RE: [OT] Lightening Conductors

["Keith Doxey" <lists.diyha@xxxxxxx>]

What you really need is a metal lamp post NEAR the house but substantially taller. That should attract the lightning rather than anything on your house.

 

If you DID try to earth it you need 2 things....

 

1. A VERY THICK EARTH CONDUCTOR - Lightning conductors typically use a copper bar of at least 25 x 5 mm which by my calculations is a minimum of 125mm sq conductor.

 

2. A Large and extremely low resistance earth spike to ground the lightning.

 

The problem you will have by earthing it is that it will become MORE attractive to lightning. The instantaneous currents that flow are many thousands of amps and will simply vapourise conductors that are not large enough. The moment the conductor ceases to conduct the lightning will leap to the nearest earthed thing, normally some nearby wiring. Once it gets into that it will wreak havoc with any electronic equipment.

 

Even if the lightning conductor does its job there may be enough of a localised electromagnetic pulse to kill sensitive electronics anyway.

 

Having spent a long time as a BT maintenence engineer I saw, repaired and "TRIED" to protect against lightning damage. There is so much energy in one direct hit that you cannot easily or cheaply protect against it. Better to purchase increased insurance cover to replace any damaged items.

 

Keith

www.diyha.co.uk
www.kat5.tv

-----Original Message-----
From: nick_towers2000 [mailto:nickt@xxxxxxx]
Sent: 23 April 2002 16:52
To: ukha_d@xxxxxxxSubject: [ukha_d] [OT] Lightening Conductors

SWMBO has purchased a windvane which needs to be fixed on our roof.
Made of metal, with quite a few pointy bits so I think it might
be "attractive" to lightening.  It will be fixed on a small, lead
covered dome with a central steel mounting post.
1) Am I being paranoid - is there really likely to be much increased
danger? If so, would it be any worse than a TV or other aerial on the
roof?
2) Does anyone know anything about DIY installing lightening
conductors, what materials to use etc.
Any help or advise appreciated.
TIA
Nick


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