OT Lightning Protection- 2,000 sf residential new construction in rural NY - Page 2
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  1. #21
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    Quote Originally Posted by Dumpster_diving View Post
    Much appreciate all the input. For the moment, no details on what the GC is thinking in the $8k (but I will get behind that number before proceeding). No CNC, just manual equipment in a home shop. But VFDs and PCs and the like (even refrigerators have computers in them nowadays). In my circumstances, I could tolerate a surge taking out the electronics but want to avoid burning the new house down. And it is an exposed hill-top location.

    So from the collective wisdom I'm gathering $2-4k is more reasonable with the caveat that a paired-down system won't protect electronics from surges and the further disclaimer that my millage may vary on whether lightning protection works at all.

    Very helpful.
    Different regions have strikes with differing severity. I believe the right practice is (or was, when I did all the reading many moons ago) is to pick a percentage of the strongest recorded strikes in the area, and protect to that value. I seem to recall that my house is protected against an 85th percentile strike. I can't remember where I found the numbers for NY, I'm afraid, but our strikes tend to be less strong than those at or near the equator because the altitude of thunderstorms is greater near the equator, and it takes more voltage to get from ground to cloud and back.

    The 100th percentile for a particular area has reasonably predictable characteristics, though very high voltages associated with electrostatic discharge seem capricious. Lightning acts very much like 50Mhz or so RF. This makes having very low inductance of the ground conductors very important, in addition to low resistance. Typical conductors are woven aluminum and copper strap, which both have a lot of surface area (the key to low inductance).

    NASA, with the Kennedy Space Center located in Florida, did much of the important work here to protect spacecraft from damage on launch pads. Although I don't have numbers for either NY or FL, the Polyphaser book tells me the median current for the first pulse of a strike (there is an average of three pulses per strike) for the entire US is 18,000 amperes. The ground conductors don't have to carry that current for very long, but they need to be big enough in addition to having a low enough inductance.

    The repeater shack and my house both have 1 1/2" copper strap for all the ground connections except the one from the antenna entry cable to the ground ring, which is larger (in my case, about 12" wide). Copper flashing cut lengthwise works great here. Fold the needed length over itself, and cut with a big shear. My house has never been hit, but as I wrote before the strike counter at the repeater site read nine when last I saw it, and there was never any damage to the shack or the equipment inside (five repeaters, repeater controllers, telephone, and associated other stuff).

    This can be done. It is critical to have a ground ring with everything in and out bonded to it to prevent significant differential voltages inside the structure you want to protect. Here's an example of what that matters...

    Consider a lightning strike in a cow pasture. Two cows are the same distance from Ground Zero. One is facing the strike, the other is facing 90* away from the strike. The one facing the strike dies. The other lives. Why? In the zone that distance from the strike, the voltage differential of the ground for the distance from the front hooves to the rear is high enough to kill the first cow, but the differential from left to right is not high enough to kill the second. Had the first one been standing on four bonded copper plates, she'd have been fine.

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  3. #22
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    This is a historical map of the lightning hits in 2018.
    Does not look like upstate NY is at much risk.
    Where I live (Central Florida)….zap city!

    2018_lightninghits

  4. #23
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    This is not the article I read some years ago, but it is from the same research facility https://www.lightningsafetyalliance....ific_basis.pdf

    The article I read years ago gave me the impression that lightning rods were like lucky rabbits feet, you carry one around, nothing bad happens, therefore you think it works

    Lightning protection on the electrical service to your home I understand, lightning rods on the roof I'm skeptical of their effectiveness. My home in Nv is the tallest building in town, has metal trim around perimeter of roof, and copper downspouts to just a few inches above ground, it has stood for 100+ years sans lightning rods, to the best of my knowledge (only 17 years) has never been hit by lightning.

  5. #24
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    Quote Originally Posted by fish123 View Post
    This is a historical map of the lightning hits in 2018.
    Does not look like upstate NY is at much risk.
    Where I live (Central Florida)….zap city!

    2018_lightninghits
    I happen to live right in the most active zone for lightning in NY, per that map.

    FL is definitely the Lightning Capital of the USA, and possibly the world...

  6. #25
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    Yes, Central Florida is pretty darn sparky, but central Africa…WOW.
    Africa would not even need an electrical utility there, if they could just put all this energy in a giant capacitor…
    world_lightninghits

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    An average duration of time for a stroke of lightning is about 30 microseconds. The average peak power of a stroke of lightning is about 10^12 watts. That's .33 Kw-Hr.

    Tom

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    Quote Originally Posted by fish123 View Post
    Africa would not even need an electrical utility there, if they could just put all this energy in a giant capacitor…
    "Mother Earth" - and its atmosphere - IS a "giant capacitor".

    Someone with nothing more useful to do has even worked out the value in Farads.

  9. #28
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    Quote Originally Posted by thermite View Post
    "Mother Earth" - and its atmosphere - IS a "giant capacitor".

    Someone with nothing more useful to do has even worked out the value in Farads.
    And the number is?....

    Tom

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    Quote Originally Posted by TDegenhart View Post
    And the number is?....

    Tom
    I already know it, thanks. Didn't find a use for it, so filed it somewhere loose and grubby.

