Smoke with cat engaged - Chinook

[QuarryHouse]

My new Chinook 20.2 has been great so far. I'm wondering whether others see smoke from the chimney even after the cat is engaged? Especially running on high the see a fair amount of smoke. It seems to go mostly away after awhile, but if I adjust the thermostat I'll often see smoke for awhile. For instance, right now its 25F outside, I just opened the thermostat to about half way and there's steady white smoke coming out. I just checked a fresh split of the logs I loaded this morning (mix of white ash and cherry) and they are showing about 18% MC.

Does a cat need some time to adjust to higher or lower airflow?

 

[chetaget]

What does your cat gauge say, can you see it glowing ?

 

[QuarryHouse]

Cat gauge is around 2 o'clock. Where would I see it glowing? when I look in the front glass, I just see black metal.

 

[chetaget]

My stove is identical to yours, and to see the Cat on mine, I need to get my head down towards the floor and look up. Near the front there is a metal plate with holes in it, that is the flame shield. Behind there is the cat. When my gauge is at that position, you can see it glow faintly. Page 33 in the manual shows the flame shield and location pretty well.

Chinook 20.2 manual

I get a little bit of smoke after loading before the fire is back up to temp, but once its up an running i get little to no smoke depending on the wood.

Hopefully some other users chime in.

 

[EatenByLimestone]

White smoke that dissipates quickly is often water vapor.

 

[QuarryHouse]

My stove is identical to yours, and to see the Cat on mine, I need to get my head down towards the floor and look up. Near the front there is a metal plate with holes in it, that is the flame shield. Behind there is the cat. When my gauge is at that position, you can see it glow faintly. Page 33 in the manual shows the flame shield and location pretty well.

Chinook 20.2 manual

I get a little bit of smoke after loading before the fire is back up to temp, but once its up an running i get little to no smoke depending on the wood.

Hopefully some other users chime in.

With the cat gauge around 2 o'clock, peering in through the glass door, I don't see a glow. Maybe it's easier to see if you're reloading and the door is open?

What comes out of the chimney is definitely not water water - it goes in a plume above the house maybe 40 - 50 feet before starting to dissipate. Eventually, like an hour after a reload, it calms down, but an hour seems like a long time for a stove that was already hot. Tonight I reloaded on a bed of coals, cat around 12 o'lock, wood caught fire immediately, closed the door, engaged the cat. I waited 30 minutes, walked the dog, and I can see in my headlamp a plume of white/gray smoke drifting away.

I loaded the stove at 6AM this morning - after 14 hours there was still a coal bed, house is warm - I'm very happy. I can't imagine I'd be getting a 14-15 hour burn if the cat wasn't doing something.

 

[Highbeam]

Mine does it. Especially if I turn up the thermostat until it reaches equilibrium again. Honestly, these things smoke quite a bit. At the beginning and then on and off throughout the burn when the thermostat cycles. Regardless of cat temperature.

It gets way better at the last half of the burn.

Sometimes white, sometimes blue. I’m burning softwood with bark.

 

[QuarryHouse]

Mine does it. Especially if I turn up the thermostat until it reaches equilibrium again. Honestly, these things smoke quite a bit. At the beginning and then on and off throughout the burn when the thermostat cycles. Regardless of cat temperature.

It gets way better at the last half of the burn.

Sometimes white, sometimes blue. I’m burning softwood with bark.

Interesting. I turned up the stove this morning to warm the house up a bit. Before - no smoke. After turning it up - smoking, so that matches your description. I wonder how that squares with the stated 0.7 grams per hour of particulate emission? Is that only for steady state fires? This is all burning ash/cherry mix with about 18% MC (measured on the face of a newly split chunk).

chetaget, once I turned the lights off and peered up through the glass I could see a dim glow of the cat, so it's definitely hot.

 

[stoveliker]

The cat does not need to be glowing to work.

Visible smoke would indeed persist longer (distances from the cap) than steam. Steam can sometimes appear a foot or so outside the (shimmering) cap, or it can appear from right inside the cap, but (in my case) it disappears within 6 ft - rather than slowly dilutes as smoke would do.

Smoke, even from a working cat, depends on the residence time of the exhaust gases in the cat. The longer they are there, the more complete the combustion will be. And the hotter the cat the more complete the combustion will be.
So if you open the Tstat, what you are doing is almost instantaneously increase the airflow = decrease the residence time. So combustion will be less complete. After a while, the cat has seen more fuel (because larger air flow, assuming the primary combustion efficiency is not changing, see below), and will get hotter. At that point, the combustion gets more complete again, and smoke may disappear.

