education in chimney fires
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I've been heating with wood for 20+ years and am still learning the art of properly firing a wood burner. Our is a one story house with the boiler in the basement. The boiler connects into a massive brick chimney in the center of the house with three tile lined flues. We have never had a chimney fire. We burn both pine and hardwoods that have been seasoned at leasst one year, but generally two years. I do have the chimney cleaned every year prior to heating season. Each cleaning produces about five pounds of fluffy creosote that is knocked of the flue tile by the cleaning brush. After cleaning there remains a coating of hard, somewhat shiny black tar like coating on the flue tiles.
That we have never experienced a chimney fire is partially good luck, because I know now that there were times when I was seriously overfiring the boiler and undoubtedly dumping dangerously hot exhaust gasses into the flue. About 10 years ago I started using a flue gas thermometer to monitor temperature in the flue and have come to realize that this is the most valuable indicator I have for monitoring and controlling the wood burner. There has always been a barometric draft damper in the flue, but I found this was not sufficient to control the firing rate and flue gas temperature, so I have added a manual draft damper which I tweak as needed to keep the maximum flue gas temperature below 800 degrees.
A couple years ago I added heat storage, with which I was able to reduce the percentage of time the boiler was idling nearly to zero, but to my suprise I am still getting about the same amount of creosote each year when the chimney is cleaned. What I did find is much less creosote accumulation in the boiler's fire tubes.
Based on my experience I believe the amount of creosote deposited in the chimney is mostly related to the amount of wood burned, and if I clean the chimney regularly and control flue gas temperature I will not experience a chimney fire.
That we have never experienced a chimney fire is partially good luck, because I know now that there were times when I was seriously overfiring the boiler and undoubtedly dumping dangerously hot exhaust gasses into the flue. About 10 years ago I started using a flue gas thermometer to monitor temperature in the flue and have come to realize that this is the most valuable indicator I have for monitoring and controlling the wood burner. There has always been a barometric draft damper in the flue, but I found this was not sufficient to control the firing rate and flue gas temperature, so I have added a manual draft damper which I tweak as needed to keep the maximum flue gas temperature below 800 degrees.
A couple years ago I added heat storage, with which I was able to reduce the percentage of time the boiler was idling nearly to zero, but to my suprise I am still getting about the same amount of creosote each year when the chimney is cleaned. What I did find is much less creosote accumulation in the boiler's fire tubes.
Based on my experience I believe the amount of creosote deposited in the chimney is mostly related to the amount of wood burned, and if I clean the chimney regularly and control flue gas temperature I will not experience a chimney fire.
Have you noticed more buildup in the stovepipe connecting the boiler to the chimney than the chimney itself? I've only been running my setup for about 6 weeks and i've noticed creosote buildup in the boiler itself and in the connecting stovepipe but the chimney seems to be clean other than the fine film of glassy black creosote like you mentioned.
I cant be sure but usually stuff described as "fluffy creosote" Is burnt creosote and is evidence of a chimney fire. When was the last time you had your flue scanned and professionally inspected? And if you are getting 5 pounds of it every year with glaze left in the chimney it sounds like you need to clean more often and change your burning practices.
I can't comment on the thickness of accumulated creosote on the chimney wall as I have not looked down the chimney just before the chimney sweep does his thing with the brushes. I do remove the connecting stove pipe and clean it every year and routinely find about a 1/2" layer of fluffy creosote and ash clinging to the inner surface of the pipe (my stove pipe is 6" diameter). Next time I will look down the chimney before it is cleaned. What I can say for certain is that the tar & creosote buildup on the inside of the boiler (in the firebox) is minimal and has vastly decreased since I added heat storage.
I really don't know what the significance of fluffy creosote is. Maybe some others can comment on that. I have not had my flue scanned, however the gentleman who cleans my chimney is a professional chimney sweep. He does a visual inspection of the chimney as part of his service and tells me when he sees something that needs attention. I estimate that I burn about five cords of wood per year. Should I be conceerned that this produces five pounds of creosote?
Yes i burn about 6 cords and make about a quarter gallon on a 40 year old stove
I think I need to get a moisture meter and check my wood for moisture content. I know it has been down and cut and split since before last winter so it is reasonably dry. The chimney doesn't seem bad and the connecting stovepipe has some buildup but the inside of the boiler seems to have a lot of creosote buildup. For my boiler it doesn't seem that bad to me because I have heard stories of people with my boiler that get large amounts of creosote running out the doors like thick tar and making a complete mess. I don't have that problem but i do notice once in awhile the door sticks a little and i see a spot where some creosote ran down the door and stuck the door to the frame. I also notice that sometimes there is creosote running down the door frame after a burn. Sometimes I see it even if I had a hot burn. It is soft a gooey and I try to scrape as much of it off with a putty knife as I can. Sometimes I can even see a couple of runs on the wall of the firebox inside the boiler. I try to use the Kwik-Shot sticks twice a week as it recommends to dry out the creosote. I do notice after using those a layer of creosote drys and peels off the next I have a really hot burn.
maple1
Minister of Fire
Fluffy creosote doesn't mean chimney fire. A chimney fire leaves nothing behind if it burns out on its own accord.
