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Lighting Risk of Chimney Caps + Liners

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by vgrund, Jun 29, 2007.

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  1. vgrund

    vgrund Feeling the Heat

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    Walking around my yard last weekend, it occurred to me that the tallest part on my house is the stainless chimney cap that is connected to a metal liner for my LP gas insert. The insert has a blower that is connected to an AC outlet (plug includes ground wire). I'm wondering, what is is the lightning risk with this setup? Someone must have accommodated this in the design of caps and liners?

    Victor

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  2. webbie

    webbie Seasoned Moderator Staff Member

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    It does seem so, but in all my time I have heard of it perhaps once...or maybe not at all. Maybe telephone poles, transformers and towers are just the ultimate targets these days.
  3. mayhem

    mayhem Minister of Fire

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    I thought of this the other day as a lighting storm was rolling toward my house. I took a look up there on the roof and sure enough, there it is...a big steel tube coming rihgt out of the roof and running directly into my living room...extending about 3' above the peak of my roof and within 10-15' of the tops of any surrounding tree. I'll be calling an electrician for an estimate on a lightning rod.
  4. begreen

    begreen Mooderator Staff Member

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    You might want to hire someone who knows roofing and grounding. Here's a link for a family company that specializes in lightning rods in Mass.:

    http://www.smokestackusa.com/
    Telephone: (508) 867-9233
    Fax: (508) 867-3586
    E-mail: williamsimpson@smokestackusa.com

    Mailing Address
    37 Upper River Street
    Brookfield, MA 01506
  5. senorFrog

    senorFrog New Member

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    I had a lightning strike come right into our living room. No cap, clay liner w/masonry blocks, stove pipe to stove. I think the lightning must have followed the water from the rain spilling into the chimney and making contact with the metal stove pipe.

    I have since added a nice cap and replaced that stove. Luckily, I haven't had one since, but whenever a thunder storm comes through We move away from the stove.
  6. Todd

    Todd Minister of Fire

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    I remember not to long ago hearth member rmcfall had a thread on his chimney struck by lightning. I think he had some pictures of some pretty good damage.
  7. rmcfall

    rmcfall Feeling the Heat

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    That's right, Todd. I've attached a photo of the damaged. We had not moved into the house yet when this happened, so there was no stove or liner installed at the time. There were, however, three chimney caps at the top. Two remained on the chimney after the lightning strike and the other one was thrown off by the strike. Brick flew everywhere, even onto the roof of our neighbor's house about 100 ft away). Upon further investigation, the lightening strike appeared to hit a tree that was growing up through our deck first before jumping over to the chimney. There was a fresh scar we found on the tree that made us think that... I guess we were lucky in the sense that the lightening didn't damage the tree to the extent that it fell on our house.

    Attached Files:

  8. rmcfall

    rmcfall Feeling the Heat

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    another pic...

    Attached Files:

  9. vgrund

    vgrund Feeling the Heat

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    Rmcfall, that damage is astounding! Have you taken any subsequent steps to mitigate lightning risk?
  10. rmcfall

    rmcfall Feeling the Heat

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    Aside from removing the tree that the lightening appeared to jump from, I haven't taken any steps to mitigate any lightning risk. It has crossed my mind from time to time, but I am not sure what approach I would need to take. I'd be happy to hear any suggestions you might have.


  11. vgrund

    vgrund Feeling the Heat

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    Don't ask me, my expertise is in lawn care, cooking and enterprise IT architecture. :)
  12. jjbaer

    jjbaer New Member

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    Food for thought....lightening generally strikes the highest object and a pointed one helps attract it..........that's why protection systems are generally located at the highest point and pointed AND run to ground with a LARGE copper wire.......

    also.....the following may save your life...if you're ever walking outside and you feel a "tingling" on your body, hit the ground immediately...this is the precursor to the bolt as it tries to set-up a ground-to-cloud leader path (pathway for the lightning to follow) and if you sense it early enough and make yourself the lowest point in the surrounding area (by dropping to the ground) you stand a better chance of not getting hit.....i.e., before lightening strikes the pathway is set-up first and recognizing this and acting fast can save your life.....
  13. Rob From Wisconsin

    Rob From Wisconsin Minister of Fire

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    At our previous house, we were getting struck way too ofter for the first couple of
    years after we first moved in. After we installed our stainless chimney, it stopped
    all together. Figure that out......


