Smoke with cat engaged - Chinook

[TheElementalCashew]

I guess I should clarify, the stove cruises pleasantly for 2-3 hours after a reload and proper charring, right at about 2. Then it just slowly gets hotter, with flames filling the firebox as if more air is being introduced, though the thermostat setting hasn't changed.

 

[Ashful]

No OAK here, just normal warm air from around the stove.

I don't seem to have more adjustment, if I turn down below ~2, the cat will stall. But if I leave the firebox raging at 2 once it hits that point, the house will be 85* and the wood will have burnt out by 1am.

Just seems odd to me, based on what I've read here. My workaround as mentioned above is to just snuff the fire at 11 for a bit, then slowly turn back to 2. After that it seems to run ok, though I've never gotten better than 12-15 hours of burn time on a full load of wood. This generally works with my schedule so I can't complain too much, but it would be nice to be more "set it and forget it".

Seeing the firebox flame out when initially turning down, and then coming back 2 hours later to see flame show would be normal behavior. Essentially, the thermostat allows more air after the rig has cooled, from your initial high burn setting. We eventually learn the knob setting that gives us the steady-state behavior we desire, not to be fooled by the temporary squashing of the fire at initial turn down after 20 minutes of running the thing on high.

But a cat stall is not normal behavior, in this scenario. Are you sure you're using the term correctly? The only way I can imagine to stall a cat at setting that would eventually steady-state toward "raging", would be wet wood.

 

[TheElementalCashew]

Seeing the firebox flame out when initially turning down, and then coming back 2 hours later to see flame show would be normal behavior. Essentially, the thermostat allows more air after the rig has cooled, from your initial high burn setting. We eventually learn the knob setting that gives us the steady-state behavior we desire, not to be fooled by the temporary squashing of the fire at initial turn down after 20 minutes of running the thing on high.

But a cat stall is not normal behavior, in this scenario. Are you sure you're using the term correctly? The only way I can imagine to stall a cat at setting that would eventually steady-state toward "raging", would be wet wood.

Ok, so you think perhaps that 2 is still not the lowest setting I could go, hence the flames continuing in the box. Just seems odd that it seemingly continues to get hotter and hotter, rather than maintain some sort of average temperature.

My experience with turning down the thermostat below 2 is that the cat thermometer will begin to drop, eventually plummeting to inactive rather than maintaining somewhere along the line. I thought that was a cat stall, but feel free to correct me if it isn't the correct terminology.

My wood is pretty dry, moisture tested on a room-temperature freshly split face usually around 17-18%. That aside, I experience the same sort of behavior when using bio-bricks.

I only brought this up as BKVP mentioned that the thermostat should not make a difference below ~2 for most people. But I can clearly snuff the fire by turning to 11, so it seemed there was more play in the thermostat flap on mine. My understanding is that the thermostat should automatically adjust the flap open/close to maintain a given setting, but mine gets hotter and eventually burns up quickly. It seemed reminiscent of my VC Encore days where the flap would over-rotate past the air intake, eventually allowing more air rather than cutting it off.

 

[BKVP]

No OAK here, just normal warm air from around the stove.

I don't seem to have more adjustment, if I turn down below ~2, the cat will stall. But if I leave the firebox raging at 2 once it hits that point, the house will be 85* and the wood will have burnt out by 1am.

Just seems odd to me, based on what I've read here. My workaround as mentioned above is to just snuff the fire at 11 for a bit, then slowly turn back to 2. After that it seems to run ok, though I've never gotten better than 12-15 hours of burn time on a full load of wood. This generally works with my schedule so I can't complain too much, but it would be nice to be more "set it and forget it".

There is by law a minimum low air inlet. It can be located in different places and is not to be mucked with. So even when the blade is fully closed, a minimum amount of air is still getting to the firebox.

 

[stoveliker]

Ok, so you think perhaps that 2 is still not the lowest setting I could go, hence the flames continuing in the box. Just seems odd that it seemingly continues to get hotter and hotter, rather than maintain some sort of average temperature.

