Do any stoves last longer than 24 hours on a fill?

[Ambull01]

Sorry, that is not a fact. Size does not really matter in the case of burn times, otherwise OWBs would burn for a week, simply because the fireboxes are HUGE compared to wood stoves. I also had one of the largest wood stoves ever made which was an Earth Stove, and the firebox in that thing was also huge. The burn times on that and the Central Boiler OWB and this Englander stove I have now were and are all about the same. None of them can or could get a full 24 hour burn time, even stuffed full. Close, but not 24 hours. More typical is 12-18 hours for all of them, large or small splits, oak or locust or madrone or any other hardwood out here in the wild west. You might have some coals last that long, but not anything to heat much with.

What I have found burning in a lot of different stoves , inserts and boilers is that if you stuff them full and damp them way down, you just make a lot of charcoal. The wood gasses escape unburned and you get charcoal. That is how charcoal is made actually. Fill a steel box with wood, heat it up, and let it smolder by cutting off the air supply. Also by making charcoal the heating efficiency drastically drops and you do not get as much heat out of the wood compared to burning it. You may get heat for a longer period of time by damping your stove down, which is what most people do, but you are not going to get more total heat energy into your house. You get the most heat by burning dry wood hot and fast, like in a wood gassifier. Then the problem is what to do with all that heat energy released in a short period of time. The answer is to either build a large masonry fireplace with a long flue to capture the heat and radiate it slowly, or build a water jacket around the burn chamber and trap the heat in a large tank of water and run a hydronic loop to radiate it slowly.

From my experience, I have found that I get the most heat out of my wood by burning fewer splits in wood stoves at a time and feeding them a steady diet. I rarely stuff my stove here full of wood, and I keep a smaller, hotter fire going here. If it gets colder, I add more wood more often and open the damper more, if it is warmer I add less wood, less often and damp it down more. I also vary my wood species that I am burning; cold temps I burn oak and locust, warmer temps I burn cedar and pine. It varies as to what wood I have available. I also burn 20% moisture or less dry wood.

Have you experimented with building a "water jacket" around the burn chamber? Something that would be so simple even a Marine could make? Just curious.

 

[NSMaple1]

A water jacket around the burn chamber complicates things, efficiency wise. You are then in effect liquid cooling your firebox - which doesn't do too much for hot burn temps & burning of all the wood product. Gasifiers do have a water jacketed chamber that you put the wood in & get burning, and they have another section with tubes surrounded by the same water, that the burned gases pass through before they hit the chimney. But they also have another section in between that is not surrounded by water but rather by refractory, where the gasses released in the first chamber can all burn up, very completely & very hotly (1500-2000°f). No creosote or smoke beyond here, everything gets turned into heat.

 

[Marine5068]

Sorry, that is not a fact. Size does not really matter in the case of burn times, otherwise OWBs would burn for a week, simply because the fireboxes are HUGE compared to wood stoves. I also had one of the largest wood stoves ever made which was an Earth Stove, and the firebox in that thing was also huge. The burn times on that and the Central Boiler OWB and this Englander stove I have now were and are all about the same. None of them can or could get a full 24 hour burn time, even stuffed full. Close, but not 24 hours. More typical is 12-18 hours for all of them, large or small splits, oak or locust or madrone or any other hardwood out here in the wild west. You might have some coals last that long, but not anything to heat much with.

What I have found burning in a lot of different stoves , inserts and boilers is that if you stuff them full and damp them way down, you just make a lot of charcoal. The wood gasses escape unburned and you get charcoal. That is how charcoal is made actually. Fill a steel box with wood, heat it up, and let it smolder by cutting off the air supply. Also by making charcoal the heating efficiency drastically drops and you do not get as much heat out of the wood compared to burning it. You may get heat for a longer period of time by damping your stove down, which is what most people do, but you are not going to get more total heat energy into your house. You get the most heat by burning dry wood hot and fast, like in a wood gassifier. Then the problem is what to do with all that heat energy released in a short period of time. The answer is to either build a large masonry fireplace with a long flue to capture the heat and radiate it slowly, or build a water jacket around the burn chamber and trap the heat in a large tank of water and run a hydronic loop to radiate it slowly.

