Long Burn vs Efficiently

Treestuff
Advertise with us
Shop deals on ebay
Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
flotek,
I put 5 smaller splits in my stove this morning around 6am. Temp in house was 69.
With a clean burn going I adjusted my controls and walked away. I went all day with the temps around 70-72. Finally at 6:30 this evening I checked the stat and it said 69. Then I re-loaded. Hi temps today were 27

I'm sorry but you can't heat a house when your stove is smoldering. It just won't put off enough consistent heat. Sure it will throw some but if you're measuring burn time as when your thermostat drops then smoldering just won't do it.

I have a bigger fire box then you but still 5 smaller size splits is probably what you can cram in yours as well.

So now what we are up against is the definition of burn time and how well our houses are constructed and laid out.

I can't get 15 hours of actual flames but I can get 15 hours of burn time if I want. I do 12 hours every single day I go to work. Without smoldering.

I think the new stoves are good just not as good as everyone who owns them seem to believe they are.
JMHO
 
I don't get why some are equating burn time with heat output. A given building at given temp and given wind condition will lose a specified number of btu's over a given time.

If the loss is 25000 btu's per hour and your stove can put out 50000 an hour. If you put a cubic foot of wood in it it matters not if it burns full bore for 30 mins or for an hour at 50%, as the latter can not exceed the the the former.

Now choking off to a smoldering fire you LOSE as the burning efficiency goes down. Remember that cubic foot has a set amount of btu's in it you can't increase it by burning longer, only decrease it. If I take a cubic foot of wood and set the air at say 60% so it burns correctly and it burns for four hours while I am at work it will be the same temp or even less(never more) if I choke it down and it still has coals when I come home if all the other conditions are equal. It's part of the laws of thermal dynamics.

Now if the stove is grossly oversize then you might need to choke it down to keep it from running you out of the room, then it's a selection problem. Otherwise long burn times is code for "I am lazy and don't want to start another fire later, but later I will pay for it by cleaning out the chimney more often".

It better to control a stove with wood sizes and batch fires than to choke one off.
 
That doesn't make any sense at all. You contradict yourself in the same paragraph.

If you put a cubic foot of wood in it it matters not if it burns full bore for 30 mins or for an hour at 50% The end result is the same.
Click to expand...
The end result is not the same because the transfer of BTUS to a thermal holding device (stove/room) is greater when heated by a 100% fire vs a 50% fire.
Next you say

Now choking off to a smoldering fire or adding wood you LOSE as the burning efficentcy goes down. Remember that cubic foot has a set amount of btu's in it you can't increase it by burning longer, only decrease it
Click to expand...

Above you say that the wood has a set amount of BTUs in it and it doesn't matter how you burn it. A sentence later it does matter how you burn it because you say that you can't increase btus by burning longer, only decrease it.
How does one decrease the amount of BTUs in a piece of firewood?


If I take a cubic foot of wood and set the air at say 60% so it burns correctly and it burns for four hours while I am at work it will be the same temp or even less if I choke it down and it still has coals when I come home if all the other conditions are equal. It's part of the laws of thermal dynamics.
Click to expand...
No that is simply not true and your statement doesn't really make sense. It needs a few more words in it to be understandable. You're saying in the above statement that it doesn't matter if you burn at 60% or choke it down that the temp will be the same?

The first law of Thermodynamics states there is no heat transfer between objects of the same temperature.
If your room and your stove are both in equilibrium then the remaining energy in the stove is being wasted. There is a point where the stove reaches a temperature that it can no longer heat the surrounding area, just maintain the current temperature. So if the stove can last all day long but never increase the temperature then theoretically the combustion or creation of some of the heat inside the box is wasting energy and is no longer being efficient.


The second law of Thermodynamics is Entropy
The measure of how evenly heat is distributed. In order to measure how the heat is distributed I have to know the rate at which it is being created. So burn time and heat output is relatable and IS in fact Thermodynamics.

The third law of Thermodynamics is that 100% efficiency is impossible.
We will never be able to harness all of the heat from our stoves, plain and simple.

So to sum it up Thermodynamics is the reason we correlate burn time vs heat output.
It's like Love and Marriage, it fits together like a horse and carriage.
You can't have one without the other!

I do agree with your last sentence though!
 
I also agree with you last sentence!


I see what you are saying and for this reason, I am switching appliances.
 
