Material and Thickness for Lightning Arrester Earthing Strip

Install an actual lightning rod to the highest point of the roof, and run a rated cable straight to ground, as should be outlined in some building code somewhere. I don't believe it would be a good idea to ground your entire roof rather than a lightning rod isolated to ground. DO NOT use the same ground as the rest of your house. Use a lightning Rod with it's own ground rod/strap. As for the powder coating, I have no answers for you. Maybe someone else will come along and help. Good luck, be safe. Cheers!

I have neither seen nor heard of a metal roof attracting lightning!

I lived under one for 17 years in the tropics where most houses had metal roofs with no lightning rods - I never saw or heard of a lightning strike on a house roof.

Likewise power lines are rarely struck - they are high and metal but neither pointed nor low resistance to earth.

I have heard of more trees and tiled roofs being struck than metal roofs ..... but a properly designed lightning rod .... that is another matter entirely - it will attract any nearby lightning strikes because it is:

1. high

2. pointed at the top

3. very low resistance to earth

Thanks for this reply. It lifts a heavy burden from me. The point was that mine is a two storey house and after erecting the roof the height will be almost that of few nearby palm trees which are prone to attract lightning. So I thought of installing a lightning arrester. My worry was that the very lightning arrester should not be counter productive and hence requested for the tech details.

If you wanted to be doubly sure you could mount a lightning arrestor to one of those nearby palm trees - of course it would need to protrude somewhat beyond the top of the palm tree, and the flexing of the palm tree could be an issue but that would actively attract any nearby lightning strikes away from your house ......

Earthing the roof is a good idea but it need be not connected to house earth. If a lightning strikes a nearby palm tree there could be an induced strike on nearby tall objects too.

Fellows;

I heard a presentation about 15 years ago about separate grounds for power, telephone and lightning. Assuming that the strike comes on the lightning rod, the lightning ground will rise in potential by many volts. The voltage at the power ground will be different as will the telephone. Depending on the "earth" resistance, there may be significant differences between electric ground and telephone ground. This may cause telephone modem failure and possibly computer failure. The point of the presentation was that all the grounds should be at the same point so that everything floats together.

What you say is true, however at the point of a lightning strike the lightning ground can rise kV in which case you will still experience equipment failures with the surge flowing from the ground into the mains!

The best solution is to move the lightning strike as far as possible from the other grounds, thus my suggestion of a lightning rod at one of the palm trees -

A lightning rod on the house and/or earthing the roof would probably be the worst thing to do,

No lightning rod and electrically isolated roof, probably the best.

a lightning rod 20+ metres away, probably a close second.

For a lightning rod to be effective the ground impedance of the soil and the rod's connection to it also needs to be very low.

At one point when I was a teenager visiting my grandparent's house (with a metal roof) in the country there was a lightning strike in the paddock alongside the house - about 20-30 yards/metres away - now admittedly there were no computers then and they did not have a phone, but radios and tv, etc were ok. ..... it was VERY loud!

I have read about a device,similar to a surge protector,used to interconnect lightning earth to other earths.

http://www.google.co.uk/search?q=lightning+arrstor+design&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8&rlz=1I7ADFA_en&redir_esc=&ei=TsGBTZKGF862hAfX-7TEBA

I have lived long in Trivandrum in a flat well above the surrounding coconut palms. The pattern of rains is not all that different. We never had a problem with lightning strikes.

As an aside, there is a saying,'Lightning never strikes the same place twice. Because the place is no more after the first strike'.

I wonder how aluminum surface will be cooler than the usual tiled roof, which is good enough for rain harvesting. A metal surface does not actively attract lightning. A sharp metallic point tends to concentrate charges and provides an entry point.

If you want to ground the roof, never use copper in contact with aluminum. In Kochi humidity and salt laden breeze from the sea (if you are near the sea) bimetallic corrosion will quickly destroy the contact.

bioramani

http://cr4.globalspec.com/thread/65851

Just in case you didn't see this thread.