No not necessarily many times it leaves behind a fluffy expanded creosote. There are times that it burns clean but that is actually pretty rare and only comes from very intense fires which are much less common that the slower ones that leave behind the expanded fluffy stuff. Now without seeing the dirt that the poster was talking about i cant say but fluffy is a common description of it
So, what should the creosote look like in a chimney? I was under the impression that if you had the fluffy ash looking stuff that it meant you burned cleaner and there was nothing in your chimney that was at risk of catching on fire? What I'm hearing from everyone is that if you have fluffy looking stuff it means that the actual creosote has burned off and what you are actually scraping out of the chimney is the ash that is left. Is this really a problem as long as the creosote doesn't actually catch fire and get out of control?
maple1
Minister of Fire
Thats interesting. I have no clue as to why my wood burner should be making so much more creosote on less wood burned. I do have a barometric draft damper in the flue and it is usually partially open when I am burning. I'll bring that up with my chimney sweep next summer and get his take on the amount of creosote my wood burner is producing.
I have experienced the runny tar-like goo running down and out the primary air draft door beneath the grate. It became a problem when the boiler was idleing a lot. Now that I have heat storage, the boiler rarely idles and I have not had to deal with the goo. I think this tarry liquid comes from liquid and vapors emitted from wood baking in the firebox that condense on walls of the boiler when the boiler is idleing and it is not hot enough to burn them. If you load the firebox very full, the wood near the top of the firebox isn't very hot and may be emitting vapors that create the tarry liquid.
I've thought about getting a moisture level meter as well. Here in Western Pennsylvania we have a lot of humid days that makes air drying wood challenging.
In the last week or so my girlfriend has loaded the boiler at bed time when I was at work and forgot to open the small draft adjustment on the loading door. This small draft is supposed to allow air in to mix with the flue gasses and burn them when they mix while getting sucked back through the bed of coals. I have noticed that makes a huge difference. If this draft is open I don't get too much buildup. If this little draft is closed the amount of buildup is unbelievable. It runs down the inside of the door and is dripping off the top and walls of the firebox. it doesn't appear like it does much as far as gunking up the chimney but it sure makes a mess of the boiler. I haven't decided what to do about this yet. The reason that little draft gets closed is because when you open the cleanout door to poke the fire and move around the coals it put a lot of smoke out that little draft. To stop the smoke we shut the draft and then open it up again when we close the cleanout door. If it happens many more times I may just tell her to leave the draft open and let the smoke in the house and just be quick when opening the cleanout door. Its a real mess to clean up after the boiler gets full of that nasty black gunk.
Interesting. Currently the draft on my loading door is open about the width of two fingers, but it hasn't always been that way. This past summer I did some major maintenance on the boiler which included freeing up that draft which had been stuck closed for some time.
The only time I ever had a boiler discharge through the pressure relief valve was when the black tarry stuff pooled up on the primary draft door preventing it from closing completely.
I was unfamiliar with the OT-50 so I looked it up in the Tarm archieves. It looks like the OT-50 might be the predicessor to the Tarm 502. How hong has your boiler been in service?
I had my boiler installed about 2 months ago. When i got the boiler back in September it had some issues that needed to be fixed but nothing major. It appeared to me like the previous owner only used the oil side. When i got the boiler it had last been serviced about a year before so it hadn't been sitting for too long. One of the flanges on the back had to be replaced because it had a pinhole in the weld and was rusted pretty bad because someone had neglected to fix the original leak. at least one hinge pin on all three doors was broke and had to be drilled or pounded out and replaced. The domestic hot water coil was blown but i wasn't planning on using it anyway so I removed the coil and put in plugs. The gasket for the cover of the hot water coil was also dry rotted and leaking. After fixing all that stuff the boiler looked almost new. Because no wood had ever been burned in it the inside was immaculate. It seems like a lot of work on an old dinosaur but it was what I wanted and at the right price. I only paid $650 for it. There is a guy near me that refurbishes them and sells them on ebay and he gets about $2500 for one. I've also seen plenty of other ones in worse shape than mine that people have wanted $2000-$3000 for them. As I was trying to upgrade from oil to a wood oil combo and do it as cheaply as possible i was willing to put in a little elbow grease and get the cheaper one. For now I have also skipped the thermal storage. after a year or two and I've recouped the money I invested I'm going to install some storage. After that I'm going to try to upgrade to a gassification boiler. I haven't decided how i'm going to do things yet. I may go cheap and get an excel 2200. This would allow me to upgrade to a gassification model but keep the oil backup.
has anyone had an issue with their chimney cap falling apart. I just found the top of my chimney cap in the middle of my yard. There is a little creosote built up on it and it appears almost like the creosote mixed with some moisture and ate the spot welds that held the cap on. Has anyone ever seen this before? I think I'm going to just drill some holes and bolt the top to the screen instead of buying a new cap. It just amazes me that it fell apart. I have never seen this before.
maple1
Minister of Fire
I found my cap in my yard once, but it blew off. I straightened it out, climbed on my roof, & screwed it back on. I must not have screwed it on tight enough.