Bushmans said:
I'm sorry but you can't heat a house when your stove is smoldering. It just won't put off enough consistent heat. Sure it will throw some but if you're measuring burn time as when your thermostat drops then smoldering just won't do it.


I think the new stoves are good just not as good as everyone who owns them seem to believe they are.
JMHO
Click to expand...

I agree. I have a new stove and it's great till you get to coals and it starts to smolder. Coals are fine on a warmer day but during the brutal cold they did not put enough heat off to keep the house at the temp I wanted. Had to shovel a lot of them out every 2nd or 3rd day which made me end up grilling a lot so I guess that is a small silver lining. When it is below 10* day and night which we had for basically the last couple months, my EPA stove can not put enough heat off the coals unless I turn up the draft and rake them around every 5-10 minutes. If people are believing they are great I would assume they live in a warmer climate than I do. My experience is it is great at 20 degrees and up, but when it gets brutal out I have to babysit it like a drunken Toronto Mayor when it gets to coals.
 
Exactly. I am having this issue with my 30. I had to shovel out coals to reload early cause when it was -5 here it would not keep up.
 
I really like the fact that technology has allowed us to burn cleaner but everything is a trade off in the end. In a normal winter I probably would be just fine with an EPA certified stove. Without prior experience I would probably be advocating as well. This year? I'm glad I was able to blast some serious heat.
That being said I still strive to make my stove burn better. I am still going ahead with the secondaries and if I find I don't like them I can always turn off the valves.
Everyone has a different situation.
 
Bushmans said:
flotek,
I put 5 smaller splits in my stove this morning around 6am. Temp in house was 69.
With a clean burn going I adjusted my controls and walked away. I went all day with the temps around 70-72. Finally at 6:30 this evening I checked the stat and it said 69. Then I re-loaded. Hi temps today were 27

I'm sorry but you can't heat a house when your stove is smoldering. It just won't put off enough consistent heat. Sure it will throw some but if you're measuring burn time as when your thermostat drops then smoldering just won't do it.

I have a bigger fire box then you but still 5 smaller size splits is probably what you can cram in yours as well.

So now what we are up against is the definition of burn time and how well our houses are constructed and laid out.

I can't get 15 hours of actual flames but I can get 15 hours of burn time if I want. I do 12 hours every single day I go to work. Without smoldering.

I think the new stoves are good just not as good as everyone who owns them seem to believe they are.
JMHO
Click to expand...
how can the btu's that 5 small splits provide heat a house for that long no matter what stove it is?
 
how can the btu's that 5 small splits provide heat a house for that long no matter what stove it is?
Click to expand...

Quite simple actually. The house was almost up to temp already. The sun was shining, the wind was minimal and the outside temps were in the 20s. The stove burned for several hours heating up the house even more and then by the time the house returned to the original 69 degrees it was 12 hours later.
I did not express that the splits burned for 12 hours, I simply stated that it kept my home heated for 12 hours.
I do it everyday when I leave for work. 4:30 am to 4:30 pm.

It is a matter of variables like house design, climate, several temperatures and how you define burn time?
There is no definitive answer on this forum.
 
Well, since no one else has... I guess I'll go ahead and bring this up.
One qualifier before I start... I'm talking non-cat stoves, I have never used a cat-stove and wouldn't have a clue.

The article quoted by the OP eludes to something I've mentioned before. I've read the EPA test procedure several times, and I simply cannot find where "heat" or "time" is measured in any way shape of form. The only thing actually measured and quantified is per hour particulate emissions; which makes sense when you think about it... the EPA is (supposedly) concerned solely with "protecting" the environment, but in no way concerned with heating your home. The "efficiency" rating attached to a certified stove by the EPA is simply the combustion efficiency... the stove could actually dump 100% of that heat out the flue and still receive and 80% efficiency rating from the EPA.

