Internal stove temps to get secondary burn?

Drach

New Member
Dec 2, 2011
9
South Central WI
Just wondering what is going on in my stove. I know that secondary burn is the smoke and gasses that would go out the chimney if the stove isn't up to temp. Wondering what the internal temp needs to be to burn that stuff off. I usually start getting secondary burn at around 350 stove top temp, so whats the temp inside?
 
W

WellSeasoned

Guest
When my stove top shows about 500 f, and the splits are beginning to char and burn a bit/ cherried up a bit, then I start shutting down the air little by little, then the secondaries start taking off. Good secondaries need properly seasoned wood, and they will take off. Be well.
 

ozzy73

Burning Hunk
Jan 31, 2008
195
ON, Canada
The temp in the firebox is always way more than the stove top especially when the 2ndary's kick in. If you have probe thermo on your flue you can get a good idea what the temp is inside the firebox : ) I wondered about this myself....
 

Seasoned Oak

Minister of Fire
Oct 17, 2008
6,397
Eastern Central PA
I read somewhere that Wood smoke needs 1100 Deg F to light off. Anything below that you get creosote. Unless you have a cat stove and i think the magic number falls as low as 500 Deg to have smoke passing through a cat to burn.
 

Drach

New Member
Dec 2, 2011
9
South Central WI
Seasoned Oak said:
I read somewhere that Wood smoke needs 1100 Deg F to light off. Anything below that you get creosote. Unless you have a cat stove and i think the magic number falls as low as 500 Deg to have smoke passing through a cat to burn.
I had heard that 1100 + deg number before, it just seemed crazy to me to me to have something that hot in my house. I love that heat though :)
 

Wood Heat Stoves

Minister of Fire
The temperature can be a lot hotter inside the stove before it makes it's way to the surface so surface temperature is not a good indication. Just get a good hot fire going with the air control wide open to heat the chimney up and get the wood in full combustion. When you close things down if you have secondary air tubes you'll see bluish jets of flame coming out the holes like a gas stove and you'll know it's working.
 

Martin Strand III

New Member
Nov 20, 2005
763
NW MI near nowhere
Boyz:

In a nutshell, the temperatures required
for wood combustion (a chemical
reaction with oxygen giving off heat)
goes about like this:

300 - 350*F
Hydrogen (one of the volatile gasses in wood)
ignites first forming water vapor. Water in wood
evaporates. The flame itself is about 800*F
which heats the fuel and firebox up so at about

700*F
Carbon in the fuel begins to ignite forming combustible
gasses which are thick and black (smoke, soot, VOCs,
CO, etc) at first. If burning continues with enough oxygen
(air), the temperature reaches about

900 - 1100*F
burning the smoke, soot, CO, VOCs, etc.

> 1100 - 1200*F
More complete clean combustion of vapors and
fuel ultimately forming carbon dioxide and water.
Here, higher means cleaner.

Too little or too much air and your fire gets stuck
in the 700 - 900*F range unless you have a
catalytic converter which has a precious metal
element allowing the burning of the smoke, soot, etc
at a lower temperature.


Aye,
Marty
 
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tfdchief

Minister of Fire
Nov 24, 2009
3,336
Tuscola, IL
myplace.frontier.com
There are obviously a lot of variables, but my Hampton (which has a s/s baffle/secondaries) often has some, not strong, secondary combustion very early in start up, way before the stove top reaches any appreciable temperature and the same for the probe stack temperature. I attribute that to the s/s baffle/secondaries probably heating up fast ?????? I don't know, just my observation.
 

Armoured

New Member
Feb 6, 2012
94
Russia
There are obviously a lot of variables, but my Hampton (which has a s/s baffle/secondaries) often has some, not strong, secondary combustion very early in start up, way before the stove top reaches any appreciable temperature and the same for the probe stack temperature.
The actual flames may be higher temperature and enough to ignite smoke - just not as consistently as the secondary air tubes in a very hot stove. So there's a bit more 'luck' involved of the gases being hot (close to igniting) and flame touching them off.

[Add: just after posting when I stoked I noticed some flame up top, with no flame obviously "touching", but clear clouds of intense action up top - so another case where secondary can occur likely because baffle or other stove part or just accumulated gases hot enough to ignite.]
 

Woody Stover

Minister of Fire
Dec 25, 2010
10,627
Southern IN
There are obviously a lot of variables, but my Hampton (which has a s/s baffle/secondaries) often has some, not strong, secondary combustion very early in start up, way before the stove top reaches any appreciable temperature and the same for the probe stack temperature. I attribute that to the s/s baffle/secondaries probably heating up fast ??????
I wonder if the introduction of secondary air lowers the temp at which the smoke burns below the 1100 figure...
 

bluedogz

Minister of Fire
Oct 9, 2011
1,247
NE Maryland

Armoured

New Member
Feb 6, 2012
94
Russia
I wonder if the introduction of secondary air lowers the temp at which the smoke burns below the 1100 figure...
I don't see why it would - from diagrams it is just extra oxygen (or more exactly, air which has not been oxygen depleted by burning below), heated, at a place where smoke would accumulate and already be hot.
 

Seasoned Oak

Minister of Fire
Oct 17, 2008
6,397
Eastern Central PA
I wonder if the introduction of secondary air lowers the temp at which the smoke burns below the 1100 figure...
I dont think so, in a non epa stove things get pretty hot as well. It seems smoke needs both introduction of super-heated fresh air AND at least 1100 degrees internal stove temp to light off. My harman is a good example without a good bed of red hot coals ,no secondaries. Once it lights off though its self sustaining as long as you have steady draft and dry wood.