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Classic case of Bridging

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by infinitymike, Nov 19, 2012.

  1. infinitymike

    infinitymike Minister of Fire

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    I've been concerned with the size of my splits.
    I was worried that they were to small and were burning up faster than if they were bigger.
    So back in June I split 3 cord of ash and cherry.
    I split it almost double the size of what I was splitting everything else at.
    I have 12 cord of oak all split around 2x4, 3x3, 3x5.
    This stuff is about 4x5 or 5x6 and even 6x6.
    It is next in line to burn and is down to 22-24% mc
    I went out to take a peek and this is what I found,.

    It's hard to see in the picture but There is about a 8" space from the bottom of the black split to the thin layer of coals on the bottom of the firebox.
    I don't think it would have dropped had I not gone out there.
    And probably would have burned out leaving all that wood suspended.
    [​IMG]
    [​IMG]

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  2. Nofossil

    Nofossil Moderator Emeritus

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    I've done some long-term tests on my EKO 80. Seems like I get bridging if my primary airflow is too low. My theory is that with low primary airflow, the fire in the primary chamber is smaller and concentrated around the nozzle. For me, increasing primary airflow virtually eliminates bridging.

    I was running 4mm gap on each shutter - bad bridging. Now running at 9mm - no bridging. Don't know if this is EKO specific.

    My goal in running with lower airflow was to stretch the burn time a bit, allow longer dwell time in my secondary chamber and ridiculously short HX tubes.
  3. infinitymike

    infinitymike Minister of Fire

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    The WG doesn't have the ability to adjust the air flow like an eko or other units. It has an adjustable damper but no real settings. You just eyeball a position.
    And it will move on its own due to vibration or a puff back upon re-ignition .

    I've only experienced it about 3 maybe 4 times since I started using the WG. I think it is only because the large splits wedged together.
  4. avc8130

    avc8130 Minister of Fire

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    This isn't good new Mike.

    I just started splitting a bit bigger when I bought the boiler, figuring I can fit some decent size wood through that 14x14 door.

    Are you going to continue to burn this larger split wood? I'm curious to hear if you continue to experience bridging.

    I played with the damper last night. I ROCKED through wood last night with the damper 1/2 closed. It's going back to open tonight.

    ac
  5. infinitymike

    infinitymike Minister of Fire

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    I will continue to try to burn this stuff and will keep you posted.
    I actually keep my damper about a quarter open. Around the 10 o'clock 5 o'clock position
    And I still rocket through wood. I'm not sure where AHS gets their 12 hour burn from but I've yet to experience that.
    Problem with our damper is it doesn't hold it's position very well and can slam shut with a puff back which tend to happen quite often upon re-ignition. I just had a puff back that exploded the two 24" pieces of air intake pipe apart!
    It popped open the seams! So I snapped them back together and taped them.
  6. Fred61

    Fred61 Minister of Fire

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    I don't believe those sizes are too large for your unit. I would forget about what your moisture meter reported. The wood is just too wet. This is the stuff you split last June, Right? I can see by the photos of the fire that coals are only consuming about 3/8" of the split. That's the part that the fire has dried and will continue to burn in that fashion and consume the coals before the split produces more until the log is burned away.

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