My experience with turning down the thermostat below 2 is that the cat thermometer will begin to drop, eventually plummeting to inactive rather than maintaining somewhere along the line. I thought that was a cat stall, but feel free to correct me if it isn't the correct terminology.

My wood is pretty dry, moisture tested on a room-temperature freshly split face usually around 17-18%. That aside, I experience the same sort of behavior when using bio-bricks.

I only brought this up as BKVP mentioned that the thermostat should not make a difference below ~2 for most people. But I can clearly snuff the fire by turning to 11, so it seemed there was more play in the thermostat flap on mine. My understanding is that the thermostat should automatically adjust the flap open/close to maintain a given setting, but mine gets hotter and eventually burns up quickly. It seemed reminiscent of my VC Encore days where the flap would over-rotate past the air intake, eventually allowing more air rather than cutting it off.

If you stall (indeed the cat drops out of the active zone is what is called stalling - by me...) below 2, than that is (close to) your lowest setting (at THIS weather...).

I do think it is a bit strange that you go from a high burn to "2", and for 2-3 hours it runs stable, and THEN it starts heating up. It is normal for the stove to have to open the air a while after turning it down, because when you turn down and the stove is hot, the air will close as far as it can (see the law quoted by bkvp). Then, after reaching equilibrium temperature it will slightly open the air to keep it at the temperature the Tstat "wants" at "2". (Just like taking your food of the gas pedal and coast down from 80 mph to 50 mph - after a while you'll have to add a bit of gas to keep you at 50.)

That "while" seems long here, though, at 2-3 hours. Although this depends on the situation of the stove (hence ashful's OAK and "in a fireplace" remarks), so it could be correct for your situation. This depends on how well the stove can shed its heat, how long it takes for the Tstat to cool down etc.

If all indeed works as it should, that suggests that "2" means "85 F" (in THIS weather) in your home.
That seems a rather high temperature to me. But the layout of the home matters here; 85 in the stove room, where, is a ceiling fan on, how does the heat move to the rest of the home, etc. etc.

So, while the general features seem to be consistent with what I would expect, the timescale seems long to me, and the data (85) appear to be high. "Long" and "high" together is two datapoints that hint that something may not entirely be operating as intended in my view. I'm not 100% sure though.

 

[TheElementalCashew]

There is by law a minimum low air inlet. It can be located in different places and is not to be mucked with. So even when the blade is fully closed, a minimum amount of air is still getting to the firebox.

Sure, I get that, and I wasn't suggesting modifying that minimum air amount. Just seeing the ability to snuff the fire turning to 11 seemed odd, especially when I can hear the flapper clank closed ~2 when cold.

I was mostly just curious, given that the fire flares up more when it should be cruising, if it was possible that the flapper was being manipulated incorrectly by the thermostat, opening when it should be closing, etc.

 

[Ashful]

Next time this scenario repeats, i.e. you come back to a previously dark stove and find it raging, turn the t'stat knob and listen for it to close. Let's see how much the clock position has changed from the original 2 o'clock position it had snapped shut earlier.

Bottom line, if it's raging, and if we can generally agree on what "raging" means, and if your wood was already acceptably dry, it would seem to imply new air is getting in somewhere. Based on this, we'd assume your t'stat now has the flapper snapping shut at 11 o'clock, rather than the prior 2 o'clock. If we can confirm that's true, then I guess we'd be down to asking why, as it's not something I've ever seen reported here before.

I've never made a point to measure it, but I'd guess the "closed" position of my thermostat dials never vary by more than an hour on the clock face, from cold stove to hot stove. This seems to make sense, as it only takes very small adjustments in inlet air to make huge differences in temperature and burn time, on most non-thermostatic stoves with manual controls.

 

[TheElementalCashew]

If you stall (indeed the cat drops out of the active zone is what is called stalling - by me...) below 2, than that is (close to) your lowest setting (at THIS weather...).

