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Epiphany for Greenwood, Greenfire, Seton, etc... Induced draft theory vs creosote and moisture issue

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by sparke, Dec 11, 2010.

  1. sparke

    sparke Minister of Fire

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    I have said many times that draft is one of the most critical issues for proper operation with this style boiler. I posted this thread last year: http://www.hearth.com/econtent/index.php/forums/viewthread/53980/. Basically I just say how much better my unit performs with proper draft after having run with out the draft inducer for a few weeks.

    I am also a huge advocate of storage. Most especially in shoulder seasons. But when the temps. turn cold I find it just as easy to burn 24/7 and use storage as a high temp dump zone. I like the convenience of a constantly lit boiler and I may use a tad bit less wood.

    This week the temps have been cold enough to run 24/7 but in the back of my mind I was hesitant because I remembered last year when I ran a constant fire/no storage. I did not like the smell the boiler was making in my cellar and I noticed a small amount of dripping from the side panels on the bottom. I figured if the cellar was smelling of creosote I knew my hex and chimney were getting mucked up. So I went back to running storage.

    Here comes the epiphany: I have been running non stop for 4 days and it occurred to me there was absolutely no bad small, no dripping. and when I checked the hex it was clean. What was so different hmmmm. I finally figured out that last year I had the draft inducer uninstalled at the time I was trying to run 24/7. Now it is installed again and whamo no problems at all.

    So this is what I think is going on. When the damper first closes the wood inside the boiler smokes for a while before it enters the "charcoal mode". That trapped smoke is what causes the creosote build up and moisture issues. With my draft inducer still running, it is sucking that crap right out of the unit and sending it up the chimney. Now I know this will cause a bit more wood usage BUT it is minimal. I still get 12 hour burns easy enough. For you guys with the additional damper in the stove pipe, the problem is even more magnified.

    I have seen so many posts with people complaining about creosote and moisture issues. I always thought I was immune because of storage but now I think people with severe problems are lacking draft and especially draft induction.

    Anyway, I just thought this theory is strong enough for other people to experiment with...

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  2. tom in maine

    tom in maine Minister of Fire

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    Sparke, I am glad to hear that all your hard work has paid off.
    It seems that the induced draft is part of the explanation.
    I think what you are seeing is the fact that trying to shut down an actively burning wood fire
    for later use or for the purpose of controlling the fire like one would with a fossil fuel device
    just does not work well.
    The ID fan prevents this from happening in your case.

    I suspect there will be people who think this is blasphemy but turning stickwood fired
    devices on and off is not efficient and is at best very difficult and creates more problems than it is worth.

    Any time I have discussed this concept of boilers that try to turn a wood fire off with Dick Hill, he rolls his eyes and usually says "I don't believe it".

    There are several things that make for efficient wood burning:
    -high temperature
    -storage (does not have to be a tank, it could be a slab or massive building) since the fire needs to operate unfettered until all fuel is consumed
    -some residence time in a combustion chamber
    -turbulence (proper carburetion)
  3. sparke

    sparke Minister of Fire

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    Tom, what you say is true however, these units do work, work well, and burn clean when they are up to temp. When the damper is shut I do not see smoke coming out of the chimney. The wood does go into a charcoal state at some point. I just don't know how long it takes to get there. I believe this in between point is where the issue lies. The whole point is draft is critical for proper function and I now believe, induced draft will cure the problem of creosote and dripping for folks that have those problems. The fire is still shut down, but with ID you force the crap out of the stove until the wood charcoals and stops smoking... The huge amount of refractory mass is baking the wood like a kiln when the oxygen is depleted(damper closes)...
  4. tom in maine

    tom in maine Minister of Fire

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    All mostly true, but the ID fan is pulling air through from somewhere and allowing the creosote and unburned materials to combust as they exit the stove.

