2022-2023 BK everything thread

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

NHWS

New Member
Nov 10, 2022
38
Seattle
I'd think if you want to go PID, better off getting a stove without a mechanical thermostat. The extra time constant involving the native thermostat behavior will do nothing but frustrate any attempt to tune a PID, I suspect.

<-- not a controls engineer, but did get an "A" in both controls courses during BSEE studies
The change in burn rate of a wood fire is eons by even tiny SBC standards. Take relatively infrequent sensor readings, use slow-decay exponential smoothing, and only make small infrequent adjustments. An electronic PID might be hard to tune, but a good-enough software version could probably run on a 6502.

There's a lot of value in the continuous analog computation and slow reaction time of a bimetallic strip, though.
 

Highbeam

Minister of Fire
Dec 28, 2006
20,232
Mt. Rainier Foothills, WA
The change in burn rate of a wood fire is eons by even tiny SBC standards. Take relatively infrequent sensor readings, use slow-decay exponential smoothing, and only make small infrequent adjustments. An electronic PID might be hard to tune, but a good-enough software version could probably run on a 6502.

There's a lot of value in the continuous analog computation and slow reaction time of a bimetallic strip, though.
Meh, not needed for a stove and if you’re interested the wood furnace and wood boiler guys already have this. Some even use oxygen sensors in the exhaust.
 
  • Like
Reactions: Ashful

kennyp2339

Minister of Fire
Feb 16, 2014
6,831
07462
Worth mentioning for the princess and king owners, I think it’s fair to say when your running a black box to pay attention to how the blackened glass forms, especially for stoves that are 4+ yrs in service with no gasket change outs. The glass should look like an ugly V with the obvious cleaner section in the upper middle.
 

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
Since it is a little quiet I have had I small annoyance with a common frame of thought on this forum (not directed at anyone in particular). The “Minumum Dial Setting” seems to get so much attention and I do not understand why. The dial is a thermostat, and your room / house heat sink and comfort will determine where it could be set. Conditions like size of the room your stove is in, size and build quality of your house and outside conditions will influence the setting and is not static for me. The only thing I could see as a indicator of operation is if and when your stove can ride the hole and for how long. This would also be affected by several things like wood quality and draft which both can vary often. Kinda just throwing out the observation so if someone new is researching to buy or looking for info on operation they realize there is not “One” minimum setting in my opinion. Thoughts?
 
  • Like
Reactions: BKVP

kennyp2339

Minister of Fire
Feb 16, 2014
6,831
07462
@shgRUSS - right, draft and wood quality are very important, there is no standard setting since it’s all different based on those elements, my 1 0’clock minimum before stalling the cat could be someone else’s noon setting or 2 o’clock setting.
This is why I always say, take the time and learn the stove. People in warmer climates may have a different experience than someone in the Arctic circle.
In my head I have 3 settings, black box mode (were only the cat provides the consistent heat through the stove top)
Normal fire - gentle flames coming from the wood through as much of the burn as possible
And high setting - ripping for how ever long I need it to rip
 
  • Like
Reactions: BKVP

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
@shgRUSS - right, draft and wood quality are very important, there is no standard setting since it’s all different based on those elements, my 1 0’clock minimum before stalling the cat could be someone else’s noon setting or 2 o’clock setting.
This is why I always say, take the time and learn the stove. People in warmer climates may have a different experience than someone in the Arctic circle.
In my head I have 3 settings, black box mode (were only the cat provides the consistent heat through the stove top)
Normal fire - gentle flames coming from the wood through as much of the burn as possible
And high setting - ripping for how ever long I need it to rip
I am going to pick on you because you were the first to reply, and to extend my opinion. Right away you have stated your “Minimum Setting” is 1 o’clock, how can that be static? Unless your stove can ride the hole nonstop or you turn up the dial over your preferred room temp and the thermostat does not fully close the flapper for any length of time, then dump the excess heat out of your house( like open a window)? Not trying to sound rude just challenging the mindset I see on the forum.
 

