What is the most efficient stove on the market today?

[tlhfirelion]

Not including masonry heaters and the like, what is the most efficient wood burning stove on the market today? I'm must curious.

Thanks!

 

[webbie]

No such thing.
We could only say this if each and every stove were tested for actual efficiency. They are not. Most of the figures given are "default" efficiency standards. Also, EPA tests are done with pine 2x4 and 4x4.

Based on all this and more...I would say the most efficient stove is the one burned correctly and that has at least 8 feet of single wall stovepipe exposed in the house!

Catalytic test more efficiently in many cases, but might lose their advantage as the cat ages....and so on, and so on.

 

[tlhfirelion]

No such thing.
We could only say this if each and every stove were tested for actual efficiency. They are not. Most of the figures given are "default" efficiency standards. Also, EPA tests are done with pine 2x4 and 4x4.

Based on all this and more...I would say the most efficient stove is the one burned correctly and that has at least 8 feet of single wall stovepipe exposed in the house!

Catalytic test more efficiently in many cases, but might lose their advantage as the cat ages....and so on, and so on.

Fair enough. I see masonry heaters typically quote a 90% efficiency rating and I just wondered if there are any typical wood burning stoves that are above epa 85%. I guess with so many variables it' s hard to answer.

 

[webbie]

No wood stove is going to return 80% or more of the heat into the house on a constant basis....given cordwood, variable burns and normal conditions and testing. Most of the figures you see are either guesswork, wishful thinking, or omissions. Unless...and until we get an actual standard for cordwood and real world testing, it is always better to figure low and work with 65-70% efficiency with the best woodstoves, and less with most inserts due to heat loss.

I think a properly built masonry heater can probably meet or beat many stoves.

 

[cmonSTART]

Based on all this and more...I would say the most efficient stove is the one burned correctly and that has at least 8 feet of single wall stovepipe exposed in the house!.

Interesting. Why the 8 feet of exposed single wall? Heat transfer?

 

[webbie]

Yeah, a lot of modern stoves put vast amounts of heat up the stack when burned hot. It is tough to design enough exchange into a little stove that must fit dimension requirements. I think some setups would see 10-15% increase from some exposed stack....

 

[cmonSTART]

Makes sense. And they would probably still have hot enough gases leaving the stack to keep the chimney clean.

 

[Dix]

I think a properly built masonry heater can probably meet or beat many stoves

On the style of a "Russian Fireplace", or something else???

 

[crazy_dan]

Yeah, a lot of modern stoves put vast amounts of heat up the stack when burned hot. It is tough to design enough exchange into a little stove that must fit dimension requirements. I think some setups would see 10-15% increase from some exposed stack....

That much 10-15% wow

 

[woodjack]

How exactly does the stack affect efficiency. I thought a double wall flue was more efficient and drafted better.

 

[begreen]

Flue heat radiation is not really stove efficiency. One may be able to recoup more heat, or not, but this is not a measure of stove efficiency.

 

[Hanko]

Geez Im surprised someone didnt chime in saying the stove they owned was the most efficient. My vote Big MF barrel stove

 

[crazy_dan]

Geez Im surprised someone didnt chime in saying the stove they owned was the most efficient. My vote Big MF barrel stove

single or double barrel?

 

[downeast]

Craig's Palin Cat Super Heater: " it won't heat you out of the house " . :snake:

 

[ControlFreak]

No such thing.
We could only say this if each and every stove were tested for actual efficiency. They are not. Most of the figures given are "default" efficiency standards.

Just in case anybody is curious:

I spoke in detail with one of the EPA test lab reps at last years HPB Expo. I asked how they measure the BTU output and efficiency rating for a stove. He said that they don't directly measure the heat output of a stove, but rather, they calculate it. Here's how it goes (from what I recall):

1. They start with a load of wood that is precisely weighed.
2. From this load of wood, they calculate the total BTU content in the wood.
3. As they burn the fire, they continuously monitor the temperature of the exhaust gases, and the flow rate.
4. Knowing the exhaust gas temperature and the rate of flow, they can calculate the BTU's going up the chimney.
5. Whatever heat does not go up the chimney, they conclude is being extracted by the stove.
6. Heat output is total wood BTU content - BTU's going up the chimney.
6. From this, they can calculate the "efficiency" of the stove.

I didn't ask if they take into account the level of unburned gases since smoke is energy going up the chimney that doesn't produce any heat, and could lead to an artifically high efficiency.

Interesting stuff...

Dan

 

[mikepinto65]

I think a properly built masonry heater can probably meet or beat many stoves

On the style of a "Russian Fireplace", or something else???

I think the Russinan Fireplace would trump almost anything out there no?

 

[Todd]

The highest number I've seen so far is the Blaze King stoves at 82.5%. But I agree with Craig, there is no real world test for efficiency just guesses or estimates.

 

[woodjack]

No such thing.
We could only say this if each and every stove were tested for actual efficiency. They are not. Most of the figures given are "default" efficiency standards.

Just in case anybody is curious:

I spoke in detail with one of the EPA test lab reps at last years HPB Expo. I asked how they measure the BTU output and efficiency rating for a stove. He said that they don't directly measure the heat output of a stove, but rather, they calculate it. Here's how it goes (from what I recall):

1. They start with a load of wood that is precisely weighed.
2. From this load of wood, they calculate the total BTU content in the wood.
3. As they burn the fire, they continuously monitor the temperature of the exhaust gases, and the flow rate.
4. Knowing the exhaust gas temperature and the rate of flow, they can calculate the BTU's going up the chimney.
5. Whatever heat does not go up the chimney, they conclude is being extracted by the stove.
6. Heat output is total wood BTU content - BTU's going up the chimney.
6. From this, they can calculate the "efficiency" of the stove.