I do think it is a bit strange that you go from a high burn to "2", and for 2-3 hours it runs stable, and THEN it starts heating up. It is normal for the stove to have to open the air a while after turning it down, because when you turn down and the stove is hot, the air will close as far as it can (see the law quoted by bkvp). Then, after reaching equilibrium temperature it will slightly open the air to keep it at the temperature the Tstat "wants" at "2". (Just like taking your food of the gas pedal and coast down from 80 mph to 50 mph - after a while you'll have to add a bit of gas to keep you at 50.)

That "while" seems long here, though, at 2-3 hours. Although this depends on the situation of the stove (hence ashful's OAK and "in a fireplace" remarks), so it could be correct for your situation. This depends on how well the stove can shed its heat, how long it takes for the Tstat to cool down etc.

If all indeed works as it should, that suggests that "2" means "85 F" (in THIS weather) in your home.
That seems a rather high temperature to me. But the layout of the home matters here; 85 in the stove room, where, is a ceiling fan on, how does the heat move to the rest of the home, etc. etc.

So, while the general features seem to be consistent with what I would expect, the timescale seems long to me, and the data (85) appear to be high. "Long" and "high" together is two datapoints that hint that something may not entirely be operating as intended in my view. I'm not 100% sure though.

It almost seems as if once the stove is set at 2, the flapper is able to open to add more air when needed, but doesn't ever really close when it isn't needed. The gas pedal analogy is a good one, and basically how I understood this to work.

It's true, I do have a poorly laid out house for a stove, but over the years I have figured out strategic floor fan placement to get cooler air sent back to the stove and heat well-distributed. In my ~2600 sq. ft. home, if the first floor ends up at 85*, the second floor bedrooms would be ~80*. Again, that is only if I allow the fire to continue burning high, rather than snuffing it out and eventually returning it a "normal" burn rate.

 

[TheElementalCashew]

Next time this scenario repeats, i.e. you come back to a previously dark stove and find it raging, turn the t'stat knob and listen for it to close. Let's see how much the clock position has changed from the original 2 o'clock position it had snapped shut earlier.

Bottom line, if it's raging, and if we can generally agree on what "raging" means, and if your wood was already acceptably dry, it would seem to imply new air is getting in somewhere. Based on this, we'd assume your t'stat now has the flapper snapping shut at 11 o'clock, rather than the prior 2 o'clock. If we can confirm that's true, then I guess we'd be down to asking why, as it's not something I've ever seen reported here before.

I've never made a point to measure it, but I'd guess the "closed" position of my thermostat dials never vary by more than an hour on the clock face, from cold stove to hot stove. This seems to make sense, as it only takes very small adjustments in inlet air to make huge differences in temperature and burn time, on most non-thermostatic stoves with manual controls.

Thanks for the suggestion. Sounds like a good test, I'll report back.

 

[moresnow]

Ok, so you think perhaps that 2 is still not the lowest setting I could go, hence the flames continuing in the box. Just seems odd that it seemingly continues to get hotter and hotter, rather than maintain some sort of average temperature.

My experience with turning down the thermostat below 2 is that the cat thermometer will begin to drop, eventually plummeting to inactive rather than maintaining somewhere along the line. I thought that was a cat stall, but feel free to correct me if it isn't the correct terminology.

My wood is pretty dry, moisture tested on a room-temperature freshly split face usually around 17-18%. That aside, I experience the same sort of behavior when using bio-bricks.

I only brought this up as BKVP mentioned that the thermostat should not make a difference below ~2 for most people. But I can clearly snuff the fire by turning to 11, so it seemed there was more play in the thermostat flap on mine. My understanding is that the thermostat should automatically adjust the flap open/close to maintain a given setting, but mine gets hotter and eventually burns up quickly. It seemed reminiscent of my VC Encore days where the flap would over-rotate past the air intake, eventually allowing more air rather than cutting it off.