Now, I won't argue that burning 30% more of the available fuel (in this case a portion of the particulate emissions supposedly not burned by a smoke dragon) will result in more heat... it flat has to result in more (generated) heat from the same amount of fuel loaded in a box. What I will argue is whether-or-not you receive, or realize, all of that extra heat in your home. Lot's of things determine the amount of "heat" exiting, or "lost", through the flue, but the three major ones are;
  • The amount of air entering the box - More air (gas) entering has to equal more gas exiting, and those exiting gasses are hot... they carry heat with them. I only have extensive experience with one make and model of EPA certified stove... but that one model required more air and the flue ran hotter than any "smoke dragon" I've ever used. Admittedly nothing measured, just perception and "feel"... but c'mon, holding your hand by the pipe is pretty a damn good comparison. I actually ran the "stovace" circulation blower with a snap disk mounted a few inches away from the flue pipe, I couldn't do that with the prior "smoke dragon". I've read here from users both ways, some say their EPA stove pipe runs cooler, some say hotter; but the temperature of the stove pipe is near 100% user controllable with an "air tight" box... so what users are experiencing doesn't mean much. I mean, using a flue damper with the old dragon I could touch the pipe above it at times (when I tried the flue damper with the EPA box I could also reduce pipe temp somewhat, but not to the same extent without killing heat output). Secondary burn stoves need secondary air, they need more air (or mine did); if more air is entering, a greater percentage of the generated heat must be exiting (if all else remains equal).
  • The temperature of the fire - Again, if all else remains equal, a hotter fire will make for hotter gasses exiting the flue... i.e., proportionally more generated heat lost through through the flue. A hotter fire also means faster combustion... and there ain't any magic to get around that. The secondary combustion stoves increase fire temperature by pumping more of the above mentioned air in, insulating with refractory brick (ain't the same as true "fire brick"), and whatnot (I understand there are exceptions, not all have brick). The EPA certified, secondary combustion stoves use more air and an insulated box to increase combustion rate, thereby increasing heat, thereby increasing combustion efficiency (or, at least mine did). Again, if all else remains equal, there ain't any magic to get around the fact that a hotter fire will burn faster, and put proportionally more generated heat out the flue. If all else remains equal, a 30% increase in combustion efficiency cannot equal a 30% increase in heat transfer to the room... at best, maybe half that.
  • Stove design - This is where all else does not remain equal. For example, you can add a highly efficient heat exchanger to extract more of the generated heat before it exits. But that has nothing to do with combustion efficiency, it's just a more efficient heat extraction method (i.e., heating efficiency). A highly efficient heat exchanger can be added to a non-EPA certified box also... but because of the (supposedly) dirtier burn, it may require cleaning more often. Yeah, the combination of more efficient combustion and heat extraction will result in more realized heat... but now things are equal again, and you won't realize 30% more heat... maybe half that at best. The "secondary heat chamber" in my DAKA furnace is nothing more than a crude heat exchanger... that, because of design, doesn't require cleaning.
    Another example is an IR transparent glass door... and this is where my application(s) fell flat. My PE stove has an insulated firebox, the floor, both sides and the back. The "flame stage" (the stage when most particulate emissions are generated) of my PE is fast, damn fast... causing the fire to collapse into coals pretty damn fast. At the coaling stage the box actually "smolders" the fire by passing air over the top of that coal bed, and because the box is insulated it relies on the glass door to transfer the low heat into the room via IR radiation. That's great if the stove sits in a room full of solid surfaces, and would likely increase "usable" burn (heating) time. The problem with that, for my application as a "stovace", I needed the heat transferred via conduction to the forced air... and that's why removing the fire brick (insulation) helped some. And another problem with IR radiation is it passes through air without warming it... it needs to be absorbed by something solid, which in turn warms the air by conduction. The "glass door" design falls on it's face in my shop also, because even though it ain't all that big, it is open... there flat ain't anything to absorb the IR radiation (other than the cold walls).
    Now possibly a different design EPA stove would work better... such as a cast iron, non-insulated design. But even so, the IR radiation escaping the glass is basically wasted heat for my applications. "Smoldering" the coal bed to increase burn (heating) time actually cause me to burn more wood, for a net of less usable heat, and shorter (perceived) burn times.
So I go back to what I keep saying...
Combustion efficiency does not automatically equal heating efficiency (more usable, or realized heat). The (current) EPA certified designs are not always "more better" for every application. In fact, in certain applications the result will be less (realized) heat, more fuel burned, and shorter (perceived) burn times... resulting in more overall particulate emissions than a properly operated smoke dragon. Nothing in this world is a "one-size-fits-all" sort of thing... that ain't how it works. I can even extend this to another thread... the Tundra thread... it ain't so much the combustion efficiency that putting heat in your home, it's the heat exchanger (the more efficient heat extraction method) that deserves the credit. No doubt, from just holding my hand in front of the glass door during coaling, if my PE was sitting in a nice cozy den or family room filled with solid surfaces it would near heat you out'a the room on low setting, and likely go several hours without needing a reload to maintain that... but that's not every application, is it??
*
 
Exactly, and that is the thing. I think Jotul is stressing the same fact. I believe that if we like the epa design than good but for those that love our system they should still make our products.

