education in chimney fires

[mike van]

Carl, just my 2 cents again. Its only Dec 2nd, you are in for a long winter if you have to light a fire every 2 to3 hours with wood split smaller than 4'" You need to let it go out, pull the pipe, and see how bad that 8" flue really is. Do you have a chimney brush? See how hard it is to push up & down the flue - A really bad chimney fire will crack that chimney & spread to the framing of the house. Small hot fires every few hours just let the chimney cool off in between them....starting the problem all over. Do you have the oil furnace in that flue too? You said before it used to be? If not, why is there a baro. damper? If you were putting an air tite stove in that flue [basically what your wood boiler is] you wouldn't have a baro. damper. Someone else correct me, but I think it cuts down on draft through the fire, lets cold air up the chimney, not helping your problem. That pipe thermometer should be a lot hotter right behind the unit. As you get farther up the chimney, it drops like a rock. I wish it was easy, but I know what I went through for 16 years, I don't believe there is an easy "fix" for what you have.

 

[peakbagger]

I have a non gasification boiler and my neighbor had a non gasification boiler. He has multiple chimney fires despite cleaning his chimney monthly in the winter. He got to the point that he cracked his masonry liner and then burned up an insulated liner. I have cleaned my chimney twice in 25 years as it doesn't need it.

What is the difference? He burns wood that at best is 6 months old. He runs the boiler continuously allowing the damper to operate when there is no heat demand. He has a exterior masonry chimney. I have an interior one. I added 550 gallons of unpressurized water storage 3 years ago and prior to that only ran the boiler when there was heat demand and watched the fuel so the damper rarely closed. The vast majority of gasification boilers have storage and most companies will not guarantee units that don't have it. My goal is to season my wood 2 years but the reality is that I have burnt wood that as cut in March and burned In December. I use more wood when the wood is not super dry but I have not seen an increase in creosote.

To me the biggest thing you can do is add storage. Even if you upgrade to a gasifier in the future, the tank will still be needed. That's what I plan to do. If you don't have storage, you have to accept significant temperature swings in the house and match your fuel load so that the boiler always stays below the temperature where the damper closes. This effectively limits you to only very cold weather.

 

[maple1]

Ok, since someone brought this up I have some questions. I have heard that the damper puts cold air into the flue so it cools things down and this isn't always good for a wood burning setup. The guy that put in my system put my damper about 6 inches behind the boiler. Then there is about 2 feet to the chimney thimble. Is this a good setup, or should the barometric damper be further up the pipe?

I have a thermometer on the stovepipe so I have some idea how well i'm burning. It is just one that sticks on the outside because I have single wall pipe. I put it on the elbow right before it goes into the chimney. This is about 2 feet above the barometric damper. Is that a good place for it? Where it is now, when the fire is burning good i can get readings of up to 450 from the outside of the stovepipe. According to the thermometer that is in the optimal burning range. But of course that doesn't take into account the added cool air from the damper. So really the fire is burning hotter but the damper is cooling it down some. Should i move the Damper and then put the thermometer below the damper or is it better the way it is set up now? Is one way better or worse as far as creosote goes?

Just speaking from experience - but IMO anyone burning with a non-gassifying boiler will get creosote. You can limit it somewhat with procedures - but you will in no way eliminate it. And not having a barometric damper will not eliminate it - and again from my experience, not having a baro can let a chimney fire sneak up on you. You could have a week of calm weather during which your chimney quietly builds up creosote, then an overnight storm comes up where a big wind gust goes across the top of your chimney just after your fire door damper opens up way down below and wham your firebox flames get sucked up to meet the creosote and you've got excitement happening in a hurry.

Constant monitoring of creosote buildup, and getting a regular chimney cleaning regimen in place (you will need to sweep AT THE VERY LEAST once in the middle of winter) is a necessity. Do what you can to make that easier. For me, having the baro where it was made it easier. Even if it accumulated more creosote just downstream from it or around it. You won't avoid cleaning or eliminate buildup by not having a baro. And I also got a routine sorted where I could pull down my stove pipe between the boiler & chimney a bit easier (it was still a royal pain though).