From my experience, I have found that I get the most heat out of my wood by burning fewer splits in wood stoves at a time and feeding them a steady diet. I rarely stuff my stove here full of wood, and I keep a smaller, hotter fire going here. If it gets colder, I add more wood more often and open the damper more, if it is warmer I add less wood, less often and damp it down more. I also vary my wood species that I am burning; cold temps I burn oak and locust, warmer temps I burn cedar and pine. It varies as to what wood I have available. I also burn 20% moisture or less dry wood.

Physics Theory doesn't change by adding more or less wood...it stays constant.
So it is in fact "a fact"
The part of that statement that you are missing is that the OWB is using more flame along with that "more fuel" and that's the reason why it burns faster or as fast as a smaller amount of wood in a wood stove.
Larger wood = larger flame. Smaller wood = smaller flame.
It's not rocket science, but it is Physics.
Now how, when and where that heat is transferred, that's another matter.
A straight-up answer to the original question of "does size of wood amount matter?" is YES
Size matters.
More wood=more heat

 

[windthrown]

Have you experimented with building a "water jacket" around the burn chamber? Something that would be so simple even a Marine could make? Just curious.

I have not built one, but I have bought them. That is the basic design of just about every OWB or IWB out there. They have a water jacket around the burn chamber.

 

[windthrown]

Physics Theory doesn't change by adding more or less wood...it stays constant.
So it is in fact "a fact"
The part of that statement that you are missing is that the OWB is using more flame along with that "more fuel" and that's the reason why it burns faster or as fast as a smaller amount of wood in a wood stove.
Larger wood = larger flame. Smaller wood = smaller flame.
It's not rocket science, but it is Physics.
Now how, when and where that heat is transferred, that's another matter.
A straight-up answer to the original question of "does size of wood amount matter?" is YES
Size matters.
More wood=more heat

I was a rocket engineer once. At General Dynamics in San Diego. We built Atlas-Centaur rockets there. I mostly worked on the F-16 when I was there though. Different kind of rocket. I can talk about physics all you want. And the math behind it.

In theory your premise would be correct that 2x the wood generates 2x the heat, in some ideal optimum world. The problem is that we are talking about cordwood here, and not wood pellets, NG, or some other constantly fed fuel. If you are loading a burn chamber with chunks of wood there are many variables, such as water content of the wood, species and density of the wood, and size of the wood. I could load in more wood and get more heat faster if it has been cut smaller, because there is more surface area to burn. Larger splits would burn slower and longer due to less surface area exposed to the air. But burn results are also greatly affected by the duration of the burns, the firebox design, secondary or tertiary air injection and/or variable burn process (such as a wood gassifier or CAT), and the amount of heat being extracted and how it is extracted.

My statements are referring to the 24 hour burn times that the OP is referring to, and not fast burns in boilers like 2 vs. 4 hours. In the short burn cases the damper would likely be wide open the whole time, and depending in the stove design, may or may not result in 2x the heat from 2x the wood. If the stove or boiler is not designed to extract all the heat with the firebox filled and burning full blast, excess heat is going to escape from the system into the air out the flue. Similarly, which is more my point, if you stuff your burn chamber full and damp it down to get long burn times, the less efficient it will become because you will lose unburned wood gasses out the flue when the boiler damper is closed, or the stove is smoldering below the temp. point where the secondary air injectors take effect, or the CAT works. Just about every wood burning appliance I have seen preaches in the instructions that you build a smaller hotter fire to get the best results. That is because there is usually not a 1:1 linear correlation between the amount of wood that you stuff into a wood stove, and the resulting heat that you get out of it. Efficiency drops the more you load them and the more you damp them down.

 

[Whitespider]

 

[Woody912]

I was a rocket engineer once. At General Dynamics in San Diego. We built Atlas-Centaur rockets there. I mostly worked on the F-16 when I was there though. Different kind of rocket. I can talk about physics all you want. And the math behind it.

In theory your premise would be correct that 2x the wood generates 2x the heat, in some ideal optimum world. The problem is that we are talking about cordwood here, and not wood pellets, NG, or some other constantly fed fuel. If you are loading a burn chamber with chunks of wood there are many variables, such as water content of the wood, species and density of the wood, and size of the wood. I could load in more wood and get more heat faster if it has been cut smaller, because there is more surface area to burn. Larger splits would burn slower and longer due to less surface area exposed to the air. But burn results are also greatly affected by the duration of the burns, the firebox design, secondary or tertiary air injection and/or variable burn process (such as a wood gassifier or CAT), and the amount of heat being extracted and how it is extracted.

