I've noticed that my boiler burns a lot cleaner when the grates are clean and the ash pan has been emptied. Does it naturally follow that I'm getting better combustion efficiency as well?
Clean Burn vs. Efficiency Question
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What naturally follows is the same as with my big insert. Emptying the ash pan and cleaning the grate lets the stove suck air through the leaky gasket on the ashpan door.
To me, there are two efficiencies - efficient combustion and efficient heating. If you firebox / flue look cleaner and there is less visible smoke, that would seem to indicate more efficient combustion. However, if you are burning twice the wood for the same heat, that isn't very efficient. Sometimes there can be trade-offs between these two.
Corey
Corey
Thanks Corey. I'll have to keep an eye on wood consumption.
Come to think of it, my fireplace burns pretty clean, but it's obviously not very efficient. On the other hand, one would assume that stoves, furnaces and boilers were designed to burn most efficiently when they are well maintained, and clean grates and frequent ash removal are part of a good maintenance regime.
Come to think of it, my fireplace burns pretty clean, but it's obviously not very efficient. On the other hand, one would assume that stoves, furnaces and boilers were designed to burn most efficiently when they are well maintained, and clean grates and frequent ash removal are part of a good maintenance regime.
Hi Guys:
Again, here's the poop on burning efficiency of a stove:
The amount of the heat that is actually transferred into the room depends on a number of factors:
1. COMBUSTION EFFICIENCY: In all new technology stoves this percentage is in the high nineties.
2. HEAT TRANSFER (Thermal) EFFICIENCY: How much of the heat generated in the firebox escapes through the chimney into the atmosphere (stack loss) depends on the firing strategy and the thermal mass of the heater. Newer metal stoves and fireplace inserts with firebrick lining are designed to be clean.
3. LINEARITY OF OUTPUT: For clean combustion, wood requires a brisk, hot fire which results in short burn times. If the heater has no storage capacity the fire must either be damped, otherwise all the heat is transferred into the room during the burn time. As a result, the room becomes overheated while the fire is burning and under heated after the fire has died down. An overheated room loses more heat to the environment because of the higher temperature differential between the room air and the outdoor air.
4. PARTIAL CHARGE EFFICIENCY: Many stoves do not handle small fuel charges efficiently because high temperatures are needed to obtain non-smoldering combustion. Many heaters cannot handle all reasonable fuel charges with equal efficiency which is important during milder days of the heating season when only a partial charge is required.
Boiller plate, but it's the real deal.
Aye,
Marty
Again, here's the poop on burning efficiency of a stove:
The amount of the heat that is actually transferred into the room depends on a number of factors:
1. COMBUSTION EFFICIENCY: In all new technology stoves this percentage is in the high nineties.
2. HEAT TRANSFER (Thermal) EFFICIENCY: How much of the heat generated in the firebox escapes through the chimney into the atmosphere (stack loss) depends on the firing strategy and the thermal mass of the heater. Newer metal stoves and fireplace inserts with firebrick lining are designed to be clean.
3. LINEARITY OF OUTPUT: For clean combustion, wood requires a brisk, hot fire which results in short burn times. If the heater has no storage capacity the fire must either be damped, otherwise all the heat is transferred into the room during the burn time. As a result, the room becomes overheated while the fire is burning and under heated after the fire has died down. An overheated room loses more heat to the environment because of the higher temperature differential between the room air and the outdoor air.
4. PARTIAL CHARGE EFFICIENCY: Many stoves do not handle small fuel charges efficiently because high temperatures are needed to obtain non-smoldering combustion. Many heaters cannot handle all reasonable fuel charges with equal efficiency which is important during milder days of the heating season when only a partial charge is required.
Boiller plate, but it's the real deal.
Aye,
Marty
Gracias, Marty, for the boiler plate. Is it safe to assume that circulating water does not provide the same kind of thermal mass (though probably pretty efficient heat transfer) as firebrick and cast iron?
But nobody really answered the question in a way that I can understand. Does a clean burn necessarily (or realistically) indicate greater efficiency? Seems to me that ought to be a "yes/no/not necessarily" answer.
But nobody really answered the question in a way that I can understand. Does a clean burn necessarily (or realistically) indicate greater efficiency? Seems to me that ought to be a "yes/no/not necessarily" answer.
Hey Eric:
I realize boiler plate is non-specific and sort of impersonal for which I send my apology. I'll try again.
It's my understanding water is a terrific heat storage meduim and heat transfer medium as well. But, if it had the (thermal) mass of firebrick or cast iron, these would float. That aside, circulating water is used for home heating and I would deduce from this, it is a fairly good "medium".