I didn't ask if they take into account the level of unburned gases since smoke is energy going up the chimney that doesn't produce any heat, and could lead to an artifically high efficiency.

Interesting stuff...

Dan

To get a true efficiency reading wouldn't they have to take into consideration the material the stove is made from and how well it radiates heat?

 

[_CY_]

seems like EPA needs to work backwards. measure BTU that actually comes out of wood stove, then subtract from total BTU available = efficiency ratio

heat transfer is where my JUCA custom insert excels at. constructed out of 1/4in plate. it's one HUGE heat exchanger. it's 12 cubic feet firebox is wrapped in forced air flow. entire structure is hollow with HUGE heat exchange tubes running across up draft area.

here's a picture of my insert which was custom made to fit within 1/4 in of fireplace's internal dimensions. weight is 500+ lb, blower is thermostat controlled.

has the highest square inches of heat exchange area of any insert that I'm aware of. internal angles are carefully constructed to create max updraft. uses original firebrick floor with bottom ash dump for 100% outside air source.

not sure how JUCA would rate against a Russian Fireplace..

No such thing.
We could only say this if each and every stove were tested for actual efficiency. They are not. Most of the figures given are "default" efficiency standards.

Just in case anybody is curious:

I spoke in detail with one of the EPA test lab reps at last years HPB Expo. I asked how they measure the BTU output and efficiency rating for a stove. He said that they don't directly measure the heat output of a stove, but rather, they calculate it. Here's how it goes (from what I recall):

1. They start with a load of wood that is precisely weighed.
2. From this load of wood, they calculate the total BTU content in the wood.
3. As they burn the fire, they continuously monitor the temperature of the exhaust gases, and the flow rate.
4. Knowing the exhaust gas temperature and the rate of flow, they can calculate the BTU's going up the chimney.
5. Whatever heat does not go up the chimney, they conclude is being extracted by the stove.
6. Heat output is total wood BTU content - BTU's going up the chimney.
6. From this, they can calculate the "efficiency" of the stove.

I didn't ask if they take into account the level of unburned gases since smoke is energy going up the chimney that doesn't produce any heat, and could lead to an artifically high efficiency.

Interesting stuff...

Dan

 

[_CY_]

just google "russian fireplace" ... WOW....
the designer below claims to light a fire once a week. takes all day to heat, but radiates heat for 3 days.

"Masonry stoves are designed to burn a hot fire, with the air supply and chimney damper wide open. This results in a clean burn, with little visible smoke."

this is identical to how my JUCA operates...

http://www.grannysstore.com/Do-It-Yourself/masonry_stoves.htm

http://www.grannysstore.com/Do-It-Yourself/diyimages/masonrystove.d.jpg

 

[Todd]

Isn't Juca out of business? How the heck can you get a clean efficient burn out of that large fire box? Does it have some kind of secondary burn system?

 

[_CY_]

last time I heard JUCA were still producing a small number of custom inserts like mine. good luck getting them to make you one though. it took me several years of trying to get them to make mine.
prices are very reasonable... if you can get them to make you one... seems I paid $1,700 including shipping for a custom build to fit insert with all the options.

JUCA burns hot and very clean. it uses the same system as Russian Fireplace...
no it doesn't have a secondary burn system. plans are to install a secondary burn inside.
no idea if it will improve or hinder performance.

will fab secondary burn system to allow removal if it doesn't improve performance.

Isn't Juca out of business? How the heck can you get a clean efficient burn out of that large fire box? Does it have some kind of secondary burn system?

 

[Hogwildz]

The Juca is basically a Heatform like firebox, with heat exchange tubes at the top.
Think fireplace grate heater, but at the top of the fire box.
Much like a fireplace, alot of heat is going up & out.
Not knocking it, I was considering one a few years back.
If you can get a secondary baffle in there, you would then realize the heat your losing, or with secondary, losing much less of.

 

[_CY_]

not knocking your analysis... but with such a HUGE heat exchange area ... heat is getting pulled out of smoke at a much higher rate than a wood burner with a tiny heat exchanger area.. the longer smoke has to hand off heat, the better...

at full steam outside of JUCA barely heats up as most of heat has been extracted. without question JUCA has one of the most efficient heat exchangers of any wood burner. can it be made more efficient by adding more heat exchange area... why sure... seems that's how russian fireplaces do it.

possibly where JUCA falls short is lack of secondary burn... don't know until I add a secondary burn system. any system can be made more efficient and that's what I'm after.

The Juca is basically a Heatform like firebox, with heat exchange tubes at the top.
Think fireplace grate heater, but at the top of the fire box.
Much like a fireplace, alot of heat is going up & out.
Not knocking it, I was considering one a few years back.
If you can get a secondary baffle in there, you would then realize the heat your losing, or with secondary, losing much less of.

 

[Hogwildz]

Thats all good, unless you have to have that 12 sf loaded up with wood? then its apples to apples.
If you could put a channel or even plate the bottom with support between the steel plate & the brick floor, then connect a vertical channel in the back like my PE has., then make a similar S.S. baffle that you could mount under the heat exchanger tubes and it sits over the rear vertical channel. You might get some great heat & secondary burn. And not lose your heat from the exchangers and the outgoing gases & heat would still heat them up. Not to mention being over the secondary baffle. Then just an air intake on the lower front. Might work.