Most efficient air setting?

[heydan]

Do wood stoves burn most efficiently with the air control all the way open or all the way closed or somewhere in the middle? By "efficient" I mean complete and clean combustion that also maximizes the amount of heat that goes into the room, not up the chimney.

I'm pretty sure that having the air control all the way closed on my Regency I2400 is not the most efficient setting because the glass smokes up in that case which indicates less than complete combustion. I would have thought that keeping the air supply all the way open would be most efficient but the manual that came with my stove says: "Once a bed of coals has been established, you may adjust the draft control to a low setting to operate the unit in its most efficient mode." So they seem to be saying an air setting on the low side is most efficient. But how low?

Am I right to think that the more air you give the stove the more complete the combustion but also the more heat you lose up the chimney? How do you decide what air setting is best?

 

[MountainStoveGuy]

It COMPLETLY depends on the currnet stage of combustion in your stove. If you have a super hot coal bed, and a fresh split or round on top, a low setting will be appropriate. It also depends on draft. the better the draft, the better the lower settings will work. Every install and stove is unique. You will have to do alittle expermentation.

 

[heydan]

My stove manual says that when I add new fuel I should keep the air supply wide open for 15 minutes (or 45 minutes in the morning after a slow burn the night before): "Burn the insert with draft control wide open for about 10 - 15 minutes every time you add fresh wood. This allows the wood to achieve the charcoal stage faster and burns up any wood vapors which might otherwise be deposited within the system. Burn the insert with draft control wide open for about 45 minutes every morning during burning season. This helps to prevent creosote deposits within the heating system."

They also recommend adding more than one split at a time: "Rake the coals toward the air inlet (and woodstove door), creating a mound. Do not spread the coals flat. Reload your woodstove by adding at least three pieces of wood each time, on and behind the mound of hot coals. Avoid adding one log at a time."

So I know I'm going to have the air wide open for a while after reloading. It's after that point, when the volatile gasses have been burnt off and the wood is mostly charcoal, that I'm wondering how the air supply affects efficiency.

 

[MountainStoveGuy]

Manuals in reguards to stove operation are generic instructions. Its like a car manufacture telling you how to drive. Like i say, every stove is different. If i have a hot enough coal bed, i can turn it down immediatly. One shure fire way to tell, once you load your stove, check your chimmey 15 minutes later. If its smoking, then your not burning at the most efficient rate. A typical cold start for me: I pack the firebox with the air wide open. I let it burn untill its a extremly hot coad bed, with no uncombuted wood left. I take my poker and break up the pieces, i thow a log on and shut the air all the way down. The smoke coming off the frest split is combusted from the heat of the stove. Once that cooks down the original coal bed is all but gone, then i start the process over again. I have very good draft, and my stove works well shut down. It doenst work well if i shut it down to soon. Pratice makes perfect.

 

[biggins08]

I a, running a Harmon Exception insert and find that if I build a good coal bed I can set the air low as well and get a good burn. As long as the stove is up to temp, the new log burns fine with the air on low.

 

[heydan]

I tried to duplicate the experiences described by others above by establishing a hot bed of coals and then reloading with just one split. I found that the new wood caught quickly and burned brightly BUT it could NOT generate enough heat to sustain secondary combustion, even with the air supply all the way open -- when I went outside I could see and smell the smoke coming from the chimney.

This must be why my stove manual says "Reload your woodstove by adding at least three pieces of wood each time, on and behind the mound of hot coals. Avoid adding one log at a time." It seems that in this case the manufacturer knows something about their product (Regency I2400) but it would have been nice if they'd included the reasoning behind their instructions so I wouldn't have to rediscover it on my own.

Anyway, I'll be reloading with at least three splits at a time now just like the manual says.

 

[Sandor]

I tried to duplicate the experiences described by others above by establishing a hot bed of coals and then reloading with just one split. I found that the new wood caught quickly and burned brightly BUT it could NOT generate enough heat to sustain secondary combustion, even with the air supply all the way open -- when I went outside I could see and smell the smoke coming from the chimney.

This must be why my stove manual says "Reload your woodstove by adding at least three pieces of wood each time, on and behind the mound of hot coals. Avoid adding one log at a time." It seems that in this case the manufacturer knows something about their product (Regency I2400) but it would have been nice if they'd included the reasoning behind their instructions so I wouldn't have to rediscover it on my own.