    Rob
  14. Gooserider

    Gooserider Mod Emeritus

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    I didn't bookmark the site unfortuneately, but I think it was a link off the vendor site mentioned a few posts previous. However it was a site for one of the standards bodies that works on certifying lightning protection installers, and the stuff in their FAQ seemed to contradict you in a few ways Cast...

    1. Lightning protection stuff does NOT "attract" lightning, at least not more than within a hundred feet or so... Tall objects do help, but also projections and corners are important factors.

    2. Pointed objects are not actually the best, attractors, but they are easy to make. The best is actually a round ball by a small percentage, but the difference is not real significant, location matters more.

    3. While lying down in order to avoid being the highest point in an open area might be a good idea, they claimed that the most dangerous part of being near a strike (not being struck, but near one) is the voltage differential in the ground as the strike charge dissapates - This differential is going to be less if one is standing, and any current flow will be through non vital organs. (Though it may knock you off your feet) They said the risk of serious shock damage would be greater if lying down.

    Not saying who is right, but something to consider...

    Gooserider
  15. jjbaer

    jjbaer New Member

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    Hi Goose....might want to re-read my posts...I never said it hits the highest point..........but on EVERY building you see with lightening protection, the spikes ARE at the highest point............but if you find the post, please send it my way as I'd like to read it. Thanks.


    Goose...this may be true but the location on every lightening system out there is at the highest point.......also, 99.9999% of them are pointed spikes........ as you state, it may be economics.....



    Goose

    Actually, I think we're both close..........if you feel the tingling, get down ASAP......but into a ball and not lying flat as I said.......but you do want to get down so as to not be the highest point in the immediate vicinity....go here to see it.

    http://www.drdaveanddee.com/lightening.html


    thanks
  16. kevinmoelk

    kevinmoelk New Member

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    Hummm. This is an interesting subject. I've never though about adding lightning protection to or near my stovepipe, but it seems to be good common sense. I smell an invention coming again...

    How's that fire extinguisher adapter port to stove coming? Where's Robbie?

    -Kevin
  17. Gooserider

    Gooserider Mod Emeritus

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    Found the website I was mentioning earlier, it is the Lightning Protection Institute. Their home page intro states:

    They have a lengthy FAQ section that seems to suggest things that are somewhat different than those in the site you pointed at Cast. Among other things they seemed to think that picnic shelters were reasonably safe. They also agreed in many areas, however it seemed they were much calmer and less "paranoid" than the Dr. Dave site. I found the Dr. Dave site to be really over cautious to the extent where one should barely dare to venture out the door, while the LPI site didn't have as much direct advice, but seemed much more fact oriented and practical in their descriptions of what lightning does, and the implied means of making the best odds out of whatever shelter you have available.

    However Wrench, I think you would find that there isn't much of a need for an invention - lightning seems to be a pretty well understood problem with a known technology for dealing with it. Judging from what LPI seemed to be saying, there are probably a lot of homes out there that are unprotected than should be, but it's basically a gambling call - odds of getting hit and suffering expen$ive damage vs. the known cost of installing a protection system...

    Gooserider
  18. jjbaer

    jjbaer New Member

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    if caught in the open, any shelter is better than none however, it's still possible to get killed when in an open shelter....
  19. Gooserider

    Gooserider Mod Emeritus

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    True, and it is possible that much depends on the design of the shelter, and how much (if any) protection the shelter has in it. However the LPI seems to claim that if you have a shelter with an LPI approved protection system then you are as safe as anyone knows how to accomplish.

    The basic problem is the ground voltage differential I mentioned earlier, and "flashover" where lightning that is traveling to ground through one conductor decides that an alternative path offers a lower resistance and jumps from one path to another. The human body is a fairly good conductor once one gets past the skin, thus it makes an attractive target for flashover compared to most non-metallic building materials (wood, trees, etc.) If the sheltering object is metal or contains a metal subsystem, and connects to ground, the odds of a flashover are pretty low. Note that DRY skin is fairly high resistance, wet skin is not - This implies that one is better off in a shelter that keeps one dry even if open, all else being equal.

