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Martian
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# Posted: 5 Mar 2012 14:35 - Edited by: Martian
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Well, I've been living in my place for 6 months, and this morning, my wood stove didn't want to burn, and even though I have double wall pipe, there was creosote running down in a couple of places. HMMM. I'd noticed over the last few days that smoke had started billowing out whenever the door was opened; something it never had done before. So, when it didn't want to burn this morning, I decided to check the flue. Luckily, its easy for me to do, or at least, relatively easy. I got the ladder and climbed up onto the roof. When I approached the chimney, it was pretty evident that the cap was clogged. I removed the cap and saw the top of the triple wall pipe was practically closed off with a black, lacy, very brittle material. I tried to get as much out as possible, but some fell down into the stove. It didn't extend too far down the pipe, maybe 12" or so, but it had completely blocked the pipe. The stove is now burning at its usual efficient self, again.
What happened? Well, we've had a pretty mild Winter, and I've closed the damper quite often to keep it from getting too warm in the house. In addition, the stove has spent many hours on slow burn while I was at work or sleeping. Even though I use only well seasoned hardwood, the stove wasn't burning efficiently with the damper closed. My stove is rated for 1000sqft and I have only 500sqft of well insulated space. It wasn't the stove's fault, the chimney's fault, or the wood's fault; it was my fault.
I remember reading about how important it is to properly size your stove to the space it will heat. This experience has taught me what happens when you try to control the heat in a stove that is somewhat over sized for the space. I'm not going to change the stove, but I will change my procedures. From now on, I'll monitor the chimney on a regular basis and open a window when I'm home instead of closing the damper. While I'll still dampen it down at night, it won't be as far as before, and I won't load it up so much just before going to bed.
Now, I'm going to use some mineral spirits and try to clean the creosote off the stovepipe. I hope somebody learns something from my experience, but then, maybe all of you guys/gals already knew this stuff.
Tom
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toyota_mdt_tech
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# Posted: 5 Mar 2012 14:47 - Edited by: toyota_mdt_tech
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Green wood will do that. Let it season, it can be wet, just not green. You are lucky you didnt have a chimney fire.
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trollbridge
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# Posted: 5 Mar 2012 15:15 - Edited by: trollbridge
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 Glad you got it cleaned out Tom...........you don't need to be smoked out of your own place! Good thing you were home today and not out working while a fire was burning inside your chimney..............not good!!!!!!!!!
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MtnDon
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# Posted: 5 Mar 2012 15:45
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As you found out even well seasoned wood can produce creosote build up when the stove spends a lot of time in a very slow burn mode. It's an easy error to make.
We let the interior cool off to 58 -60 most nights and then do a very hot burn to get the chimney very hot first thing in the AM. Even burning mainly pine (seasoned two and three years) the chimney seldom has much creosote. Most of it within the last foot or so below the cap as that is the coolest portion.
It's nice to have the chimney top easy or at least fairly easy to access.
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Martian
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# Posted: 5 Mar 2012 17:07
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The wood I use is Bodark, also known as hedge and Osage orange, that has "seasoned" for many years. It is very hard and dense and burns really hot. I just screwed up by damping it down too much.
The easiest way I found to remove the creosote from the chimney cap was to use my propane torch and burn it off. The little streaks down the outside of the stove pipe weren't even touched by mineral spirits. But, I have a nice clean chimney again. Just in time for a little cool weather later this week. Good thing a friend has a chinmey brush and extensions.
Tom
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trollbridge
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# Posted: 5 Mar 2012 20:44
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Quoting: Martian The easiest way I found to remove the creosote from the chimney cap was to use my propane torch and burn it off. The little streaks down the outside of the stove pipe weren't even touched by mineral spirits.
Good to know! Thanks for the info Martian.
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SE Ohio
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# Posted: 5 Mar 2012 20:57 - Edited by: SE Ohio
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I've attached a picture of my cabin stove pipe as left by the previous owner. I don't know how they ever got a fire to light! Fortunately I checked the pipe before my first fire. Was I surprised!
