There's a BS (6651 ?) standard you have to
comply with, if it's to be seen as a "competent" system.

Earthing the things to BS (7430 ?) is as complicated as putting in the
conductor, if not more.

There's also a working at height problem, which often involves renting
a tower / scaffolding or whatever (and you now need sign-off by a
qualified rigger if you erect scaffolding).


I used to know some of this stuff (I was working on GSM base station
configuration) and it's not as simple as you might hope. It's really
not something I'd want to go through "for a friend" - it's the sort of
job that's a pain to do, it will take you longer (and maybe cost more)
than someone who does it regularly, and the comebacks if there's ever
any sort of lightning strike really will put you in the position of
having been personally responsible for an act of God. On the whole,
I'd rather replumb their gas cooker.

I'd probably do my own. But there's no way I'd do someone else's.

--
Die Gotterspammerung - Junkmail of the Gods

"DKSanders" wrote in message
...
Hi All,
I have been asked to fit a lightning conductor to a friends house
extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.

As others have said, it is a job for an expert. FYI, you don't use ordinary
earthing rods, but large plates buried in the ground, and the flat copper
strip is chosen because, for transmitting lightning, surface area is more
important than cross-sectional area.

Colin Bignell

DKSanders wrote:

Hi All,
I have been asked to fit a lightning conductor to a friends house extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.




Long, fat, and pointed, and as conductive as you can make it.

The protection partially comes from the conductor bleeding charge away
from the tower and lowering teh potentil difference around it making it
less likley to be a strike target.

Once struck, even the thickest copper strap is likely to melt. Strikes
can take out power lines easily.

Just hope that MOST of the energy goes down it before it deoes.

nightjar

"DKSanders" wrote in message
...

Hi All,
I have been asked to fit a lightning conductor to a friends house

extension

(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.


As others have said, it is a job for an expert. FYI, you don't use ordinary
earthing rods, but large plates buried in the ground, and the flat copper
strip is chosen because, for transmitting lightning, surface area is more
important than cross-sectional area.



Yes. I forgot to mention the flat plate in the earth. Or morte likley a
few square meters of wire mesh with a solid plate in the middle

That spreads the charge around a bit and avoids localised hot spots of
high voltage.


Colin Bignell

In article , DKSanders nospamdavid.k
writes
Hi All,
I have been asked to fit a lightning conductor to a friends house extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.



Have a look at http://www.furse.com/home.htm these are the lightning
conductor people in the UK and this is an interesting website. In fact
you can download their risk calculator, you have to give them some info
to get it.

However you can take the advice "dont touch with a barge pole" or you
perhaps can come to some agreement with your friend not to be held
liable if it all goes wrong!..

Most of the parts are available from Newey and Eyre the Air terminals
they may have to get in, the copper tape 1 x 1/8" copper they normally
stock and the extensible earth rods and couplers they normally keep too.
FWIW we maintain some radio base stations and after a job a few years
ago we had quite a bit of this stuff left over so I fitted our gaff up
with a system, according to the strike risk calc we were in the "at
risk" grade. We have quite a bit of electronic gear about too.

Back in June one morning this year there was a bad storm and there came
an intense flash and explosion which must have meant that the strike was
very close as the whole house shook!. Last month I had to upgrade our TV
aerial and whilst up on the roof I noticed a burn mark on the Air rod
which definitely was not there when I originally put it up so it seems
to have done some good!.

Of course you have to be very careful when installing to make sure the
routeing is as straight and short as possible and than you have the
ground system just so to avoid any danger from step grade potential
which means that there is a very large distribution of voltage potential
around where your earth rod is, but there are ways to overcome this etc.
Your earth system is a far better one than that required for electrical
earth systems normally about 8 or so earth rods 1500 mm long are
hammered deep in the ground or you could use an earth mat but this will
have to go in at some depth. FWIW we managed 10 rods before we hit
something solid!

But I somehow doubt your friend would stump up for a steeplejack to do
this so it will probably not get done, so if it does get struck the
discharge will go and damage all and sundry!...
--
Tony Sayer

On Sat, 25 Oct 2003 13:09:02 +0100, The Natural Philosopher
wrote:

nightjar

"DKSanders" wrote in message
...

Hi All,
I have been asked to fit a lightning conductor to a friends house

extension

(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.


As others have said, it is a job for an expert. FYI, you don't use ordinary
earthing rods, but large plates buried in the ground, and the flat copper
strip is chosen because, for transmitting lightning, surface area is more
important than cross-sectional area.