Ashful

Minister of Fire
Mar 7, 2012
18,045
Philadelphia
Since it is a little quiet I have had I small annoyance with a common frame of thought on this forum (not directed at anyone in particular). The “Minumum Dial Setting” seems to get so much attention and I do not understand why. The dial is a thermostat, and your room / house heat sink and comfort will determine where it could be set. Conditions like size of the room your stove is in, size and build quality of your house and outside conditions will influence the setting and is not static for me. The only thing I could see as a indicator of operation is if and when your stove can ride the hole and for how long. This would also be affected by several things like wood quality and draft which both can vary often. Kinda just throwing out the observation so if someone new is researching to buy or looking for info on operation they realize there is not “One” minimum setting in my opinion. Thoughts?
You're misinterpreting the "minimum dial setting", it has nothing to do with the heating needs of your house, but is where (for some) they will stall the cat. For those who cannot "ride the hole" indefinitely, which will be most, there will some setting on your dial below which the cat will fall out of the active before the wood is mostly consumed. On some, there may even be a setting where the stove can go out completely, leaving half the load unburned in the stove. The higher of these two settings would be referred to as your minimum dial setting, in the parlance that has evolved on this forum.
 
  • Like
Reactions: Highbeam

kennyp2339

Minister of Fire
Feb 16, 2014
6,831
07462
Right away you have stated your “Minimum Setting” is 1 o’clock, how can that be static?
Its only static to my particular setup, I know anything before 1 O'clock will cause the cat to stall, for my particular application, the stove is in the basement, the heat either conducts through the non insulated wood floors to the upstairs, or goes through the convection loop of the top of the basement stairs and down to the stove, for this reason.. on warmer days here 1 o'clock on the t stat will keep an active cat, but the room wont press the stove so hard to shed heat and force the t-stat to open more and call for additional air to boost the fire box.
Obviously things change when the blower is on, or I'm burning at a higher rate because I need more heat.
 

Highbeam

Minister of Fire
Dec 28, 2006
20,232
Mt. Rainier Foothills, WA
You're misinterpreting the "minimum dial setting", it has nothing to do with the heating needs of your house, but is where (for some) they will stall the cat. For those who cannot "ride the hole" indefinitely, which will be most, there will some setting on your dial below which the cat will fall out of the active before the wood is mostly consumed. On some, there may even be a setting where the stove can go out completely, leaving half the load unburned in the stove. The higher of these two settings would be referred to as your minimum dial setting, in the parlance that has evolved on this forum.

Thank you for writing this.

Too many folks make the mistake of letting the house operate the stove when the stove is actually operated by the human. You as a human can choose to run the stove at any thermostat setting you want to regardless of whether this overheats or underheats the home. The minimum setting we refer to is the minimum setting which results in the cat not stalling during the burn cycle even if the stove is out in a field. It can be different for every installation.

The lowest setting to guarantee 70 degrees inside the home is not constant.
 
  • Like
Reactions: Ashful

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
I will slightly disagree with all replies so far in that the dial is just a thermostat and has no direct connection to cat stall. The dial sets the temp at which the room or house will be heated to. Cat stall is related to minimum requirements for combustion which has a bunch of variables like draft and fuel. Example my minimum dial on a warm fall day above freezing with no breeze and sunny is much higher (3 o’clock) than a sunny windy day at -40* (I can ride the hole forever at this point).
 

showrguy

Minister of Fire
Aug 2, 2015
587
Marysville, Pa.
I will slightly disagree with all replies so far in that the dial is just a thermostat and has no direct connection to cat stall. The dial sets the temp at which the room or house will be heated to. Cat stall is related to minimum requirements for combustion which has a bunch of variables like draft and fuel. Example my minimum dial on a warm fall day above freezing with no breeze and sunny is much higher (3 o’clock) than a sunny windy day at -40* (I can ride the hole forever at this point).
That doesn’t make any sense at all !!
If it’s -40 and blowin hard, why would you have your stove set at the lowest heat level possible ??
 