I pulled the indoor pipe and gave it a whack. The creosote crumbled to nothing. I was able to slap the vertical pipe but it had much less buildup. I've read that the horizontal sections get the most build up (as shown in my picture)
Lehman's sells a stove pipe thermometer that shows when a fire is too cool or in the "creosote zone". Small split wood pieces give a good hot fire.
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TomChum
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# Posted: 5 Mar 2012 22:10
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Quoting: toyota_mdt_tech You are lucky you didnt have a chimney fire.
Has anyone had a chimney fire? What happens? Can you have a chimney fire with an airtight stove (doors closed etc)?
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turkeyhunter
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# Posted: 6 Mar 2012 05:34 - Edited by: turkeyhunter
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Quoting: Martian Bodark, also known as hedge and Osage orange,
that is really pretty wood ---too nice for fire wood!!!! 
glad you got it fixed Martain and glad you did not have a chimney fire!!!!
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Martian
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# Posted: 6 Mar 2012 06:33
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Quoting: turkeyhunter that is really pretty wood ---too nice for fire wood!!!!
It is a pretty wood! But, its really difficult to find planks without checks and cracks. I have several hundred Bf of slabbed out planks 1 1/2" thick. I'm saving them for a table I'll build some day. The local saw mill gets $10-12/bf for it. Recently a farmer had a hedgerow cleared. I had hoped to get some of the larger trunks for lumber, but they had all split when the dozer pushed them over. All the woodburners around here decended on them like a flock of vultures.
Tom
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Martian
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# Posted: 6 Mar 2012 06:51 - Edited by: Martian
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Quoting: TomChum Has anyone had a chimney fire? What happens? Can you have a chimney fire with an airtight stove (doors closed etc)?
Tom, I've never had a chimney fire, but based on how the creosote reacted when I was burning it off the chimney cap, I'd say it would take a LOT of creosote to sustain a fire. When I hit the roughly 1/8" thick congealed creosote with the MAPP gas, it expanded like spray foam and formed the lacy, honeycomb like residue. The residue seemed to act as an insulator because, even if I held the flame in the same spot, it quit expanding. But, after brushing off the residue and applying the flame again, it would once again expand. It took three or four applications of the flame to get down to bare metal. There were practically no residual flames after the heat was removed.
I think a properly sealed stove and pipe would prevent enough oxygen being available to support a fire if the doors were closed. Chimney fires would be a much greater risk with an open hearth fireplace than with a freestanding stove, I would think. Now, if somehow, there was air available from a leak in the stove pipe/chimney, then closing the doors would be less effective obviously.
Tom
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TomChum
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# Posted: 6 Mar 2012 11:08 - Edited by: TomChum
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I had a similar experience, sort of. I burned a lot of pine over the course of about 4 days. Creosote was even dripping down into my stove one morning, & oozing out of leaks in the stovepipe, dripping onto the floor.
I was changing to a shorter (bigger) stove, and I had to add a foot of pipe, and adjust the slider connection too, and I thought it would be all gummed up.
I stuck a propane roofing torch inside the flue, from below, and blasted it up for awhile. It "seemed" like it also cleared some blockage, because it seemed like the flow/draft increased. But this was not a passive "draft" situation, it was a propane BLAST.
But anyway the flue got hot as expected and I could see a change in the surface color as the hot-zone moved up the stovepipe. I did not see it turning red as it was daylight. What I was seeing was a different shade of grey advancing up the stovepipe. My assumption was that the "visible" hot zone was advancing just behind as the inside creosote layer burned away. Some "ash" came down. Not a LOT, but a noticeable amount.
Having a safety observer to watch would have been wiser but I was all by myself (!) so no wisdom anywhere. Also I would remove the chimney cap if I had to do this again. My "safety net" was the expectation that if the creosote started to burn too hot I would close up the airtight stove and shut off the torch (no wood burning either). I would not have done what I did, on a "house", with neighbors, or with a flue going thru a 2nd story chase, etc etc etc. It's just a 17 foot straight vertical pipe.