Its like going to mcdonalds and ordering a big mac. EPA says big mac make you fat so we no longer make sell or trade them by law!
 
Let me start off by saying I was tired when I wrote this and there was some small choice but important words I left out. The Whole point of my post was to show that one can not release more embodied energy out of a given piece of wood by burning a longer time that the rate that their stove burns a peak efficiency.

Bushmans said:
That doesn't make any sense at all. You contradict yourself in the same paragraph

The end result is not the same because the transfer of BTUS to a thermal holding device (stove/room) is greater when heated by a 100% fire vs a 50% fire.
Click to expand...

In this paragraph I was trying to convey that one can not get more heat value out of a given amount of fuel by burning it slower.





Bushmans said:
No that is simply not true and your statement doesn't really make sense. It needs a few more words in it to be understandable. You're saying in the above statement that it doesn't matter if you burn at 60% or choke it down that the temp will be the same?
Click to expand...

I think you missed the words "or even less".

Bushmans said:
The first law of Thermodynamics states there is no heat transfer between objects of the same temperature.
If your room and your stove are both in equilibrium then the remaining energy in the stove is being wasted. There is a point where the stove reaches a temperature that it can no longer heat the surrounding area, just maintain the current temperature. So if the stove can last all day long but never increase the temperature then theoretically the combustion or creation of some of the heat inside the box is wasting energy and is no longer being efficient.
Click to expand...
Ummm
If the house reaches a temp that the stove can no longer add heat to the surrounding area then more than likely your house is on fire to! And you negate that btu's are escaping constantly from the building envelope.


The best way to make your wood go further is to insulate and weatherproof
It amazes me the number of people who will spend 10 grand on an outside boiler for just a house and not 500-700 dollars on getting their attic to r60.

Also a great way is to add heat sinks around their stove to absorb excess energy while the stove is running and release it afterwards. We put down 1/2 concrete backer board and thick Italian tile in brindles and slate shade. It amazing the heat it stores. Needs to be a dark earth tone color as most of the heat it does store is radiated from the stove not from convection. The most good is going to be on the sides and front(unless your stove doesn't have rear/bottom heat shields).

And of course dry wood.
 
513yj said:
My experience is it is great at 20 degrees and up, but when it gets brutal out I have to babysit it like a drunken Toronto Mayor when it gets to coals.
Click to expand...

Man you could be the best mayor on earth, but admit to smoking crack one time, and you will always be a crack smoker in every ones jokes !!:ices_rofl:
 
That extra reburn secondary combustion that is claimed at 30% really does become available in the real world it's noticeable extra btu at least from what I've experienced running them . During a reload Ask anybody that has a EPA stove . There is a brief time where you let it burn giving it ample air with the door cracked Until it's up to the appropriate temperatures and hot .. Then you close it up good and secondary's flare off doing there job . Immediately the stove surface temperature will raise up if you have a gage on it it will be apparent it's spiking up in temperature on the surface and usually about 30% surface temperature on my gage . ( mine goes from just over 200 to close to 300 on outside face surface ) As long as secondary's are rolling you will maintain that increase . Just an observation ..I think most EPA stove guys would clearly notice ( of coarse dry wood is required to realize this effect)
 

Similar threads

D
Advice on new EPA wood burning fireplace zero clearance
Replies
17
Views
2K
Tony Mayhew
Tony Mayhew
A
Wood Stove Firebox Size vs BTU
Replies
7
Views
2K
nathan4104
N
IHDiesel73L
Increasing fireplace efficiency without an insert?
2
Replies
23
Views
6K
Del_
Del_
G
Replace my Vigilant? How much better is a new stove?
2
Replies
31
Views
5K
sunfish
sunfish
L
Trump Administration to change Obama era wood stove and boiler emission regulations
Replies
19
Views
2K
sb47
sb47

Latest posts

Back
Top