Replies

1. 
   maddog3 | Jul 15, 2007 01:32am | #1

   .the new thinking is that it is better to keep the lightning AWAY from the building .......in most cases above a building rather than on it...

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1. 
   DougU | Jul 15, 2007 02:40am | #3

   Maddog

   I dont question your answer but how far can the lightening rod pull the lightening? does that make sence? What I'm saying is that is the lighening rod really capable of pulling the lightening down to the house if it were the only going to fall short of hitting anything?

   I'm looking at an old house that has lightening rods on it and wonder if they should be taken off.

   Doug

1. 
   DanH | Jul 15, 2007 04:22am | #11

   There's always been a debate as to whether lightning rods "pull" lightning to any great extent, or whether they discharge the air to prevent strikes. It is known that at the very least a lightning rod (of sufficient size to absorb a jolt) produces a "cone of protection" with about a 45 degree downward angle. But this requires either very tall (5-feet plus) lightning rods or lots of them to protect the average house.
   So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin

2. 
   maddog3 | Jul 15, 2007 05:14am | #14

   I apologize Doug, I shot right past your post...they don't attract anything..they simply make the house appear as nothing more than another spot of ground.....the theory was that they would cause any strike to disperse like rain on an umbrella, but spacing and height were very important and the method of splicing over time would of course fail .... I would suggest that it's time to take the thing down.

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1. 
   caseyr | Jul 15, 2007 07:16am | #15

   There is a fairly extensive discussion of lightning rods and associated circuitry on Wiki. Seems to be fairly well done. Lots of other articles on the web but it has been several years since I looked at any of them.

2. 
   DougU | Jul 15, 2007 05:13pm | #16

   I would suggest that it's time to take the thing down

   Well if I bought the house it'd need a new roof so I wouldnt bother putting them back on then. One of the rods is next to a chimney and the chimney is actually higher then the rod!

   I assume the copper from the lines would be worth a buck or two!

   Doug

1. 
   maddog3 | Jul 15, 2007 10:08pm | #20

   most of the hardware could be scrapped out if it's that old.... there maybe some online sources for DIY LP, but I wouldn't suggest any such thing...Harger Lightning Protection specializes in the field..perhaps you could look them up: http://www.harger.com/
   there may be some FAQs or other info......but they are mainly commercial and industrial.I have done the rough-in work for them on several sites in the past..including two DOE campuses.

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2. 
   DougU | Jul 15, 2007 10:59pm | #21

   Its not likely that I'd put any effort into keeping them, hell thats what I get insurance for!

   I know these date back to at the very least 1930-35.

   Doug

3. 
   FrankDuVal | Jul 15, 2007 06:20pm | #17

   "I'm looking at an old house that has lightening rods on it and wonder if they should be taken off."Are there other taller objects nearby that offer the cone of protection for the house? Farm houses had the most lightning rods installed as the house was the tallest structure around, so lightning would strike it whether or not rods were installed. Like the other poster noted, his house on a hill was protected by the nearby power pole.If the air terminals (lightning rods) look good on the house then I would check out the ground bonding cables and ground rods and keep the system operational. Remember, lightning travels in straight lines, even along the ground cable. Do not run the cable with right angle turns. If you make a square around an object in the way, lightning will just blast through the object to get to the cable on the other side.Frank DuVal

1. 
   DougU | Jul 15, 2007 08:16pm | #18

   Frank

   Are there other taller objects nearby that offer the cone of protection for the house?

   Yes, several trees and the chimney that I mentioned in another post.

   This had to have been put it way back judging by how everything looks.

   Doug

4. 
   edlee | Jul 16, 2007 03:01am | #24

   Doug,

   Around here there are a lot of old barns and house with lightning rods/systems. The farmers still like them generally.

   There's a good chance that someone put them on that house for a good reason and if they hadn't the house might not have lasted.

   I wouldn't be in any rush to remove the system without someone local and knowledgable telling me it would be ok.

    

   Just my opinion..........Ed

2. 
   Luka | Jul 15, 2007 02:08am | #2

   It caught fire ?

   Maybe they lightened the home too fast, and the fire resulted from the friction ?

   ;o)

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   Yeh... That'll work.

1. 
   maddog3 | Jul 15, 2007 02:49am | #5

   what a comedian, hey howse the vacuum thingy coming along ?
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1. 
   Luka | Jul 15, 2007 02:56am | #6

   Thank you. I'm here every thursday.Vacum thingy is fixed. Moved on to the next problem down the line.

   Yeh... That'll work.

2. 
   homedesign | Jul 15, 2007 03:07am | #7

   sorry, I even used spell check

   wonder why lightning rods were once thought to be a good idea?

1. 
   Luka | Jul 15, 2007 03:23am | #8

   Don't be sorry. There's some guy further down the page that is apparently feeding his well way too much bleach. He says the lightening is blowing out his pressure relief valve...;o)I think the intention with the rods was to attract the lightning to the rod, and direct the electricity down the cable to the ground. Keeping the lightning from hitting the house directly.

   Yeh... That'll work.

