Possible Chimney Fire Version 2

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Shorty

Member
Jan 10, 2017
19
Texas Panhandle
Hi all,
I just spent an hour or so reading @rosen431 post and all the replies last night while I let the adrenaline wear off. I learned a huge amount but I still left with a question or two since my stove is different. I have a Jotul F118 Black Bear stove placed in my basement in the center of the house. I have double wall pipe with an adjustable connector near the ceiling. Then I have approximately 20' of triple wall that goes through my main floor and attic then exits close to the center peak of the roof.

So it was late evening and there was a bit of a rush to get a fire going so that we could eat. There is story in between but the end result was that we had the firebox full of much smaller splits than we usually use including a couple 1" pieces of pine and one of those tiny square fire starters (I thought I could cheat and not have to sit there so long trying to get it started....:( ) . The fire was left unattended while we went upstairs to nuke leftovers real quick. We were walking by the stove pipe on the main floor with our plates and were headed downstairs to eat when I thought I heard maybe a mouse by the pipe. I quickly realized it was the pipe making little tinkly noises. We raced down the stairs and the stove top temp was around 500° but the flue temp was at 1200°. I had NEVER seen the flue temp exceed 500°.

My first reaction was to slam the air on the door closed. Obviously nothing happened in the first few seconds and I changed my mind and threw the door wide open. My husband looked outside to see if there was anything visible and I futilely directed a small fan at the stove. The tinking sound continued for what seemed forever but was probably only a couple minutes.When the flue temp did come down it fell extremely fast. It did slightly melt the labels on the adjustable elbow but I didn't feel heat at the floor penetration into the main floor.

I'm assuming, based on reading the other post, that we most likely had a small chimney fire. After all this reading I'm wondering if our stove top Thermometer is really showing stove temps since it sits on top of the stove and there is this heat exchange chamber between it and the actual fire? Jotul says to burn between 400°-600° as indicated on a thermometer "placed directly on the top plate". It also says in the event of an overfire or chimney fire to close the air on the front door and let it cool.
Also, if I have never seen flue temps above 500° before this are we burning way too cold? We generally start shutting the stove down when the stove top thermometer gets to around 350° which is in the middle of the "best operation" zone on the thermometer. It may register 50° low. I'm going to try to post photos with this post.

I've plan to have a timer handy and have ordered an electronic thermometer with an alarm. We will never again use that many small dry pieces of wood and walk away. Any other bits of advice for this stove would be welcome.


Ok need some help understanding this. Forgive the long post....Started a fire today loaded up beech and ash in my Woodstock ideal steel hybrid, very well seasoned. Filled the fire box. 35 ft stainless liner from the basement wood stove up through middle of my house, so drafts hard. Especially when cold. I had her cruising along nicely in a black box cat burn (no flames). Pipe damper half closed and stove damper almost all the way closed. Stove top temp starts to get near 600 flue gasses at 500 and I close the intake air on the stove all the way (still gets some air, but basically had it on the lowest air setting), and closed the pipe damper all the way to cool it down and keep the burn where it is. I have a probe thermometer in my double wall so that’s where I’m getting the flue gas readings. Now things get interesting - stove temp stays around the same, creeps up a little but the flue gas temperature starts rising FAST. Goes from 500 to 1200 in like 2 minutes and I smell that paint curing smell. Outside double wall at the hottest spot was about 500 degrees! I call a buddy of mine, he says “open up the pipe damper all the way and the stove damper all the way. If that doesn’t work open the door - you need to flood it with cold air”. Sure enough I opened up the pipe damper all the way and the intake air halfway and the flue temp starts dropping immediately. What am I missing here? Only thing I can think of is I kept more smoke in the stove and that just got the cat going even crazier? Second time this has happened in 10 days and last time I warped the radiator cover pretty good. Aside from adding less fuel, what’s actually going on?
 