Yes. I forgot to mention the flat plate in the earth. Or morte likley a
few square meters of wire mesh with a solid plate in the middle

That spreads the charge around a bit and avoids localised hot spots of
high voltage.



I installed one on an explosives store back in the 60s. I used inch by
eighth copper strip and buried it in a loop around the whole building.
Any joins had to be copper riveted and soldered. It must have worked
okay since I never heard of any big bangs there until they shut the
mine in the 90s.



--
Alan G
"The corporate life [of society] must be
subservient to the lives of the parts instead
of the lives of the parts being subservient to
the corporate life."
(Herbert Spencer)

In uk.d-i-y, AlanG wrote:

I installed one on an explosives store back in the 60s. I used inch by
eighth copper strip and buried it in a loop around the whole building.
Any joins had to be copper riveted and soldered. It must have worked
okay since I never heard of any big bangs there until they shut the
mine in the 90s.

Excellent! And it kept the elephants away too, right? ;-)

(No nastiness intended, Alan - jsut that it's hard to do realistic
tests of a lightning conductor installation; hence the need you and
others have pointed out to follow well-researched design codes. 'Course,
you could always just slap something together based on misreading
something in one manufacturer's brochure, but no-one in this NG would
do such a thing. At least, no-one in *my* view of this NG. Ah, the
peace of a small but perfectly-formed killfile ;-)

On 25 Oct 2003 17:27:40 GMT, wrote:

In uk.d-i-y, AlanG wrote:

I installed one on an explosives store back in the 60s. I used inch by
eighth copper strip and buried it in a loop around the whole building.
Any joins had to be copper riveted and soldered. It must have worked
okay since I never heard of any big bangs there until they shut the
mine in the 90s.

Excellent! And it kept the elephants away too, right? ;-)

And the tigers

(No nastiness intended, Alan - jsut that it's hard to do realistic
tests of a lightning conductor installation;

You find out it doesn't work then it's too late. I reckon this one
must have worked okay or you would have heard the bang 10 miles away.
Possibly have debris rained on you 10 miles away too. There was a lot
of stuff from the Nobel works in that store.

hence the need you and
others have pointed out to follow well-researched design codes. 'Course,
you could always just slap something together based on misreading
something in one manufacturer's brochure, but no-one in this NG would

We put this one in according to instructions from the chief engineer
based on regulations in mines and quarries legislation. I haven't the
faintest idea how to design one. At the same time we installed an
alarm system too. Until then the place only had a padlock on it. More
innocent days then.

do such a thing. At least, no-one in *my* view of this NG. Ah, the
peace of a small but perfectly-formed killfile ;-)

I have a large kill file but I inhabit a political group too. I mostly
lurk in this one.

--
Alan G
"The corporate life [of society] must be
subservient to the lives of the parts instead
of the lives of the parts being subservient to
the corporate life."
(Herbert Spencer)

In uk.d-i-y, AlanG wrote:

.................................................. ... There was a lot
of stuff from the Nobel works in that store.

As in ICI Nobel Division?

"DKSanders" wrote in message
...
Hi All,
I have been asked to fit a lightning conductor to a friends house extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.

---------------
The general consensus seems to be that this is not a wise thing to attempt. I
concur.

Does your friend live atop a barren hill? Do they really need, or simply want,
one of these things? Are they aware of the downside of having one?

A conductor will attract the very strikes they seek to avoid. Which can be quite
dramatic, scary in fact.

I lived in South Africa for quite some time and I must say the electrical storms
around Johannesburg are spectacular, and quite dangerous to boot. Those of us
that lived in houses of bricks and mortar with tiled roofs had little to fear,
not so for those that chose the picturesque thatch style. Storms, and fireworks,
were a worry. While little could be done to combat fireworks much was done to
combat lightning.

This meant having a dirty great metal pole or two sticking up way higher than
the rooftops. Rather like giant tapered flagpoles. These flagpoles were situated
a metre or two from the outer walls. And they were sufficiently high that the
building being protected fell within a 60 degree cone as drawn from the point of
the rod.

They did work, mostly. But they draw lightning like you can't believe. With one
of those things you get to see, hear and smell all the effects, real loud and
real quick. The thatch dwellers had little choice as the gasses given off by wet
thatch render them at risk. Your friends perhaps do have a choice.

With a lightning conductor you can be reasonably sure that you will get struck.
Again and again. So I think a risk assessment might be in order because the
fright you get when you do get struck is not pleasant.

On Sun, 26 Oct 2003 03:39:55 -0000, "gandalf"
wrote:

With a lightning conductor you can be reasonably sure that you will get struck.
Again and again. So I think a risk assessment might be in order because the
fright you get when you do get struck is not pleasant.

