Wood Stove & Piping

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mgookin said:
My point is it's the top of the stove pipe that would be more prone to take a hit if the stove were bonded to Earth. The lightning is not going to strike the stove in the living room.
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And I am again going to have to respectfully disagree with you. Don't think that lightning won't go into a house. I know of two instances where it has. One instance, from a fireman I know, lightning came into a house and struck an antenna on a cordless phone and the result was a burned down house.

Another was at the house of a friend of mine. A bolt of lighting went straight through is breezeway, melting a hole in a pane of glass about an inch and a quarter in diameter.
 
One of my favorite pictures. Is the shuttle bonded, or is it not? Notice how the lightning goes right around the metal structures in favor of the path created by the ionized air.

shuttle_lightning.gif
 
interesting...

interesting...

This is actually an intriguing question.

A quick search on the internet via Google shows that diy'ers, homesteaders, and fireplace forums have covered this very question for a few years. There are several stories from homeowners who have taken lightning strikes to metal chimneys and chimneys with metal flue liners and cases where damage ensued.

The NFPA went out of their way to include a special section just for antenna masts, and here is another potentially large metal object sticking up over the roof line. In my case, the chimney/flue is for my propane stove with a bonded gas line and electric blower with an EGC.

Why no section or even a simple paragraph/sentence which allows for this situation?


p.s., I grounded my chimney because I caught it smoking :slaphead:
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K8MHZ said:
And I am again going to have to respectfully disagree with you. Don't think that lightning won't go into a house. I know of two instances where it has. One instance, from a fireman I know, lightning came into a house and struck an antenna on a cordless phone and the result was a burned down house.

Another was at the house of a friend of mine. A bolt of lighting went straight through is breezeway, melting a hole in a pane of glass about an inch and a quarter in diameter.
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I agree lightning will go inside a house.

The point I was trying to make is that the probability of a stove pipe sticking out of a roof has a greater chance of taking a hit if it's bonded to Earth than if it's just sitting on a wood floor and not bonded to Earth. Lightning wants Earth!
 
K8MHZ said:
From Glen K9STH, a former engineer for a large utility company in Texas:

I wrote a fairly lengthy dissertation yesterday about dissipation devices that, somehow, was "dissipated" from this thread!

There are those persons who consider dissipation devices ... The purpose of dissipation devices is to reduce, as much as possible, the chances of taking a strike and not to absolutely prevent a strike.
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That's really good stuff. Good read. Thanks for the post. That's how we do light poles on top of parking garages around here. Two dissipation devices atop each light pole.

As to regular roadway lighting, they don't get squat.
 
First hand experance

First hand experance

Last year my house was hit by a "super bolt" this is one that will start a fire instantly, they say only 1 in 100 will do that. It struck my roof about 20 feet from my stove pipe, which sticks up 4 ft. above roof line. The pipe runs to the wood stove in the basement 25 feet straight down. The stove sits on the concrete which should cause it to be at ground at that level of voltage. But it did not hit the BIG pine trees 30 feet from the house either.
 
mgookin said:
I agree lightning will go inside a house.

The point I was trying to make is that the probability of a stove pipe sticking out of a roof has a greater chance of taking a hit if it's bonded to Earth than if it's just sitting on a wood floor and not bonded to Earth. Lightning wants Earth!
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I know of many wood stoves that are sitting on concrete in basements, garages and other buildings which presents much less impedance to earth than a bonding wire to a stove setting on wood, yet I have never heard of one getting hit.

And what about stoves that ARE bonded to the earth? Like through the EGC of a blower connected to the stove. If connecting an EGC to a metal stove with a metal pipe increased the likelihood of a lightning strike, don't you think the NFPA would be all over that???? Or what about stoves that are on concrete, bolted to the floor with big metal bolts? Those are earthed very well, yet I have yet to hear of them attracting lightning any more than if they were insulated from the ground. In fact, being insulted poses an even greater hazard. That's why we protect our stuff by connecting it to the earth with very short conductors.

One cannot think of lightning as 'regular' electricity. There can be a potential of up to a billion volts pulsating at millions of cycles per second carrying up to a million amps and it has traveled miles. Yes MILES to get to it's destination. There is no way a few feet or a hundred feet of wire will make a bit of a difference.
 
just the cowboy said:
Last year my house was hit by a "super bolt" this is one that will start a fire instantly, they say only 1 in 100 will do that. It struck my roof about 20 feet from my stove pipe, which sticks up 4 ft. above roof line. The pipe runs to the wood stove in the basement 25 feet straight down. The stove sits on the concrete which should cause it to be at ground at that level of voltage. But it did not hit the BIG pine trees 30 feet from the house either.
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Thanks for that post.