Regarding primary combustion: if one opens the air flow, a new steady state will eventually appear where more fuel is combusted in the primary fire, and that can result in less fuel for the cat, so it may cool down again. This may h appen for larger Tstat adjustments. For smaller ones, I think the above assumption of similar primary efficiency is fair.

However, a cat cooling down will less likely give smoke because it's exhaust-combusting capabilities are high (because of the high temperature) for the amount of fuel it is given.

 

[Highbeam]

As the thermostat opens I think two big things occur, less residence time and more smoke per second. Both increase smoke until the cat can catch up.

I’m looking at my cruising stove right now, and I am impressed with its performance. It really delivers on keeping the house warm for long periods of time on minimal fuel. I’ve never been impressed with its smoke emissions, flue debris accumulation, or glass dirtiness. The noncats are way better at that cleanliness stuff but the performance aspects of the BK more than make up for being dirty.

 

[Diabel]

As the thermostat opens I think two big things occur, less residence time and more smoke per second. Both increase smoke until the cat can catch up.

I’m looking at my cruising stove right now, and I am impressed with its performance. It really delivers on keeping the house warm for long periods of time on minimal fuel. I’ve never been impressed with its smoke emissions, flue debris accumulation, or glass dirtiness. The noncats are way better at that cleanliness stuff but the performance aspects of the BK more than make up for being dirty.

Mine behaves very similarly. Sometimes I call it “dirty Princess?😝

 

[Highbeam]

Mine behaves very similarly. Sometimes I call it “dirty Princess?😝

I run two stoves on the same fuel often at the same time. One a noncat and this BK. The BK, at all output levels, is much smokier during the burn and much much smokier during startup. I don't know how it passed EPA testing but the BK has brought us a lot of happiness with it's extreme comfort, long burn times, and miserly fuel consumption. I start/reload it in the dark if at all possible as it floods the pasture with a fog.

I would have a hard time 24/7 heating with a noncat after being spoiled by the BK.

 

[Diabel]

I am not worried about neighbors, closest one is about 2000ft away. We are in a cottage country and all places are more less vacation places.

What is interesting, my old VC (city stove, house sold) produced less smoke (same fuel) compare to the bk but when cleaning the flue VC generated more soot. No idea why.

The Princess still puts a smile on my face (after 4 yrs) every time I look at it. Amazing heater.

 

[QuarryHouse]

The cat does not need to be glowing to work.

Visible smoke would indeed persist longer (distances from the cap) than steam. Steam can sometimes appear a foot or so outside the (shimmering) cap, or it can appear from right inside the cap, but (in my case) it disappears within 6 ft - rather than slowly dilutes as smoke would do.

Smoke, even from a working cat, depends on the residence time of the exhaust gases in the cat. The longer they are there, the more complete the combustion will be. And the hotter the cat the more complete the combustion will be.
So if you open the Tstat, what you are doing is almost instantaneously increase the airflow = decrease the residence time. So combustion will be less complete. After a while, the cat has seen more fuel (because larger air flow, assuming the primary combustion efficiency is not changing, see below), and will get hotter. At that point, the combustion gets more complete again, and smoke may disappear.

Regarding primary combustion: if one opens the air flow, a new steady state will eventually appear where more fuel is combusted in the primary fire, and that can result in less fuel for the cat, so it may cool down again. This may h appen for larger Tstat adjustments. For smaller ones, I think the above assumption of similar primary efficiency is fair.

However, a cat cooling down will less likely give smoke because it's exhaust-combusting capabilities are high (because of the high temperature) for the amount of fuel it is given.

This makes a lot of sense and does seem to match what is happening. Lowering the t-stat does not seem to produce smoke - or not nearly as much. I did notice it smoking some this afternoon without any t-stat adjustment but much less. It's also quite windy today, which is probably pulling smoke through the cat in bursts. Seems like the cleanest way to run would be to adjust the stove in small increments. When it's time to reload, I've been turning the t-stat from lowest setting to highest in one go.

I don't remember where I read it, but I believe that much of the indoor particulates come from opening the stove door to reload and since I'm opening the Chinook only twice a day as opposed to every 3 hours or so for my previous Jotul, I hope I am making a net gain in my indoor air quality in addition to having the benefits of steady even heat that lasts for 12 hours. Certainly compared to the smoke dragon I grew up feeding.

 

[stoveliker]

Increments: yes.
And indoor air quality: yep. And having a chimney with good draft (and modern stoves already need higher draft than smoke dragons) will further minimize indoor air pollution because most is sucked into the chimney.

There is a thread here (started by Poindexter) about indoor air quality. Including measurements for his home and a cheap but.very effective home made filter box.