When turning down from wide open where are you pointed when you hear the stat clank closed (I mark that with a tiny magnet). Small adjustment either side of that point encompass most of my normal burn range. Exception being starting a fresh load or nuking coals with a single split etc. Then its WFO

 

[TheElementalCashew]

When turning down from wide open where are you pointed when you hear the stat clank closed (I mark that with a tiny magnet). Small adjustment either side of that point encompass most of my normal burn range. Exception being starting a fresh load or nuking coals with a single split etc. Then its WFO

I typically don't hear a clank when turning down, just because I do it in increments. My assumption based on when it clanks cold and where it likes to cruise is that it is right around 2 though. I do have a marker on the thermostat as well just for ease of use.

 

[Nealm66]

I notice my princess will get hotter after I turn the dial down but not much for flames. I just assumed it was the cat doing its thing. I’ve gotten really lazy and spoiled with the whole process. I don’t even look for the glow anymore. Sure sounds like something’s not quite right. Some great people on here so hopefully will get it figured.

 

[Highbeam]

I typically don't hear a clank when turning down, just because I do it in increments. My assumption based on when it clanks cold and where it likes to cruise is that it is right around 2 though. I do have a marker on the thermostat as well just for ease of use.

I too have a princess and have had similar behavior. In my case, the flapper is sticking a bit and not closing down to zero as it heats up. When I catch it flaming when it shouldn’t be I can twist the knob ccw to hear the flapper clack shut and then put it right back where it was and the flapper stays closed and the fire cools.

Just not enough spring tension in the cooling bimetallic coil to close the flapper. This doesn’t happen every time but I’m now in the habit of a quick extra spin ccw before setting to cruise or before going to bed.

I’ve tried lubing the throttle blade shaft but only very light lube works because the torque from the spring is pretty low.

 

[Diabel]

My Princess smokes like a coal locomotive. It is what it is. Life is good.

 

[TheElementalCashew]

Next time this scenario repeats, i.e. you come back to a previously dark stove and find it raging, turn the t'stat knob and listen for it to close. Let's see how much the clock position has changed from the original 2 o'clock position it had snapped shut earlier.

Bottom line, if it's raging, and if we can generally agree on what "raging" means, and if your wood was already acceptably dry, it would seem to imply new air is getting in somewhere. Based on this, we'd assume your t'stat now has the flapper snapping shut at 11 o'clock, rather than the prior 2 o'clock. If we can confirm that's true, then I guess we'd be down to asking why, as it's not something I've ever seen reported here before.

I've never made a point to measure it, but I'd guess the "closed" position of my thermostat dials never vary by more than an hour on the clock face, from cold stove to hot stove. This seems to make sense, as it only takes very small adjustments in inlet air to make huge differences in temperature and burn time, on most non-thermostatic stoves with manual controls.

I tested this out today. I confirmed I could hear the flapper close at the 2 position while the stove was cold. After the stove had been running for a bit, when the fire started flaring up while the thermostat was in the 2 position, I quickly turned the knob counterclockwise and was able to hear the flapper close now at about the 11 position. As before, I let it sit there for a few minutes, before slowly turning it back to 2, where it cruised pleasantly.

Do you think perhaps my incremental closing of the thermostat knob is just too slow to actually close the flapper correctly? Perhaps something is sticking/binding inside. I'm not familiar with the design of the mechanism where the thermostat knob connects to the flapper.

 

[TheElementalCashew]

I too have a princess and have had similar behavior. In my case, the flapper is sticking a bit and not closing down to zero as it heats up. When I catch it flaming when it shouldn’t be I can twist the knob ccw to hear the flapper clack shut and then put it right back where it was and the flapper stays closed and the fire cools.

Just not enough spring tension in the cooling bimetallic coil to close the flapper. This doesn’t happen every time but I’m now in the habit of a quick extra spin ccw before setting to cruise or before going to bed.

