Author Topic: Lightning rods  (Read 201 times)

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Offline dumbass

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Lightning rods
« on: June 18, 2018, 08:48:03 AM »
So last night after paddling some we we sat on the front porch in a spectacular storm.  I got to thinking about our tin roof.  Were on a ridge with larger trees around but those hits were close and loud.

The porch probably isn't safe but what about inside?  I built it with a steep peak.
huh?

Offline wsdstan

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Re: Lightning rods
« Reply #1 on: June 18, 2018, 11:41:57 AM »
A house on a ridge is far more likely to get hit than a house down in a hollow.  At least that is what I have read.  There are a lot of factors that come into play.  One thing is that an adjacent building like a barn that has lightening rods will attract lightening away from a nearby structure with no lightening rods.  Not 100% but it reduces the chances substantially.  When we removed our asphalt shingle roof we also removed the lightening rod system on the house.  So far, so good but I do worry about it.  Our electrical panel is grounded and the house wiring is three wire.  In the old days that wasn't the case.  Hopefully that will minimize the damage should it get hit.

I had ancestors killed by lightening while sitting in an upstairs bedroom of their farmhouse in North Carolina.  It was in 1803 so there were a lot of differences from today's houses such as a wood shingle roof and no electrical system.  Don't know if they had lightening rods either. 

I saved our rods and the copper cable and a 8 foot section of copper rod to pound in the ground and may reinstall it. 

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Offline Old Philosopher

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Re: Lightning rods
« Reply #2 on: June 18, 2018, 12:08:50 PM »
We have predominantly metal roofs around here, and a lot of lightning on occasion.  I have yet to hear (in 20 years) of a house with a metal roof being hit.  The believe is that a metal roof is no more conductive than a shingle roof, the reason being that in most installations the metal on the roof is insulated (by the wooden house) from the ground. Not being grounded, it's not an attractant.
That said, it's true the higher structures are more vulnerable.  Evidence points to attractants being "sharp pointed" (e.g., lightning rods, tree tops, etc.). If a metal roof was grounded to the earth, it would be a big "Welcome!" sign, but it's not (hopefully).
It's always been my understanding the lightning rods were attached to the high points on barns, not to keep lightning away from other structures, but to provide a path for a possible strike without getting your barn blown up!
Just my 2-cents.
I only do what the voices in my wife's head tell her to tell me to do.

Offline wsdstan

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Re: Lightning rods
« Reply #3 on: June 18, 2018, 01:50:03 PM »
You're sort of right that the lightening rods were not put on barns to keep strikes away from adjacent buildings but that turned out to be the result.  If the adjacent building is close enough to the other structure there is a much smaller chance of it being struck than the barn.  There is some formula to calculate the distance that involves the height of the lightening rods and the distance away the adjacent structure can be.

Your comment about ungrounded metal roofs is worth pondering.  Most of the metal roofs are not grounded unless having a downspout off of the gutter counts (which it doesn't as it isn't buried in the ground in most instances).  Does adding a lightening rod system to a house with a metal roof make the whole roof a lightening rod? It might.

In Max's case he might be at higher risk of a strike just because he is on a ridge.   
A man who carries a cat by the tail learns  something he can learn in no other way. 
(Mark Twain)