2. 
   maddog3 | Jul 15, 2007 04:18am | #10

   probably because older homes were made of wood and rather than have it burn down it was thought that dispersing the charge was sufficient. but lightning pretty much does what it wants and sometimes it would scorch the whole thing and with asphalt roofing and dry lumber...well, most homes and barns were nothing more than kindling anyway and electricity was still a new thingthose folks didn't have all the electronic gizmos that a modern society must have at home..and newer homes are an amalgam of building materials and that makes it difficult to "bond " the whole house...... so, any LP design would have to include surge supression, and I don't mean the plug-in, buy it at Lowes kind.....the whole system is expensive to install, and does require a level of maintenance..this is not the sort of thing you can install and forget about
   and since most homeowners don't even test the GFIs in their homes, it ain't gonna happen !that's why we have Fire Departments and 911.if you look at high voltage transmission towers, at the top are two smaller wires , those are the LP for the towers which put the whole structure at ground potential and are the basis for the current thinking for keeping the wiring and rods above a structure rather than on it....

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1. 
   Luka | Jul 15, 2007 04:30am | #12

   I've seen where towers were put up at each end of a farmhouse, to get the lightning rods well above the roof. And then a steel cable run across between the two. Towers and cable all a good 15 feet from the house.

   Yeh... That'll work.

1. 
   maddog3 | Jul 15, 2007 04:46am | #13

   yup.....goofy lookin.

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3. 
   maddog3 | Jul 15, 2007 02:48am | #4

   there is also some evidence that LP on a home has caused fires..
   but the drains installed above a structure seem to work the best.

   which is why I put one over our vegetable garden...:)
   so you could build a "faraday cage" above your house but it would sure look goofy and probably make it hard to sell the place

   BTW..it doesn't work at all if the strike hits near a house,

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4. 
   DanH | Jul 15, 2007 04:14am | #9

   Mostly it's an expense that isn't required by code. Not worth it for every home, from a statistical standpoint, and it's hard to predict which homes will be hit and which ones won't. My parents owned a two-story house on top of a hill that was never hit, though lightning hit the power pole 30 feet away a dozen times. (Pole was right outside my bedroom window, so I knew when it was hit.) OTOH, a home about 5 blocks away from here was hit -- a small one-story home in a subdivision, nowhere near the highest in the area.

   Finally, lightning rods don't offer 100% protection: Had a situation a couple of miles from near here about two years ago where lightning struck a tree, traveled along an underground propane line and into a house, starting a fire. Burned down a brand new $250K home.

   So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
5. 
   TJK | Jul 15, 2007 08:22pm | #19

   Lightning rods are still used on homes and outbuildings in flat areas like Kansas and Nebraska. If other tall objects such as trees or power poles are nearby, the house is less likely to get hit.

6. 
   masterartisan | Jul 15, 2007 11:09pm | #22

   In central New Mexico, near Qhemado, there is a unique area of interest. It's a tourist attraction where the people on a ranch have installed a series of lightning rods in a long row at exactly the same height. When there is a storm the rods attract and direct the lightning to the rods just for show for the tourists. My point is that there is a purpose for lightning rods and we use them for what they are designed for, to attract and redirect lightning. When properly installed they are very useful and will prevent damage to structures in the area.

1. 
   john7g | Jul 16, 2007 01:12am | #23

   from http://science.howstuffworks.com/lightning7.htm there's more at the link

   Lightning Rods

   Lightning Myth #3Ben Franklin was not struck by lightning. Contrary to popular school teachings, Mr. Franklin was very lucky to survive his experiment. The spark he saw was a product of the kite/key system being in a strong electric field. Had the kite/key actually been struck, Mr. Franklin would surely have been killed. As we all know now, his experiment was extremely dangerous and should not be repeated. Lightning rods were originally developed by Benjamin Franklin. A lightning rod is very simple -- it's a pointed metal rod attached to the roof of a building. The rod might be an inch (2 cm) in diameter. It connects to a huge piece of copper or aluminum wire that's also an inch or so in diameter. The wire is connected to a conductive grid buried in the ground nearby.

   The purpose of lightning rods is often misunderstood. Many people believe that lightning rods "attract" lightning. It is better stated to say that lightning rods provide a low-resistance path to ground that can be used to conduct the enormous electrical currents when lightning strikes occur. If lightning strikes, the system attempts to carry the harmful electrical current away from the structure and safely to ground. The system has the ability to handle the enormous electrical current associated with the strike. If the strike contacts a material that is not a good conductor, the material will suffer massive heat damage. The lightning-rod system is an excellent conductor and thus allows the current to flow to ground without causing any heat damage.

   Lightning can "jump around" when it strikes. This "jumping" is associated with the electrical potential of the strike target with respect to the earth's potential. The lightning can strike and then "seek" a path of least resistance by jumping around to nearby objects that provide a better path to ground. If the strike occurs near the lightning-rod system, the system will have a very low-resistance path and can then receive a "jump," diverting the strike current to ground before it can do any more damage.

   As you can see, the purpose of the lightning rod is not to attract lightning -- it merely provides a safe option for the lightning strike to choose. This may sound a little picky, but it's not if you consider that the lightning rods only become relevant when a strike occurs or immediately after a strike occurs. Regardless of whether or not a lightning-rod system is present, the strike will still occur.

   If the structure that you are attempting to protect is out in an open, flat area, you often create a lightning protection system that uses a very tall lightning rod. This rod should be taller than the structure. If the area finds itself in a strong electric field, the tall rod can begin sending up positive streamers in an attempt to dissipate the electric field. While it is not a given that the rod will always conduct the lightning discharged in the immediate area, it does have a better possibility than the structure. Again, the goal is to provide a low-resistance path to ground in an area that has the possibility to receive a strike. This possibility arises from the strength of the electric field generated by the storm clouds.