lightning rods any believers ?

[Giles]

Just a thought---What about homes with metal roofs? A few years ago, I had a home with aluminum roof--Looked like wood shakes---and my home insurance company wanted me to install lightening protection. Another insurance company didn't inform me that I needed the protection. Maybe they didn't realize I had a metal roof.
That was several years ago and now many homes have metal roofs, are they required to have lightening protection?

 

[Mark @ Everlast]

They do work. My brother in law makes his living selling lightening protection systems to commercial companies for large buildings. A good living at that. They guarantee their systems. Many of their installs are after lightening has struck repeatedly. As already said, insurance requires it in many cases. After having your computers blown to bits, it makes good sense to do so.

Yes, building burn down all the time after a lightning strike. That's a lot of heat and voltage as it passes through nails, and cables and all sorts of things. Older barns are typically one spark away from a bonfire as it is with the majority of it being fat wood and lots of hay and dry material accumulated under it. I seen lightning hit trees, split them and watched them burst into flames. If it will do it to living trees, it'll do it to a barn.

 

[MMagis]

You fellas need to read closer. I didn't saying lightning COULDN'T burn a place down. I said that it's not a given that one strike will burn a place down. Big difference. Plenty of houses and barns have been struck by lightning without burning.

 

[Gale Hawkins]

Yes lighting rods work and why they are installed every few hundred/thousand feet all across the USA.

 

[inveresk]

If the system is already there and just needs refitted, it's a no brainer, but the system needs more than just a lightning rod. It needs the copper tape from the rod to an earth spike.

I've only ever seen the results of one lightning strike but the force was enough to blow a hole in a slate roof. A properly designed system will likely pay for itself in the amount of reduced damage the building will suffer in the event of a strike but it does depend on the value of the building.

I've attached a shot of one high end building on top of Mount Tuam that we're in the process of constructing which we're fitting a lightning protection system to. The building itself will have one - maybe two - conductors. In this exposed location and with this value of building, it makes sense. For other sites and buildings, the argument isn't quite as compelling. It's therefore a judgment call whether the exposure of your site and the value of your building and contents warrant one.

 

[SPYDERLK]

I am not an expert and Have never seen any evidince either way but I have my doubts that they will work.

The only ones you see around here anymore are on OLD barns and structures. Dads place (early 1900's farm house) has them on a few of the structures. [[They are aluminum with and aluminum cable. I have my doubts how good this would be in a lightning strike. I would think that it would just vaporize the cable in an instant.]]

Also, If he is putting on a metal roof, what good are the rods sticking up in the air? The whole roof is metal and will be electrified.

Again, this is just my opinion and observations so take it with a grain of salt because I may have no clue at all. But whatever you do, follow the code in the area. Regardless of what you "want" to do, They are always right

[] Im with you there. The vaporizing current for even sizable wire is well below the current delivered in a lightening strike. Even if not vaporized, a red hot wire surviving a strike is its own fire hazzard. ... The value of a lightening rod is more toward "dissipation". A sharp point [or very abrupt curve] has high potential because anything approaching or leaving it does so at a position extremely proud to the surface. There is nothing to interfere with the transition. In comparison to a normal [non pointed] surface this lack of interference amounts to a tremendous impetus for the transition. So, in this case it suggests that the lightening rod would actually attract [] lightening. .... Well-l, it actually does, but very slowly. The property inherent in the high potential point causes a corona discharge effect -- continuous electron exchange as the cloud approaches, thwarting the build up of a huge charge differential between cloud and ground. Amps are drawn for minutes instead of tens of thousands for milliseconds as would happen in a big strike. If a strike happens at all it has been significantly weakened by the bleedoff. Otherwise the cloud just continues on its way past the energy sapping point til it can recharge enuf to strike elsewhere.
larry

 

[MikeD74T]

I tore down a barn 10 years ago to rebuild on my property, 150 miles away. I have the lightning rod system but have not installed it yet. The house that was built within 200' of the barns original location has been hit 3 times since built 4 years ago. All three resulted in fire. House is still unsold. Don't know whether the lightning rods were ever hit but I've stood in the milkhouse & observed strikes so close that I heard no noise. MikeD74T

 

[eepete]

I've seen about 5 homes struck by lightning, 2 burned (one to the ground ), 2 had substantial electrical damage, one had very little damage.

The two with substantial electrical damage included appliances that had circuit boards in them fried. The houses lost everything that was plugged in. One might have been a strike on the arial distribution coming into the house. On another, the oven turned on both heating elements full bore.

The one that had little damage had a shingle roof and a vinyl covered aluminum facia. From the strike point on the roof to the facia, you could see where the shingles burned (the rain put them out). The current then raced around the house on the facia and found a coax from the satellite dish to the ground block. That coax was vaporized, the vinyl trim had a dirty film on it where the cable was. From the ground block to the ground rod was OK, the cable into the house was OK, the satellite receiver was fried, but it did not go back into the AC for the house. If that had been a more powerful strike, the outcome might have been worse.

A metal roof does not protect you per say. You have to provide a path for the current that hits the structure to go to ground. So lightning rods on a metal roof will protect the house. If the lightning hits the roof and not the rods, it will "bounce around" and find either the rods or the cable going to the grounding system. The challenge with a metal roof is finding someone who can install the system without damaging the roof. The people who put my roof one said there was no one they could recommend .

I think lots of houses don't have lighting protection just due to costs. I've heard some say that their insurance is all the protection they need, but I've never met anyone when their house was burned down that was all bubbly and said "It's OK, I had insurance!". We have around 2000 homes in our district, I've seen 5 struck by lighting in 18 years. That's one fire district in our county. Those are your odds. Note also that some areas (and therefore houses) seem to be more prone to lightning strikes that others. No good explanation, but seems to be true. Different parts of the country have different average number of strikes per year too, so there is some local history that needs to be considered here too.

Do you feel lucky :confused3: ?

To the OP: If the ground system is there, agree with iveresk. Put up a few rods and the wire to the ground system.

 

[riptides]

They are visually pleasing too, especially on old barns.

The system must work, if you think about it, look how many old barns are still around....

 

[Danno1]

.


Re-read what Spyderlk wrote in post # 16.



Do a Google for lightning protection or lightning protection systems. Lots of info out there.


.