 

[QuarryHouse]

Increments: yes.
And indoor air quality: yep. And having a chimney with good draft (and modern stoves already need higher draft than smoke dragons) will further minimize indoor air pollution because most is sucked into the chimney.

There is a thread here (started by Poindexter) about indoor air quality. Including measurements for his home and a cheap but.very effective home made filter box.

This morning I tried opening the t-stat about a quarter turn, wait 5 minutes, until I got it all the way up. The smoke was much reduced - still a little at wide open, but much less and it didn't last as long. It is also very still - smoke going straight up - which undoubtedly makes a difference to the consistency of the airflow to the cat.

 

[Todd]

I run two stoves on the same fuel often at the same time. One a noncat and this BK. The BK, at all output levels, is much smokier during the burn and much much smokier during startup. I don't know how it passed EPA testing but the BK has brought us a lot of happiness with it's extreme comfort, long burn times, and miserly fuel consumption. I start/reload it in the dark if at all possible as it floods the pasture with a fog.

I would have a hard time 24/7 heating with a noncat after being spoiled by the BK.

I think the difference is when they test they use smaller sized splits spaced a certain way to maximize air flow in the firebox. We stuff our stove as full as possible with little to no space for the air to flow around. Maybe too much smoldering going on at times for the cat to handle.

 

[stoveliker]

I think most of the smoke is upon reload, and indeed the cat is then often cooler, when a ton of fuel is fed. So that's going to result in smoke getting past the cat. The longer smoldering of a packed load only gives me shimmering warm air at the cap (or steam).

At least, that's my experience.

 

[Ashful]

I think the difference is when they test they use smaller sized splits spaced a certain way to maximize air flow in the firebox. We stuff our stove as full as possible with little to no space for the air to flow around. Maybe too much smoldering going on at times for the cat to handle.

I'd be surprised if you could pack it tight enough for that to make a difference. I'd bet you a beer that total surface area is total surface area, unless you're literally jointing and skiving the pieces together with a hermetic-level seal.

 

[QuarryHouse]

I think most of the smoke is upon reload, and indeed the cat is then often cooler, when a ton of fuel is fed. So that's going to result in smoke getting past the cat. The longer smoldering of a packed load only gives me shimmering warm air at the cap (or steam).

At least, that's my experience.

This is also what I've seen so far in my two weeks with it.

I reloaded this morning with 3 inches or more of coals plus a few larger chunks still in there after running wide open for about 20 minutes. I put in 3 larger splits and two or three smaller ones in and around the bigger ones. The new wood took off immediately, and I ran on high for 20 minutes or so. It was not smoking (or hardly so) before loading. Post-load, it was smoking a fair amount, decreasing over time.

 

[Todd]

I'd be surprised if you could pack it tight enough for that to make a difference. I'd bet you a beer that total surface area is total surface area, unless you're literally jointing and skiving the pieces together with a hermetic-level seal.

Maybe BKVP can post a pic of a BK EPA crib test load?

 

[Diabel]

I had a chance to do a burn today. Cold start. Stuffed it full, 4 yr old yellow birch round, barkless hemlock round, two rounds of sugar maple and two splits of sugar maple. Fire took off as normal, after 15min was able to close the bypass as the thermo approached active zone. 20min char, flue probe 400, cat sort of glowing, cat thermo at 12:00. Lots of smoke out the pipe. Turned the thermostat to 3:30, cat thermo went to 2:00pm cat sort of glowing (one side only), smoke out the pipe. 1h later turned the thermostat to 3:00pm some flame in the box cat not glowing, some smoke out the pipe. Two hrs later turned thermostat to 2:30 (usual cruising spot) glowing firebox, cat not glowing smoke out the pipe.

 

[stoveliker]

And in between these observations of smoke (which presumably were shortly after adjusting the Tstat)?

If this was constantly like that, it's very different from my stove. Hours of zero smoke. Only when I reload and go full bite for a while do I have (quite a bit, but only shortly) smoke.

 

[Diabel]

Sometimes it will stop suddenly with zero visible smoke, for few hrs. Then 5h later smoke again. I am used to it but it makes me wonder. I mentioned this some time ago (two yrs maybe). Did not get many comments. One comment I remember was to close bypass once the needle in past active zone around 9:30 - 10:00

 

[Ashful]

While I'll never want to squash anyone's curiosity, for me... it doesn't matter. Sometimes I see a little smoke, and wonder for a few seconds if it's really smoke or steam. Then I go back to work, and forget about it. At the end of the year, my chimney is relatively clean, despite burning an obscene amount of wood on relatively low-rate 12 or 24 hour cycles. I'm not living under the Fairbanks smoke police watch, so...