Just wondering aloud - there is an awful lot of instantaneous power
transferred when lightning makes contact. I imagine that this would
fry any puny lightning conductor on the first occasion.

Presumably lightning conductors are designed such that they can carry
the enormous load the instant of a second?

PoP

On Sun, 26 Oct 2003 03:39:55 -0000, gandalf wrote:

With one of those things you get to see, hear and smell all the
effects, real loud and real quick.

Then there is the noise from explosive expansion of the ionised air
and the stromng smell of ozone. B-)

--
Cheers
Dave. pam is missing e-mail

On 25 Oct 2003 19:47:38 GMT, wrote:

In uk.d-i-y, AlanG wrote:

.................................................. ... There was a lot
of stuff from the Nobel works in that store.

As in ICI Nobel Division?

Yes.
I think they were up in Scotland.


--
Alan G
"The corporate life [of society] must be
subservient to the lives of the parts instead
of the lives of the parts being subservient to
the corporate life."
(Herbert Spencer)

Huge wrote:

Friends who have had amateur radio antennae struck have had them vanish
altogether, or had to sweep up the congealed droplets of metal
afterwards.

My father had a 23' mast antenna on top of his 3 story house. When
lightening struck, it vapourised the glass fuse in his radio equipment. It
didn't just melt - it simply disappeared. The noise was terrifying, and
the smell wasn't great, either.
My mother refused to have the antenna reinstalled.

"The Natural Philosopher" wrote in message ...

The protection partially comes from the conductor bleeding charge
away from the tower and lowering teh potentil difference around it
making it less likley to be a strike target.

Wrong. This is a myth, still perpetuated, it seems, by school physics
teachers who ought to know better. To quote from BS 6551: "A lightning
conductor is incapable of discharging a thundercloud without a lightning
flash." Lightning protection systems are there to take strikes and divert
the current safely to earth.

Once struck, even the thickest copper strap is likely to melt.

Utter twaddle. Lightning currents are high (98 percentile range 3 - 200 kA,
median value 28 kA), but the duration is very short (typically 100 us), so
the I-squared*dt integral is quite low. The temperature rise of the usual
25 x 3 mm copper conductor taking a 100 kA strike is only about 1 degree C.
The energy dissipated as heat is about 400 J per metre of the conductor's
length. Large conductors are used for reasons of mechanical strength and
robustness, to withstand both the normal knocks they'll get on the outside
of a building and the considerable magnetic forces arising during a strike.

The conductor(s) can carry strike current easily. The danger, and damage,
come when the current leaves the conductor and forms an arc - in a 'side
flash'. The peak power in the arc can reach 100 MW/m, heating the
surrounding air to 30,000 K and initiating a shock wave. It's the shock
wave that blows tiles off roofs, etc.

To avoid side-flashing you have to consider inductive (and mutual inductive)
effects. The rate of rise of current in a strike can reach 200 kA/us, and
hence will drop 200 kV across each microhenry of inductance - i.e. something
on the order of 200 kV per metre of conductor!

Finally the earth system design is not trivial. BS 6551 requires an earth
system resistance not exceeding 10 ohms. 200 kA through 10 ohms will drop 2
MV, so voltage gradients at the ground surface (between someone's feet, for
example) become an important consideration...

--
Andy

"Andy Wade" wrote
| The conductor(s) can carry strike current easily. The danger, and
| damage, come when the current leaves the conductor and forms an arc
| - in a 'side flash'. The peak power in the arc can reach 100 MW/m,
| heating the surrounding air to 30,000 K and initiating a shock wave.
| It's the shock wave that blows tiles off roofs, etc ...
| Finally the earth system design is not trivial. BS 6551 requires an
| earth system resistance not exceeding 10 ohms. 200 kA through 10
| ohms will drop 2 MV, so voltage gradients at the ground surface
| (between someone's feet, for example) become an important consideration...

Memo to self: Do not pee against a church tower during a thunderstorm.

Owain

"PoP" wrote in message
...
On Sun, 26 Oct 2003 03:39:55 -0000, "gandalf"
wrote:

With a lightning conductor you can be reasonably sure that you will get
struck.
Again and again. So I think a risk assessment might be in order because
the
fright you get when you do get struck is not pleasant.

Just wondering aloud - there is an awful lot of instantaneous power
transferred when lightning makes contact. I imagine that this would
fry any puny lightning conductor on the first occasion.

Presumably lightning conductors are designed such that they can carry
the enormous load the instant of a second?