    The previous condition was distilling creosote/polycyclic hydrocarbons and they were condensing on the skins.
    This material is now not condensing since, even with the damper closed, combustion air is finishing off the process.

    All is good.

    I think the changes you made on the construction of the unit are a vast improvement over the "original" design.
  5. sparke

    sparke Minister of Fire

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    Don't get me wrong, I think downdraft gasification is the best technology out there right now. Although I am relatively happy with my unit, I would prefer a Froling, Eko, Tarm, etc... But I have to do the best with what I have. So I try to make my beast run as efficient as possible.

    The purpose of my post was to help people with mass refractory boilers. Especially those that have creosote and moisture issues. I honestly feel induced draft will help those folks. Especially if they use a manometer and dial the draft in to where it should be roughly .05 WC.

    BTW Tom, I eagerly await more info on your new invention. As soon as my finances loosen up I have a few ideas I would like to tinker with and build a gasifier myself...
  6. tom in maine

    tom in maine Minister of Fire

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    We are in total agreement. I was not being critical of your work. I think everything you have done is a vast improvement over the original unit.

    My sole purpose for commenting was just to suggest what I thought was going on.
  7. sparke

    sparke Minister of Fire

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    No problem I appreciate your viewpoints : )
  8. 2.beans

    2.beans Minister of Fire

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    "For you guys with the additional damper in the stove pipe, the problem is even more magnified. " that may be true for some but i have damper that shuts when the draft door shuts and had hardly any build up on the hx after a year. i do run storage and when temps are cold like now it runs 24/7 no drips no smell no inducer draft at .05 .
  9. sparke

    sparke Minister of Fire

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    .05 draft is perfect. Since you are running storage, your unit probably does not idle as much as people with out storage. My post was meant for all the folks who have posted in the past complaining about creosote and moisture/dripping issues. Those are the people I think will benefit most from a draft inducer.
  10. bigburner

    bigburner Feeling the Heat

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    My two cents, again. Posted some opinions about these before, here I go again. Draft is everything to these units, it keeps the whole heat exchanger covered in hottest possible flue gasses, also the other issue is the temp of the water. "WATER TUBE BOILERS" are super sensitive to water flow, because of the rapid heat transfer. It's like dripping cold water pipes in the summer, just every thing is hotter. I believe that running full out is REQUIRED, maintaining the highest possible temp in the HX is a must and having the .05 draft is a minimum requirement. It may require more draft on some installations.
  11. willworkforwood

    willworkforwood Feeling the Heat

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    Not a Greenie/Seaton owner, but I think this is generic to all wood boilers. I agree with the above post, insofar as maximizing boiler efficiency. But I also believe that if you don't have storage, the Catch-22 in doing so is a probable increase in idling (unless the boiler is undersized). I recently made some changes to my boiler, one being fan speed which is indirectly related to draft. The boiler was always good, but after the changes it runs like it's on steriods. I run very small fires during the day, but at night with even a medium load, the thing is producing massive amouts of heat. I'm trying to figure out what to do with extra heat, or load differently to cut down the idling (storage is not in the budget right now). I'm looking forward to -10* outside, so the boiler can just rip it up. I think that the most important thing for any WB is to run with storage, as the previous poster said, or at least a buffer tank to help reduce idling. Bigburner, if you were assuming also using storage in your post, then I guess I'm just blowing smoke here %-P
  12. bigburner

    bigburner Feeling the Heat

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    Ya guess i didn't come out and say that, storage was needed but implied it. at least in my head Sorry. I have my indirect storage down right now and it's getting cold in Michigan this week, Time to fill her up amp up the loads.
  13. stokes79

    stokes79 Member

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    I burn green wood in my Greenfire. It deals with it. I have a tall house so lots of draft. I open the ash pan cover on startup and run draft inducer fan on high. Start fire. Wait fifteen minutes till its rippin. Close ash pan access turn off draft inducer. Everything is cool
  14. stokes79

    stokes79 Member

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