Chimney designed to burn Creosote

[pen]

if your burning 24/7 i think the ticker metal would hold heat longer also.

That is right, it will hold heat longer, but will it be long enough to keep it over 200 towards the top of the chimney by the next time you put a fresh load in? I don't personally think so.

Since most of your accumulation (when burning properly) should happen at the start of a fresh load, you want that chimney to warm up as quickly as possible. If the stove has been sitting under 400 for a few hours before that reload happens, I just don't see any thickness of metal maintaining 200+ degrees above the roof line in that situation.

The only thing I could possibly see thicker steel helping with is burn through protection. However, burn through protection hasn't been a problem with a UL class A chimney that I have heard of, even in extreme cases.

pen

 

[greythorn3]

if your burning 24/7 i think the ticker metal would hold heat longer also.

That is right, it will hold heat longer, but will it be long enough to keep it over 200 towards the top of the chimney by the next time you put a fresh load in? I don't personally think so.

Since most of your accumulation (when burning properly) should happen at the start of a fresh load, you want that chimney to warm up as quickly as possible. If the stove has been sitting under 400 for a few hours before that reload happens, I just don't see any thickness of metal maintaining 200+ degrees above the roof line in that situation.

The only thing I could possibly see thicker steel helping with is burn through protection. However, burn through protection hasn't been a problem with a UL class A chimney that I have heard of, even in extreme cases.

pen

is the problem heat transfer thru the thinner metals that is causing house fires?

 

[pen]

if your burning 24/7 i think the ticker metal would hold heat longer also.

That is right, it will hold heat longer, but will it be long enough to keep it over 200 towards the top of the chimney by the next time you put a fresh load in? I don't personally think so.

Since most of your accumulation (when burning properly) should happen at the start of a fresh load, you want that chimney to warm up as quickly as possible. If the stove has been sitting under 400 for a few hours before that reload happens, I just don't see any thickness of metal maintaining 200+ degrees above the roof line in that situation.

The only thing I could possibly see thicker steel helping with is burn through protection. However, burn through protection hasn't been a problem with a UL class A chimney that I have heard of, even in extreme cases.

pen

is the problem heat transfer thru the thinner metals that is causing house fires?

No, not at all if the chimney was installed properly. The problem is mostly with masonry chimneys, not Class A units. If a structure has a fire with a Class A chimney that was installed properly, even a bad fire, by FAR the odds are that the fire was a result of what exited the chimney through the top, not a failure in the chimney itself.

There is a study bopping around from the 70's or early 80's where their goal was to MAKE chimney fires and compare chimney's, and no matter what they did back then, most masonry chimneys showed significant damage after 1 or 2 fires, but the SS chimney's from way back then in the same situation showed no significant damage. The standards for testing of class A certainly haven't gotten softer since then.

pen

 

[pen]

God love google, found it http://fire.nist.gov/bfrlpubs/fire83/PDF/f83003.pdf it's from 1983 and called "Intensity and Duration of Chimney Fires"

It's 142 pages so I hope you are in the mood for some reading. In reality though, many of the pages are index, reference, and diagrams. If you do decide to read through it, I'd suggest you do read all of the text because this is a study where quoting single line or reading bits and pieces, may be misleading at times. I haven't read it in a good while, but if I remember correctly, the air cooled chimney (which you wouldn't consider installing anyway) is largest failure as far as metal chimneys go. However, while the masonry chimneys would have protected the structure through their tests due to their extreme mass, they were significantly damaged and would be susceptible to problems in the future. Also remember, this is from 1983.

Every now and again this study gets brought up by someone who is trying to prove that unseasoned wood is fine to burn since it shows that they are able to make more creosote in their test by using well seasoned wood, however, if one actually reads how they were running the stoves to produce the creosote, and remembers that their goal was to produce creosote, one would figure out why they found what they did.


pen

 

[peakbagger]

I run into stainless steel chimneys on occasion during my travels that are obviously built out of surplus piping from a local papermill. They look to be schedule 10. Usually they are outdoors with no insulation. I expect they are reall good at creating creosote due to the lack of insulation but I expect they go throuhg a chimney fire quite well.

 

[Battenkiller]

I can't think of a way to decrease the risk of what would leave the chimney.

Metal roof.

 

[pen]

I can't think of a way to decrease the risk of what would leave the chimney.

Metal roof.

I mentioned that earlier as well.

