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Internal stove temps to get secondary burn?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Drach, Feb 25, 2012.

  1. Drach

    Drach New Member

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    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?

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  2. WellSeasoned

    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.
  3. ozzy73

    ozzy73 Member

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    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....
  4. Seasoned Oak

    Seasoned Oak Minister of Fire

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    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.
  5. Drach

    Drach New Member

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    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 :)
  6. Wood Heat Stoves

    Wood Heat Stoves Minister of Fire

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    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.
  7. Martin Strand III

    Martin Strand III New Member

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    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
    Armoured likes this.
  8. tfdchief

    tfdchief Minister of Fire

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    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.
  9. Armoured

    Armoured New Member

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    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.]
  10. Woody Stover

    Woody Stover Minister of Fire

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    I wonder if the introduction of secondary air lowers the temp at which the smoke burns below the 1100 figure...
  11. tfdchief

    tfdchief Minister of Fire

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    I would say it does.
  12. bluedogz

    bluedogz Minister of Fire

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    Chief, isn't secondary combustion in a stove what you old smokeeaters call a flashover?
  13. Armoured

    Armoured New Member

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    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.
  14. Seasoned Oak

    Seasoned Oak Minister of Fire

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    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.
  15. tfdchief

    tfdchief Minister of Fire

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    Pretty much.

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