Thermostat range limits?

[Tron]

All,

I'm just wondering if someone knows the answer to this: is the BK thermostat limited (by design or construction) in any way regarding opening the flapper?

Now that it's cold outside and I need some more heat output from the stove, I notice that with the knob set at around 4 o'clock (6 o'clock being wide open) I get a nice and steady heat output exactly the way it should be as long as unburnt wood is in the stove. When that's gone and only coals are left, the heat output drops considerably.
However, by turning the thermostat to wide open in this situation, I'm able to get the heat output back up to the previous level by burning down the coals.

So my question is: is it just that the thermostat is not able to open the flapper completely when the knob is at 4 o'clock? I.e., by turning the knob to WOT I'm giving the thermostat that range of movement back to open fully? @BKVP, is that the case?

If it's not and the thermostat is functioning correctly, it should be able to maintain stove temperature and heat output even with only coals left (at least until the flapper is wide open).

Thx!

 

[m37charlie]

You can actually visualize the flapper valve simply by removing the steel cover, which has the approximate dimensions of a rectangular box minus 1 side (bottom).
Be careful replacing it, the thin slot on 1 side for the round “axle” rod can interfere with rotation if not carefully replaced.
I again reiterate that hardwood coals (in Alaska birch is the hardwood) tend to burn slowly and build up quickly, unless the operator develops a rhythm of hardwood at night, softwood (spruce is our softwood) in daytime if needed, and after sunset till bedtime, when stove (by then all birch coals from previous night should be gone) is loaded with hardwood.
This pattern will guarantee no unburned coal buildup and ability to get maximum heat output quickly on demand.
I’m not sure however what I’d do if ONLY hardwood is available. If someone wants to mail me excess oak or hickory or ash or whatever I would be delighted to accept it.

 

[Murray01]

That’s exactly how my BK stove works, as the wood burns down I have to add air to keep the heat production constant. Usually about 2 hours before a reload I turn my thermostat control to WOT(6:00 o’clock position).

I’ve always ASSUMED that by turning the thermostat control to WOT the air inlet is wide open. BK calls the knob the “thermostat” I call it the “air inlet control”. As you dial the thermostat knob down you are limiting the air into the firebox. To me, a thermostat is something that I would set to say 23C and the heating appliance would maintain room temperature at 23C, my Princess has no way of knowing what temperature I want in the room just more or less heat depending on where my thermostat control is set.

What I have noticed is after a reload and the initial 20-30 minutes of running the stove at WOT to char the wood and after turning the thermostat knob to the 4:00 position I will get a lazy flame that comes and goes for the next hour or so. I’ve always assumed that the wood was gassing off, hence the short lived flame. Maybe I’m wrong in my assumption and it’s the thermostat making small adjustments to the air inlet to maintain a constant heat at the 4:00 o’clock position?

 

[Tron]

I’ve always ASSUMED that by turning the thermostat control to WOT the air inlet is wide open. BK calls the knob the “thermostat” I call it the “air inlet control”. As you dial the thermostat knob down you are limiting the air into the firebox. To me, a thermostat is something that I would set to say 23C and the heating appliance would maintain room temperature at 23C, my Princess has no way of knowing what temperature I want in the room just more or less heat depending on where my thermostat control is set.

You're right, it's not a thermostat in that sense, but rather a heat-output regulator. In that sense it works fine as the heat output is constant mostly independent of the burn stage.

What I have noticed is after a reload and the initial 20-30 minutes of running the stove at WOT to char the wood and after turning the thermostat knob to the 4:00 position I will get a lazy flame that comes and goes for the next hour or so. I’ve always assumed that the wood was gassing off, hence the short lived flame. Maybe I’m wrong in my assumption and it’s the thermostat making small adjustments to the air inlet to maintain a constant heat at the 4:00 o’clock position?

I don't think so, I also get that "lazy flame", that's more the wood gassing off and occasionally hitting a hot spot so the gas ignites in the firebox instead of being consumed by the cat.

 

[Tron]

I’m not sure however what I’d do if ONLY hardwood is available.

I exclusively have softwood, loblolly pine. There may be the occasional piece of gumwood in there, but 99+% it's pine.

 

[Murray01]

Why does BK call it a thermostat? To be called a thermostat it must/should be able to adjust the incoming air to maintain a constant temperature?

 

[Tron]

Why does BK call it a thermostat?

Probably the closest term they found?
THB, if the heat output remains constant, and the heat loss of your home is, too, you do get a thermostat function, your room temperature will reach an equilibrium at some point.

 

[Murray01]

The one thing I have noticed if I run a small fan behind the stove the wood in the stove will glow brighter than without the fan running. No adjustment made to the thermostat knob. Maybe that’s the thermostat allowing more air in since I’m cooling the stove with the fan?

 

[Tron]

Maybe that’s the thermostat allowing more air in since I’m cooling the stove with the fan?

I think you're rather pushing in more air into the intake than the thermostat accounts for.

 

[Murray01]

I think you're rather pushing in more air into the intake than the thermostat accounts for.

That shouldn’t matter if the air intake(thermostat) is set. My fan is above the air intake, blowing about the in the middle of the back of the stove.

 

[Tron]

Well, if you're actively cooling the thermostat, i.e. the bimetallic coil in particular, I'm not surprised it opens up more.
Your HVAC thermostat reacts the same way.