2022-2023 BK everything thread

Question for you guys. I try to keep my flue temp at 250 or above. For those who have run longer burn times (24 hours or more), how low do you let your flue temp get?
I’ve never actually run my stove so low that the cat went out of the active zone during the burn. So I don’t know when that will actually happen.
I’m regularly getting 20-24 hour burns (and still overheating the house), just wondering what it takes to get up to 30 hours.

For what it's worth, in 32 years I've never worried about flue temps. I burn on high for 20 minutes or so, then close it down.

DonTee said:

Question for you guys. I try to keep my flue temp at 250 or above. For those who have run longer burn times (24 hours or more), how low do you let your flue temp get?
I’ve never actually run my stove so low that the cat went out of the active zone during the burn. So I don’t know when that will actually happen.
I’m regularly getting 20-24 hour burns (and still overheating the house), just wondering what it takes to get up to 30 hours.

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I go for 24 hours with Doug fir softwood and internal flue temperatures measured with a probe meter hold pretty steady at 400 until the end. You can go lower but at some point the temperature at the top falls below 212 and you could get a gooey tar mess.

I have pitch pine in. This is a piece that I actually measured (i.e. it's half of a split) - it was 14 pct moisture content.

The pitch is melting out... It started with bubbly yellow whitish foam (burning, so not water,. consistent with the mc). A few hours later it is a goey blob of tar that's breathing....

Some splits stay dry, others sweat out a ton of pitch. During the charring phase they can even drip. I've seen drips going into fluffy ashes, creating a circular hole that then gets a candle flame from the burning pitch. (Video, flame right below the stock).

I hope the cat does its thing ...

stoveliker said:

I have pitch pine in. This is a piece that I actually measured (i.e. it's half of a split) - it was 14 pct moisture content.

The pitch is melting out... It started with bubbly yellow whitish foam (burning, so not water,. consistent with the mc). A few hours later it is a goey blob of tar that's breathing....

Some splits stay dry, others sweat out a ton of pitch. During the charring phase they can even drip. I've seen drips going into fluffy ashes, creating a circular hole that then gets a candle flame from the burning pitch. (Video, flame right below the stock).

I hope the cat does its thing ...

View attachment 304486

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You can even hear it hiss like water would when starting a fresh load of pitchy wood.

stoveliker said:

MidWest Hearth should have them. Don't know if they ship to Europe.

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Are they selling authentic, the same quality ?

Highbeam said:

I go for 24 hours with Doug fir softwood and internal flue temperatures measured with a probe meter hold pretty steady at 400 until the end. You can go lower but at some point the temperature at the top falls below 212 and you could get a gooey tar mess.

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I’m trying to figure out how low I can go without the “gooey tar mess”. So far I’ve been burning for over a month like this pretty consistently. And the chimney still looks good.

If I’m at 250 degrees 18” above the stove, the smoke still has to go another 20’ to the top of the chimney. It is a newer triple wall chimney, so heat loss should be lower, but still there of course.

This is a new to me stove. So I’ll probably check the chimney once a month during the burn season. For the first year. Just to see if what I’m doing is right or wrong. So far I already have a much cleaner chimney than I did with my old stove.

DonTee said:

I’m trying to figure out how low I can go without the “gooey tar mess”. So far I’ve been burning for over a month like this pretty consistently. And the chimney still looks good.

If I’m at 250 degrees 18” above the stove, the smoke still has to go another 20’ to the top of the chimney. It is a newer triple wall chimney, so heat loss should be lower, but still there of course.

This is a new to me stove. So I’ll probably check the chimney once a month during the burn season. For the first year. Just to see if what I’m doing is right or wrong. So far I already have a much cleaner chimney than I did with my old stove.

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Keep an eye on your cap... what I do is pretty much wait till the day or two before the first major snow, I'll clean the chimney and cap really good and then I'm good to go until the spring. My usual first big snow that can stick around is mid December for my area.

peano said:

Are they selling authentic, the same quality ?

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Yes, to my knowledge.

Highbeam said:

I go for 24 hours with Doug fir softwood and internal flue temperatures measured with a probe meter hold pretty steady at 400 until the end. You can go lower but at some point the temperature at the top falls below 212 and you could get a gooey tar mess.

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Chimney length plays a role in this too. The further from the stove you go, the more Build up is likely. At 15' in my install, I have virtually no greater accumulation at top versus halfway down. Longer, unprotected stacks need higher operating temps.

The flue temp discussion tends to come up every season, which is good. Every set up is different as we all know. If I set my stove up for 20-24 hr burn the flue 18” above will travel between 200 and 350 degrees. If I want a hot quick burn (say 6h) the flue will range between 400 and 500.

My pipe is 2/3 exposed. When I clean it, most of the gunk is in the first 1/2 of the pipe. Total opposite from what I had with the VC.

