2017-18 Blaze King Performance Thread PART 3 (Everything BK)
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jetsam
Minister of Fire
My tip is to do the break-in fires outside on the lawn! My flame shield is warped after several years of burning, but not yet bad enough to impede its function (I'll hammer it flat if that ever happens).
It's going in the shop for now so not a huge deal. That's kind of why we're doing it in there to begin with.
I didn’t think the smell was very bad. More hot skillet than acrid burning plastic.
The flame shield does not need to be perfectly flat. Reasonably flat is fine. Flames will be sucked right through the holes regularly and sometimes you can even get a little flameshow all by itself between the flame shield and the cat.
The flame shield does not need to be perfectly flat. Reasonably flat is fine. Flames will be sucked right through the holes regularly and sometimes you can even get a little flameshow all by itself between the flame shield and the cat.
jetsam
Minister of Fire
Trial and error. It changes some with your fuel quality and some with your draft, but it's pretty easy to get a handle on.
This year with a brand new steelcat, my lowest setting is all the way down to the stop, which is awesome.
Basically just pick a low setting and keep an eye on it. Maybe check it every 4 or 8 hours, and make sure the cat thermometer is staying in the active range. If it goes inactive before all the fuel is gone, that was too low. If not, maybe you can go lower.
You can also burn lower than the lowest setting in two ways:
1) Accept that the cat isn't going to be active and let it smolder. This is a high creosote decision and you should plan to sweep a lot. It is also not efficient and you will actually go through more wood than if you kept the cat in.
2) Catch it before it dies and turn up the air for a few minutes to warm up the firebox and cat, then turn it back down.
Most people don't want to mess with that and just figure out where the low setting is.
I’ve found that it’s either a very active cat or inactive. It’s pretty difficult to be just barely active for any length of time. That might just be because of my low btu fuel though.
Questions!
- Does the cat combustor have to be glowing to be active or should I strictly go off the thermometer? Stove is in a dark room, cat was glowing so I turned down the thermostat to 10 oclock. In a short while the cat stopped glowing and the temperature started dropping quickly. I turned it back up but would it have died out if I left it alone?
- What temperature does the end of the cat thermometer represent? If the beginning of active is 500f wouldn't the end of active be 1500f?
- Does the cat combustor have to be glowing to be active or should I strictly go off the thermometer? Stove is in a dark room, cat was glowing so I turned down the thermostat to 10 oclock. In a short while the cat stopped glowing and the temperature started dropping quickly. I turned it back up but would it have died out if I left it alone?
- What temperature does the end of the cat thermometer represent? If the beginning of active is 500f wouldn't the end of active be 1500f?
The cat does NOT have to be glowing to be active. Incandescence starts at around 1,000F. The cat starts to become active at around 500F. When the thermostat is shifted to a lower set point the air damper pinches off the airflow greatly. After the stove cools down to the new setpoint, it will open somewhat to maintain the new setpoint. The opposite happens when the thermostat is moved to a higher set point. Flames might suddenly appear and persist until the stove comes up to the new, higher set point is attained then the flames will die down, perhaps all the way out as the thermostat maintains the new set point.
Except in the beginning, wait at least an hour between thermostat changes. Only make small changes.
Sometimes if the the thermostat is turned down the cat temperature will drop. Sometimes it will rise! That is because if the wood is out gassing, the majority of the "combustion" shifts from the firebox to the cat. In older stoves these gasses (think evaporated wood) went up the stack wasted (unburnt) as pollution. A lot of it would deposit in the stove pipe as creosote.
BKs can be run very low. In certain cases creosote can still form-especially with wet wood- but keeping the flue above 212F can help prevent this. This is experimental. Have a flue probe. Burn for 30 days and check the flue. At the very end of the burn, the cat need not be active as the amount of pollutants being created will be very low.
All that being said, I frequently burn with a flue below 212F with no problems.
Don't make the mistake of using thermometers to control the burn, that is old school. Set the thermostat according to the heating needs. That is burning the BK way!
Except in the beginning, wait at least an hour between thermostat changes. Only make small changes.
Sometimes if the the thermostat is turned down the cat temperature will drop. Sometimes it will rise! That is because if the wood is out gassing, the majority of the "combustion" shifts from the firebox to the cat. In older stoves these gasses (think evaporated wood) went up the stack wasted (unburnt) as pollution. A lot of it would deposit in the stove pipe as creosote.
BKs can be run very low. In certain cases creosote can still form-especially with wet wood- but keeping the flue above 212F can help prevent this. This is experimental. Have a flue probe. Burn for 30 days and check the flue. At the very end of the burn, the cat need not be active as the amount of pollutants being created will be very low.
All that being said, I frequently burn with a flue below 212F with no problems.