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Shorty

Member
Jan 10, 2017
19
Texas Panhandle
IMG_20210302_1107488.jpg IMG_20210302_1108079.jpg IMG_20210302_1108033.jpg IMG_20210302_1107552.jpg
 
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begreen

Mooderator
Staff member
Nov 18, 2005
89,766
South Puget Sound, WA
The flue temps do sound a little low. It's possible that the stove pipe thermometer is in error. Now that we are running with an Auber on the flue I see over 500º flue temps quite a bit. Our stove pipe thermometer lags by 100-150º.

How well seasoned is the firewood?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,654
central pa
Hi all,
I just spent an hour or so reading @rosen431 post and all the replies last night while I let the adrenaline wear off. I learned a huge amount but I still left with a question or two since my stove is different. I have a Jotul F118 Black Bear stove placed in my basement in the center of the house. I have double wall pipe with an adjustable connector near the ceiling. Then I have approximately 20' of triple wall that goes through my main floor and attic then exits close to the center peak of the roof.

So it was late evening and there was a bit of a rush to get a fire going so that we could eat. There is story in between but the end result was that we had the firebox full of much smaller splits than we usually use including a couple 1" pieces of pine and one of those tiny square fire starters (I thought I could cheat and not have to sit there so long trying to get it started....:( ) . The fire was left unattended while we went upstairs to nuke leftovers real quick. We were walking by the stove pipe on the main floor with our plates and were headed downstairs to eat when I thought I heard maybe a mouse by the pipe. I quickly realized it was the pipe making little tinkly noises. We raced down the stairs and the stove top temp was around 500° but the flue temp was at 1200°. I had NEVER seen the flue temp exceed 500°.

My first reaction was to slam the air on the door closed. Obviously nothing happened in the first few seconds and I changed my mind and threw the door wide open. My husband looked outside to see if there was anything visible and I futilely directed a small fan at the stove. The tinking sound continued for what seemed forever but was probably only a couple minutes.When the flue temp did come down it fell extremely fast. It did slightly melt the labels on the adjustable elbow but I didn't feel heat at the floor penetration into the main floor.

I'm assuming, based on reading the other post, that we most likely had a small chimney fire. After all this reading I'm wondering if our stove top Thermometer is really showing stove temps since it sits on top of the stove and there is this heat exchange chamber between it and the actual fire? Jotul says to burn between 400°-600° as indicated on a thermometer "placed directly on the top plate". It also says in the event of an overfire or chimney fire to close the air on the front door and let it cool.
Also, if I have never seen flue temps above 500° before this are we burning way too cold? We generally start shutting the stove down when the stove top thermometer gets to around 350° which is in the middle of the "best operation" zone on the thermometer. It may register 50° low. I'm going to try to post photos with this post.

I've plan to have a timer handy and have ordered an electronic thermometer with an alarm. We will never again use that many small dry pieces of wood and walk away. Any other bits of advice for this stove would be welcome.
If it actually was a chimney fire opening the door was the absolute wrong thing to do. Your first instinct was correct
 
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MongoMongoson

Member
Feb 6, 2021
173
Wisconsin
Do you have access to the roof? If you can look up there and see a bunch of black stuff... cinders, burned up creosote on the roof around the chimney then yes you probably did have a chimney fire.

If you didn't have a lot of fuel (creosote) in your pipes, you can get the flue temp up to 1200 degrees, get the inner layer of your double wall pipe glowing a nice orange and everything without having a chimney fire. It will make noise, for sure.

I DID have a chimney fire once, for certain, and it was definitely in the stove pipe. I never want to hear that again. My labels didn't melt, but I have a different brand of pipe so maybe that doesn't mean much. I understand what you mean about the adrenaline.

It looks like bholler beat me to it while I was typing this. Do not open the door when you have a chimney fire. That allows the fire in the stack to suck as much air as it wants, and just feeds the fire. So I guess the good news is, if you did have one it must have been a small one because otherwise the opening of the door would have created even more excitement.
 