I’d love to stick a temp probe at the top of my chimney too. To compare with the temp data right above the stove. But, probably not gonna happen

BKVP said:

Chimney length plays a role in this too. The further from the stove you go, the more Build up is likely. At 15' in my install, I have virtually no greater accumulation at top versus halfway down. Longer, unprotected stacks need higher operating temps.

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Of course. Also, chimney construction matters. If it’s an air cooled pipe vs. insulation packed. Also a factor is whether that chimney is outside exposed to -30 temperatures and wind or if it is internal to the home.

Then there is variability throughout the season with regard to fuel quality, fuel moisture, and burn rate.

I like the idea of checking the top every month or so to try and get your comfortable minimum. My experience is that I need to run a little warmer flue temperatures than the stove could possibly make while still keeping an active cat.

Really enjoying the stove this season with 3+ year shed stored Doug fir. Very predictable and steady.

DonTee said:

I’d love to stick a temp probe at the top of my chimney too. To compare with the temp data right above the stove. But, probably not gonna happen

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Be careful reading people’s posts about their experiences here. Some report surface temperatures of single wall and some report internal probe meter temperatures of double wall and many don’t specify which they are reporting.

Huge difference. Factor of 2. An internal temperature of 400 is roughly equal to an external temperature of 200.

Highbeam said:

Be careful reading people’s posts about their experiences here. Some report surface temperatures of single wall and some report internal probe meter temperatures of double wall and many don’t specify which they are reporting.

Huge difference. Factor of 2. An internal temperature of 400 is roughly equal to an external temperature of 200.

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For sure there’s a big difference. I use a 4” internal temp probe with mine. So I tend to pay attention to people that also use internal temp probes.

Personally I would call that the “flue temp” versus the “pipe temp”. Or something like that. But I know it can be confusing depending on who you’re talking to. Maybe something like “flue gas temp” versus “pipe surface temp” would be better.

This is also my first year with a flue temp probe, so sorry if I have some noob questions. I appreciate all the good info from this site.

On a side note, I can also verify that single wall exterior temp versus interior temp. I’m using a 4” temp probe in single wall pipe. Right now the inside temp is 422, and the outside temp is 221.

Sorry guys. I did not specify. Internal probe here. The seniors here know that😝

Lol. I’m only 38, so I’m not old enough to know about internal probes yet.

I've been burning NIELS exclusively since October 15th. I have KE40. I've not emptied any ashes thus far. Looking forward, I'm thinking end of December will be the first emptying of ashes.

DonTee you might try some smaller loads. I will turn mine way down sometimes during a warm spell but only after it’s been burning for quite a while and don’t have any chimney issues. I really like the Neil’s logs as well bkvp. They actually seem to burn at a lower heat than Doug fir and no problems at all controlling them in my princess. It’s been perfect princess weather here( cold) for a good spell. Burning up some cotton wood and finding it’s a perfect 12hour ( ish) cycle

My understanding has always been that, as long as cat is active, there's no "too low" for a chimney temp.

I see my one stove typically set for 24 hour burns runs about 200F on outside of single-wall pipe. The other typically set for 12 hour burns has double wall pipe and probe, but I never pay any attention to what it reads after dialing down, it was installed solely for watching high pipe temps during bypass and initial charring phase.

On high, we know it's possible to push more volatiles thru the cat faster than it can fully burn them, but that will never correspond to low flue temps. On low, if the combustor is active, then there really shouldn't be enough of anything going up the pipe for any serious concern. The only issue I see with low pipe temperature is if it gets low enough to stall your draft, causing the combustor to fall out of active, classic "cat stall".

Though when I start charring, the pipe (flue probe) often is quite low - because it was the end of a burn and because I had the stove door open a bit.
The question is then what goes faster: the warm up of the pipe or the smoke coming out of the stove.

I think it's splitting hairs. If we char/bake properly, use dry wood, it shouldn't be a big deal. Or, in other words, if accumulation IS a big deal, then something in the system (wood, stove, flue) is not functioning as it should.

Oak and pitch pine Northern lights tonight.

After burning just over a month 24/7 with KING 40, decided to sweep the chimney just to see, I had zero come down. nothing, zilch!! but inside the stove a whole different story, looks like chard sheets pulling from the wall of the stove. Is this normal? coating on the inside? should have took a pic but seems to be everywhere inside?
I did get the condar fluguard probe. I've always learned to keep the flue at least 400, but I see on this forum less is ok? I tend to at least get her up to about 800 and let her cruise at 400 .

If the buildup looks paper thin and flacky, no need to worry, normal. If it's thick chunky debris, Keep bypass closed, load up smaller pieces and burn it hot.

The inside of my fireboxes look like a mess. I never worried about it, the chimney is clean.

So, BKVP, what's the actual concern if it's thick and chunky? Is it corrosive?

I've never cleaned anything inside my stoves, I only pull the combustor to vacuum that clean, sweep the pipe thru the bypass damper, vacuum any debris out of the bypass damper area, slide the cat back in with a new gasket, and put it back into service. Seven years now, no problems yet.