Secondary Burn

[513yj]

I just did some research of the woodpiles this morning and so far this year I burned about 1/3 of the wood I did last year with the exact same stove and house. I'm going to venture out on a limb here and guess it is because the temp outside is a lot warmer overall than last year at this time. If the winter is milder, such as the overall temps for the last 10 years(except for last year) I don't have a problem with this stove, but in cases like last winter it just did not cut the mustard (grey poupon nonetheless ). In the past 4 years of owning this thing it was great years 1-3 but in year 4 when the Upper Peninsula winter decided to make a comeback, I felt it wasn't up to the task. The bright side of shoveling a lot of coals is this

 

[Whitespider]

I was really concerned about cat replacement cost in '07 when I bought the Englander...
Wood burns on the brick floor. No grate.

Yeah, I'm seein' a couple different approaches to cat technology... some burn on a firebrick floor, some on a grate. And a couple different approaches to the grate also... some actually feed some air under the grate, some expect(?) the air to find it's way under (which is sort'a like one of my experiments with the PE). If I did get one, it would have to be one burning on a grate (easy ash removal if nothing more)... whether-or-not it directly fed air under it is still in my thought process.

OH‼ By-the-way...

 

[Del_]

I wondered about overfilling also. I can't think of many reasons to find unburned wood in the middle of a hot fire. Lack of oxygen to the center of the fire is all I can really imagine. It seems like overfilling or a major problem in the box itself so it's not working as intended.

Unburned wood in the firebox is a result of using firewood not seasoned properly.

 

[Chris-PA]

I was really concerned about cat replacement cost in '07 when I bought the Englander. I thought that would give secondary burn a real advantage. Blaze King warrants the converter for ten years but the initial price for the stove is so high that imo you're essentially buying the first replacement converter with the stove. Still, the investment may be worthwhile.

The cat stoves are interesting, but given my expectations for severe economic disruption in the near future I did not want to be dependent on replacements parts from some small company that might not make it. If the secondary combustion stoves give up something in performance to the cat stoves I'm OK with that, as they depend only of the shape of the steel/iron and refractory parts. In fact when we bought the little stove (Hampton H200) I eliminated several stoves as they had very complex cast refractory combustion chamber parts that I would not be able to duplicate. The Magnolia has only firebrick.

 

[1project2many]

Unburned wood in the firebox is a result of using firewood not seasoned properly.

Maybe. I thought he'd said the stove had gotten hot and achieved secondary combustion before dieing back. I can't get secondary unless the moisture content in the stove is low.

 

[Locust Cutter]

I just did some research of the woodpiles this morning and so far this year I burned about 1/3 of the wood I did last year with the exact same stove and house. I'm going to venture out on a limb here and guess it is because the temp outside is a lot warmer overall than last year at this time. If the winter is milder, such as the overall temps for the last 10 years(except for last year) I don't have a problem with this stove, but in cases like last winter it just did not cut the mustard (grey poupon nonetheless ). In the past 4 years of owning this thing it was great years 1-3 but in year 4 when the Upper Peninsula winter decided to make a comeback, I felt it wasn't up to the task. The bright side of shoveling a lot of coals is thisView attachment 386638

I've started my frill and smoker more than once on live coals out of my PE. I guess you have to find your silver linings where you can. LMAO

Unburned wood in the firebox is a result of using firewood not seasoned properly.

Or a sign of insufficient airflow/fuel where they're getting smothered. They hey to the fire triangle is having enough fuel, heat and oxygen to burn (and then to regulate the efficiency of burn thereafter). If the air and air/fuel ratio is out of spec with it's relationship to the heat, the fire suffers. I think that after the secondary dies, the airflow to the bottom isn't enough for the remaining fuel quantity to burn efficiently/properly resulting in charcoal or what the pellet stove guys call clinkers (albeit via a different process).

 

[Del_]

Or a sign of insufficient airflow/fuel where they're getting smothered. They hey to the fire triangle is having enough fuel, heat and oxygen to burn (and then to regulate the efficiency of burn thereafter). If the air and air/fuel ratio is out of spec with it's relationship to the heat, the fire suffers. I think that after the secondary dies, the airflow to the bottom isn't enough for the remaining fuel quantity to burn efficiently/properly resulting in charcoal or what the pellet stove guys call clinkers (albeit via a different process).

But we are talking about unburnt splits of wood, not charcoal or clinkers. The heat of the coal bed sitting on top of the unburnt wood should force out the pyrolytic gasses. If there is not enough oxygen for these gasses to mix and burn then they just go up the chimney unburnt. Being this is not happening moisture in the wood is likely the cause. In a furnace with forced draft when the draft blower is off the pyrolytic gasses are still being released, they just go up the chimney unburnt. Cutting off the air supply to a burning load of wood does not stop the release of these gasses. This is a main reason for a loss of combustion efficiency and increased particle output of this type of heating device. Even with the loss of efficiency though these heating devices control heat output well and run for a long times but they do consume larger amounts of fuel for the same btu output.

 

[Locust Cutter]

I've never had entire un-burnt splits of wood but have had "leftovers" which were up 8-10" long by 2-4" wide. If I have them, they'll be at the back of the stove buried at the bottom where the airflow is the worst.