I took the stovepipe down, and laid it on the ground outside. There was still creosote in there. I took my propane roofing torch and blasted it (inside) horizontally on the ground, and could see more clearly the surface gray moving 'up' the pipe. Then I tapped on the pipe and ash fell off and the pipe was clean (sort of, clean enough to work on), and I was able to work the slider and get my job done.
I'm fairly interested in this "chimney fire" issue, wondering if it has become just an old husband's tale in relation to a modern airtight steel flue. Does a genuine chimney fire require an un-controllable flow open hearth and a pile of bricks with crumbling mortar?
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exsailor
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# Posted: 6 Mar 2012 14:29
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I have heard throwing a box of baking soda in the stove willl kill a chimmney fire once it starts. I have also been told a road flare on the stove will do the same thing. Don't know if either one of those are true, but I would hate to be in a situation to have to test either one.
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MtnDon
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# Posted: 6 Mar 2012 14:45 - Edited by: MtnDon
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I am not certain on this, but I think a chimney fire is more likely with an open hearth fireplace than with a wood stove. I also think it is more likely with a masonry chimney but could be dead wrong on that. For certain with a wood stove that has a door it is easier to get things under control. Closing the door helps. Closing a flue should also help. There are even chemical sticks that help smother a fire once they are chucked into the fire.
You hear a woosh, a roaring that increases in intensity. I've not had the experience, just read about them. There are also a few videos on youtube.
Here's one
If you ever have one there is great danger that the chimney can be damaged and cause a serious house fire when the next fire is started. Chimney fire = time for a thorough inspection.
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TomChum
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# Posted: 6 Mar 2012 15:17 - Edited by: TomChum
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Good stuff. Lots of scary looking chimney fires on YouTube.
If a steel chimney gets hot enough, I wonder if it can burn a hole in itself, then closing the doors on the stove won't stop it. Stainless steel would add a level of safety over carbon steel.
I suspect a tall chimney poses more danger than a short chimney. And the amount of flammables nearby to the chimney adds more danger. The taller the chimney the more creosote/fuel it holds, and it also may have more draft.
One of the comments I read on YouTube was to pour water on the fire from below, and the draft will carry steam up the chimney, reducing the temperature. I suppose you would not want to let air into the fire, except for the short period while it was carrying steam up the flue.
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groingo
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# Posted: 6 Mar 2012 16:17
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This has been a mild winter for my 200 square foot place as well, have had to clean the chimney out twice so far, burning 3 year old very dry wood but was damping down after 9:00 in the evenings to keep from cooking myself out and getting up at 3 in the morning to open all the windows because of over heating.
Now I add no new wood after 8:00, have a divider between my sleeping area and living are so if it does over fire I just need to cool my area and not the entire place, plus the cat loves it hot!
Have been through my share of chimney fires, usually the most dangerous thing is if you try to let it burn out it melts the chimney cap which falls down onto the roof and that is where the real trouble can start especially if you have a Comp or wood roof, so I have learned to just check the pipe on a regular basis and avoid the whole darn mess.
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PA_Bound
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# Posted: 7 Mar 2012 08:51
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I would agree with groingo- don't fool around with chimney fires. They almost always damage your flue and can indeed (albeit not always) burn your place down- as a firefighter I've witnessed that first-hand.
A couple thoughts to remember:
A chimney fire does not require an old, crumbling chimney to be dangerous. Chimney fires burn very hot. The high temperatures will exploit any cracks that already exist, or possibly create them on their own. Also, if tolerances are not adequate, the fire can sometimes spread even where no cracks exist.
If you have a fire, put it out. The easiest and safest method is to pull out your trusty A-B-C fire extinguisher (every cain has at least one, right!?! (mine will have 5, by the way)) and shoot it into the fire box. The draft of the actual fire will pull the chemicals into the chimney and extinguish the fire. It doesn't even take all that much. Don't use water. It's more dangerous and the steam can actually further damage some chimneys.