The problem still remains that most homes have lots of opportunities for something flaming hot and flying around to cause trouble. Of course this is only a real concern in a worst case scenario, but, a worst case scenario is what is being described here so I guess it's appropriate.

I suppose that would be reduced if he gets good snow around, but other than that, it's a tough thing to stop I'm afraid. Considering many of of do not have a steel roof, this risk is something we all deal with daily. Since most of us still have a structure that is standing, I think prevention is simply the best way to go.

pen

 

[BobUrban]

Well it seems that there is no realistic(financial) way of dsigning this super chimney so it would need to be a "money is no object" situation which completely defeats at least 99% of those who burn solid fuel. At least those of us who are burning 24/7 for heat. As a group I think our main objective is staying warm while saving money. A $20,000.00 chimney is certainly going to take a lot of free burning, no cleaning, to make that thing pay. I am guessing that if money were no object then the dial on the thermostat would be the safest and easiest method to get heat w/o cleaning. Or, if ecology is your main reason for burning solid, replacable fuel, and you had that level of jack you could have a service on schedual clean it while you are not even there. Shoot, hire a certified fire attender to keep it cooking safetly so you never have to touch the stove. Again not realistic.

I am thinking the only thing close to a "Never Clean" system is to go about 100' or more up with a seamless, fully insulated(possibly pre-heated) unit with a slate or steel roof on an all stone and morter house and a custom built stove that can handle the draw and remain efficient. Again, rediculously impractical.

All that said I do think it would behoove you to not be so confident in some Government organization that is supported by lobbyists to tell you what is safe??? Money talks and contrary to what some believe, the Govermnent is not concerned with yours or mine when it comes to safety. Especially when they can make money going with something less safe. I know a certified welder and an engineer could easily construct a better, stronger, safer stove system than is available on todays UL approved market and still not get it insured. Just the world we live in.

My shop stove pipe and the one in the sauna I am building(stove and chimney - will only be burned periodically, not 24/7 and not in a building I am sleeping in. They will also get cleaned periodically so my goal is not to go w/o cleaning - just not needing to purchase Class A for the units.

Fun to think about this stuff but seems practicality is winning

 

[MrWhoopee]

Did anyone mention that burning the creosote in the chimney is wasting heat that could be put to use? The problem with my Buck 81 is that by the time the secondaries are fully ignited the room is getting too hot to stand. I think cats are heading in the right direction, but I like the idea of an actual afterburner. Perhaps a separate secondary chamber/boiler, use that heat for hot water? The hard part is getting the necesary temp for ignition of the gasses (and, of course, all the other engineering challenges).

 

[Chettt]

Since we are "what iffing", why not design a flue with a built in brush and pulley system that the owner could pull up and down, daily if they like. My chimney sweep tells me stories of people who burn 24/7 but only call him once every 5 years and then only because their draft is so bad. He has to use metal bar to bust through the build up.

I think there are still things we don't understand about chimney fires when some people seldom clean their flues and live to tell about it and others clean regularly and have a fire.

 

[firebroad]

I think Pen has a point, there may be a reason why no one has come up with a better mousetrap yet, and flue temperature might be one on the impediments. However, having looked at that Irish set up made me wonder how feasible a self-cleaning chimney would be. Don't laugh, but I wonder if there could be some kind of pulley-operated gizmo that would slide an inner ring down the length of the flue to loosen ash between more serious annual sweeps. An old broad like me who cannot reasonably climb up there would benefit. Of course, taking the baffle plate off would be another can of worms...maybe a swing-away latch? Go ahead and poke fun if you want...

 

[Adios Pantalones]

Masonry heaters extract as much heat as possible from the exiting gas. They burn very hot and efficient, with plenty of air, so creosote formation is very limited, but the heat is still not wasted. This got me thinking about a chamber where creosote is extracted from the smoke on purpose.

What if the stove had a secondary chamber where the creosote was removed from the cooling gas- this chamber would greatly improve efficiency, and a fire could be lit in there occasionally to clean it out- or it would happen naturally during a hot startup in the primary chamber.

edit: essentially this would be a self-cleaning "magic heat". It may cause a draft issue.

 

[flhpi]

first company to make a real chimney i will buy it and replace all my chimneys with it. and run my class a over with my truck.

Shouldn't you use the class A in a homemade smoker instead? The truck would be fun but only last a short while. The smoker would last for years. Mmmmmmm brisket.

