Mini chimney fire?

[dh1989]

I've been doing a hot reload late at night since it's been so cold and I've been running the stove hot. I turned the thermostat up all the way and opened the bypass, waited 1-2 min and opened the door. Fire blazing at the back of the box with a strong draft. Stuff it full of wood, close the door and bypass. Suddenly I hear the cracking metal expanding noise and smell paint cooking. Flue probe is reading 1100F. I cut the thermostat and heard the raining creosote noise very briefly in the pipe. It stopped within a few minutes and the flue clinked it's way back down to 400F. I never made it outside to check the stack before it stopped.

I last cleaned the flue a few weeks ago using my sooteater and got a small amount of flaky creosote out. I doubt there was much in there. My theory is that the strong draft sucked the flames up the open bypass and ignited whatever was in there, which quickly burned off.

Any thoughts or recommendations? Is this common with a hot reload?

 

[jb6l6gc]

Had that kinda on a reload on furnace recently. Don't think it was so much a chimney fire as much as wood taking off too fast

 

[kennyp2339]

I have that happen at least once a year with this stove and a few times with the other stove, I also clean my chimney 3 times a year and really never get a lot of crud, while its possible that some creosote that is stuck to the pipe call fall off making that noise, I firmly believe that it's the sound of the metal chimney pipe expanding.
Think about it, with everything running flue temps on out stoves hold between 350 & 400, open the bypass and suddenly get a spike of 800 or more, that's going to cause some rapid expansion then contraction when the bypass is closed, especially if it's cold outside

 

[saskwoodburner]

I'm with kennyp2339 on this, I'd say it's the metal expanding from rapid heating.

 

[dh1989]

I noticed today that I now have a black ring about 3' up the double wall pipe where the paint discolored. Also noticed my flue probe had the face aimed at an upward angle and was actually jammed in the pipe. It appears the inner liner moved a bit with the expansion. I slid it back using the probe and my thermometer slides in and out easily once again.

(broken link removed)

 

[rdust]

Had it happen to me twice since owning my BK. Flames get sucked up fast with the bypass open and can really overheat the pipe/chimney. Once was the day after cleaning the chimney so no fuel for a fire. Strong draft days and hot reloads I close the bypass as soon as I have flames. Also try to load the stove without a gap down the center of the stove. When I leave the gap it like a blast furnace down the center and right up the flue. A split placed dead center usually saves the drama.

 

[Highbeam]

Burning with the bypass open and 1000+ degree flue temps is a problem. Quit doing that. The length of time that you burn with the bypass open to heat the flue and improve draft for reloading must be minimized to only the time needed. By dumping all of that heat straight up the flue you also risk melting the bypass gasket retainers.

On your photo with the black ring. That looks like the end of the overlap inside your telescoping section. There is a point on your flue where there are four layers of metal between flue gas and the outside. Your overlap looks to be fairly small like 6". Nothing you can do now.

You know it got hot and I suspect the open bypass was the problem and not a creosote fire. That's why the discolored paint stops as you go up.

Where your probe meter sits there is only two layers of metal and the inner layer can't move independently permanently. The inner layer is stainless steel and gets hotter so if you drilled the hole when the pipes were cold you will find that the face of the meter points up more when the flue gets real hot. It will go back when cool.

 

[begreen]

If the sounds was like rice showering down in the chimney it was probably a layer of sote burning off. If the sound was more of tick click sound then probably metal heating up.

 

[2broke2ride]

I had a full fledged chimney fire last winter from doing this, old smoke dragon with no baffles and a hot reload plus burning poorly seasoned wood where all contributing factors.

 

[dh1989]

Thanks for all the input. It was the raining rice noise so I suspect it may have been some creosote burning off. It didn't last very long. I keep an eye on the flue by sticking my phone up into the bypass when the stove is cold and snapping a picture every now and then. There couldn't have been much in there to burn off.

I wonder if my issue is the way I'm doing the hot reloads. I open the thermostat all the way and wait a minute or so. Next, I open the bypass and wait another minute or so. Then I slowly open the door. By the time I get the door open the dark firebox is now blazing like a blast furnace with the remaining wood chunks at the back and empty space to fill at the front. I shove in as much wood as I can, which typically ends up going in E-W. This can take a few moments as I want to make sure the wood is stable and not going to roll out against the glass as I close the door. Bypass is closed immediately when the door closes and I then start dialing back the thermostat.

The night this happened it was about 20F with winds of around 15-20 MPH and I was reloading with 12-15% MC birch which lit very fast. I suspect the strong draft was a factor, but want to make sure I'm using the best burning practice for safe hot reloads while giving the cat a chance to cool before opening the door. Is there anything I should change?