I’ve tried lubing the throttle blade shaft but only very light lube works because the torque from the spring is pretty low.

Thanks for the input! I'll have to try a quick turn to re-seat the flapper when this happens and see if that corrects the issue. I was just wondering in an above post if something was getting hung up in the mechanism, perhaps due to slower incremental turning of the thermostat knob. That's an interesting thought about the tension in the coil. I suppose it is plausible that there could be an improperly wound coil or just a manufacturing defect, as my stove is pretty new.

 

[Ashful]

I tested this out today. I confirmed I could hear the flapper close at the 2 position while the stove was cold. After the stove had been running for a bit, when the fire started flaring up while the thermostat was in the 2 position, I quickly turned the knob counterclockwise and was able to hear the flapper close now at about the 11 position. As before, I let it sit there for a few minutes, before slowly turning it back to 2, where it cruised pleasantly.

Do you think perhaps my incremental closing of the thermostat knob is just too slow to actually close the flapper correctly? Perhaps something is sticking/binding inside. I'm not familiar with the design of the mechanism where the thermostat knob connects to the flapper.

This is good info, but I think Highbeam or BKVP can give you better answers than me, as I've never seen any behavior like this from either of my BK's. If you had said 11 o'clock is the new 2 o'clock, I would've just told you to mark that new position on your dial with some tape, and use some position relative to that to set the stove for cruising in the future. But the fact that turning it to 11 and then right back to 2 gets it cruising as desired, it would appear that indeed something must be sticking inside, which I've never seen on my stoves.

The mechanism is beautifully conceived, in it's outward simplicity. Your control knob drives worm gear to translate shaft direction, and this drives an axle around which a bimetallic coil is wrapped. Bimetallic coil looks like a clock chime coil (shown below), with your knob driving the center and the air flapper connected to the outer end. The whole "spring" turns with your knob, moving the air flapper with it:



As this spring heats and cools, it pulls or pushes the flapper a little more open, or a little more closed. But as small movements in an air control translate to big changes in burn rate on any stove, the movement is small relative to your turning of the knob.

Getting the ratio of temperature to degrees of movement, as well as the critical time constants required to prevent oscillation, is where the beauty and real engineering comes into the design. Several other stove companies have tried similar mechanisms with various degrees of success or failure, but BK is one of the few that really nailed this.

 

[moresnow]

I tested this out today. I confirmed I could hear the flapper close at the 2 position while the stove was cold. After the stove had been running for a bit, when the fire started flaring up while the thermostat was in the 2 position, I quickly turned the knob counterclockwise and was able to hear the flapper close now at about the 11 position. As before, I let it sit there for a few minutes, before slowly turning it back to 2, where it cruised pleasantly.

Do you think perhaps my incremental closing of the thermostat knob is just too slow to actually close the flapper correctly? Perhaps something is sticking/binding inside. I'm not familiar with the design of the mechanism where the thermostat knob connects to the flapper.

When you experience the "flaring up" a few hrs into a fresh load what happens if you simply leave it alone? That is relatively normal imo. The flame will extinguish given time and patience. The stove is rebounding from the high initial heat cycle being shut down to zero. After this cycle it should cruise. Easy to get caught up chasing the flame/no flame with the stat knob!
Now if you are truly blowing off a complete load on the "flare up" you have an odd issue?

 

[TheElementalCashew]

This is good info, but I think Highbeam or BKVP can give you better answers than me, as I've never seen any behavior like this from either of my BK's. If you had said 11 o'clock is the new 2 o'clock, I would've just told you to mark that new position on your dial with some tape, and use some position relative to that to set the stove for cruising in the future. But the fact that turning it to 11 and then right back to 2 gets it cruising as desired, it would appear that indeed something must be sticking inside, which I've never seen on my stoves.

