Loose Creosote Flake Accumulation Falling Down Chimney

[wjohn]

I completed my pre-season cleaning today now that wasp activity is slowing down. There is a decent amount of very dry, light, loose flaky creosote on top of the insulation blanket/baffle area under the stove outlet. It's the stuff that falls down from the walls of the chimney during use, when the wind blows, etc. I cleaned about halfway through last year and found about the same accumulation, so this is more or less what happened in the second half of the burning season. At the time I chalked the initial accumulation up to some of my break-in fires and the learning curve of using this stove.

I burnt almost exclusively 14-17% MC mulberry last year after the first cleaning. Am I doing something wrong here? Is there something I can learn? The chimney itself looked pretty darn good when I cleaned today. Mostly I am annoyed since it winds up covering the temp probe that operates the air inlet damper in my Aspen C3.

 

[Kevin Weis]

Looks like its accumulating on the stove pipe when it's cool then when it heats up dries to a flakey coating then falling off. Maybe start up fires need to be hotter to prevent this. Does this stove have a permanent air intake setting (non-adjustable)? If so then only recourse is adjusting your burning habits likely.

 

[Eman85]

I can bang on my stovepipe and shake stuff like that loose

 

[EbS-P]

If run efficiently the flue temps may cool off enough and you get some condensation on the coldest part of the flue. I’m not seeing anything alarming. We have to clean burning is dirty. Are you restricting the intake? I forget.

 

[wjohn]

This stove has the air intake automatically controlled by a bimetallic coil strip attached to the other end of that temp probe. I have a blast gate on the intake so I can damp it down if it really gets raging but otherwise I don't normally restrict the intake.

I too am wondering if it's a skim from startup that then peels right off once the temp gets up. I've gotten top down figured out pretty well in this stove so I'm not sure how much more I could improve smoke on startup, other than using a blowtorch.

I'm thinking I may just have to live with it. It doesn't take long to pop the three screws out for the stovepipe connector and slide the telescoping portion upwards, so I may just have to clean this spot more frequently... Kind of annoying, but really not that hard to do.

 

[EbS-P]

This stove has the air intake automatically controlled by a bimetallic coil strip attached to the other end of that temp probe. I have a blast gate on the intake so I can damp it down if it really gets raging but otherwise I don't normally restrict the intake.

I too am wondering if it's a skim from startup that then peels right off once the temp gets up. I've gotten top down figured out pretty well in this stove so I'm not sure how much more I could improve smoke on startup, other than using a blowtorch.

I'm thinking I may just have to live with it. It doesn't take long to pop the three screws out for the stovepipe connector and slide the telescoping portion upwards, so I may just have to clean this spot more frequently... Kind of annoying, but really not that hard to do.

Thinking a little more. That part of the stove has to be hot. Anything that falls will probably start to thermally decompose if it doesn’t outright burn off. The act of unscrewing and sliding pipe sections may knock it loose too. If you didn’t find a large pile of ash covering the probe I wouldn’t be concerned. If you still want piece of mind adding probe thermometer to measure flue gas temps could easily be done.

 

[wjohn]

Thinking a little more. That part of the stove has to be hot. Anything that falls will probably start to thermally decompose if it doesn’t outright burn off. The act of unscrewing and sliding pipe sections may knock it loose too. If you didn’t find a large pile of ash covering the probe I wouldn’t be concerned. If you still want piece of mind adding probe thermometer to measure flue gas temps could easily be done.

It's hot but I don't think hot enough to burn that stuff off. I can check after we get into fire season here in a couple more weeks (maybe?) but I found the same thing the last time before I cleaned, and that would've been only a day or two after a fire vs. this time, when the pipe had had half a year for stuff to fall down. The probe was buried under that stuff (first pic). I wasn't clear but the second pic is after I had most of it scooped out, just to show where the probe was hiding under all of that.

The air intake flap tends to close down more slowly on a cold start as time goes on and I suspect this is the reason why - it takes longer to heat that probe up when it's covered. After I cleaned last time it responded well for a while but then I think the creosote built up again. Not the best spot design-wise, or I'm doing something wrong. I will do my best to get fires roaring as quickly as possible.

 

[EbS-P]

Well that’s more than I would want to see too. It looks thicker too now that I look at it again. And some looks shiney. You are double wall up to class A

 

[wjohn]

No, that's a fair point. I have single wall. That's an area that might gain me some improvement. For now lifting the pipe up and cleaning out this spot is probably the cheapest thing to do.

 

[EbS-P]

I guess you could try to figure out which section it’s accumulating in.

Smaller splits would burn faster. That’s about the only control you have. Musing more kindling on cold starts to get it all hot faster.
Some point in the burn cycle it’s not hot enough somewhere. I was trying to come up with a way to capture it before it fell on the probe. Only thing I could think of was a and angled section of pipe with a T just above the the bottom 45.

Monthly or every other week cleaning is probably best fastest most simple option followed by installing double wall. Do you have a pipe thermometer. Just the cheap magnet one would be a start.

 

[wjohn]

I'm usually burning about the biggest stuff I can fit, but for a cold start I do top down with smaller stuff up top and the magnetic stovepipe thermometer is normally indicating above 300 by the time the smaller stuff has burned down enough to reach the big piece(s). Up towards the ceiling it could be a little cooler. I can pay more attention to that this year.

I do think most of the flakes are coming from lower down in the pipe. The cap was in really good shape other than a thin but well-adhered layer around the inside, right at the exit from the class A chimney. Looking down the chimney seemed pretty good pre-cleaning.

I was also trying to figure out a way to protect or relocate the probe without blocking flow. I see what you're saying on the T and I like it. I have back to back 45s close to the adapter in the ceiling. I could relocate the 45s to right off the top of the stove, and move the stove out enough to stick a T between them and catch anything falling from 95% of the pipe/chimney... But that's going to look pretty weird, and my house is small. I'll do what I can with fast startups and just lift the pipe to clean out now and then. I won't need to sweep the chimney to clear out that pile of flakes.

I'm happy to enjoy the 75 degree days and stay out of my wood supply as long as possible until then... I am looking forward to it, though.

 

[EbS-P]

I think the 45s and T is more work and takes more space than it’s worth. I wouldn’t want to mess with moving the probe. I couldn’t come up with any deflector ideas that would work well. It going to pile up on something. And most of my ideas would
have restricted flow enough that I would be hesitant. So a quick clean every month would be my plan.