MR. GLO

Member
Jan 26, 2021
136
Massachusetts
When is the last time you cleaned your chimney and stove pipes? Lets see the cap?
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
The flue temps do sound a little low. It's possible that the stove pipe thermometer is in error. Now that we are running with an Auber on the flue I see over 500º flue temps quite a bit. Our stove pipe thermometer lags by 100-150º.

How well seasoned is the firewood?
An Auber is on the way. I don't know why I didn't consider that the pipe thermometer might be off. There's no way to double check except another probe type I guess.

The stuff that started that was well seasoned. When I've checked the moisture content of the locust that we burn a lot of its been good but I couldn't swear that all the new firewood we bought was seasoned well. We will definitely check that pile and make sure.
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
If it actually was a chimney fire opening the door was the absolute wrong thing to do. Your first instinct was correct
So I have thrown the door open a couple times when I got distracted and let the stove top temp get slightly above what is "normal" on this thermometer. Should I just stop that? If the top end of normal on this thermometer is just under 500 should I just not worry about it until it hits closer to 600?
is there any way I could have had flue temps of 1200 with STT of 500 without a chimney fire?
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
Do you have access to the roof? If you can look up there and see a bunch of black stuff... cinders, burned up creosote on the roof around the chimney then yes you probably did have a chimney fire.

If you didn't have a lot of fuel (creosote) in your pipes, you can get the flue temp up to 1200 degrees, get the inner layer of your double wall pipe glowing a nice orange and everything without having a chimney fire. It will make noise, for sure.

I DID have a chimney fire once, for certain, and it was definitely in the stove pipe. I never want to hear that again. My labels didn't melt, but I have a different brand of pipe so maybe that doesn't mean much. I understand what you mean about the adrenaline.

It looks like bholler beat me to it while I was typing this. Do not open the door when you have a chimney fire. That allows the fire in the stack to suck as much air as it wants, and just feeds the fire. So I guess the good news is, if you did have one it must have been a small one because otherwise the opening of the door would have created even more excitement.
Getting on the roof is pretty suicidal but we may be able to get the binoculars and see if there's anything.
I love your feedback on my other replies as well. I'm really trying to wrap my head around this and up my game a bit.
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
When is the last time you cleaned your chimney and stove pipes? Lets see the cap?
I cleaned the chimney just before this winter hit. It was the very first time and there was definitely stuff on the pipe but I don't think it was considered bad. I may have pictures on another post here of the chimney.
I really don't think we have a way to get to the cap...
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,654
central pa
So I have thrown the door open a couple times when I got distracted and let the stove top temp get slightly above what is "normal" on this thermometer. Should I just stop that? If the top end of normal on this thermometer is just under 500 should I just not worry about it until it hits closer to 600?
is there any way I could have had flue temps of 1200 with STT of 500 without a chimney fire?
I think you are using a pipe thermometer for a stove top thermometer. 600 is not to hot for a stovetop.

Opening the door is really just a last resort for a runaway stove that you can't get under control. Just shut the air back
 

MongoMongoson

Member
Feb 6, 2021
173
Wisconsin
is there any way I could have had flue temps of 1200 with STT of 500 without a chimney fire?

Yes, the flue can heat up much faster than the stove top when you get your stove really roaring. Lots of air, lots of fuel, lots of heat up the stack. I don't know how thick your top is on your stove, but imagine it's like 3/8" thick steel, or maybe cast iron in your case. It weighs a lot. It takes time for heat to transfer through the metal to the outside, and there is lag on both your thermometers. The bimetallic strip types take time to respond to temperature changes, and your temperature was probably ramping up pretty quickly.
 
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Woody Stover

Minister of Fire
Dec 25, 2010
12,266
Southern IN
is there any way I could have had flue temps of 1200 with STT of 500 without a chimney fire?
On a startup like you did, with a bunch of small wood, flue temps can rise fast whereas the stove top may take longer to heat up.
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
I think you are using a pipe thermometer for a stove top thermometer. 600 is not to hot for a stovetop.