 

[firefighterjake]

I think Pen has a point, there may be a reason why no one has come up with a better mousetrap yet, and flue temperature might be one on the impediments. However, having looked at that Irish set up made me wonder how feasible a self-cleaning chimney would be. Don't laugh, but I wonder if there could be some kind of pulley-operated gizmo that would slide an inner ring down the length of the flue to loosen ash between more serious annual sweeps. An old broad like me who cannot reasonably climb up there would benefit. Of course, taking the baffle plate off would be another can of worms...maybe a swing-away latch? Go ahead and poke fun if you want...

Kind of like this . . . only set up for Class A chimneys?

http://www.swiftchimneycleaner.com/

 

[firebroad]

I think Pen has a point, there may be a reason why no one has come up with a better mousetrap yet, and flue temperature might be one on the impediments. However, having looked at that Irish set up made me wonder how feasible a self-cleaning chimney would be. Don't laugh, but I wonder if there could be some kind of pulley-operated gizmo that would slide an inner ring down the length of the flue to loosen ash between more serious annual sweeps. An old broad like me who cannot reasonably climb up there would benefit. Of course, taking the baffle plate off would be another can of worms...maybe a swing-away latch? Go ahead and poke fun if you want...

Kind of like this . . . only set up for Class A chimneys?

http://www.swiftchimneycleaner.com/

WOW that would be cool!!

 

[firefighterjake]

From personal and professional experience . . . the chimney isn't the problem in most cases . . . heck, usually it isn't even the roofing material or even any other combustibles on the ground such as dead, dry grass, nearby wooden sheds, porch, etc. . . . where most folks get into trouble with chimney fires is when there is building material too close to the chimney . . . or they've had enough hot chimney fires over the years to the point where the nearby wooden 2 by 4s, 6s or what have you are suspectible to pyrophoric carbonization.

I personally like the Excel chimney . . . but again I suspect the problem in most cases is not so much with the chimney as it is with the home owner in not inspecting/cleaning the chimney on a regular basis or not installing the chimney to manufacturer and code specifications . . . and for this reason I kind of wonder if it is possible to make a fool-proof chimney.

 

[MrWhoopee]

. . . and for this reason I kind of wonder if it is possible to make a fool-proof chimney.

Make something fool-proof and someone else will make a bigger fool. ;-P

 

[Battenkiller]

God love google, found it http://fire.nist.gov/bfrlpubs/fire83/PDF/f83003.pdf it's from 1983 and called "Intensity and Duration of Chimney Fires"

Every now and again this study gets brought up by someone who is trying to prove that unseasoned wood is fine to burn since it shows that they are able to make more creosote in their test by using well seasoned wood, however, if one actually reads how they were running the stoves to produce the creosote, and remembers that their goal was to produce creosote, one would figure out why they found what they did.

Excuse me if I'm wrong, but I see nothing in the procedural writeup that speaks of deliberately using dry wood to produce more creosote than wet wood. They don't even mention the wood type or MC that I noticed (except in the overfire tests, where they apparently used continually fed oven-dry doug fir to get the stove as hot as they could get it), nor did they even attempt to quantify the amount of creosote produced by weighing the chimneys throughout the creosoting phase.

The U of A study they cited in the text was not conducted to try to make the most creosote possible, nor were any of the half dozen other studies I've seen on the subject. Each of these studies independently determined that wet wood makes less creosote when burned under normal conditions in a non-cat stove. The studies I've seen that included cat stoves showed the opposite (dry wood produced less creosote), although the difference was marginal.

As far as the masonry chimney they used, it is not a fair comparison. The ran those stoves into a 12" flue with a measured 11 1/2" ID. That is almost five times the cross-sectional area of the 6" flues used in the other tests. Very significant flue gas cooling occurs when venting an appliance with a 6" outlet into a flue that large.

I have to wonder how well a round cast-in-place chimney liner would compare to all of these others. Pretty well I'd guess. Supposed to withstand 2100ºF, so that might be the answer to the self-cleaning chimney.

 

[pen]

My apologies, posted that pretty late last night and I haven't read it in a while. What I was thinking about was what is found on the bottom of page 9 and the beginning of page 10, in that case, they were citing a previous study about creosote production.

Page 13 talks about the creosote build-up tests. Considering how they controlled the temperature of the stove to create creosote, I can see how running a wood stove in that manner could cause dry wood to create more creosote.

You are right though, they did not specify the amounts produced, simply referenced a previous study. Sorry for my forgetfullness.

Still an interesting old read that gets referenced every now and again.

