OT / Lightning Rods

[Anonymous-0]

The old 2 and 1/2 story farm house I live in needs new shingles.
I need to remove the old lightning rods and cables to do so and wonder if I should put them back on after re-roofing?
They are original to the house when built in the 1920s. They're not the fancy three footers with the glass ball on them or anything. They are just 5 simple rods about 12-18 inches tall. One on each corner of the roof and a fifth up higher on the top of the chimney. All are tied together with cable and grounded to the earth.
I know that new houses don't have them, but I wonder if they do any good or not.
In the past 30 years we've lost a microwave, a frig, a coffee maker and most recent, two years ago a nearby strike fried our computer. (A sure way to clean up 100s of e-mails, pictures and 6 months of farm records not backed up on a disk! Ouch!! ) I don't think any of these were from a direct hit on the house but in the yard nearby or on the highline wires maybe?
Also when I was a kid, lightning hit the transformer on our pole just outside the house and destroyed it. It makes me wonder if the rods are making us safer or making us a target?
Jokes aside, what experiences do you people have to say yes or no?

 

[steve n carol]

interesting topic. i did some research on these because I am building where the housetop is amongst the higher of the area. lots of thunderstorms this time of year. I will install them. (and there is a formula for coverage). I once saw where lightning struck the meter box and blew the plaster off of the inside of the house, whever there was wiring in the walls....sl

 

[Pooh Bear]

Lightening rods and surge protection are two different animals.
Lightening rods work by bleeding off the excess negative charge that
builds up on taller objects during an electrical storm.
Lightening rods do not attract or repel lightening strikes.
Their only function is to bleed off the excess negative charge
and make the building less of a target for a strike.
Surge protectors work by shunting the surge current to ground.
If you live in a lightening prone area I would recommend both.

Pooh Bear

 

[Anonymous-0]

This company has some interesting reading on their site about the subject, years ago they did a lightning protection system on a 13 story building that I was a construction manager on.

Hard to cast a vote either way, not being knowledgable enough on the subject, but if the system is in-tact and all you have to do is temporarily re-locate or disconnect the fasteners that hold it, while performing the roofing work, seems like it should stay, to replace that system would certainly be a cost and it would seem that such a system should have value in that it creates a path for the electricity to discharge, whatever way it travels.
ALRCI

 

[havvey]

my personel thoughts are they would do little good in a lightning strike. They look classy and are antique I have some. But as you stated lightning hits close by been there! There is a belive that there is 2 types of lightning one sets fire the other is like a bomb and shreds the object.

 

[HENRY E NC]

The house I grew up in in Ohio always had lightning rods and was hit by lightning three time that I know of. One time a ball of energy came down the chimney into the living room and did lots of damage. There are many pros and cons. I now live in a house with metal roofing. Don't know how that factors in. By the way, metal roofing in pretty much a longtime fix and can save you money over the long haul. More people are using it.

 

[MN Scott]

Several years ago I was in our machine shed that is 100 ft from our old barn durning a thunder shower. The barn has the three foot lightning rods on it. Lightning struck one of the rods as I watched. It was swaying back an forth after the strike, talk about hair raising experence. No damage to anything so I guess it did its job.

 

[Sand Flat Bob]

NASA seems to believe in Lightning protection. They have done the most research on lightning protection than anyone in the World over the past 40 years. They have extensive systems installed at the Cape to protect rockets and control systems. The Cape is in one of the highest lightning strike areas in the USA. You need their scientists to answer your question.

Bob

 

[Anonymous-0]

We had a surge protector on our computer and it was ruined also and would no longer work. I was told the surge protector won't protect from lightning as it's not designed for that kind of abuse. Also in our house, most of the outlets are the old two prong and don't have the third ground wire on them anyway. On most of our electronics and surge protector outlet strips, we have to use an adapter for the two prong and so nothing is properly grounded anyway. I'm not an electrition so not sure how that affects a surge protector in doing its job?

 

[VADAVE]

In 80+ years you've those close strikes but haven't been hit and the house is still standing. UMmm must be doing something. I would keep them. Lightening hits that house it burns.

