[NTLUG:Discuss] lightening!

[Tom Adelstein]

The issue of lightening rods [as explained below] in the city has more 
potential to attract lightening. The key is to have the least amount of 
footprint connected to the ground. Lightening rods work best in the 
country where a house is out in the open.

The idea that a "properly grounded lightening rod" will protect is 
accurate. The problem occurs when something interferes with the 
lightening rod's grounding. That's considered a peril by actuaries. A 
small animal could uncork the path. Ever seen a burnt squirrel? Ever 
smelled one?

I had lightening strike outside of my office. The building had the 
proper grounding and the lightening, though extremely loud and damaging 
to my ears, made its way to the ground.

My monitor caught fire from harmonic frequency rollover.

Lightening has hit people ten miles away under clear skys. This year, it 
has struck nearby my house and burned two of my UPS's and damaged a hard 
drive. It didn't hit my house.

I have my UPS's plugged into serious surge protectors which run between 
the wall sockets (grounded) and the UPS.

If it hits, it hits. I just practice backing up data as often as 
possible. If I hear th UPS's beeping, I go into action immediately.

darin_ext at darinsmith.net wrote:

> On Wed, 16 Jul 2003 23:25:35 -0500, <kbrannen at gte.net> wrote:
>
>> Actually, about 10 minutes down the road in Argyle, there's a 
>> store/service that sells them.  I have now considered paying them a 
>> visit for information. :-)  My question is, if I install lightening 
>> rods on the house, will that attract more lightening?
>>
>> I think I need to check out the UPS Chris mentioned too.
>>
>
> It's my understanding that if a lightning rod is properly bonded to an 
> earth ground, it should actually work to discourage lightning from 
> selecting your house, as opposed to say, a large tree nearby.
>
> Basically, you want the house to appear at the same potential as the 
> ground- -so that to the lightning, it appears that your house is just 
> a flat piece of land.  To do that, the highest point needs to be at 
> ground potential and the charge your house collects from the 
> atmosphere must be continuously bled off to ground.  If you look at 
> some of the really nice lighting rod installations, they usually will 
> have multiple rods to create the field you would like, all bonded 
> together by VERY heavy gauge copper cable...and multiple, bonded, 
> grounding spikes (12 footers) driven into the ground.
>
> On the other hand, the pointy nature of a lightning rod is meant to 
> help persuade lightning that does strike to choose it as the path.  
> The point will tend to collect a charge (even being grounded) and will 
> therefore produce a leader if the potential builds in that area.  
> Granted, the big charge produced going to the ground is also going to 
> leak back into your house electronics--both through the neutral and 
> the chassis ground wires which are both grounded nearby where the 
> lightning rod will be (as well as telephone, TV cable, satellite, 
> anything in the area).  In fact, any time there is lightning anywhere 
> near you, you are getting small surges coming onto your power.  Those 
> small surges, by the way, gradually make MOV-based (almost all 
> "standard") surge protectors useless--the more surges they catch, the 
> quicker the MOV is destroyed.
>
> Technically, if you have an antenna of any sort, it is a lightning 
> rod.  The reason the NEC specifies that they must be grounded is 
> because you want to bleed the charge they collect from the wind so you 
> don't make them into such an attractive lightning target.  Plus the 
> fact that your lead wire's shielding is almost certainly grounded to 
> the building (chassis) ground--if not by a grounding block (where it 
> should be), then by the equipment itself- -potentially creating an 
> attractive target that is sure to kill any electronics on the other 
> end of that wire.
>
> Lightning rods and exterior grounding in general is meant to reduce 
> the probability of catching a place on fire due to lightning strikes 
> (by both discouraging the strikes to begin with and providing a safer 
> and more direct path to ground for any strikes that occur).  You even 
> see lightning rods sold to protect trees--personally, I'd rather it 
> strike a tree than the house.  I'm personally very glad to have two 
> very large trees in the front yard.  Lightning rods not really meant 
> as a surge protection mechanism (AFAIK).
>
> Panamax has a PDF file somewhere on their site where they describe a 
> proper approach to surge protection involving both whole-house 
> protection (these are actually relatively inexpensive devices) as well 
> as individual device protection.  As soon as I can get a service 
> upgrade and extra breaker box installed, I'm getting a whole-house 
> unit.  There are some of those that also are supposed to help protect 
> against lightning-induced surges on phone and cable lines.  As a 
> simple precaution at my house, I have my cable running into a little 
> cheapo radio-shack neon-lamp-based surge protector.  Not ideal, but 
> might keep my modem from getting slowly destroyed by the dozens of 
> small surges we have around here in the spring and summer.
>