My statements are referring to the 24 hour burn times that the OP is referring to, and not fast burns in boilers like 2 vs. 4 hours. In the short burn cases the damper would likely be wide open the whole time, and depending in the stove design, may or may not result in 2x the heat from 2x the wood. If the stove or boiler is not designed to extract all the heat with the firebox filled and burning full blast, excess heat is going to escape from the system into the air out the flue. Similarly, which is more my point, if you stuff your burn chamber full and damp it down to get long burn times, the less efficient it will become because you will lose unburned wood gasses out the flue when the boiler damper is closed, or the stove is smoldering below the temp. point where the secondary air injectors take effect, or the CAT works. Just about every wood burning appliance I have seen preaches in the instructions that you build a smaller hotter fire to get the best results. That is because there is usually not a 1:1 linear correlation between the amount of wood that you stuff into a wood stove, and the resulting heat that you get out of it. Efficiency drops the more you load them and the more you damp them down.

Efficiency is not really a consideration when you are going to be away from the house for 24 hrs, you have enough wood to last until the next ice age and you just want to have a coal bed you can throw small pcs onto and get a fire going quickly. I will usually throw a green pc on top of the load when I am dealing with this scenario and then pound the air inlets shut

 

[Marine5068]

I was a rocket engineer once. At General Dynamics in San Diego. We built Atlas-Centaur rockets there. I mostly worked on the F-16 when I was there though. Different kind of rocket. I can talk about physics all you want. And the math behind it.

In theory your premise would be correct that 2x the wood generates 2x the heat, in some ideal optimum world. The problem is that we are talking about cordwood here, and not wood pellets, NG, or some other constantly fed fuel. If you are loading a burn chamber with chunks of wood there are many variables, such as water content of the wood, species and density of the wood, and size of the wood. I could load in more wood and get more heat faster if it has been cut smaller, because there is more surface area to burn. Larger splits would burn slower and longer due to less surface area exposed to the air. But burn results are also greatly affected by the duration of the burns, the firebox design, secondary or tertiary air injection and/or variable burn process (such as a wood gassifier or CAT), and the amount of heat being extracted and how it is extracted.

My statements are referring to the 24 hour burn times that the OP is referring to, and not fast burns in boilers like 2 vs. 4 hours. In the short burn cases the damper would likely be wide open the whole time, and depending in the stove design, may or may not result in 2x the heat from 2x the wood. If the stove or boiler is not designed to extract all the heat with the firebox filled and burning full blast, excess heat is going to escape from the system into the air out the flue. Similarly, which is more my point, if you stuff your burn chamber full and damp it down to get long burn times, the less efficient it will become because you will lose unburned wood gasses out the flue when the boiler damper is closed, or the stove is smoldering below the temp. point where the secondary air injectors take effect, or the CAT works. Just about every wood burning appliance I have seen preaches in the instructions that you build a smaller hotter fire to get the best results. That is because there is usually not a 1:1 linear correlation between the amount of wood that you stuff into a wood stove, and the resulting heat that you get out of it. Efficiency drops the more you load them and the more you damp them down.

I agree. Lots of variables that are constantly changing.
And as an Architectural Engineer, Mechanical Designer and licensed Welder, I have all the theoretical background, practical experience and know-how that a man needs to more than understand all that you wrote.
Any wood stove is inside of the dwelling and therefore the quality of the envelope of that dwelling plays an even bigger part in keeping the heat in. and the cold air out.
Like I said, too many variables to make blanket statements like the ones in the original post.
But we all agree that more efficiency is better. In the dwelling, in the stove and in the fuel used.