 

[Whitespider]

Unburned wood in the firebox is a result of using firewood not seasoned properly.

So... when I close the vents on my grill, and the fire goes out, it's because the charcoal is wet??

The heat of the coal bed sitting on top of the unburnt wood should force out the pyrolytic gasses.

So... where is this heat gonna' come from if the coals are dead because they've been starved of oxygen??

Give up on the wet wood theory Del... I can state as fact the wood ain't wet, I can state as fact that it is well seasoned (as dry as is possible in the local I live).
You on the other hand are just relying on a magic crystal ball.

I've never had entire un-burnt splits of wood but have had "leftovers" which were up 8-10" long by 2-4" wide. If I have them, they'll be at the back of the stove buried at the bottom where the airflow is the worst.

Yup... that's what I'm talkin' 'bout. I did say "charred and blackened."



We have a conundrum... the two thermostats are not in agreement at the moment. I've never noticed such a conundrum before
The lower one is, or was, for the gas furnace... which don't even have the gas turned on.

 

[Locust Cutter]

Are those the settings or the registering temps? A 1° isn't bad.

 

[1project2many]

I've never had entire un-burnt splits of wood but have had "leftovers" which were up 8-10" long by 2-4" wide. If I have them, they'll be at the back of the stove buried at the bottom where the airflow is the worst.

Yup... that's what I'm talkin' 'bout. I did say "charred and blackened."

Ok, not complete splits. Still a bunch of unused fuel. But even better to confirm dryness and some gasification.

 

[Cerran]

Sure I have... over and over.
Why?? Because they don't work worth sour owl crap in those cases. What more needs sayin'??
What situations?? When a relatively constant and steady heat output is required (or even desired) during the entire burn cycle.

At yet lots of us with the newer stoves get constant and steady heat output for the majority of the burn cycle. No wood stove gives out constant heat during the entire burn cycle unless you're loading it partway through the cycle since it's a batch process. Additionally you haven't provided the evidence or the data to support your assertions WS, you have simply asserted it's true.

Stove models?? Heck, I don't know... 'cause it ain't important to me, it's not something I would even think to ask. I know one was purchased at a dealer in Waterloo and one at a "big-box" store (Menards I think)... don't know 'bout the others.
Combustion types?? Huh?? What do you mean?? They are elitist stoves... secondary combustion types.
Firewood used?? You're kiddin'?? Well, the firewood came from trees I believe. B'sides, an up-draft box ain't picky.

So in other words you really don't know if the stoves really work well or not because you have already decided without any good data to support your position. If you don't understand that there are different combustion types and why the newer stoves operate the way they do, how can you make a claim what works and what doesn't? Different firewood types have different combustion characteristics, which anyone who has used several different wood types will tell you.

Sure you have... you just ain't listening.
Because of a more constant and steady heat output over the entire burn cycle... which... is... "better"... in... certain... situations.

Which you have provided no evidence for. The older stove types have the same rise and fall in heat output as a newer stove because of the nature of a batch burn process. Your claim I haven't been listening is just more obfuscation to cover up the fact that you haven't made a solid argument here.

 

[Cerran]

I've started my frill and smoker more than once on live coals out of my PE. I guess you have to find your silver linings where you can. LMAO

Or a sign of insufficient airflow/fuel where they're getting smothered. They hey to the fire triangle is having enough fuel, heat and oxygen to burn (and then to regulate the efficiency of burn thereafter). If the air and air/fuel ratio is out of spec with it's relationship to the heat, the fire suffers. I think that after the secondary dies, the airflow to the bottom isn't enough for the remaining fuel quantity to burn efficiently/properly resulting in charcoal or what the pellet stove guys call clinkers (albeit via a different process).

Clinkers are a different process, clinkers are caused by localized high temperatures that cause the incombustable portions of the wood (ash) to fuse together.

 

[slowp]

I see the problem. WS, you seem to have forgotten something I recall you posting on one of the other lengthy, I Hate My Stove threads about your start up procedure. You were doing it like you have written. However, later you read the instructions and found out that you needed to move the air control to high and then pull it back a bit to start up the stove. That's the procedure for my Elitist, communist, beyond EPA stove. Mine has a little picture at the place you put the lever. Perhaps yours is missing that so it causes you to forget?

 

[Whitespider]

The older stove types have the same rise and fall in heat output as a newer stove because of the nature of a batch burn process.

The same?? Really??
Not the ones I have and have had... not anywhere near as dramatic.

Are those the settings or the registering temps? A 1° isn't bad.

Those are the actuall temperature the thermometer is reading... right now the top thermostat "set point" is 68°, the bottom one is 60° I believe.
Yeah, 1° ain't bad... but they've come to an agreement.
And it's a bit warm in here again...

 

[Del_]

The same?? Really??
Not the ones I have and have had... not anywhere near as dramatic.

All of the old smoke dragons I've operated over the years had very similar heating curves as the modern more efficient stoves except for the peak from secondary combustion that takes place in the more efficient stoves. The smoke dragons just send the unburnt pyrolytic gasses up the flue forming a combination of creosote and air pollution.