On the temp guage, those magnetic thermometers aren't accurate for starters. I still have my old magnetic one stuck on my pipe right beside my new probe one. The magnetic one reads 100c less than the probe when burning. So keep in mind that temps inside the pipe are a lot hotter than what that magnetic guage is saying. It should be on the pipe between the boiler & barometric damper. And I liked having the barometric damper as close to the chimney as I could get it - it moves that point of slightly increased creosote accumulation further away from the boiler, and also provides for a very handy easy access point (although a small one) to the bottom of the chimney for inspection & help in cleaning.

All wood burning appliances (as far as I know) have a chimney draft specification. I don't know how that could be consistently met without the use of a barometric damper. Some use a key damper to limit draft but those have issues too and are far from consistent.

 

[bholler]

All wood burning appliances (as far as I know) have a chimney draft specification. I don't know how that could be consistently met without the use of a barometric damper. Some use a key damper to limit draft but those have issues too and are far from consistent.

No most wood appliances have a minimum draft spec. And most do not need and do not work well with baro dampers. I know some furnace and boiler makers call for them but they absolutely increase creosote buildup greatly and if using one can be avoided at all it should be in my opinion. Honestly the only reason for needing one is laziness on the stove manufacturers part in that it means they don't need to allow for varying draft which makes designing a stove much easier but not near as good. I know i will probably get slammed for that opinion on this board but that is how i feel sorry. And as far as lack of a baro making more risk of fire that may be true but if you have a fire with a baro in it will probably be much worse than it would be without one because of the increased buildup from it and because of the unlimited air supplied to the fire

 

[Whitepine2]

Before the outside boiler fires were often,what I found is a dry extinguisher at the bottom of chimney
would put out fire as quick as anything and not do any damage.THE DRAFT JUST PULLS THE POWDER UP PUTTING THE FIRE OUT.

 

[Carl Webber]

Carl, just my 2 cents again. Its only Dec 2nd, you are in for a long winter if you have to light a fire every 2 to3 hours with wood split smaller than 4'" You need to let it go out, pull the pipe, and see how bad that 8" flue really is. Do you have a chimney brush? See how hard it is to push up & down the flue - A really bad chimney fire will crack that chimney & spread to the framing of the house. Small hot fires every few hours just let the chimney cool off in between them....starting the problem all over. Do you have the oil furnace in that flue too? You said before it used to be? If not, why is there a baro. damper? If you were putting an air tite stove in that flue [basically what your wood boiler is] you wouldn't have a baro. damper. Someone else correct me, but I think it cuts down on draft through the fire, lets cold air up the chimney, not helping your problem. That pipe thermometer should be a lot hotter right behind the unit. As you get farther up the chimney, it drops like a rock. I wish it was easy, but I know what I went through for 16 years, I don't believe there is an easy "fix" for what you have.

My boiler is a Tarm OT-50, it is a dual fuel boiler. It has wood on one side and oil for backup on the other. I had to go this route because I only have one flue from my chimney that goes into the basement and my hot water is run from my boiler so I need it during the summer too. I plan to use wood during the winter and oil for the summer months or any time we are gone for an extended period of time. For this reason I have a barometric damper. Right now I have my stovepipe thermometer about 18 inches above the damper and i'm still seeing temps of 400 on the outside. What i'm wondering is if this is good or not? I realize that no matter what i'm going to create some creosote. What i'm trying to figure out is how to tell when i'm running the boiler at an optimum burn. I do understand that I need to keep an eye on my chimney, but I can't be taking the stovepipe off every five minutes to see what things look like. I'm trying to understand my setup so that I know when I am burning properly and when I am just pumping the chimney full of creosote. I should be able to tell that based on how the fire burns and my stack temps.

Is it better to have hot burning fires once every 2 or 3 hours or to put a stick of wood on the fire every half hour and let it burn really slow? Either way the flue isn't seeing the temps it needs consistently. If I keep a small fire burning the thermometer reads about 175 or 200. If I burn hot and then let things slow in between the thermometer will read 400 or more for 20 to 30 minutes before it starts to cool. By the time I start a new fire The stack has cooled to room temperature. In my opinion I thought it was better to burn hot for half an hour every couple hours then to burn slow all the time.