Anyway, I'll be reloading with at least three splits at a time now just like the manual says.

I had the medium and large Regency and my experience was the same as yours. This really drove me crazy with this stove because I could never get a low, long, clean burn. Run from medium to high, the thing would make some very serious clean heat. I could never operate the stove on the lower settings without ending up with black glass and a sooty chimney.

Those two stoves drove me to a cat stove, where I can burn with the air control almost all the way closed, and still watch the cat glow cherry red, for hours on end.

 

[laynes69]

I have a 20 year old wood furnace, and I have realized that it does me no good to shut the dampers down by alot. I used to, and I would get smokey fires and then the house would drop in temp, the forced draft would kick on and burn all of the wood up in the middle of the night. Now I have my forced draft damper open all of the way and the ash door damper open about 2 1/2 turns. it burns hot through the night, and I have more wood and coals than when I tried to starve the air. I always burn wood with a buddy or 2 (Other Piece of wood). I open my dampers wide open for a good 15 minutes, then I get all the wood in the firebox charred red on the outsides, this helps keep the wood gasses from pouring out, or smoking. Now that all the wood is ignited, the firebox is HOT so I can promote secondary combustion. I then close the dampers so I still have enough oxygen to burn off the smoke. When I peek into the door, the entire baffle is one big fireball, but the woods barely burning its burning mostly smoke. I check the chimney and no smoke, then Im off to bed. If the firebox is cool in any way, the smoke wont burn. It needs to be up to temp. Youll learn with a little practice.

 

[ertzog]

is that junky/wet wood?

we can damp down almost all the way and don't experience the "smokey" burn related above. but if some undried wood makes its way in by accident (dang dog takes/drags small logs all around, confusing the wood pile fifo progression towards the fire), it'll smoke guaranteed.

 

[Marcus]

I have a regency and as long as I get a good bed of hot coals I have no problems with great secondary burn. I have a thermometer on the face of the stove on the right side. When it reads 300 I know I will have secondary burn going. My wood last year was drier than this year. Last year I could close the air intake down a lot and still get hot fires with secondary burn. This year because my wood is not as good I have to leave it much more open.

 

[Rhone]

The most efficient air setting is as low as possible where you maintain flames & secondary burn. With an air setting too high you produce a lot of heat but it doesn't stick around long before being sucked out the flue hurting the transfer into the living area. An air setting too low, causes incomplete combustion and unburned fuel goes wasted out the flue. But, the lowest air setting that lets you maintain flames & secondary burn slows how fast the heat leaves the unit so the most can be transferred before heading out netting you the most miles per gallon out of your wood so to say.

Like Othello's advertisement, it takes only a minute to learn what air settings when but a lifetime to master. After a year you'll have it pretty good and you'll keep getting better but what works for you only works for you, each persons install, climate, wood type, moisture content, is all unique.

 

[wg_bent]

The air setting is as low as possible where you maintain flames & secondary burn. With an air setting too high you produce a lot of heat but it doesn't stick around long before being sucked out the flue hurting the transfer into the living area. An air setting too low, causes incomplete combustion and unburned fuel goes wasted out the flue. But, the lowest air setting that lets you maintain flames & secondary burn slows how fast the heat leaves the unit so the most can be transferred before heading out.

Like Othello's advertisement takes only a minute to learn but a lifetime to master. After a year you'll have it pretty good and you'll keep getting better but what works for you only works for you, each persons install, climate, wood type, moisture content, is all unique.

In general, once the flames die down and there is nothing left but coals I tend to open the stove up so as to keep the coals as hot as possible. Is this strategy wrong? Am I wasting heat up the flue by doing this?

Exactly...I still haven't mastered this!! Also, seems like different woods react differently, even at the coal stage. Pine seems to have a much shorter duration at the coal stage than any other wood (makes sense if you think about it for 2 seconds).

 

[Rhone]

I turn it up when it's at the coal stage to. When I hit just coals, and no more flames often if I go outside I'll see smoke coming out. Turning up the air usually gets the coals hot enough to have a flame rekindle and end the smoke out my flue or I open the door and give the coals a few jabs and flames start again. I think it better to open up the air during the coal stage.