As For your question:
>Does a clean burn necessarily (or realistically) indicate greater efficiency?
I have to say "No", if by "efficiency" you mean getting the most possible BTUs from the fuel into heat for your room at a reasonably constant (?) and tolerable temperature. This involves more than just "the fire" - clean or not - as the boiler plate on the previous post explains.
Hope I did better this time. Got yur Bird in the brine?
Aye,
Marty
I realize boiler plate is non-specific and sort of impersonal for which I send my apology. I'll try again.
It's my understanding water is a terrific heat storage meduim and heat transfer medium as well. But, if it had the (thermal) mass of firebrick or cast iron, these would float. That aside, circulating water is used for home heating and I would deduce from this, it is a fairly good "medium".
As For your question:
>Does a clean burn necessarily (or realistically) indicate greater efficiency?
I have to say "No", if by "efficiency" you mean getting the most possible BTUs from the fuel into heat for your room at a reasonably constant (?) and tolerable temperature. This involves more than just "the fire" - clean or not - as the boiler plate on the previous post explains.
Hope I did better this time. Got yur Bird in the brine?
Aye,
Marty
Salmon, actually.
To me, burning efficiency and heat transfer efficiency are two completely separate issues, although they both contribute to the same end goal, which of course is my comfort.
So let's forget about transfer efficiency altogether. My question is: Does a clean-burning fire necessarily produce more btus per (let's say) cord of wood, in the firebox, than a smokey fire?
I apologize if I appear a little wood-headed here. It's possible that I don't really understand enough about the topic to pose an appropriate question, but I am talking just about "the fire."
To me, burning efficiency and heat transfer efficiency are two completely separate issues, although they both contribute to the same end goal, which of course is my comfort.
So let's forget about transfer efficiency altogether. My question is: Does a clean-burning fire necessarily produce more btus per (let's say) cord of wood, in the firebox, than a smokey fire?
I apologize if I appear a little wood-headed here. It's possible that I don't really understand enough about the topic to pose an appropriate question, but I am talking just about "the fire."
Eric Johnson said:
See, the problem is as explained above! Your ? would be easy to answer if you left out the words "in the firebox"....then the answer is surely less...
BUT, given a wood boiler, it is possible that a clean burn in the firebox = more heat up the flue, whereas a fairly dirty fire means more residence time in the boiler and better transfer to the water.....
So, hope that helps you understand the difference. Let's look at it this way - if your boiler has a decent baffle system and if you have a good few feet of stove pipe exposed to help warm the basement, then probably the fast hot and ash-free burn is doing a better job all around!
Agreed, yes. If you can burn hot, you will be buring more efficiently in that there will be less unburnt gases . The term, clean-burning can be a bit ambiguous though. One can burn a hot fire in a fireplace and there are still a lot of unburnt gases heading up the chimney. A more efficient design will trap the heat and direct the exhaust so that it is reburned (secondary combustion). That is much more efficient. The key is to capture the unburnt gases and heat and not waste it up the chimney.
So in a boiler situation, it would be more efficient to have shorter, hotter fires and then store the heat in thermal mass (water storage tank), than to have a slow smoldering burn over a long period of time. Efficiencies can be improved by forced draft + secondary burn that allows the fire to be regulated in more of a burn hot, then idle fashion. In a good design this can be very efficient.
So in a boiler situation, it would be more efficient to have shorter, hotter fires and then store the heat in thermal mass (water storage tank), than to have a slow smoldering burn over a long period of time. Efficiencies can be improved by forced draft + secondary burn that allows the fire to be regulated in more of a burn hot, then idle fashion. In a good design this can be very efficient.
This boiler has a sliding bypass baffle, a conventional stove-pipe damper and an 8-inch add-on cat ahead of the chimney. I still have draft to spare. It's located in an insulated concrete-block enclosure where the ambient temps generally (thanks to the cat, I presume) exceed 180 degrees. It's got a forced draft blower regulated by an aquastat to maintain a boiler water temp of 190 and a circ pump regulated by a second aquastat that circulates water when it's above 140. I get zero creosote, which suggests to me that I have more heat going up that stack than necessary, however.
So the cat is doing the afterburn. Sounds like a pretty clean setup. But 180 degrees in the block house? Can you redirect some of that heat?
It burns clean when the grates and ash pan are cleaned out. The cat eats some of the smoke, but not all of it, and not all the time.