    There is a sort of "umbrella effect" where a tall object will act to attract strikes occurring in it's general area - for a protection system they say its a 150' diameter spherical shell with the top center surface touching the protection device - I'm not sure what the range would be on a non-protected object, but probably it would be similar. To me this would imply that if caught in the open your best bet would be to get close to tall trees or other such objects, but stay far enough away to minimize the odds of a flashover. Not sure just how far that would be, but I'd say just outside the drip line of the tree, and away from branches.

    Gooserider


    Gooserider
  20. bcnu

    bcnu New Member

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    I added 4 feet of stainless to the chimney so it's a ways above the roof. We've had record heat in Oregon and I thought the prospect of cooler air and thunderstorms would be a relief. Now, I may lie awake all night thinking about lightning. :coolsmile: I was awake last night thinking about air conditioning.
  21. NFreiermuth

    NFreiermuth New Member

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    Goose,

    You're right on track!!! ;-P

    The 'Umbrella Effect" you mentioned is actually a Farady Cage and every thing inside is safe. At least voltage wise. The voltage potentials across the cage merely cancel themselves out. This is why a four legged picnic pavilion is sometimes a "safe Place" in a lightning storm. The lightning can travel down all four leags. Thus, making a cage. Also, another reason why metal buildings, automobiles, heavy equipment, and steel skeletoned structures are safe. It's the wood dwellers with all the unprotected conductors that are vulnerable.

    When a lightning professional protects our homes, they set out to make a simple Farady Cage.

    The air terminals are installed on the roof. I think no more than 25 feet apart??? The copper conductors MUST leave the roof area on opposite corners. This is what makes that simple cage.

    Also, when the cage is formed, the lightning 'Leaders" are directed AWAY from the dewelling because the earth potential has been rasied higher into the sky. Remember, lightning travels from the ground to the sky first. The elevated ground potential pushes the "leaders" away to a lower potential source i.e. Trees, Golfers, etc :gulp:

    Trees are merely "leader" extensions because they are poor conductors. They actually help the lightning to the ground. They do not raise the grounf potential to the sky well enough. Unless, it rains first and they are wet.

    As you probably know, lightning is at it's ulimate worst destructiveness when it is BEFORE the rain.

    I'll check out the lightning sites when I get a chance.
  22. begreen

    begreen Mooderator Staff Member

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  23. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    "If someone had been sitting on the toilet - they would have been killed," said Noel. "

    http://www.kilkennyadvertiser.ie/index.php?aid=6588

    "A bolt of lightening hit the chimney at The Summit Apartments and many bricks fell... they struck Smith and left him in the hospital for five days."

    http://www.newschannel9.com/articles/lightning_13429___article.html/storm_survival.html

    "The bolt hit a chimney stack on top of Waitrose and sent bits of brick and debris flying down into the street below - luckily nobody was hurt and no vehicles were damaged, as I think everyone had dived for cover from the rain."

    http://tinyurl.com/27rlfz

    "Harms said she walked outside to find her chimney destroyed, a hole in her roof, and bricks scattered everywhere."

    http://www.ksat.com/weather/13568570/detail.html

    "A neighbour across the street saw the strike blow a hole in MacLaren's chimney, causing the bricks to fall all over the backyard and driveway."

    http://www.hfxnews.ca/index.cfm?sid=40017&sc=89


    These are just a few of the dozens of stories on chimney lightning strikes in just the last two weeks.
  24. bcnu

    bcnu New Member

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    Quite a show in the Portland area last night. Some thunder but mostly just a big lightning storm. Think I heard there were 1400 strikes but only a few small fires. Nothing right in our area so my chimney, and peace of mind, are still intact.
  25. wg_bent

    wg_bent Minister of Fire

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    Back to the original post... If you don't ground your Stove/chimney you have a LOT lower chance of it getting hit by lightening.
    So... Un-plug it.

    If it's sitting on Concrete (stone fireplace)... It's grounded, so the plug is less of an issue. Maybe put ceramic insulators of some sort under the stove feet?
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