With the fire out, immediately inspect your cabin- particularly the roof and any enclosed areas around the flue. If the fire was in my cabin, I personally wouldn't leave the place unattended for the next 24 hours. I'll start the coffee and maintain a fire watch.
Get your chimney inspected before using it again. The problem is the heat of chimney fires almost always damages the flue- greatly increasing the risk of a cabin fire.
And don't forget to get your fire extinguisher serviced after using it- even if it's not completely empty.
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Martian
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# Posted: 7 Mar 2012 09:12
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There has been some very useful information posted by my fellow cabin builders.
In the future, I will check/clean my chimney every month or so during the season. I will have another fire extinguisher in the house. I will modify my habit of loading up the stove just before going to bed or leaving for work and turning down the air; from now on, I'm going to add the wood earlier and let most of the gassing take place before I close the damper. In addition, I'm splitting my wood into smaller pieces and adding it more frequently to a smaller fire to better match the heat requirement/heat output.
I now have a clean chimney pipe, and the stove is back to its happy self. Thanks to all who contributed their thoughts and experiences. I hope someone benefited from this conversation. I know it has enlightened me as to the mistakes I made.
Tom
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analogmanca
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# Posted: 7 Mar 2012 14:31
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I am not one bit worried about a fire. Heated with wood for a decade+ with a heavly modified blazeking fireplace.
I have settled in to using Birch or Tamrack, but used all types over the years. Keep it dry let it dry out for at least one year, in racks not a pile.I have mine sit for at least 2.
Remove the cap completely, once I did that it cut creosote down by half.I suspect the fires that burn homes down are caused by the creosote that falls off this cap. I put the cap back on in the spring just to stop rain.With the cap on I was getting staining around the base of the stack.
Keep the chimney as short, and straight as possible.
It takes a lot of creosote to burn. In the pic you can see the creosote, but it is really a thin 1/8 thick layer after a week or two with the air choked back. I just burn it out with a hot fire, or let the fire cool way down, and often as everything contracts you can hear it break away, and fall back into the stove to be burnt.
When I say I dont worry its not because I am careless its because I check the chimney at least once a week. In the pic you can see the short section of chimney with the door swung open.(I choked back the fire so it would smoke for the pic) Checking is easy I just swing the door open, lean in,and I can look straight up, and out the top. Takes all of 15 seconds to do, and no having to go out side when its -30-40. I think with how tightly you can control the incoming air in theses new stoves having a run away chimney fire is much less likely.
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TomChum
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# Posted: 7 Mar 2012 15:11 - Edited by: TomChum
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Quoting: analogmanca Remove the cap completely, once I did that it cut creosote down by half.
This concerns me a bit, because I have a lot of pine needles on the ground, and at times on my roof.
Quoting: analogmanca Keep the chimney as short, and straight as possible.
Quoting: analogmanca I think with how tightly you can control the incoming air in theses new stoves having a run away chimney fire is much less likely.
These make sense. Thanks for your post. I made a new thread with a very specific subject for this important small-cabin-related topic.
http://www.small-cabin.com/forum/1_1926_0.html
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MtnDon
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# Posted: 7 Mar 2012 16:25
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No cap, or a cap without proper spark arresting, is a recipe for causing forest fires in most of the western parts of the country, not to mention illegal in some areas. It would not be a responsible thing to do, IMO.
As far as flue length, shorter is better, to a point. Many newer, EPA listed, stoves have definite manufacturer recommended minimum lengths to be sure of sufficient draft under all burn conditions. Some stoves will also have maximum lengths for the interior black pipe, FYI.
Straight runs are best for certain. try especially hard to avoid right angle bends like the ones where the chimney exits the stove back and makes the 89 degree turn outside.
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analogmanca
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# Posted: 7 Mar 2012 17:45
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MtnDon,
Its winter, a foot of snow on the ground, who heats in the summer? Even so, if I tried to blow sparks out my chimney I would have to have the air control wide open, and that would cook me out of the house. Not going to happen.
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