 

[Carl Webber]

On the temp guage, those magnetic thermometers aren't accurate for starters. I still have my old magnetic one stuck on my pipe right beside my new probe one. The magnetic one reads 100c less than the probe when burning. So keep in mind that temps inside the pipe are a lot hotter than what that magnetic guage is saying. It should be on the pipe between the boiler & barometric damper. And I liked having the barometric damper as close to the chimney as I could get it - it moves that point of slightly increased creosote accumulation further away from the boiler, and also provides for a very handy easy access point (although a small one) to the bottom of the chimney for inspection & help in cleaning.

All wood burning appliances (as far as I know) have a chimney draft specification. I don't know how that could be consistently met without the use of a barometric damper. Some use a key damper to limit draft but those have issues too and are far from consistent.

I was thinking this but I wasn't sure because the probe thermometers say they are for double wall stovepipe. It is possible that when i am burning a lower fire my stack temps are actually up closer to where they need to be but I am not seeing it. I think I'll install one of the probe type thermometers and see where that gets me.

The chimney draft spec. according to the manual I have is -0.05 inches of water. That is the same spec. for my old oil boiler. With the damper set at that setting it stays closed when i first start a fire. After the fire starts going and the temp rises to about 300 on my gauge the damper starts becoming pretty active and you can hear the air moving through it and up the stovepipe. When the oil side kicks in the damper does it usual thing that it does on oil appliances. When it first fires it jumps and then it is open just a little the entire time the burner is running.


I wasn't sure about the placement of the damper. The guy that installed my boiler put it right behind the boiler and left about 2 feet between it and the chimney. This leaves me no place for the thermometer but after the damper. So, all of my temp reading are past the damper. I was considering moving the damper but I don't really know much about them other than I need one. The guy that installed my boiler knows more than me so I just assumed he was right. I wanted to move the damper and put it just before the stovepipe goes into the chimney but I'm not sure if this is the proper place for it and I don't want to send a bunch of cold air up my chimney and screw up the draft.

 

[Carl Webber]

Before the outside boiler fires were often,what I found is a dry extinguisher at the bottom of chimney
would put out fire as quick as anything and not do any damage.THE DRAFT JUST PULLS THE POWDER UP PUTTING THE FIRE OUT.

I have a dry chemical extinguisher in the basement near the boiler. I'll have to remember this in case I have a chimney fire that the Chimfex won't take care of.

 

[Carl Webber]

I have a non gasification boiler and my neighbor had a non gasification boiler. He has multiple chimney fires despite cleaning his chimney monthly in the winter. He got to the point that he cracked his masonry liner and then burned up an insulated liner. I have cleaned my chimney twice in 25 years as it doesn't need it.

What is the difference? He burns wood that at best is 6 months old. He runs the boiler continuously allowing the damper to operate when there is no heat demand. He has a exterior masonry chimney. I have an interior one. I added 550 gallons of unpressurized water storage 3 years ago and prior to that only ran the boiler when there was heat demand and watched the fuel so the damper rarely closed. The vast majority of gasification boilers have storage and most companies will not guarantee units that don't have it. My goal is to season my wood 2 years but the reality is that I have burnt wood that as cut in March and burned In December. I use more wood when the wood is not super dry but I have not seen an increase in creosote.

To me the biggest thing you can do is add storage. Even if you upgrade to a gasifier in the future, the tank will still be needed. That's what I plan to do. If you don't have storage, you have to accept significant temperature swings in the house and match your fuel load so that the boiler always stays below the temperature where the damper closes. This effectively limits you to only very cold weather.