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
That doesn’t make any sense at all !!
If it’s -40 and blowin hard, why would you have your stove set at the lowest heat level possible ??
You beat me to my next point: how many people have tried the lowest setting in such conditions? I have because I get major solar gain and sometimes when it is actually sunny my house does not need any extra heat.
 

Ashful

Minister of Fire
Mar 7, 2012
18,045
Philadelphia
I will slightly disagree with all replies so far in that the dial is just a thermostat and has no direct connection to cat stall.
This is not correct. The flapper has a mechanical connection to the knob you turn. A bimetallic coil moves it around slightly from this set point, but you can always drive it hard shut, way beyond the operating range of the bimetallic coil. Put otherwise, the thermostat makes small adjustments, but the knob can make large adjustments.
 

Highbeam

Minister of Fire
Dec 28, 2006
20,232
Mt. Rainier Foothills, WA
I will slightly disagree with all replies so far in that the dial is just a thermostat and has no direct connection to cat stall. The dial sets the temp at which the room or house will be heated to. Cat stall is related to minimum requirements for combustion which has a bunch of variables like draft and fuel. Example my minimum dial on a warm fall day above freezing with no breeze and sunny is much higher (3 o’clock) than a sunny windy day at -40* (I can ride the hole forever at this point).
Actually, the stove thermostat responds to stove temperature, not house temperature. It’s function is to regulate stove temperature and it works well.
 
  • Like
Reactions: Nealm66

Nealm66

Minister of Fire
Sep 25, 2020
1,454
Western Washington
I can see where there’s some confusion. I have a spot marked that keeps my upper house around 72 most of the time but there’s definitely times I’m trying to find the lowest output setting to avoid overheating
 

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
This is not correct. The flapper has a mechanical connection to the knob you turn. A bimetallic coil moves it around slightly from this set point, but you can always drive it hard shut, way beyond the operating range of the bimetallic coil. Put otherwise, the thermostat makes small adjustments, but the knob can make large adjustments.
Yes you are right in riding the hole but not in context of a minimum dial setting for preventing stall in my opinion. To me it seems that bimetallic coil has a lot of movement. If you turn your dial to wide open on a cold stove that flapper is open all the way to the the screw stop that prevents over centring, when that stove get ripping hot that flapper is almost totally closed.
 
Jun 23, 2019
31
the mts of WNC
... The dial sets the temp at which the room or house will be heated to. ..
Would you want to clarify or correct this statement?
The thermostat actually reacts to the temp in the top of the stove near the catalyst. It's oblivious to the ambient temp of your house.
With a Princess insert, the basic scheme for our situation is to turn the knob to 3 o'clock when it's 30 F outside; to 4:30 when it's 45 out, etc. This keeps the house right around 70 F. When it's sunny out, less is needed; when it's windy or we need to warm things up, a bit more than the basic.
 

Ashful

Minister of Fire
Mar 7, 2012
18,045
Philadelphia
If you turn your dial to wide open on a cold stove that flapper is open all the way to the the screw stop that prevents over centring, when that stove get ripping hot that flapper is almost totally closed.
No, this is not the case. The flapper does not, nor does it ever need to, completely close when the knob is set at max. If this were even possible, people would be complaining about their stoves going "black box" when set on high.

The bimetallic coil moves the flapper over a relatively small range, by comparison to the range provided by the knob. Moreover, the knob has 180 degrees of rotation beyond where the flapper closed on a room temperature stove. You're never going to get the bimetallic more "open" than a room temperature stove, so there's always going to be a position at which you've locked that thing closed.

Now, after understanding that, go back and re-read posts 1111 and 1115.
 

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
No, this is not the case. The flapper does not, nor does it ever need to, completely close when the knob is set at max. If this were even possible, people would be complaining about their stoves going "black box" when set on high.

