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