That bolt didn't care about that few feet of metal pipe or the 70 or so feet of pine tree at the end of it's multiple mile journey 'home'. It went where the air was the most ionized, as it always does.
 
cuba_pete said:
This is actually an intriguing question.

A quick search on the internet via Google shows that diy'ers, homesteaders, and fireplace forums have covered this very question for a few years. There are several stories from homeowners who have taken lightning strikes to metal chimneys and chimneys with metal flue liners and cases where damage ensued.

The NFPA went out of their way to include a special section just for antenna masts, and here is another potentially large metal object sticking up over the roof line. In my case, the chimney/flue is for my propane stove with a bonded gas line and electric blower with an EGC.

Why no section or even a simple paragraph/sentence which allows for this situation?

...
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The difference is that the antennas are much more prominent to lightning than a stove pipe. They get hit more. There are far fewer antennas than stove pipes, yet I know first hand of several antennas getting hit, but not a single stove pipe. Remember, the NFPA is basically an insurance company and like other insurance companies, they dictate by percentages. Antennas score very high on the lightning hit list, stove pipes probably are close to being at the bottom.
 
cuba_pete said:
This is actually an intriguing question.

A quick search on the internet via Google shows that diy'ers, homesteaders, and fireplace forums have covered this very question for a few years. There are several stories from homeowners who have taken lightning strikes to metal chimneys and chimneys with metal flue liners and cases where damage ensued.

The NFPA went out of their way to include a special section just for antenna masts, and here is another potentially large metal object sticking up over the roof line. In my case, the chimney/flue is for my propane stove with a bonded gas line and electric blower with an EGC.

Why no section or even a simple paragraph/sentence which allows for this situation?


p.s., I grounded my chimney because I caught it smoking :slaphead:
...
Click to expand...


An antenna is electrical equipment,the NEC applies to it.

A chimney is not electrical equipment, the NEC does not apply to it.
 
iwire said:
An antenna is electrical equipment,the NEC applies to it.

A chimney is not electrical equipment, the NEC does not apply to it.
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Remember who writes the NEC - it's the NFPA. They have a standard which applies to chimneys (though it's not a chimney standard). But if local AHJ's don't adopt the publication, then lightning systems are not required. Some AHJ's require it and some don't; many require it on some buildings but not all.

So it would be unfair to say the NFPA addresses antennae and not chinmeys.

As iwire said, the antenna is electrical while the chimney is not.
 
mgookin said:
Remember who writes the NEC - it's the NFPA. They have a standard which applies to chimneys (though it's not a chimney standard). But if local AHJ's don't adopt the publication, then lightning systems are not required. Some AHJ's require it and some don't; many require it on some buildings but not all.

So it would be unfair to say the NFPA addresses antennae and not chinmeys.

As iwire said, the antenna is electrical while the chimney is not.
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It's NFPA 780 for lightning and it does indeed address chimneys. In a nutshell, a chimney not within the zone of protection of a strike termination device (air terminal or lightning rod) needs its own, or needs to be bonded to the system. If within a zone of protection, nothing needs to be done. Note the bonding requirements. If grounding attracted lightning, it sure wouldn't be required by the NFPA. The intentional path to ground is there to DIRECT lighting energy, is does not ATTRACT it one bit.

4.8.8 Chimneys and Vents. Strike termination devices shall be required on all chimneys and vents that are not located within a zone of protection, including metal chimneys having a metal thickness of less than 4.8 mm (3/16 in.).

4.8.8.1 Chimneys or vents with a metal thickness of 4.8 mm (3/16 in.) or more shall require only a connection to the lightning protection system.

4.8.8.2 The connection for 4.8.8.1 shall be made using a main-size lightning conductor and a bonding device that has a surface contact area of not less than 1940 mm 2 (3 in.2) and shall provide two or more paths to ground, as is required for strike termination devices.4.8.8.3 Required strike termination devices shall be installed on chimneys and vents, as shown in Figure 4.8.8.3, so that the distance from a strike termination device to an outside corner or the distance perpendicular to an outside edge shall be not greater than 0.6 m (2 ft).

Here is the rest of NFPA 780: http://www.uscg.mil/petaluma/TPF/ET_SMS/Manuals/NFPA_780.pdf
 
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