 

[Anonymous-0]

Most fires occur from "Positive Lightning" which is rarer and tends to be on the edges of storms and often travels much further (striking outside of the "rain" zone)

Positive lightning is stronger and lasts longer then 95% of cloud-to-ground lightning which is "Negative Lightning" -- before I knew about the names and differences, I did know there was a different "look" to the type of lightning that was likely to start a fire and you could usually predict which storms would start fires from looking at the bolts. Also knew we the fires usually started by strikes at the end of the storm, sometimes at the beginning -- but seldom in the middle of it.

For a fairly small town that may see 3-4 structure fires in a year, 1/4 of those are lightning strikes which always surprises me just how common it is.

Of those fires, 3/4 of them are basement fires when the lightning hits a tree in the yard or well and follows the plumbing / wiring inside. The other 1/4 are attic fires after the roof gets hit.

 

[KEB]

I've worked on lightning protection systems for aircraft and large communications facilities, so believe I have a reasonable understanding of the phenomena and protection techniques.

Lightning rods do work, provided they're reasonably well installed. Once you get past the marketing hype, the basic rods work just as well or better than any of these fancy things.

Lightning rods at the height of a house do NOT attract lightning. If you get an attachment to the rod, it would have attached to your house had the rod not been there. There is some anecdotal evidence that high structures do attrack lighting, but nothing to support any contention that something the height of a house would.

The sole purpose of a lightning rod is to minimize the chances of a fire or other physical damage due to a lighting attachment to the structure. They neither repel nor attract lighting, except over the small area that they're intended to protect. The fact that they're not required for new construction has everything to do with cost and risk management and nothing to do with whether or not they work.

Lightning effects are divided into two categories, direct effects, which are the result of the passage of the actual lightning current through a structure, and indirect effects, which are the results of the transient voltages generated by the lightning strike. Most of the effects such as burned out electronics are indirect effects resulting from the transient voltage induced on power, phone, or cable conductors. That's why stuff can get damaged from a strike some distance down the line.

In conclusion, yes its worth the effort to put the rods back, since you already have all the materials and there wouldn't be much labor involved.

Keith

 

[KEB]

No, there are not two "types" of lightning. All direct effects of a lightning attachment are thermal. If lightning hits a tree or some object containing water, the heat generated by the lightning current vaporizes the moisture into steam. Its the pressure of this steam that causes an "explosion". Other structures containing materials that can be vaporized experience similar effects.

Lightning will start a fire when the there is enough energy deposited into the material its passing through to raise the material temperature to the ignition point. Depending on how flamable the material is, a fire may or may not sustain itself once the lighting stike is over.

Keith

 

[Anonymous-0]

I would sure reinstall the system. Some prior owner evidently thought it was needed. If you are in an area where the house is the highest object around, I think it would be great insurance. Lightning rods also look appropriate on older buildings.

When I was about 12, I spent a couple of weeks visiting my cousins on their farm on the plains of Eastern Montana. I noticed that all their buildings had lightning rods, but didn't think too much about it. One night we had a tremendous lightning storm that was a real show. The next morning, their herd of cows was out, so we rounded them up and put them back in and began looking for where they had got out. On top of a small hill, we found where apparently lightning had struck the barb wire fence. One steel T post was completely gone, as was about 40 or 50 feet of wire. The barb wire looked like it had been cut off with a cutting torch and there was some slag on the ground. Probably if it hadn't rained during the storm, there would have been a grass fire. My cousins and I spent the rest of the morning fixing the fence. They said that they had seen the same thing happen before, but I was pretty impressed.

Luckily, they didn't lose any stock. About 10 years later, my Dad lost 7 head of cows to lightning. They were bedded down under a pine tree that obviously got hit by lightning in a storm. We didn't find them until the next day when my Dad counted the cattle and went looking for the missing ones. Our cattle operation sure didn't make any money that year! At least we didn't have to pay to have the carcasses hauled away--the rendering company came and picked them up for free.

Lightning is something to be concerned with. Since you already have the system, it shouldn't be too much work to put it back up after reroofing. Good luck!

 

[Anonymous-0]

Thanks for all the responses. I knew I could count on all of you for good information.