If a lightning conductor is struck, it has failed in its main purpose. What
it is supposed to do is to cause a gradual discharge of the potential
difference between earth and cloud, thus preventing a high enough charge
from building up to create a strike. A proper installation has a number of
air terminals, to create a brush discharge effect, and numerous conductors,
to distribute the load across as wide an area as possible. While copper tape
is widely used, some engineers prefer iron, because it has a higher
impedance.

Colin Bignell

In uk.d-i-y, AlanG wrote:
As in ICI Nobel Division?

Yes.
I think they were up in Scotland.

I believe so - memory augmented by Google suggests both Ayrshire and
Dumfries. Presumably they put the plants in areas of relatively low
population density ;-)

Always seemed a touch amusing to have the Nobel Peace Prize instituted
to assuage old Alfred's guilt at inventing TNT, while ICI (which I believe
bought up his business interests) kept the name going with the more
original association!

Stefek (son of an ICI engineer)

On Sun, 26 Oct 2003 13:27:37 -0000, "Andy Wade"
wrote:

Large conductors are used for reasons of mechanical strength and
robustness,

And also because of the skin effect. The current flow isn't using the
centre of that strip, even at a mere 1/8" thick.

--
Die Gotterspammerung - Junkmail of the Gods

"Andy Dingley" wrote in message
...

And also because of the skin effect. The current flow isn't using
the centre of that strip, even at a mere 1/8" thick.

True.
--
Andy

wrote in message
...
In uk.d-i-y, AlanG wrote:
As in ICI Nobel Division?

Yes.
I think they were up in Scotland.

I believe so - memory augmented by Google suggests both Ayrshire and
Dumfries. Presumably they put the plants in areas of relatively low
population density ;-)

The Stevenston ICI site (Ayrshire) is concerned with explosives manufacture.
Dunno if that's
its sole output though.
This ICI explosives site is built on the coast with lots of sand dunes
surrounding it (the folklore being that with sand
surrounding it German bombs were less likely to explode when dropped onto
sand during World War two).

Mungo

Thanks to you all for the very informative and interesting responses.

I had no idea there was so much involved or to be considered. Therefore I
will use from stores:
a No 1, Pole, Barge, Avoidance, for the use of.
and recommend that my friend contacts e.g. Furse if he is really sure he
needs one.

Thanks again all, I was very impressed by the level of knowledge out there
and found it fascinating reading.

Dave


"DKSanders" wrote in message
...
Hi All,
I have been asked to fit a lightning conductor to a friends house
extension
(a 'tower' like extra floor in the middle of the existing house!). How
should this be done, any special considerations etc, where do you get the
conductor from, do you have to use copper 'tape' like you see coming down
from church spires, does it connect to a normal earth rod?

Any help or advice gratefully appreciated, thanks.

In article , DKSanders nospamdavi
writes
Thanks to you all for the very informative and interesting responses.

I had no idea there was so much involved or to be considered. Therefore I
will use from stores:
a No 1, Pole, Barge, Avoidance, for the use of.
and recommend that my friend contacts e.g. Furse if he is really sure he
needs one.

Thanks again all, I was very impressed by the level of knowledge out there
and found it fascinating reading.

Dave



Wimp! One small flash-bang-wallop!!.........

Seriously I suggest that you have a butchers in the Yellow pages. If you
haven't anyone out your way then there is a firm W.Gray of somewhere in
the Essex area who do travel over quite a wide area, but I still reckon
that its not going to be cheap.

Perhaps you mate might like to DIY himself!..

--
Tony Sayer

Thanks Tony,

Wimp, maybe.. but at least a non-fried wimp

My mate couldn't change a torch battery safely so this is sci fi league to
him. He's checking with the architect who drew up the plans if he really
needs a conductor, I'll pass the info on in case he does.

Thanks again.


Dave

"tony sayer" wrote in message
...
In article , DKSanders nospamdavi
writes
Thanks to you all for the very informative and interesting responses.

I had no idea there was so much involved or to be considered. Therefore I
will use from stores:
a No 1, Pole, Barge, Avoidance, for the use of.
and recommend that my friend contacts e.g. Furse if he is really sure he
needs one.

Thanks again all, I was very impressed by the level of knowledge out
there
and found it fascinating reading.

Dave



Wimp! One small flash-bang-wallop!!.........

Seriously I suggest that you have a butchers in the Yellow pages. If you
haven't anyone out your way then there is a firm W.Gray of somewhere in
the Essex area who do travel over quite a wide area, but I still reckon
that its not going to be cheap.

Perhaps you mate might like to DIY himself!..

--
Tony Sayer