The bimetallic coil moves the flapper over a relatively small range, by comparison to the range provided by the knob. Moreover, the knob has 180 degrees of rotation beyond where the flapper closed on a room temperature stove. You're never going to get the bimetallic more "open" than a room temperature stove, so there's always going to be a position at which you've locked that thing closed.

Now, after understanding that, go back and re-read posts 1111 and 1115.
Just want to start with I am challenging an idea and not anyone. I think of it as debate, so in no way do want to make any one angry but more us collectively to think out of the preconceived box.
Would you want to clarify or correct this statement?
The thermostat actually reacts to the temp in the top of the stove near the catalyst. It's oblivious to the ambient temp of your house.
With a Princess insert, the basic scheme for our situation is to turn the knob to 3 o'clock when it's 30 F outside; to 4:30 when it's 45 out, etc. This keeps the house right around 70 F. When it's sunny out, less is needed; when it's windy or we need to warm things up, a bit more than the basic.
I have a princess and the thermostat is middle back behind and below the stove pipe. It is getting heat from the stove and also cooled from incoming air. On the princess it is very evident that it is designed for as little heat to be emitted to the back to allow the close install tolerances we get. So in my opinion the thermostat sees a balance of stove and room. Your whole house is a heat sink for your stove and the stove temp reflects the demand from the house. You are changing constants though, adjusting the dial for a constant house temp. I am using the constant of minimum setting to prevent cat stall.
 

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
No, this is not the case. The flapper does not, nor does it ever need to, completely close when the knob is set at max. If this were even possible, people would be complaining about their stoves going "black box" when set on high.

The bimetallic coil moves the flapper over a relatively small range, by comparison to the range provided by the knob. Moreover, the knob has 180 degrees of rotation beyond where the flapper closed on a room temperature stove. You're never going to get the bimetallic more "open" than a room temperature stove, so there's always going to be a position at which you've locked that thing closed.

Now, after understanding that, go back and re-read posts 1111 and 1115.
I agree the knob has much more rotation to keep the flapper from not opening but most of that is dead adjustment or just riding the hole until you get flapper engagement. Also I did not say it will close the flapper on high but will get close when the stove is cooking hot. It is hard to tell how much travel is actually in that bimetallic coil because we all have a very similar starting point for a cold stove (Room temperature). There is a very stern warning in the manual to not use the stoves in a unheated building as the chance for the thermostat to prevent over fire is high. I do understand what you are saying so I will challenge you to my opinion. Remember we are talking about minimum dial setting to prevent cat stall. Get your stove running on your known minimum and let cruise for a bit to stabilize. Next safety pop up some kind of portable walls around your stove to box it in and see what happens. If the heat can’t be easily transferred to your house the thermostat will keep your flapper closed more or if fully closed much longer and unless you can permanently ride the hole, it will stall. There can be many more variables that can be used in this test(minimum dial setting): anything that affects draft, any variation in fuel, etc.
 

shgRUSS

Member
Mar 28, 2021
56
Prince Albert SK
Again not trying to offend anyone but more challenging the concept of the “minimum dial setting “. I think of it like a debate. I have lots of thanks for everyone and all the info brought forward on this site.
 

Ashful

Minister of Fire
Mar 7, 2012
18,045
Philadelphia
Not offended, at all. Not sure why you had thought I was, but no worries. Just trying to help you understand the mechanism.

But your post 1123 seems to be drifting from the point we were debating, to where I'm not sure what the debate even is anymore. How does all of this relate to your issue with our "minimum dial setting", started in post #1106, 1108, and 1112?

The minimum dial setting is pretty simple, as already explained, it's simply the lowest you can turn your BK without stalling it. That position does not depend on any change in the temperature of your house, but it will depend on draft and the temperature of the stove. Any thought experiments of putting into a box would nudge it according to these parameters.