 

[olyman]

Physics Theory doesn't change by adding more or less wood...it stays constant.
So it is in fact "a fact"
The part of that statement that you are missing is that the OWB is using more flame along with that "more fuel" and that's the reason why it burns faster or as fast as a smaller amount of wood in a wood stove.
Larger wood = larger flame. Smaller wood = smaller flame.
It's not rocket science, but it is Physics.
Now how, when and where that heat is transferred, that's another matter.
A straight-up answer to the original question of "does size of wood amount matter?" is YES
Size matters.
More wood=more heat

 

[olyman]

I was a rocket engineer once. At General Dynamics in San Diego. We built Atlas-Centaur rockets there. I mostly worked on the F-16 when I was there though. Different kind of rocket. I can talk about physics all you want. And the math behind it.

In theory your premise would be correct that 2x the wood generates 2x the heat, in some ideal optimum world. The problem is that we are talking about cordwood here, and not wood pellets, NG, or some other constantly fed fuel. If you are loading a burn chamber with chunks of wood there are many variables, such as water content of the wood, species and density of the wood, and size of the wood. I could load in more wood and get more heat faster if it has been cut smaller, because there is more surface area to burn. Larger splits would burn slower and longer due to less surface area exposed to the air. But burn results are also greatly affected by the duration of the burns, the firebox design, secondary or tertiary air injection and/or variable burn process (such as a wood gassifier or CAT), and the amount of heat being extracted and how it is extracted.

My statements are referring to the 24 hour burn times that the OP is referring to, and not fast burns in boilers like 2 vs. 4 hours. In the short burn cases the damper would likely be wide open the whole time, and depending in the stove design, may or may not result in 2x the heat from 2x the wood. If the stove or boiler is not designed to extract all the heat with the firebox filled and burning full blast, excess heat is going to escape from the system into the air out the flue. Similarly, which is more my point, if you stuff your burn chamber full and damp it down to get long burn times, the less efficient it will become because you will lose unburned wood gasses out the flue when the boiler damper is closed, or the stove is smoldering below the temp. point where the secondary air injectors take effect, or the CAT works. Just about every wood burning appliance I have seen preaches in the instructions that you build a smaller hotter fire to get the best results. That is because there is usually not a 1:1 linear correlation between the amount of wood that you stuff into a wood stove, and the resulting heat that you get out of it. Efficiency drops the more you load them and the more you damp them down.

zzzziiiiiinnngggggggggg...clear outta park!!! thanks,,

 

[Gypo Logger]

Wouldn't it be great if we could trap the lost heat and gases that escape from the flue.
As was mentioned, the dwelling around the stove plays a large part in the equation.
John

 

[Ambull01]

Wouldn't it be great if we could trap the lost heat and gases that escape from the flue.
As was mentioned, the dwelling around the stove plays a large part in the equation.
John

Yeah buddy! That would be great. Although I guess that would be a masonry fireplace.

A water jacket around the burn chamber complicates things, efficiency wise. You are then in effect liquid cooling your firebox - which doesn't do too much for hot burn temps & burning of all the wood product. Gasifiers do have a water jacketed chamber that you put the wood in & get burning, and they have another section with tubes surrounded by the same water, that the burned gases pass through before they hit the chimney. But they also have another section in between that is not surrounded by water but rather by refractory, where the gasses released in the first chamber can all burn up, very completely & very hotly (1500-2000°f). No creosote or smoke beyond here, everything gets turned into heat.

Woops, missed the "burn chamber" part. I thought ya'll were talking about using water outside the firebox to store heat.

 

[maine]

Physics Theory doesn't change by adding more or less wood...it stays constant.
So it is in fact "a fact"
The part of that statement that you are missing is that the OWB is using more flame along with that "more fuel" and that's the reason why it burns faster or as fast as a smaller amount of wood in a wood stove.
Larger wood = larger flame. Smaller wood = smaller flame.
It's not rocket science, but it is Physics.
Now how, when and where that heat is transferred, that's another matter.
A straight-up answer to the original question of "does size of wood amount matter?" is YES
Size matters.
More wood=more heat

i do not want to start an arguement and I value your knowledge very much.
I just have to disagree because physics change immediately after you add more wood.

 

[Joe Blackeby]

Howdy, I have a 30 + year old Monark Ait -Tight Add-On furnace With good, sesoned TWO years, split and covered hardwood, no pine, i can keep the house 73 for twelve hours, shut it back, no less than 70+ 24 hours.
Then the oilfired heater kicks in.
I'm just saying. Cheers!