    Would you settle for the Carter carburettor SKU's, first 1 HP per CI "production" engine in the USA?

    WCFB 2635S,
    WCFB 2636S.

    No. It wasn't from GMC.


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    Quote Originally Posted by Dumpster_diving View Post
    . For the moment, no details on what the GC is thinking in the $8k (but I will get behind that number before proceeding).
    it's 4k so double that and see if it flies.

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  13. #31
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    Quote Originally Posted by n2zon View Post
    ... having very low inductance of the ground conductors very important, in addition to low resistance. Typical conductors are woven aluminum and copper strap, which both have a lot of surface area (the key to low inductance).
    Put two right angle bends along the length of a round conductor, and it becomes basically an open circuit as far as a lightning strike is concerned.

    My approach is to convince somebody to build a trailer park nearby. Also protects against tornadoes.

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    Quote Originally Posted by Dumpster_diving View Post
    Looking at estimates to construct a roughly 2,000 sf residential home in rural NY. There's a line item in one proposal that includes $8k worth of 'Lightning Protection'.

    My question is twofold:

    1- My layman's understanding is lightning protection consists mainly of several roof-top lightning rods bonded to insulated heavy gauge conductors leading directly to grounding stakes. I'm having a hard to imagining how those components plus installation could cost anything approaching $8k. Google turns up numbers in the $2-4k range. Does anyone have any direct recent experience installing a decent modern system? Is that quote way out of whack?

    2- I've always lived in urban and suburban detached single-family homes built 100 years ago (but surrounded by other homes, large trees, and with excellent access to fire hydrants and fire departments). Never seen nor heard of a lightning protection system installed in that context. The home we're building will admittedly be on an exposed hillside in a rural area, far from hydrants and emergency responders. How common is Lightning Protection for new construction in the middle of nowhere?
    That's more than two questions. In Massachusetts the taxes on your driveway pavers will be $8000. If I were quoting your job 20 years ago, $40,000. Who wants the lightning protection, you or the insurance company? If it's the insurance company, find out who can do the work the cheapest and have them sign the agreement of acceptance with the insurance company, then who gives a turd. If you want it, pay the money and you will get what you get in Massachusetts, good luck finding an honest reputable person in the state, if you do, they probably will be standing next to a unicorn.

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    Quote Originally Posted by Pathogen View Post
    you will get what you get in Massachusetts, good luck finding an honest reputable person in the state, if you do, they probably will be standing next to a unicorn.
    Meahh. Taxatwoshits? So long as they ain't standing BACK OF that unicorn, "up close and personal" like? Plenty of honest folks. Look for the vents off well dug in bunkers.

    ISTR we put our planned Boston office in Hotlanta instead and ranged off New York.. so we didn't need Soviet work visas nor passports... but that was a while ago. Seems they are trading places on that tax serfdom thing? Or is it just "parity"?


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    Quote Originally Posted by jim rozen View Post
    Put two right angle bends along the length of a round conductor, and it becomes basically an open circuit as far as a lightning strike is concerned.

    My approach is to convince somebody to build a trailer park nearby. Also protects against tornadoes.
    Make sure you perch all of the trailers up on cement blocks....an offering to the tornado.

  18. #35
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    Most homes have power brought in on poles. Those power poles will have lightning protection installed by the power company to protect their lines and your homes. In most neighborhoods, those poles are close enough and numerous enough to protect the homes from lightning strikes.

    If an area has underground power distribution then the houses may need lightning protection.

    As for $8K, what can I say? Materials: < $1K. Labor: < $2K. Profit: > $5K.

    DIY and save? Or at least bid it out.

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    Jim, That lightning bolt just crossed a mile or more of AIR, which is usually a great insulator. I can guarantee that it WILL take the path of lease resistance in that last few feet off the ground. A conductor, bent or straight, is a great, well er, CONDUCTOR. At least some of the energy in that bolt will follow any bends in an otherwise great conductor. A bent conductor is ZERO protection from a lightning bolt unless it is between a lightning rod and the ground rod.



    Quote Originally Posted by jim rozen View Post
    Put two right angle bends along the length of a round conductor, and it becomes basically an open circuit as far as a lightning strike is concerned.

    My approach is to convince somebody to build a trailer park nearby. Also protects against tornadoes.

  20. #37
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    Nope...

    Lightning is dc to daylight energy and sharp bends or even a conduit clamp adds inductance which SLOWS the charge which causes it to change directions...through equipment instead of earth

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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  22. #38
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    [QUOTE=EPAIII;3428746]Jim, That lightning bolt just crossed a mile or more of AIR, which is usually a great insulator.

    Not once it's ionized. Then it's a dead short.

    Lighting protection conductors are simple, right? You connect two things you want to be at the same potential,
    the spike at the rooftop, and the ground rod. You connect them with wires, the wires are perfect conductors,
    and the voltages are all the same thoughout the system.

    Or not.

  23. #39
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    A lightning system is not intended to conduct a lightning bolt to ground. The power of the bolt would explode the conductors. Its intended to discharge the space around the rod.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    A lightning system is not intended to conduct a lightning bolt to ground. The power of the bolt would explode the conductors. Its intended to discharge the space around the rod.

    Tom
    One of the clever bastards must have sneaked into my bank account, then.


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