How exactly do you burn? Do you burn only in really cold weather and keep a smaller fire so the damper stays open, or do you just have a fire when the heat is necessary to bring the boiler up to temp and burn hot when you do it? The other day it was cold here, about 20 during the day and 5 at night. Even then I couldn't keep a fast burning fire going without overheating the boiler. The house requires about 80k btu an hour and I also have a modine in the basement to dump heat if necessary. My boiler running wide open supposedly will put out 140k btu. If I build to big of a fire I get a bed of coals that is about 3 or 4 inches thick that give off a lot of heat and the boiler heats up really fast and takes a long time to cool down even with the over heat control running. I did find with the colder weather the damper stayed open more, but as the fire burned and I added more wood as it went down the bed of coals got bigger. I was a little nervous that If i got too big bed of coals I could overheat the boiler enough that it would get out of control. Right now If I have a small bed of coals and i throw some smaller wood on it the stack temps get up high enough and the fire burns hot and pretty fast, but if the boiler does hit 200 and the over heat kicks in it will only run for about 5 minutes to bring the boiler back down to 195. Because I'm new to this It worries me that I might get myself in a jam that I can't get out of and I might lose control of things. I've had wood stoves before but those are easy. They can get hotter and hotter and it doesn't matter, it just throws the heat into the room. With a boiler it collects the heat and stores it in the water and that makes it harder to work with. It also makes it more dangerous.

 

[Deering]

Any thoughts on the various sprays and 'presto logs' out there that claim to have some sort of catalyst that helps to break down chimney creosote? Are they effective or are they just more snake oil?

 

[BrotherBart]

They work when used as instructed. Ya still need to brush the accumulation out of the chimney after using them. They just dry out wet glazed creosote. Not clean the pipe.

 

[Deering]

Good to hear. Cleaning out loose creosote sure beats the glazed stuff. Thanks.

 

[Carl Webber]

I had heard that they were bad for wood boilers that were constructed of plate steel because the chemicals are corrosive and can eat the metal. I had heard that they work to clean the chimney but that they harm the boiler in the process.

 

[BrotherBart]

My big Sierra insert was made of 1/4" and 3/8" plate steel and 21 years of using the stuff didn't hurt it. Bought a case at the start of every season.

 

[Carl Webber]

Good to know. I think I might give it a try and see what happens.

 

[peakbagger]

I got the boiler for free and tried to run it for several years without storage. Its is a bottom grate design with air coming in under the grate so its doesn't hold coals. I tried all sorts of ways of running it without storage and ended up only using it during cold weather or when I the house was cold after I came home after being away for a few days. Unless I wanted to watch it continuously, I couldn't get it to run continuously without the air damper closing. The alternative is to have a big box of kindling and start it every several hours.

 

[Carl Webber]

That is what I have been doing with mine. I found if I ran a fire that smoldered for awhile, I could let it go out and let the boiler cool to about 155 just before the oil kicked in, then I'd start a fire and run it hot because I had the 30 degrees to go and it would burn off the creosote. So, I started burning like that. I'd light a fire once every couple hours. If I built up the bed of coals too much without letting it burn down the boiler would get too hot. The only problem I found is that it means I need to constantly keep an eye on the boiler. I was considering rigging something up so a buzzer would go off about 5 degrees before the oil kicked in so I would know the boiler needed attention. This would also be very helpful during the night. Then I could just sleep till the buzzer went off and then get up to mess with the boiler. It would take the guess work out of how long the boiler will last before needing attention. On really cold nights it might only go 2 1/2 hours. On a warmer night it might go 4 hours.

 

[Fred61]

Wow! You're making my very happy to have storage. I could just see myself stumbling around in the middle of the night pissing in the boiler and lighting a fire in the toilet all winter long.

 

[maple1]

That is what I have been doing with mine. I found if I ran a fire that smoldered for awhile, I could let it go out and let the boiler cool to about 155 just before the oil kicked in, then I'd start a fire and run it hot because I had the 30 degrees to go and it would burn off the creosote. So, I started burning like that. I'd light a fire once every couple hours. If I built up the bed of coals too much without letting it burn down the boiler would get too hot. The only problem I found is that it means I need to constantly keep an eye on the boiler. I was considering rigging something up so a buzzer would go off about 5 degrees before the oil kicked in so I would know the boiler needed attention. This would also be very helpful during the night. Then I could just sleep till the buzzer went off and then get up to mess with the boiler. It would take the guess work out of how long the boiler will last before needing attention. On really cold nights it might only go 2 1/2 hours. On a warmer night it might go 4 hours.

You could try shutting the oil burner off all together, and just make a fire when the house starts feeling cold.

