Lightning

[Easy Livin’ 3000]

The other night during a thunderstorm, I started wondering, what happens when lightning strikes my stainless steel chimney cap that is attached to the stainless steel liner that is attached to the steel stove that is attached to the blower that is plugged into the wall socket. The chimney cap is the highest point on the house. Any experience with this?

 

[bcrtops]

The other night during a thunderstorm, I started wondering, what happens when lightning strikes my stainless steel chimney cap that is attached to the stainless steel liner that is attached to the steel stove that is attached to the blower that is plugged into the wall socket. The chimney cap is the highest point on the house. Any experience with this?

It won't be pretty!
Stay away from the stove when strikes are happening nearby.

Daughter in OK had a strike hit their Propane roof exhaust a few yrs. back. Took out all the running electronics in the house, as well as the controls on the heat pump/AC units (w/propane backup) & damage to water heater & blew a considerable hole in the concrete floor in the water heater closet as it was seeking ground.
Permanent damage to hearing in one of her ears. Fortunately, they had good insurance that covered the majority of the expensive repair/replacements.

 

[Easy Livin’ 3000]

It won't be pretty!
Stay away from the stove when strikes are happening nearby.

Daughter in OK had a strike hit their Propane roof exhaust a few yrs. back. Took out all the running electronics in the house, as well as the controls on the heat pump/AC units (w/propane backup) & damage to water heater & blew a considerable hole in the concrete floor in the water heater closet as it was seeking ground.
Permanent damage to hearing in one of her ears. Fortunately, they had good insurance that covered the majority of the expensive repair/replacements.

We had a raging fire in the stove at the time and were sitting in front. I was a little worried, imagined the burning embers exploding through the glass in the front. Yikes!

 

[bcrtops]

We had a raging fire in the stove at the time and were sitting in front. I was a little worried, imagined the burning embers exploding through the glass in the front. Yikes!

Seems to me that it might be a good idea to have a stove well grounded in lightning country. Any comments from others in thunder areas?

(Some stove manuals require grounding when installing in mobile homes, e.g.)

 

[bholler]

The other night during a thunderstorm, I started wondering, what happens when lightning strikes my stainless steel chimney cap that is attached to the stainless steel liner that is attached to the steel stove that is attached to the blower that is plugged into the wall socket. The chimney cap is the highest point on the house. Any experience with this?

bad things can happen I have seen chimneys that were completely blown apart from lightning

 

[djkeev]

When my house was built in 1967 it literally sat in a treeless field.

The roof is lined with lightening arrestors with copper cables to the earth.

Dave

 

[Easy Livin’ 3000]

When my house was built in 1967 it literally sat in a treeless field.

The roof is lined with lightening arrestors with copper cables to the earth.

Dave

We have lots of tall trees around the house, so I guess that's good, but I wonder if running a grounding cable from the top plate to ground would be a good idea.

I'm surprised I haven't read any posts about this. Guess it's pretty rare, or, like you Dave, the smart folks here have taken appropriate precautions.

 

[bholler]

We have lots of tall trees around the house, so I guess that's good, but I wonder if running a grounding cable from the top plate to ground would be a good idea.

Many liner manufacturers require you to. But they give you no instructions and do not supply any parts to do it so no one does.

 

[djkeev]

It is never a bad idea to ground things...... even multiple times! Redundancy is a proven good thing.

"back in the day" lightning protection was far more common on homes. You rarely see a new house built that incorporates such protection. You often see elegant old homes with beautiful Copper and Glass spires on the roof.

Lightning hasn't gone away or lessened in any way at all..... I can guess it boils down to dollars and the odds of it being needed.

Dave

 

[double-d]

There is a publication available NFPA 780, Standard For the Installation of Lighting Protection Systems.
You can go on line and get a 3 day, free subscription, of the codes
http://www.nfpa.org/codes-and-standards

 

[Easy Livin’ 3000]

Many liner manufacturers require you to. But they give you no instructions and do not supply any parts to do it so no one does.

Thanks bholler. I'm guessing that you do it all the time. I'd appreciate any tips that you'd be willing to share on getting it done.

 

[bholler]

Thanks bholler. I'm guessing that you do it all the time. I'd appreciate any tips that you'd be willing to share on getting it done.

Nope we only do it is there is an existing lightning system then we just tie it in.

 

[djkeev]

I'd do it like a electric power meter ground. Two 8' ground rods driven 10' apart (or more) joined with copper cable which then goes to the item being grounded...... redundency.

Dave

 

[Ashful]

"back in the day" lightening protection was far more common on homes. You rarely see a new house built that incorporates such protection. You often see elegant old homes with beautiful Copper and Glass spires on the roof.

There are reasons for this. Modern houses are fully wired, and this creates a sort of built-in lightening protection.

Most lightening strikes are "safely" dissipated by the home wiring. I put "safely" in quotes, as it is less likely to burn your house down, but you may lose electronics plugged in at the time.

In the pre-electric days, the wood structure and siding would have the burden of carrying all of that charge to ground. This would often result in sufficient heating to cause a house fire, hence the necessity of lightening rods.

Now, on the question of grounded chimneys, a similar debate has been raging for decades (maybe longer) on the grounding of sailboat masts. Those without grounded masts experience far fewer lightening strikes than those with grounded masts. However, boats without grounded masts will often see extensive damage around the mast step, after a lightening strike. Same phenomena as the house, in which wet wood or fiberglass must carry an enormous charge to ground, resulting in overheating of the material.