For us the extra heat in the living space is a nice bonus along with having a great fire view. We also cook and heat water for doing dishes on the stove top.

 

[Chris-PA]

All of the old smoke dragons I've operated over the years had very similar heating curves as the modern more efficient stoves except for the peak from secondary combustion that takes place in the more efficient stoves. The smoke dragons just send the unburnt pyrolytic gasses up the flue forming a combination of creosote and air pollution.

For us the extra heat in the living space is a nice bonus along with having a great fire view. We also cook and heat water for doing dishes on the stove top.


View attachment 386739

Yep, even the baby stove is blasting us out today. I shoveled a little ash out of it today, and left the few coals that were in it there. Nice secondary burn. Just a couple of 14" ash splits.

 

[Cerran]

The same?? Really??
Not the ones I have and have had... not anywhere near as dramatic.

The curves will not likely be identical stove to stove, but the output curves will be a similar shape and the peak of the heat will come during the peak burn cycle prior to all the volatiles being driven from the wood. So yes a traditional stove and a modern staged combustion stove are going to have almost the same shape output curves when loaded with the same volume of wood. The area under the curve when you map heat output over time is going to be higher for the staged stove because the combustion is more efficient. You haven't seen the same dramatic rise with the older stove type because they are less efficient and more heat is lost up the flue. If you were to calculate output over time between a modern and an older stove, the newer stove will make more efficient use of the same mass of wood.

If you were to vary the air input with automatic control you could flatten the curve some but you're still not going to get a constant output with a batch process. This is thermodynamics and heat transfer 101.

 

[Whitespider]

...efficient. ...efficient... ...calculate output over time... ...efficient...

The efficiency argument is lost I me... which efficiency are you meaning??
Combustion efficiency??
Total heat output over the entire burn cycle??
Per hour heat output??

We're talkin' about a heater... it's the per hour output that matters (to me). If fuel load remains the same, and you double the burn cycle to output 25% more heat, you lower the per hour heat output. That ain't "heating" efficient in my mind...
The "heating" efficiency of most any other heating appliance is on a per hour bases. For example; a gas furnace rated at 90,000 BTU per hour (of run time) at 85% efficiency, will output 76,500 BTUs per hour of run time. In other words, fuel input and combustion efficiency is used to calculate per hour output. Two furnaces, both rated at 90,000 BTUs, one at 85% efficiency and the other at 90% efficiency... the 90% efficient furnace will output more heat per hour of run time.

But wood fired appliances are not efficiency rated on a per hour basis... they ain't even efficiency rated on heat output. It's simply ratio of fuel input to un-burned mass in the exhaust... over the entire burn cycle, regardless of how long that entire burn cycle may be. So the efficiency argument is lost on me, unless you provide a whole lot more information... a whole lot more‼

I've said this before...
My old pickup will get 45 MPG... if I drive it 10 MPH‼ That's pretty fuel efficient, but ain't a very efficient way to travel.
*

 

[Cerran]

The efficiency argument is lost I me... which efficiency are you meaning??
Combustion efficiency??
Total heat output over the entire burn cycle??
Per hour heat output??

We're talkin' about a heater... it's the per hour output that matters (to me). If fuel load remains the same, and you double the burn cycle to output 25% more heat, you lower the per hour heat output. That ain't "heating" efficient in my mind...
The "heating" efficiency of most any other heating appliance is on a per hour bases. For example; a gas furnace rated at 90,000 BTU per hour (of run time) at 85% efficiency, will output 76,500 BTUs per hour of run time. In other words, fuel input and combustion efficiency is used to calculate per hour output. Two furnaces, both rated at 90,000 BTUs, one at 85% efficiency and the other at 90% efficiency... the 90% efficient furnace will output more heat per hour of run time.

But wood fired appliances are not efficiency rated on a per hour basis... they ain't even efficiency rated on heat output. It's simply ratio of fuel input to un-burned mass in the exhaust... over the entire burn cycle, regardless of how long that entire burn cycle may be. So the efficiency argument is lost on me, unless you provide a whole lot more information... a whole lot more‼

I've said this before...
My old pickup will get 45 MPG... if I drive it 10 MPH‼ That's pretty fuel efficient, but ain't a very efficient way to travel.
*

Efficiency is measured in heat output versus fuel input.

Per hour heat output has nothing to do with efficiency, that is power or rate of doing work as you said.

I agree with the idea that wood appliances aren't typically rated on steady heat output and that is something the wood stove industry should work on, however given the uncertain nature of wood that is not unexpected. If you properly size a newer advanced combustion system to the application, it is going to have enough output (power) to heat the space and it will consume less wood than the older technology for the same total heat output.

Your entire argument is based on utilizing a stove for a purpose for which it was not intended. You claim the efficiency argument is lost on you without more information which is exactly the point I was making about your claims with the newer wood stoves. You have provided no data to support your assertions, you have simply asserted they are true.

I doubt your old pickup will get 45MPG if you drive it 10MPH unless you have a go-kart motor in it or possibly if it's a diesel and you're on flat ground.