I have to wonder how well a round cast-in-place chimney liner would compare to all of these others. Pretty well I'd guess. Supposed to withstand 2100ºF, so that might be the answer to the self-cleaning chimney.

Good point, perhaps a masonry chimney with a SS liner and thermix around it could be even safer than the Class A? However, is it really necessary to go to any extreme beyond class A?

Something to study next time.

pen

 

[Adios Pantalones]

As long as you know where the creosote is going, and it can be collected, a cooling box (magic heat plus) would improve efficiency and allow easy cleaning. As I said above- line that box and attach it to the stove (more space required) and the creosote could be burned off at next startup.

Come to think of it- that DIY double barrel stove may do this to some extent already. Problem solved... or safety issue traded up, at least.

 

[laynes69]

I think Pen has a point, there may be a reason why no one has come up with a better mousetrap yet, and flue temperature might be one on the impediments. However, having looked at that Irish set up made me wonder how feasible a self-cleaning chimney would be. Don't laugh, but I wonder if there could be some kind of pulley-operated gizmo that would slide an inner ring down the length of the flue to loosen ash between more serious annual sweeps. An old broad like me who cannot reasonably climb up there would benefit. Of course, taking the baffle plate off would be another can of worms...maybe a swing-away latch? Go ahead and poke fun if you want...

My uncle had a pulley system with a brush and weight on top of the chimney. One day he got the brush stuck and decided to pull the cable with a vehicle. Needless to say he ripped the large masonry chimney off the side of the house. This was the same uncle who used duct tape (not aluminum tape) on his flue pipe and a piece of a leather belt for a door hinge on his woodfurnace. It was a wonder they never burned down the house.

 

[firebroad]

I think Pen has a point, there may be a reason why no one has come up with a better mousetrap yet, and flue temperature might be one on the impediments. However, having looked at that Irish set up made me wonder how feasible a self-cleaning chimney would be. Don't laugh, but I wonder if there could be some kind of pulley-operated gizmo that would slide an inner ring down the length of the flue to loosen ash between more serious annual sweeps. An old broad like me who cannot reasonably climb up there would benefit. Of course, taking the baffle plate off would be another can of worms...maybe a swing-away latch? Go ahead and poke fun if you want...

My uncle had a pulley system with a brush and weight on top of the chimney. One day he got the brush stuck and decided to pull the cable with a vehicle. Needless to say he ripped the large masonry chimney off the side of the house. This was the same uncle who used duct tape (not aluminum tape) on his flue pipe and a piece of a leather belt for a door hinge on his woodfurnace. It was a wonder they never burned down the house.

Sounds like he subscribed to the Red Green method of home improvement hh: !

 

[Battenkiller]

Come to think of it- that DIY double barrel stove may do this to some extent already. Problem solved... or safety issue traded up, at least.

Well, glad I didn't bring those up. %-P

They are supposed to be pretty darn efficient for heat transfer, and most all the creosote condenses inside the upper chamber walls where it's dang near impossible to touch off with a hot fire. Kinda hard to retrieve it for reburning later, though. Years ago I toyed with the idea of putting one into my old basement, but I decided they creeped me out too much. Not quite enough redneck in my gene pool, I guess.

 

[Battenkiller]

I have to wonder how well a round cast-in-place chimney liner would compare to all of these others. Pretty well I'd guess. Supposed to withstand 2100ºF, so that might be the answer to the self-cleaning chimney.

Good point, perhaps a masonry chimney with a SS liner and thermix around it could be even safer than the Class A? However, is it really necessary to go to any extreme beyond class A?

Pen, I don't know if adding the SS liner would help much with a cast-in-place liner. It might actually get fried in there during a chimney fire. From reading that study you cited, it seems that the SS takes the worst beating during a chimney fire if the chimney has a lot of insulation. They spoke of single-wall black pipe faring better than insulated liners because they lose the intense heat easier to the outside of the pipe. Of course, that wouldn't do you much good except in the first few feet from the stove collar to the thimble.

I still like Sav's idea best. Burn smart and don't make a lot of creosote in the first place. A hot stove is a happy stove, and good fuel makes it easy to burn hot. ;-)

 

[burleymike]

If I ever get the stove in my shop setup I plan to use 1/8" steel pipe wrapped with Roxul and at least 40" from any wood framing. I don't intend on having any chimney fires but if I do I will feel a lot better than if I had black pipe with a little piece of class A going through the roof. Some irrigation pipe and the Roxul is much less than class A and it will not have one seam.