 

[Easy Livin’ 3000]

Interesting comparison. How does one ground the mast in water, or is it just a question when the sailboat is aground?

 

[MAD777]

Interesting comparison. How does one ground the mast in water, or is it just a question when the sailboat is aground?

Take several wraps of a very heavy steel chain around the base of the mast and drop the tag end over the side, such that it drags 8 feet or so into the water. Done it many a time but never got hit, so I never had to change my underwear.

Sent from my SM-G900V using Tapatalk

 

[djkeev]

Dragging 8' of chain....... now THAT would slow you down!

 

[Ashful]

There are thru-hull metal fittings that tie your mast step to the bottom of the hull, and hence the water. This is mostly an issue for cruisers, as most race boats are dry sailed (pulled out of the water after every race).

 

[begreen]

There are reasons for this. Modern houses are fully wired, and this creates a sort of built-in lightening protection.

Most lightening strikes are "safely" dissipated by the home wiring. I put "safely" in quotes, as it is less likely to burn your house down, but you may lose electronics plugged in at the time.

In the pre-electric days, the wood structure and siding would have the burden of carrying all of that charge to ground. This would often result in sufficient heating to cause a house fire, hence the necessity of lightening rods.

Now, on the question of grounded chimneys, a similar debate has been raging for decades (maybe longer) on the grounding of sailboat masts. Those without grounded masts experience far fewer lightening strikes than those with grounded masts. However, boats without grounded masts will often see extensive damage around the mast step, after a lightening strike. Same phenomena as the house, in which wet wood or fiberglass must carry an enormous charge to ground, resulting in overheating of the material.

Having seen the results of a few lightning struck houses, I can't agree. Lightning will seek the quickest path to ground. I have seen modern houses with the panel blown apart and assorted damages in random locations based on the proximity of ground. In one friend's house in CT the only thing that stopped the house from burning down was the fact that they were there to quickly douse the flames surrounding their electrical panel. Most commonly lightning will strike the highest point on the house and even with modern structures the most common lightning caused fires start at the roof. http://www.wolflightning.com/lightningprotection.html

 

[jetsam]

I would imagine that you're better off not grounding at all if you're going to do it with a piece of 8 gauge ground wire or whatever.

A small wire will only take a fraction of the strike, but that fraction creates an ionization path for the rest of it, which is going to ground also, just not via the wire.

(What I'm saying is that an inadequate ground is worse than no ground for lightning protection.)

I don't really know what 'adequate' looks like, but I imagine the bidding starts somewhere around 4/0 copper...

 

[Ashful]

Having seen the results of a few lightning struck houses, I can't agree. Lightning will seek the quickest path to ground. I have seen modern houses with the panel blown apart and assorted damages in random locations based on the proximity of ground. In one friend's house in CT the only thing that stopped the house from burning down was the fact that they were there to quickly douse the flames surrounding their electrical panel. Most commonly lightning will strike the highest point on the house and even with modern structures the most common lightning caused fires start at the roof. http://www.wolflightning.com/lightningprotection.html
View attachment 197937

Of course there are exceptions, begreen. That's why I included words like "most" and "less likely". I wasn't saying a house cannot burn down due to a lightning strike, of course it still happens, I was only speaking to why lightning rods were so much more common 100 years ago.

I would imagine that you're better off not grounding at all if you're going to do it with a piece of 8 gauge ground wire or whatever.

A small wire will only take a fraction of the strike, but that fraction creates an ionization path for the rest of it, which is going to ground also, just not via the wire.

You would be surprised how much current 8 gauge wire can handle, if it must do it for only one second.

 

[jetsam]

You would be surprised how much current 8 gauge wire can handle, if it must do it for only one second.

I would indeed be surprised if it coild earth a lightning strike by itself. Not ruling it out, and I'm no expert- just seems unlikely.

(Okay, now I went and googled it. NFPA 780 specifies 57,400 circular mils of conductor on the main strap for structures 75' and shorter. That's 29mm², which is in between 2 and 3 gauge. How grounded in reality is NFPA 780? I dunno, YOU google that one! )

 

[Easy Livin’ 3000]

Take several wraps of a very heavy steel chain around the base of the mast and drop the tag end over the side, such that it drags 8 feet or so into the water. Done it many a time but never got hit, so I never had to change my underwear.

Sent from my SM-G900V using Tapatalk

You're probably due for a change then, lightning strike or no. I shoot for at least every week or two, whether they need it or not.

 

[Lloyd the redneck]

Very interesting. Never really crossed my mind. I suppose it should be grounded like heavily to be safe. But it's lightning. It will vaporize things. I had a hit with my windows open last summer on a tree about 30' from the window. 2am loud boom. Dogs barking. Wife's screaming. Hell of a wake up!

 

[Ashful]

Very interesting. Never really crossed my mind. I suppose it should be grounded like heavily to be safe. But it's lightning. It will vaporize things. I had a hit with my windows open last summer on a tree about 30' from the window. 2am loud boom. Dogs barking. Wife's screaming. Hell of a wake up!

I've seen lightening split trees, but more often it just cooks those little tiny feeder roots, and leaves the owners confused. The tree appears to survive the strike, but then dies two years later.