Yours has a screen? I've never had one on my caps, but from reading of others issues they can sometimes be more trouble than they're worth, for building creosote & blocking things up. I did have a birds nest in my chimney once - and there was an episode once when I was away from home where two bats mysteriously suddenly appeared inside the house & caused all sorts of panic. Didn't see it but never heard the end of it....
Yours has a screen? I've never had one on my caps, but from reading of others issues they can sometimes be more trouble than they're worth, for building creosote & blocking things up. I did have a birds nest in my chimney once - and there was an episode once when I was away from home where two bats mysteriously suddenly appeared inside the house & caused all sorts of panic. Didn't see it but never heard the end of it....
It isn't exactly a screen, but that is the best way i could think to explain it. It the expanded metal section of the chimney cap. The actual top of the chimney cap separated from the expanded metal section. They were tack welded together and the welds are completely gone now.
This could be a lot of typing.
Carl, four years ago, I had a chimney fire that could've claimed my whole second floor and the three kids that were sleeping there. I needed to get educated quick! Most of the wisdom came from this forum. I live in nj and have been successfully burning a harman sf160 since. Chimney sweep brushed my 28' tall pipe last week---everything that came out would've fit in a coffee can. If You want some tips on running that smoke dragon cleanly, call me any time @ 609-868-1878. Would be glad to help you out as others have helped me.
Carl, four years ago, I had a chimney fire that could've claimed my whole second floor and the three kids that were sleeping there. I needed to get educated quick! Most of the wisdom came from this forum. I live in nj and have been successfully burning a harman sf160 since. Chimney sweep brushed my 28' tall pipe last week---everything that came out would've fit in a coffee can. If You want some tips on running that smoke dragon cleanly, call me any time @ 609-868-1878. Would be glad to help you out as others have helped me.
maple1
Minister of Fire
as far as I can tell my chimney is pretty clean. I cleaned it a week or two ago and got almost nothing. I have found that the majority of the creosote is in the boiler and in the stovepipe that connects the boiler to the chimney. I'll have to check it again sometime in February or march just to see what it looks like but I think I will probably only have to clean my chimney once a year. The connecting stovepipe and the boiler will need some attention a little more frequently. I can look through the boiler and see right into the stovepipe and I can also look into the barometric damper. By doing this I can keep an eye on how things look and just clean it as i feel is necessary.
I agree with what most are saying. I have a stainless liner inside the normal liner with insulation poured all around it. I also have fiber blanket on the stove pipe on its way to the chimney in the wall in my boiler room to keep as much heat as possible in the stove pipe.
The other thing i do is check my wood and burn what shows to be the lowest % moisture. The thing that i think helps me a lot too is that i don't have room in the house for hot water storage so i turn down the heat to 50F when i go to work and when i get home i fire up the wood boiler and it runs wide open (about 500-550F) with a IR for about 1.5-2 hours to bring the house back up to temp after that the amount of wood i put in the boiler is much less. I have a harmon SF-260 that i bought used and i am making it work. I also don't use the boiler much unless the outside temp is below 25F or so. If it is warmer then that i burn NG.
The other thing i do is check my wood and burn what shows to be the lowest % moisture. The thing that i think helps me a lot too is that i don't have room in the house for hot water storage so i turn down the heat to 50F when i go to work and when i get home i fire up the wood boiler and it runs wide open (about 500-550F) with a IR for about 1.5-2 hours to bring the house back up to temp after that the amount of wood i put in the boiler is much less. I have a harmon SF-260 that i bought used and i am making it work. I also don't use the boiler much unless the outside temp is below 25F or so. If it is warmer then that i burn NG.
I have also found that if it gets to be between 25 and 30 outside I have a hard time running the boiler without making the house get up to 80. On the warmer days I let the wood burn out in the morning and i turn on the oil and let that keep the boiler warm all day. Then I start a fire again at night once it starts to cool off. Usually I watch the temp outside and I wait to see what the house does. When I see the heat kicking on in the house and the outside temp is getting lower I will turn off the oil and let the boiler temp drop down to the point that it shuts off all the circulators usually about 160. Then I start a fire. Usually this first fire will get good and hot and build up a good bed of coals and will burn hot for about 2 hours. By that time the boiler will be up to temp and the house will also be up to temp.
Where did you get the fiber blanket to insulate the connecting stovepipe? I have thought about doing this but don't know where to get the right kind of insulation. Just to be safe I wanted to insulate the connecting stovepipe but I'm not sure that I need to. My boiler is only about 50% efficient on wood so a lot of heat goes up the chimney. I've seen times where the stack temp before my barometric damper were 1100 and and after the damper they were 800. I try not to get things this hot but it does happen once in a awhile. On a normal day my stack temps are about 450 before the barometric damper and between 250 and 300 after. What I was hoping was that with a little insulation I might be able to get the temps before and after the barometric damper to be a little closer. If the connecting pipe is seeing 450, it would be nice if the chimney could consistently see 300 to 350.
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