I'm near the east end of "lightning alley" in Florida, which runs from Tampa to Daytona. There are two buildings, a small house (standing steel roof, steel trusses and frame) and a 50 by 90 steel hangar 17 feet high at the ridgeline.
We've been here 11 years and haven't had a direct lighting strike yet BUT we've had some phones and computer stuff cooked by nearby strikes and we had a large pine tree perhaps 150 feet from our front door take a direct hit - and that was exciting! (The cat is still hiding under the bed . . . it's been a year.)
I've been poking around the internet looking for lightning protection since I regard lightning protection sort of like seat belts - you may never need them but if you do, now it is too late to fasten them.
Lot of information - first, lightning often strikes twice or more than twice. In fact, when there is a lightning strike, it creates a momentary channel of ionized air, and you can have multiple strikes through that channel in a matter of milliseconds. (Thunder is caused when that channel collapses.)
Second - lightning can be ground to air as well as air to ground, and it is just as destructive either way. Cloud to cloud lightning is harmless.
The ground rod(s) required by NEC (National Electric Code) and your building inspector is completely inadequate for lightning protection, and that isn't what it is for anyway.
Lightning can strike (or depart) from any structure no matter what it is made of. Stone, wood, metal, doesn't matter. It doesn't even have to be raining (although that helps by making the structure more conductive). In the middle ages, churches and cathedrals were often hit by lightning because they were the tallest things in town. People were advised to get out of the rain anywhere BUT the church or cathedral!
Now down to lightning protection on buildings we have . . .
Steel roof buildings need to use braided aluminum conductor wires (big, fat things, look like battery cables) because copper conductors on a galvanized steel roof will result in dissimilar metal corrosion. All the tie points, mount plates, air points and so forth need to be aluminum as well. If you don't want to drill holes in the building to mount the stuff, there is a construction adhesive (sells for $8 for a 10 ounce tube) which has a shear strength of 380 pounds per square inch (!) when it dries.
Down near the ground, we need to use a bimetallic connector, aluminum to copper, to make the final run to the ground rods, which are copper or copper plated steel, about eight to ten feet down, and about three feet from the building. Many buildings are built on a concrete slab which extends out a bit past the walls, and it is kinda tough to drive a ground rod through concrete ;-)
The "air points" (lighting rods) are spaced about 15' apart along the ridge line, with the two on the ends within 24" of the end of the roof. I also have a 35 foot communications tower (wireless internet), which is tied into the system and grounded as well.
All this stuff combined costs under $400, mostly because the aluminum conductor is only 76 cents a foot, whereas copper is $2.08 a foot, and I need 250 feet. (90 feet along the ridge, and the rest for the down-links along the edges of the ends of the building.) I already had the ground rods. There will be three ground rods, one at the NW corner, one at the SW corner, and one at the tower, which is about 15' south of the NE corner. I'm supposed to have a ground rod at every 100' of the building circumference, but the vendor says I'm OK with only one ground rod at the tower end. (I might add a fourth ground rod at the SE corner anyway.)
This gets built starting at ground level and working up. I don't want to put up the lighting rods (air points) first, get called away, and have them hit by lightning with no place for it to go!
(The house gets done next, all the valuable stuff is in the hangar. You know where my priorities are.)
There's a lightning arrestor in the cable from the antenna to the routers which I suspect will get blown to smithereens if there's a hit, but the internet guy owns it, not me, so he gets to replace it. There are two large surge supressors each with their own dedicated breaker, one at the main service entrance (200 amps) and another at the hangar service entrance, which is 70 amps. These cost about $70 each, the power company will rent you one for only $15 a month forever, like the phone company used to do with black dial phones in the bad old days (and I am showing my age with that one!).
The ground bar in the breaker panel has the green wire going out to yet another ground rod which was installed when the building was constructed. An electrician told me that the green wire was the most important wire in the system, it could save your life.
There are several sources for lighting system parts on the internet, Google is your friend. Prices vary widely, I found two good places but one of them had an attitude, so I wound up with a guy in Missouri named Jay, whose area code is 314. (I'm saying it this way because I can't put a URL here). He's helpful, his prices are right, and he knows what he's talking about. (The other guy does, too, but as I said, he has an attitude, and I prefer not to deal with him.)
Again, I feel that if I suddenly realize I need a lightning protection system RIGHT NOW, it is too late . . . $400 and a day's work is definitely worth it in peace of mind for me.
Best Regards,
Mike/Florida
