[NCSA-discuss] lightning protection on ethernet

[Joseph Mack NA3T]

On Sat, 17 May 2008, Jeff The Riffer wrote:

> I've rarely heard of power surges over ethernet taking out 
> equipment.

me neither. It's only happened to me that I know about. I 
was wondering why no-one seems to be worried/affected by it.

> But there's a big difference between residential homes and 
> office buildings. Most large commercial buildings are 
> required to have lightning rods and grounding all over the 
> roof.

I hadn't thought about that

So why aren't lightning rods code for homes? They can't be 
that expensive. Is it a matter of no better than absolutely 
neccessary? I had a friend whose cement driveway exploded 
when hit by lightning. The lightning went for the copper 
water pipe buried in the cement. He had to have bypass 
surgery on the water system to get water back into his 
house.

I bet the insurance companies know how much damage is done. 
Hmm. Let's see (reaching for google "lightning residential 
damage insurance")

http://www.americanlightningrod.com/residential/

$10^9/yr. 5% of insurance claims are due to lightning.

> The building itself is almost always in a sea of 
> asphalt/concrete with very little open ground. Trees, if 
> they exist, are smaller than the building. So the 
> probability of a lightning strike going a path anything 
> from "lighting rod"->"ground" is very small.

or that either

still I expect a lightning strike going down a thick Cu rod 
on the outside of the house would induce enough current in 
ethernet cables to take out every piece of equipment in the 
house.

Here's another google find

http://www.lightningsafety.com/nlsi_lls/nlsi_annual_usa_losses.htm

> Well I certainly wouldn't bother if all the cabling is 
> going to connect together is some WAPs. You'd probably 
> end-up replacing the access points with newer upgrades in 
> a few years anyways...

I hadn't thought that far ahead :-)

The problem isn't the value of the waps. It's the downtime 
that costs the money.

thanks Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
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