Wood Stove & Piping

[K8MHZ]

I created an NFPA account and got the 'free access' to the 2014 NFPA 780 in a format that is a total PITA to use. There is a link to click on to buy a .pdf file of said code for $50.50.

Thanks mgookin anyway. If I really had to look something up and had lots of time, I would probably do it. I don't see myself shelling out $50.50 for a .pdf anytime soon, though.

 

[mgookin]

I created an NFPA account and got the 'free access' to the 2014 NFPA 780 in a format that is a total PITA to use. There is a link to click on to buy a .pdf file of said code for $50.50.

Thanks mgookin anyway. If I really had to look something up and had lots of time, I would probably do it. I don't see myself shelling out $50.50 for a .pdf anytime soon, though.

I just paged through it. There is quite a substantial amount of new or modified content.
I'm not spending the $50 either, at least now right now anyway.
Lightning protection is big business around here. Also lightning prediction and warning systems. Once one kid takes a bolt, suddenly public money is available in unlimited amounts to make sure it never happens again. All of our major league baseball stadiums have them (we have four). The two used by pro sports teams today have silent notification to staff and the ones used by colleges and the like have public notification sirens.

 

[cuba_pete]

I'm convincing enough that my work subscribes to the entire code set each year. It's only $1,450 but one would only need it every couple of years due to the review cycle.

 

[alex111]

I live in an area that has many thunder storms (we had a dandy last night) and thousands of wood stoves.

I have NEVER heard of a metal wood stove chimney being struck by lightning.

It happened to a sleeping cabin at our island family cottage. It came down the side of a pine tree, blasting off strips, and jumped to the stove pipe. It arced at a rusty pipe joint bending the metal. Once inside it arced to metal heat shields and a metal trash can. The paint on the nails in the floor changed color. From the shield it blasted from nail to door hinge screw splitting the door frame. It exited the screen door at the lower corner (broken) where is split the wood step and shattered a granite rock then blew out a rotten tree root on its way in to the lake. A nearby bed and an old cotton mop in a distant cupboard burned and smoldered, possibly started by induction heating of the metal springs and wires contained in both. Near by walls were charred. The hardwood feet on the bed exploded and left dents in the walls. The cabin was closed up for the winter which likely helped starve the fire of oxygen.

If the stove were grounded it might have reduced the damage.

The military spends big bucks trying to protect their explosives. Nothing is 100% with lightning protection.

We used to say there was no electricity on the island....it passed through for a very brief visit and left an impression.

Alex

 

[K8MHZ]

It happened to a sleeping cabin at our island family cottage. It came down the side of a pine tree, blasting off strips, and jumped to the stove pipe. It arced at a rusty pipe joint bending the metal. Once inside it arced to metal heat shields and a metal trash can. The paint on the nails in the floor changed color. From the shield it blasted from nail to door hinge screw splitting the door frame. It exited the screen door at the lower corner (broken) where is split the wood step and shattered a granite rock then blew out a rotten tree root on its way in to the lake. A nearby bed and an old cotton mop in a distant cupboard burned and smoldered, possibly started by induction heating of the metal springs and wires contained in both. Near by walls were charred. The hardwood feet on the bed exploded and left dents in the walls. The cabin was closed up for the winter which likely helped starve the fire of oxygen.

If the stove were grounded it might have reduced the damage.

The military spends big bucks trying to protect their explosives. Nothing is 100% with lightning protection.

We used to say there was no electricity on the island....it passed through for a very brief visit and left an impression.

Alex

Wow, that's pretty crazy! One can only guess if any grounding would have made a difference. That sounds like a big bolt of lightning (they aren't all the same).

Grounding is meant to provide a low impedance path for the bolt, so the only thing that may have changed if the stove was grounded would possibly be the path from the stove to ground. Above the grounding point would not have been changed, unless possibly for the worst. We don't know the role grounding plays in the formation of stepped leaders in every scenario.

In an NWS severe weather class one year they had a video of a bolt of lighting hitting a power pole and vaporizing the GEC running down the pole. They are #4 or #6 solid CU. I asked why a larger conductor wan't used. The answer I got was that the size they use works 90 percent of the time and it would be more expensive to get closer to 100 percent with flat copper strap than it is to repair the damage from using smaller conductors.

FWIW, 3" wide .030" copper strap will carry a direct hit without fusing open 99 percent of the time.