Clean burning older stove?

[mtcates]

My house takes about 80 million btu's per winter to heat it according to a program I used and punched in all the stats of my house. The house is tight but it has 400 square feet of windows (R2) and a poorly insulated roof (R7). The only source of heat I have is an indoor woodstove. Last year I burned exactly 5 chords of mixed hardwoods. This equates to about 125 million or so btu's of heat in the wood. At that rate I'm extracting about 65% of the heat from the wood. Not too bad for a 30 year old stove. In years past it was never this efficient until I made some modifications.

I installed a 6 inch insulated flue liner. It keeps an incredible draft with this 6 inch insulated liner. I am getting some air leak around the loading door because there is no gasket on the door. I tried to install one but it is so tight of tolerance I cant close the door with the gasket installed. The door does flush the stove frame however and its nearly a machined metal to metal fit. It fits so close of tolerance that I can shut off the draft controls and the fire will just smolder or go out so there can't be much air leaking around the door.

I have also installed more fire brick to go higher up the back wall of the stove and a ceramic baffle at a 45 degree angle between the back and the top. This extra brick and the baffle reflects the radiant heat back to the fire for a hotter burn. They also reflect the radiant heat to the front wall of the stove making it hotter. The baffle at the top also forces the gas to take a much longer path by flowing to the front and along the top on its way to exit at the back. These internal mods made a huge difference in the heat output of this stove, however I still don't have a secondary air supply.

If I have no smoke coming out of my chimney, can I assume complete combustion is taking place? I have no secondary air supply but once the stove gets hot the exhaust gasses are clear and doesn't smell of smoke at all. Whats happening here? Are some of the gasses coming out of the chimney still combustable even though they are clear gasses with no particulates? Anybody up on their chemistry care to explain? Am I getting enough of an air leak at the top of the door as to provide enough secondary air to make a cleaner burn? I don't really know but it sure is efficient at extracting heat from the wood.

This old stove has one of those fans on the side with a maze of 1 inch steel pipes inside of the stove at the top to heat the air from the fan. I have thought about drilling a bunch of small holes in this maze of pipes and making a valve to regulate the air flow and use it as my preheated secondary air at the top of the stove. What do you guys think about this? I am thinking I should probably leave well enough alone as it works well enough now.

Read This http://mb-soft.com/juca/print/315.html

Thanks for reading, I look foreword to your reply.

 

[vvvv]

yes, CO is a combustible gas & invisible. try to burn from the top down to avoid excessive wood gassification.
c- co = 1 energy unit
co- co2=2.5 energy units
full combustion is= c-co-co2. lack of combustion air results in smokeless ineficiency & excessive CO up the chimney

 

[Battenkiller]

If I have no smoke coming out of my chimney, can I assume complete combustion is taking place? I have no secondary air supply but once the stove gets hot the exhaust gasses are clear and doesn't smell of smoke at all. Whats happening here? Are some of the gasses coming out of the chimney still combustable even though they are clear gasses with no particulates? Anybody up on their chemistry care to explain? Am I getting enough of an air leak at the top of the door as to provide enough secondary air to make a cleaner burn? I don't really know but it sure is efficient at extracting heat from the wood.

Can't advise you on any mods, past or future, but there are plenty of "invisible" gases that can leave the stack in a combustible state. Carbon monoxide is a major one, caused by insufficient oxygen or poor mixing in the combustion chamber. There are numerous other burnable compounds formed in the confines of your stove that will enter the atmosphere undetected (unless you have sensors looking for them) if they escape the high-temperature, oxygen-rich burn zones of your stove.

You can't look at published efficiency ratings when you are figuring out your heats needs. Those ratings are hypothetical burn efficiencies, not heat transfer efficiencies. And they are only valid in ideal (i.e. test) conditions. If you are truly getting 65% of the heat potential of your wood delivered into your living space as sensible heat, you are doing as good or better than anyone is. I'd be ecstatic to get that kind of performance.

 

[Battenkiller]

Or what BLIMP said. :lol:

 

[vvvv]

If I have no smoke coming out of my chimney, can I assume complete combustion is taking place? I have no secondary air supply but once the stove gets hot the exhaust gasses are clear and doesn't smell of smoke at all. Whats happening here? Are some of the gasses coming out of the chimney still combustable even though they are clear gasses with no particulates? Anybody up on their chemistry care to explain? Am I getting enough of an air leak at the top of the door as to provide enough secondary air to make a cleaner burn? I don't really know but it sure is efficient at extracting heat from the wood.

Can't advise you on any mods, past or future, but there are plenty of "invisible" gases that can leave the stack in a combustible state. Carbon monoxide is a major one, caused by insufficient oxygen or poor mixing in the combustion chamber. There are numerous other burnable compounds formed in the confines of your stove that will enter the atmosphere undetected (unless you have sensors looking for them) if they escape the high-temperature, oxygen-rich burn zones of your stove.

You can't look at published efficiency ratings when you are figuring out your heats needs. Those ratings are hypothetical burn efficiencies, not heat transfer efficiencies. And they are only valid in ideal (i.e. test) conditions. If you are truly getting 65% of the heat potential of your wood delivered into your living space as sensible heat, you are doing as good or better than anyone is. I'd be ecstatic to get that kind of performance.

what are the other combustible invisible gases?

 

[PastTense]

See:
http://msuextension.org/publications/HomeHealthandFamily/MT198405HR.pdf

The number produced by your computer program is just an approximation; to get accurate results you would need to do very specialized measurements.

 

[summit]

2ndary air is not always required to achieve high levels of combustion. Plenty of time, temp, and turbulence has alot more to do w/ a complete burn that a bunch of 2ndry air shooting thru your woodstove.

 

[tickbitty]

This video is pretty short and basic but interesting, indicates how you can reduce pollution from woodburning correctly even in an old stove, but also notes that even newer certified stoves can be burned wrong. I guess point being, an older stove run "right" can potentially be a lot better than a new stove run "wrong" - though I suppose the best would be a new stove run right!

 

[vvvv]

This video is pretty short and basic but interesting, indicates how you can reduce pollution from woodburning correctly even in an old stove, but also notes that even newer certified stoves can be burned wrong. I guess point being, an older stove run "right" can potentially be a lot better than a new stove run "wrong" - though I suppose the best would be a new stove run right!

oops, different from Vanessa!

 

[begreen]

The stove is burning cleaner than many older stoves. Good work! But even with the best of burning practices, it is still putting out many times the pollutants of a modern stove.