The boiler/enclosure is in an unheated barn. No place to put the radiant heat, except to try to retain it. The boiler is insulated with vermiculite poured between the vessel and the shroud, so it's not coming from the boiler per se, but from the pipe and the cat. Somebody suggested that combustion air pre-heated to 180 or 190 would result in a nice efficiency bump and since the blower currently draws air from outside through a vent, drawing it directly from the ceiling is on my Thanksgiving to-do list.
I've thought about building a sauna in the attic space directly above the boiler room. Seriously. Build the sauna right around the chimney and run a little radiator up there. That's about all I can think of in the way of heat recovery.
The boiler/enclosure is in an unheated barn. No place to put the radiant heat, except to try to retain it. The boiler is insulated with vermiculite poured between the vessel and the shroud, so it's not coming from the boiler per se, but from the pipe and the cat. Somebody suggested that combustion air pre-heated to 180 or 190 would result in a nice efficiency bump and since the blower currently draws air from outside through a vent, drawing it directly from the ceiling is on my Thanksgiving to-do list.
I've thought about building a sauna in the attic space directly above the boiler room. Seriously. Build the sauna right around the chimney and run a little radiator up there. That's about all I can think of in the way of heat recovery.
Hey You Thanksgiving FishEater, Eric:
Some of the chiming-in makes sense. Will it to Kingdom Come, you don't control the 'clean burn' (OK, maybe some incoming air) as much as the design of your burner - boiler. What year was it made? Newer models burn "cleaner" than older pre Phase II ones. Design does a lot for a "clean burn", but so do other things (see boiler plate). And, sorry, you can't wish some of it away. It just doesn't work that way.
To burn your wood "clean", about 1100* F is needed, minimal, to convert the creosote, smoke and other wood combustion products to heat. Catagorically, this means to me a "smoldering fire" doesn't cut the mustard.
Not looking at molecules, to get the most heat from wood, burning hotter is better.
Aye,
Marty
Some of the chiming-in makes sense. Will it to Kingdom Come, you don't control the 'clean burn' (OK, maybe some incoming air) as much as the design of your burner - boiler. What year was it made? Newer models burn "cleaner" than older pre Phase II ones. Design does a lot for a "clean burn", but so do other things (see boiler plate). And, sorry, you can't wish some of it away. It just doesn't work that way.
To burn your wood "clean", about 1100* F is needed, minimal, to convert the creosote, smoke and other wood combustion products to heat. Catagorically, this means to me a "smoldering fire" doesn't cut the mustard.
Not looking at molecules, to get the most heat from wood, burning hotter is better.
Aye,
Marty
Thanks everyone. If I could wish the smoke away, it would have long since departed.
Basically, I got all the answers I was expecting, i.e., "yes.....no.....it depends." Take your pick.
Time to start keeping track of this stuff and figure it out for myself. I'll let you know what I think I know when I think I know it.
Happy Thanksgiving, everyone. And Marty, there's always another piece of high-efficiency "smoked" salmon waiting for you.
Basically, I got all the answers I was expecting, i.e., "yes.....no.....it depends." Take your pick.
Time to start keeping track of this stuff and figure it out for myself. I'll let you know what I think I know when I think I know it.
Happy Thanksgiving, everyone. And Marty, there's always another piece of high-efficiency "smoked" salmon waiting for you.
Thanks, Eric, and Happy Thanksgiving!
Good luck with your smokin'.
Just before now putting my bird in my Big Green Egg, I opened the cover (it was HOT) and singed the left side brows, lid and temple hairs (few left). I kinda smell like a burned chicken. Better stay away from those dogs...
Reminds me to be careful out there. So, Eric, beware of small fish bones and keep the home fires goin'.
Aye,
Marty
Good luck with your smokin'.
Just before now putting my bird in my Big Green Egg, I opened the cover (it was HOT) and singed the left side brows, lid and temple hairs (few left). I kinda smell like a burned chicken. Better stay away from those dogs...
Reminds me to be careful out there. So, Eric, beware of small fish bones and keep the home fires goin'.
Aye,
Marty
Marty S said:
Nope. They don't float. And, water has about 8 times the thermal mass per pound as cast iron, and almost exactly ( within 2%) the same thermal mass per volume as cast iron.
Whether something floats is not a good way to determine its thermal mass.
Phil Marino
Eric, sorry I couldn't help you but Happy Thanksgiving to you too. Now we'll try to send some of this wind your way.
He probably figured it out since he posted this back in 2005. In fact he replaced that boiler a long time ago.
Ya, I had noticed it was really old but decided to post anyway. Eric is not on the forum much any more but it would be nice to see more from him.
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