The mechanism is simple. Your control knob drives worm gear to translate shaft direction, and this drives an axle around which a bimetallic coil is wrapped. Bimetallic coil looks like a clock chime coil (shown below), with your knob driving the center and the air flapper connected to the outer end. The whole "spring" turns with your knob, moving the air flapper with it:

View attachment 304207

As this spring heats and cools, it pulls or pushes the flapper a little more open, or a little more closed. But as small movements in an air control translate to big changes in burn rate on any stove, the movement is small relative to your turning of the knob.

Thanks for taking the time to explain that! Hopefully BKVP will chime in with some suggestions for fixes to try.

When you experience the "flaring up" a few hrs into a fresh load what happens if you simply leave it alone? That is relatively normal imo. The flame will extinguish given time and patience. The stove is rebounding from the high initial heat cycle being shut down to zero. After this cycle it should cruise. Easy to get caught up chasing the flame/no flame with the stat knob!
Now if you are truly blowing off a complete load on the "flare up" you have an odd issue?

If I leave it alone, the stove will burn off everything in the firebox in less than 8 hours and the house will get very warm, definitely not self-adjusting and burning at a low controlled rate as preferred.

 

[moresnow]

Thanks for taking the time to explain that! Hopefully BKVP will chime in with some suggestions for fixes to try.


If I leave it alone, the stove will burn off everything in the firebox in less than 8 hours and the house will get very warm, definitely not self-adjusting and burning at a low controlled rate as preferred.

Next reload try swinging the stat to your established low set point in one move (after initial char period). I have experienced irregularity in getting to my low set point by closing in small increments. Worth a try.

 

[Nealm66]

I’ve never dialed down incrementally. I’ve heard some people have issues but I never have

 

[BKVP]

This is good info, but I think Highbeam or BKVP can give you better answers than me, as I've never seen any behavior like this from either of my BK's. If you had said 11 o'clock is the new 2 o'clock, I would've just told you to mark that new position on your dial with some tape, and use some position relative to that to set the stove for cruising in the future. But the fact that turning it to 11 and then right back to 2 gets it cruising as desired, it would appear that indeed something must be sticking inside, which I've never seen on my stoves.

The mechanism is beautifully conceived, in it's outward simplicity. Your control knob drives worm gear to translate shaft direction, and this drives an axle around which a bimetallic coil is wrapped. Bimetallic coil looks like a clock chime coil (shown below), with your knob driving the center and the air flapper connected to the outer end. The whole "spring" turns with your knob, moving the air flapper with it:

View attachment 304207

As this spring heats and cools, it pulls or pushes the flapper a little more open, or a little more closed. But as small movements in an air control translate to big changes in burn rate on any stove, the movement is small relative to your turning of the knob.

Getting the ratio of temperature to degrees of movement, as well as the critical time constants required to prevent oscillation, is where the beauty and real engineering comes into the design. Several other stove companies have tried similar mechanisms with various degrees of success or failure, but BK is one of the few that really nailed this.

 

[BKVP]

Thanks for taking the time to explain that! Hopefully BKVP will chime in with some suggestions for fixes to try.


If I leave it alone, the stove will burn off everything in the firebox in less than 8 hours and the house will get very warm, definitely not self-adjusting and burning at a low controlled rate as preferred.

Chiming-in!! The thermostat is an east part to replace. I don't think there is an issue with yours, but not being able to "touch" it makes that determination very difficult. You can call and ask the dealer initiate a warranty claim, but that moves this from this wonderful hearth site to the process we use. Always free to report back of course!!

 

[Nealm66]

I’m still curious about the smoke. I never see any once my stove is up and running. I mostly run on 12ish hour reloads. Could it be that I’m just running mine a little hotter?

 

[Highbeam]

I’m still curious about the smoke. I never see any once my stove is up and running. I mostly run on 12ish hour reloads. Could it be that I’m just running mine a little hotter?

I suspect you're right. Blowing through a firebox in 12 hours is way closer to maximum output than minimum which is where the huge majority of folks run these stoves even in Alaska. I keep forgetting the exact statistic.