Princess not working with my Flue?

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New Member
Dec 12, 2022
Hey all, I've posted a few times now about having troubles with creosote buildup in my flue with a new BK Princess this season, and I'm wondering if it just isn't going to work with my flue setup.

Quick background, I had an insulated liner put in an existing masonry flue. This was initially done incorrectly by the chimney sweep, but has since been corrected.

I was still getting more smoke produced and creosote build-up than seemed appropriate, turns out I wasn't fully latching the catalyst shut, with that fix, smoke out the top of the flue seems very good.

A week ago, I put in a new shorter double wall pipe section to make the horizontal run in to the flue as short as possible. After a week of burning, that brand new section (along with everything else horizontal, that I cleaned at the same time) is completely glazed over with a thin, hard layer of shiny creosote, which is exactly the same problem I'd been having previously.

My flue setup is less than ideal in a few ways, none of which I was told would be a concern when I bought the stove or had the flue lined. The chimney sweep doesn't seem to know anything about cat stoves, and since I bought the stove used (from a dealer), they haven't seemed very invested in things. First off, the stove runs as well as I expected when I bought it. I'm not experiencing any obvious draft issues; no pooling of smoke, no blowback when opening the door on reloads, etc. Once I got all the controls and use right, I've been satisfied with burn times, I can set the thermostat and it will not need adjustment unless I want more or less heat in the house, and the cat stays well in the active range at low air settings and has no problem getting up to max temp if I leave the thermostat at or near wide open.

My flue setup itself is as follows: I have 33in from stove-top to the bottom of the pipe where it enters the flue thimble. I'm using 2 45 degree elbows to make the 90, so the vertical run is about 25in from stove top until the first bend of a 45. The 2nd 45 is attached directly to the 1st, and it is also attached directly to the thimble adaptor piece, so there is about 4-5 inches of horizontal run before the thimble into the masonry chimney. The thimble itself is roughly 9 inches before meeting the vertical flue. The flue then only runs about 12 inches before taking a 45 degree angle for about a foot, and then goes vertical for about 23 more feet to the top of the chimney. When I bought the stove, the shop only mentioned I needed 24in from stove-top to the bottom of the horizontal run, but in reading the finer print on the stove manual, blaze king recommends 3ft before the first bend in the pipe or flue. I'm wondering if the relatively cool flue temps of a cat stove, plus all of the bends and non-vertical runs in a small section of the flue are causing the flue gasses to travel too slowly, causing the build-up.

I've been running sub-20% MC wood all season, but to try and give the stove its best shot in this past week's test, I took some wood from my parents, who no longer burn, but keep about a cord as backup in an enclosed shed. This was all 3-10 year old oak, measuring 12-15% MC. I also ran the stove a bit hotter than needed, keeping the probe thermometer above 400 at all times (until down to a coal bed when it couldn't stay above 400 at any setting). did 1 cold start after the new pipe install, and I don't think the cat went down to inactive a single time otherwise in 6 days. I could try running the stove even hotter, but I was running it hot enough that I was only getting about 8 hour burn times on a full (but not tetris stacked full) load, so having to run it even higher would be defeating most of the benefits of the BK stove.

So, I'm not sure what else I can do to make this stove work in my flue. I'm open to any and all suggestions, maybe there is a creosote removal/converter product that may help? I'm happy enough with the way the stove itself has worked that I would be ok with having to do multiple cleanings a season, but what I'm getting is baked on, shiny creosote in under a week, which is difficult to clean and seems like an unsustainable cleaning interval.

Would a modern non-cat EPA stove have these same problems? The pre-EPA VC Defiant (circa 1980) that was in the house seemed to have much more normal buildup (just needing a yearly sweep) for the winter I used it in the same flue before it was lined.

Thanks for everyone's help.
Where is your probe thermometer? What kind? And did you check its calibration?

Thin glaze you said how thin? What does the liner look like how about up at the cap?

Where is the cat probe running?

Never use creosote remover in a cat stove it will poison the cat.
Condor probe thermometer, located about 20in above the stove-top. I have not checked the calibration. What would that involve, putting in the oven?

1mm thick, maybe. Ive attached pics from both ends where the pipe goes into the thimble adaptor and from where it attaches to the stove. You can see on the pic from the thimble end the clear line from where it goes into the thimble adaptor (clean/grey steel with a distinct line to the shiny black). That line is thick enough to feel running your fingernail across, but no more.

The flue pipe going up looks better than the horozontal pipe, though not great, probably 70% of whats visible is light grey build-up, interspersed with maybe 30% of blacker creosote. It is a little more crunchy/flaky looking and not glazed. I can only see about 2-3 feet up though, do to the 45 degree turn it takes. I need a 25ft ladder to get on my roof, so inspecting that would take till the weekend and I can get someone to help me set it up.

Cat probe runs at about 2 o'clock at the temp setting ive been using this week (with the fan on, that supresses its readings a bit). If I turned the fan off the cat probe would be reading about 80-90% of the way to max, for the first 3-4 hours. After about 4 hours of an 8 hour reload it would be down to 12oclock, and then slowly work down from there to around 10 o'clock when I reload at 8 hours.

Princess not working with my Flue? Princess not working with my Flue?
I see nothing to worry about with those flue pictures.
I see nothing to worry about with those flue pictures.
I don't know that's a fair amount of glaze in the pipe for a week of burning