That's what I did with my old one. Just wired in a simple wall switch between the burner & aquastat that I kept turned off when I was around & able to make fires & didn't need backup heat.

(i.e. let the boiler go colder than 155).

Or change your stat settings so it doesn't kick in until it gets down lower - like 130-140.

You could also heat the house warmer while burning & use the house itself as heat storage. For example with a well insulated basement you could heat that up to 80 (or whatever), then that heat might rise up over night & help you make it through the night.

With my old one I had a hard enough time just dealing with trying to load late & refill as soon as I woke up in the morning - can't imagine getting up in the middle of the night multiple times to tend it. I think I would have to let the oil burn some rather than do that, would have sent me off the deep end. Storage does indeed change everything - now my fire is about out when I go to bed and I don't relight it until the next afternoon sometime.

 

[Carl Webber]

I made some changes to my system and it has changed how I burn. I took apart the stovepipe and cleaned it. It had a good layer of creosote on it from me learning how to burn properly the first couple days I burned. Since I started out bad it has continued to accumulate pretty good. So, after cleaning I took a camera and held it in the chimney facing up and took a picture and the chimney doesn't look too bad. There is definitely some creosote buildup but not too much. The other thing that made me happy was that it was the dry crusty stuff and no the glassy sticky stuff. The way things are looking I'm pretty sure I could burn for probably 2 months without having to worry about the buildup. After that amount of time I don't think the chimney would be anywhere near plugged but it would have a pretty thick layer and it would mean the risk of a much worse chimney fire would be higher.

When I put the stovepipe back together I moved the barometric damper so it was just before the elbow into the chimney. This put it about two feet from the boiler. I also went and bought a probe type thermometer and installed it before the damper. It said to install it a little more than 18 inches up the stovepipe, I went to 19 inches. After setting the boiler up like this I have discovered that I have been burning too hot. With the baffle in the top of the boiler at a 45 I can easily overfire the boiler in about 10 minutes even with the draft door almost closed. It doesn't take much and the temp is up to 900. If I put the baffle straight up (the way it is meant to run), the fire burns much longer and it burns between 400 and 500. Its not in the middle of the optimal burn zone but it's in. Lesson here is the right thermometer and the location of the thermometer make all the difference in the world.

Burning like this, I see more glassy creosote buildup in the boiler but the stovepipe seems to be pretty clean. I've been watching it through the back of the boiler and through the damper and I can see a little creosote buildup but nothing compared to the inside of the boiler. What I have done to combat this is about twice a day I'll move the baffle in the top of the firebox and i'll throw in a stick or two of wood and have a small fire that burns really hot, about 900, right at the top of the optimal burn zone but not yet overfiring. I'll let it burn like this for 10 or 20 minutes watching it and adjusting as necessary to make sure the temp doesn't climb too high. This seems to burn off a lot of the buildup in the boiler. Then I can take a wire brush to the doors and openings in the boiler and everything just flakes right off and I clean it up pretty nice in about 5 minutes.

Running like this has made the boiler much more manageable and burns much less wood. Last night I went to bed at 11:30pm and I stoked the fire and filled the firebox up to the bottom of the door, about 5 or 6 sticks of wood. When I got up this morning at 7:30am the boiler was still at 180 and there was enough coals for me to be able to throw a couple smaller pieces of wood on and start a new fire without having to use kindling. That works out to roughly an 8 hour burn on one load of wood. Much, much better than I was getting before.