Don't make the mistake of using thermometers to control the burn, that is old school. Set the thermostat according to the heating needs. That is burning the BK way!
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Here is a picture of my t-stat label when it was still useful. When the stove is cold close the t-stat, when you hear the “flapper” close(metallic sound) consider that your low setting if you want to “run on the hole”. Turning any lower than that will make no difference. On my stove that is around the number “1”.
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Turning the thermostat fully CCW (also) is setting the burn rate to that governed by the EPA hole. That is the lowest burn setting possible but it might cause the cat to drop out, cause creosote and inefficient burning. Some stoves can do this without problems and others can not. It also depends on a legion of changing particulars: Flue height, outside air temp, type amount of wood, just where you are in the burn cycle and moisture content of the wood, etc.
Just find the lowest setting that keeps the cat active. Don't worry if the cat ends up crawling into the inactive zone, just turn it up a little. Eventually you will find a position that reliably keeps it active.
Each stove will have a different thermostat position, do not compare your setting to other stove positions and think yours is broken. Experiment.
If at the lowest setting the house is still too hot just crack a window.
OK thanks guys that clears things up at least a little. I do understand how moving the thermostat up or down changes the dynamics of the stove. Seems like the cat is the most active at 2 oclock which pegs the cat thermostat. Lower then that drops the cat activity, higher than that also drops the cat activity. This is ignoring short term changes. Above 2 oclock I start to get spontaneous combustion inside the chamber (temp is rising) so obviously there's less fuel for the cat. A little less heat out the top, but more out the front.
Well going out to the farm to check on it, I set it to 12 oclock and will see if it is still active. It seemed ok after the change but it likely needs more time to get a good gauge. The flue is long so I imagine it should be able to run low. Fuel is well seasoned American Elm.
Well going out to the farm to check on it, I set it to 12 oclock and will see if it is still active. It seemed ok after the change but it likely needs more time to get a good gauge. The flue is long so I imagine it should be able to run low. Fuel is well seasoned American Elm.
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Great post until the last paragraph that maybe misses one important point. You need to use the cat meter to control the burn because it tells you if the cat is active. You also need the flue meter if you’re trying to run super low or super high in order to maintain the safe range.
Stove top temperature, which you probably meant, is mostly irrelevant!
Yes, to the above. The stove top thermometer is not a useful way to gage the heat output.
The new cat will be really active. 2 o’clock-3 o’clock is where my stove has spent most of its life.
jetsam
Minister of Fire
OK... I don't know if this is the end of the season, but I am letting the stove go out Tuesday! Woo!
Let's make smoke now
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AlbergSteve
Minister of Fire
Totally agree, except that even when I was burning with an EPA tube stove I never used thermometers for stove top or flue temps. Yeah, maybe in the first hour of the burn I'd fiddle with the air to keep a lick of flame going, but I didn't obsess about system temps. After five months of burning, I might get a quarter cup of black powder out of 25 feet of pipe. For the last six years I used that stove I only cleaned the pipe every other year. My point is, you don't need thermometers to burn wood, especially in a BK.
spudman99
Feeling the Heat
Can you elaborate on this? As a lurker trying to learn all about BK, and for those like me new to inserts, it is helpful to understand this issue.
In the first 1/2 hour the stove is run wide open to prepare the wood for the long burn. Moisture and a lot of volatile gasses are driven out and the stove and chimney system are warmed up to operating temperature. Then I turn the stove down to the desired temperature in a few steps. All that takes about an hour. From then on the thermostat is only moved slightly to suit the heating needs. Wood in a BK stove is burned in batches. No plopping a log or two in it every few hours. Except in shoulder season always completely stuff the stove full.
Ashful
Minister of Fire
Basic control theory. After an adjustment, it takes some time for the stove to stabilize at a new equilibrium. If you make adjustments at a rate greater than your feedback system bandwidth, you will have an oscillator.
Make adjustment, then wait to evaluate new equilibrium before making another adjustment. An hour is extreme, in my opinion, but that’s the basic idea.
This is not unique to BK, any stove is operated in the same manner. The only thing unique about BK here is that the burn time is actually sufficient to play out multiple adjustments at 1 hour intervals.
jetsam
Minister of Fire
If you never touch the thermostat at all, you will have an (irregular) oscillator- that's what the thermostat does.
I turn the dial to where I want it and walk away. The thermostat will work out the rest.
I agree that if you adjust it every 30 seconds, using 'do I see flames?' as a yardstick, you will get random results. However, if you make the biggest adjustment you can and walk away, it does not hurt anything- the thermostat will open or close air to get to the new temperature, which is what it would also have done if you hadn't adjusted it.
I have the "green" version.
I use mine nearly daily no matter the season. Ceramic Kamados are the BK's of outdoor cookers!- Status