Opening the door is really just a last resort for a runaway stove that you can't get under control. Just shut the air back
Ok. I'll look when I get home but I bet you're right. I will cut the air back from here on out.
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
Yes, the flue can heat up much faster than the stove top when you get your stove really roaring. Lots of air, lots of fuel, lots of heat up the stack. I don't know how thick your top is on your stove, but imagine it's like 3/8" thick steel, or maybe cast iron in your case. It weighs a lot. It takes time for heat to transfer through the metal to the outside, and there is lag on both your thermometers. The bimetallic strip types take time to respond to temperature changes, and your temperature was probably ramping up pretty quickly.
Totally helps. I'm starting to get it now I think.
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
We've been discussing our wood and trying to decide what's good and what not. If I understand right, wood that has been laying around for years but not cut up or split would still be considered to be not seasoned, right?
We love to put one big round in the stove for the night. That's about all that will fit. Is that round going to be something that creates creosote since its never been split and may still have a higher moisture content in the center?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,654
central pa
We've been discussing our wood and trying to decide what's good and what not. If I understand right, wood that has been laying around for years but not cut up or split would still be considered to be not seasoned, right?
We love to put one big round in the stove for the night. That's about all that will fit. Is that round going to be something that creates creosote since its never been split and may still have a higher moisture content in the center?
Get a moisture meter. No need for anything fancy or expensive. Then split open a few prices and test on the fresh face. That is the best way to know for sure
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
Not horrible but definitely room for improvement
Probably consistent with too low of temps on a regular basis? That was a years worth of burning I think. We have burned a lot of wood since that sweep with our recent cold snap. Should we pull it apart now and check it or would we probably be ok to just finish out the season?
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,766
South Puget Sound, WA
So I have thrown the door open a couple times when I got distracted and let the stove top temp get slightly above what is "normal" on this thermometer. Should I just stop that? If the top end of normal on this thermometer is just under 500 should I just not worry about it until it hits closer to 600?
is there any way I could have had flue temps of 1200 with STT of 500 without a chimney fire?
Yes, it's possible with just a normal fire with the air control left open too long. It's happened to me and why I have an alarm on the thermometer. It's just too easy to get distracted.

We've been discussing our wood and trying to decide what's good and what not. If I understand right, wood that has been laying around for years but not cut up or split would still be considered to be not seasoned, right?
We love to put one big round in the stove for the night. That's about all that will fit. Is that round going to be something that creates creosote since its never been split and may still have a higher moisture content in the center?
Rounds dry slower than splits. I'll bet if you split open that round that the moisture content is higher than expected.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,654
central pa
Yes, it's possible with just a normal fire with the air control left open too long. It's happened to me and why I have an alarm on the thermometer. It's just too easy to get distracted.
No idea what condition your chimney is in without seeing it. If burnt properly you can easily go s year. Or it can need cleaned in a month. It depends on your fuel and operation
 
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Shorty

Member
Jan 10, 2017
19
Texas Panhandle
Get a moisture meter. No need for anything fancy or expensive. Then split open a few prices and test on the fresh face. That is the best way to know for sure
Ok. I have a cheap moisture meter that works if I hold my tongue right. I'll test a few. I guess they would just need to season a bit longer than splits..
 

Shorty

Member
Jan 10, 2017
19
Texas Panhandle
Yes, it's possible with just a normal fire with the air control left open too long. It's happened to me and why I have an alarm on the thermometer. It's just too easy to get distracted.


Rounds dry slower than splits. I'll bet if you split open that round that the moisture content is higher than expected.
Oop. Didn't get caught up before I asked. That's what I was wondering. Will absolutely check.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,654
central pa
Ok. I have a cheap moisture meter that works if I hold my tongue right. I'll test a few. I guess they would just need to season a bit longer than splits..
Yeah a bit longer like an extra year or two or three depending upon size and species
 
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