I don't know if anyone else has experienced this, but I did notice something about my boiler that I'm not sure If its a good or bad thing or what to do about it. I noticed that running the boiler like I am the wood doesn't burn as fast and that means that it sits in the firebox and tuns to coals. Once I get a good bed of coals going everything burns nice and slow and clean. The problem I am seeing is with heat. I had about 3 or 4 inches of coals in the firebox and 3 sticks of wood on top. They had worked their way down as the wood under them burned. These three sticks of wood were charred and ready to burn but because of the way the draft was controlling the boiler they hadn't burned yet. I went to check on the fire and as soon as I opened the door to see what the wood and the fire looked like they lit and because of the way the boiler is designed the smoke and flames shot through the bed of coals and up through the heat exchangers. It caused a pretty loud roar and the stack temp almost immediately went to overfire, somewhere near 1000. Of course as soon as this happened I shut the door to starve the fire of the extra oxygen it was pulling through the door. After shutting the door and closing everything up tight it took about 15 or 20 minutes for the stack temps to come down into the normal operating range below 800. What makes me nervous about all this is that it reminds me of what firefighter would call backdraft. Everything is ready to burn but not enough oxygen is preventing it from burning. As soon as it gets the oxygen it burns super hot and fast and almost instantly. It made me nervous that some day I would go to check on the fire and just by opening the door I would cause a chimney fire. For now what I've found is that after the fire burns down to only a few coals and really needs to have wood added the stack temps drop down to about 250 or 300. Just below the optimal burn range. When I check the fire now I check the temp of the boiler and the temp of the stack. If the stack temps are still in the optimal burn range I leave everything alone. I won't even open the door. If the stack temps are low then I open the door to check the fire. If anyone has any experience with this or any suggestion It would definitely be helpful.

 

[brenndatomu]

Sounds like you should give 'er some air for a few minutes before opening the door. Prop open the damper or whatever controls the air on that machine...

 

[b33p3r]

I am not 2 years ahead with my wood storage yet but I haven't had any problems with creosote in my chimney. In fact my wood is about 1 year dry at best. I do however clean the chimney every 3 months. Been burning since September so am due to clean now.
I have also been told by an old timer that if you throw an aluminum can into your stove the chemicals it produces when it burns helps clean the creosote. I don't know if it works but I do so enjoy that beer as I load the stove for the night I think he said it had to be a beer can?

 

[Carl Webber]

Do you have a traditional boiler or a gassification boiler? Do you have storage?

 

[Carl Webber]

I just cleaned my chimney today after 1 month of burning just to see what it looked like. To my amazement my chimney was absolutely clean except for a very thin layer of glassy creosote that was fresh. The fresh creosote was because apparently one of the sticks of wood that was put in the boiler last night was not very dry. It made a real mess of the inside of the boiler and put a layer of creosote up the chimney. I did notice one problem that I kind of expected. The chimney is clean but the stovepipe that connects the chimney and the boiler had a pretty good layer of creosote. Because I've been using Kwik Shot creosote sticks the stuff in the stove pipe came right off and cleaned up nicely. There was quite a bit. I would say at least a quarter inch all the way around maybe a little more. Does anyone have any solutions to this? Is it possible to insulate the stovepipe somehow so it doesn't collect so much creosote? What about double wall insulated stovepipe? Has anyone tried something like this before? If so, how did you connect the insulated pipe to the uninsulated thimble in the chimney without switching back to the regular single wall stuff?

 

[bpirger]

I was driving home late (about 2AM) a couple of weeks ago from work, out in the rural area. I came across one of those giant clouds of wood smoke settling in the small valley....could see it 0.5mile ahead. As I got closer I noticed someone was out burning a fire (at 2AM) in the yard, really close to the house. Then I noticed there were three separate fires! It was clear the guy had a chimney fire occurring/just over/or just coming and stuff had belched out his pipe and started the fire. I turned around and went back, knocked on the door, and was somewhat concerned I might get shot. No answer....so I tried to stomp out the fire a bit....then started knocking on windows. Loud "hellos" to help thwart the bullets from flying. He came out and was stunned. We put out the fires....which had started in the leaves right next to the house and in the bushes. Looked like the leaves hadn't been raked in years. His wood pile, nothing split, stacked along the side of the house, was actually on fire. Imagine a couple of camp fires....that is what was going on...less than 3' from the house wall. Looked like the shingles on the walls of the house were old particle board/asbestos type...and one of them was quite severely burned. We put out the fires, he brought water out one gallon at a time, and I mentioned the idea of cleaning the chimney! No cap either. Without a doubt, I saved his house that night....who knows about people inside Next day I see he had raked the leaves up.....a good start. Thought about calling 911 and was just about to when he emerged. As I drove away I still wondered if I should call....maybe there'd be some education involved. It was apparent he didn't have too many resources to do things right. It's scarey how so many people do things.....and clear why so many fires happen.