LIGHTNING...

[frhrwa]

another good question, ... will lightning rods "draw" lightning to you? I was hit a year ago August, came through my bedroom ceiling at 1:15AM and took out my ceiling fan, melting, blasted it apart.. blew out the windows, set fire to the house, and a year later I'm finished rebuilding with exception of... LIGHTNING RODS.. I was going to put them up, but I get conflicting story's.. One person says, IF it strikes your house, it will be drawn down the rod and cable to the ground rod.. OK.. granted, that's a big IF.. but, IF it weren't going to hit my house, would the rods draw it because of the quick access to ground via the copper line and rods? so, which is safer if you live in a lightning prone area?

[ltx71cm]

Really interested to hear some input on this, I've often wondered about the answer.

[MicroRem]

I believe a lightning rod has roughly the same electrical potential as a any other object sitting on the earth. It would only "attract" more than, say, a house or barn because of its altitude. The difference is that a well grounded lightning rod will allow the charge to make it to ground safely, whereas a non conductive object like a house struck by lightning gets heavily damaged as the lighting makes it way to ground.

When I used to work on Lake Ontario there were a lot of sailboats, and we saw the same thinking, some of the owners would remove the bonding straps that attached the masts to the keel shoe or grounding plate of the hull, thinking it would protect them from strikes. It didn't. And when those ungrounded masts were struck , the result was usually a big fat hole right through the bottom. The properly grounded masts usually had no hull damage, but did often have damaged electronics.

that's my .02

Tom

[dyarker]

Which raises a question. When you were hit and had lightning rod and a fire, was the rod properly grounded? Low resistance driven rod, and large radius curves in down conductor (vs 90 degree bends)? Gauge of down conductor?

[frhrwa]

actually at the time I was hit, I had no lightning rod on the house.. but I do have a 40x48 Metal shop building about 250' away and its a good 10' taller.. also a really tall flag pole right out front, but neither one took a hit.. just my ceiling/roof? with regards to the path to ground, what size copper cable running across your roof peak to each spike would you use, and then down to the ground rods in the ground? seems lightning carries a heck of a punch and 8 gauge, or even 6 gauge would just melt..?

[Janitor Tzap]

Hi Frhrwa,

Found this on Wikipedia.
http://en.wikipedia.org/wiki/Lightning_ ... tem_design


Signed: Janitor Tzap

[dacflyer]

the fact is.. lightning rods will help protect your property. ( house barn shed etc.) if properly installed.
sure you might have a little damage, but your house will not be destroyed by it.
they just guide the lightning to ground,, thus it is not traveling thru the house lighting everything a blaze.
last year several houses were lost to fire from lightning, because the builders were too cheap to install lightning rods. there were several other houses that had them, and had proof that they were struck, and survived with minimal damage.

a good system is one with several grounds. at least 2, one on each end of the house and several spires ( rod tips ) at least every 10 ft apart.
and on chimneys. and at the end of all roof peaks.
also some people and business have installed lightning rods in large trees to help protect them.
the local hospital here has several of them.

the material of choice now days is heavy braided aluminum, you can still get copper also, but it cost way more.
i recently updated the system on my house. it was incomplete when i got the house.
and updating it was less than $200.00
there are places that you can buy online, install it yourself, there are diagrams also for suggested installs..
i have tall trees and power lines around my house, they would likely get hit 1st, but you cannot trust lightning..

again,, nothing will protect you 100% from a direct strike, but it will greatly minimize the damage.
and rods do not draw lightning they just help direct it to ground.. if you did not have rods, the lightning was going to hit your house anyway.. they rods just gave it a path to travel.
the potential was there none the less.

in Europe, its mandatory to have lightning rods on almost any structure including sheds and work shops.. you will be hard pressed to find any structure damaged by lightning related fires.
also if you do not have any,, you will not be able to get house insurance. ( Germany/Austria )

me, i believe in them

[dyarker]

At 250' away the metal building and flag pole would have to be more than 250' tall to be any protection at all! And I'd make a small wager the flag pole is not EFFECTIVELY grounded. (drilled hole in ground, put in pole and level it, then fill hole with concrete) In the link provided by J. Tzap, they mention 45°, I believe in Europe they use a more conservative 30° cone.

Never heard of a 6AWG down conductor melting. Even if it did, the lightning strike would be done before it went open. Lightning is FAST. Most of the current would be on the surface, more like following the conductor than flowing in it.

Cheers,

[dacflyer]

6ga or 8ga is whats typically used on telephone poles, never seen one burned in 2 yet.
now we had a pole once that had 2" wide copper ribbon used as a ground once.
contractor used that on a wooden pole with a camera on it.
and needeless to say, it was zapped in a bad storm we had. the copper ribbon was badly damaged,but still not burned in 2.
we cound out later that everything was not properly grounded. and the camera and other related equipment was destroyed.
contractor was cited for improper installation and had to foot the $4,000.00 bill :O
i have seen other camera poles struck ( scorch marks ) and the cameras were still working.
one had only a tripped breaker. but still worked after resetting.

[frhrwa]

saved that site above to browse through in a bit.. was going to print it, but its pretty long.. good! the flagpole by the way is grounded.. has copper lug fastened to it, #4 copper going to an 8' copper rod driven 7'10" into the ground.. like you say, lightning can't be trusted.. so, from the looks of it, I will be installing the lightning rods (spires) across the roof, each corner, and down each corner of the house to ground rods.. I do have some heavy copper that I can use, so that will save a lot. and I think i have about 4 8' ground rods left, so I'll see if I need more.. thanks for all the info..

[dacflyer]

remember to use proper connectors ,aluminum and copper do not mix and will corrode. i think you have to use galvanised coated connectors if trying to bond copper and aluminum together.
example.. if you use aluminum braid cable, you must use a galvanised ground rod.
not a copper clad rod..
see link below..
http://www.lightningrodparts.com/installation.html

Cautions in the Use of Both Copper and Aluminum.
Copper equipment shall not be used on aluminum roofs, aluminum sidings, or other aluminum surfaces - including bare galvanized steel.
(Use Aluminum Equipment for these).
Copper and aluminum conductors shall not be interconnected except with acceptable bimetallic connectors (Order #A-100)
Aluminum equipment shall not be used underground.
Aluminum equipment shall not be used on copper roofing or other copper surfaces.

heres a few links i thought might be interesting if your looking for parts..
http://www.lightningrodparts.com/parts4.html

[Robert Reed]

Oh would Chris Smith have a ball with this!
Sorry Dac, I just couldn't resist

[gerty]

[quote]
Posted: 16 Nov 2010 09:55 pm Reply with quote

Oh would Chris Smith have a ball with this! [/quote]
There's a name I haven't heard in a long time..
And yeah, you're right, he would be in the middle of it..

[dacflyer]

hehehehh,, fuNNiE

[Lenp]

A thought would be to check with your insurance company. If they offer a discount for lightning protection then it must be viewed as at least some protection. Most insurance companies do not offer a discount, except in the case of very tall structures, like towers and smoke stacks. I was in commercial construction in the Mid-East and in only 2 or 3 projects was any lightning protection included for the job, and those were all solitary high structures. One a transmitter tower and the others had tall stacks.

Thoughts....
Lightning makes, then follows, it's own rules,sometimes.
What would the speed of lightning be if it didn't zig-zag?
Thunder is good, thunder is impressive, but it is lightning that does the work

Len