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Anyone have experiance with a greenwood boiler

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by tuolumne, Apr 30, 2007.

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  1. tuolumne

    tuolumne New Member

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    My apologies if this is the wrong forum. We would like to use a Greenwood (indoor) boiler to heat our new home. Does anyone have personal experiance with these? They are significantly heavier than similar output competition (Eko, KpPyro, HS Tarm etc.) which is due to a huge cast ceramic refractory. Supposedly it will store the excess heat internally instead of using external water tanks like Tarm recommends. Any comments appreciated. Total load load at -15 F is around 50k BTUs.

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    The only thing I've heard about the Greenwoods was some guy on the Internet who says his new unit developed a crack in the refractory mass, and the company send him a can of refractory cement.

    Don't know if that's even true; you've probably seen the same posts.

    I think that gasification technology is the way to go, especially if you have a reliable supply of dry wood. There are a couple of other similar, refractory-heavy boilers out there, namely the Black Bear and one made by Dirigo Mfg., also of Maine. You might check out the Garn as well.
  3. webbie

    webbie Seasoned Moderator Staff Member

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    I have seen this unit burn and studied the design and think it is probably a good unit - BUT, in terms of total efficiency it may be a step below the Tarm and other gasification boilers. It is not a true gasifier, but more related to downdraft systems such as the VC acclaim, etc. -

    As with any comparison, there are advantages and disadvantages - while this may not meet the standards of a true gasifier, it does take much larger logs rounds. Also, since most of the boiler is not "wet" (surrounded by water), this means less potential of steel or weld failure due to chemicals created by slow combustion of wood (this was a problem with early gasifiers, but is solved by storage).

    Heat storage is a function of mass, and there is no magic in the Greenwood that would make it store any more heat than another boiler is the total wet (filled with water) weight was similar. BUT, again it may not need storage as much as others because it has a more conventional design.

    When it comes to boilers, you want to look at the total system - climate, heat load, wood supply, lifestyle, etc. and then see if certain advantages of one boiler put make it superior to the others. Compare cubic ft of firebox size, ask for some kind of proof of total efficiency, etc.

    Sounds like you are on the right track asking the questions...
  4. alfio

    alfio New Member

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    Hi , I have seen two other boilers that have the same fire box , the seton by rohor, and the adobe boiler . The adobe has a bypass damper but other then that, they are the same.

    P.S. check out the boilers at new horizon corp, they have sum good units
  5. alfio

    alfio New Member

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    I just read the rest of your post, AND has for the tarm and other grasfiers, you really don't need any storage, because they store the wood gas eternally and only use it when needed.
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    Did you really mean "eternally" alfio, or "internally?"

    My (ongoing) education about gasification boilers leads me to believe that when they're idling, you get the potential for creosote buildup in the firebox, heat exchange tubes and chimney. If you have adequate heat storage, you have more flexibility to run the boiler more efficiently.

    Is that true in your experience?
  7. Corie

    Corie Minister of Fire

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    I'd say you're dead on with that statement Eric. There is no mystical tank where the wood gas is stored until it is needed, the operation principles are not THAT much different than a regular woodstove.

    If you're kicking the boiler on to heat the water for the house everytime the demand is called for, the boiler will be forever jumping between idle and heat. Like Eric said, its the idle periods that generate creosote and the other nasties and offset the gain of having a gasifier in the first place. The best application of the gasifier is precisely how Eric is planning to use it.
  8. alfio

    alfio New Member

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    hi eric yes i ment to say to say internally , as you can see my spelling is terrible . tanks bringing it to my attention .
  9. alfio

    alfio New Member

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    hi eric yes i ment to say to say internally , as you can see my spelling is terrible . tanks bringing it to my attention .

    And for the heat storage , you are right it is more efficient to have heat storage , but with gasification you have the apt-ion ,if you don't want to spent the extra money for the heat storage . I also want to say its not from my personnel experience, i was quoting tarm's ad on there web site .
  10. tuolumne

    tuolumne New Member

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    Thanks for all of the input thus far. I have looked a the Eko boiler at New Horizon Corp and it is number two on my list. With this boiler or other "lightweight" varieties, I would consider water storage for greater efficiency. I do not like the thought of the boiler idleing. In my opinion, it should burn its load hot which is most efficient and store the heat somewhere. I knew an engineer that had a 5000 gallon storage tank and only needed to fire his wood boiler every few days. My research so far seems to indicate that the Greenwood is a compromise, offering some additional storage in the refractory mass over other boilers, and perhaps allowing me to do without the water storage. If this boiler is reburning wood gas at 2000 degrees, what would preclude calling it true wood gasification? I have spoken to all of the above mentioned manufacturers in some detail, so I know what the efficiency claims etc. are across the board. Has anyone heated with this boiler, and at what load? Thanks for all the advice thus far.
  11. Andre B.

    Andre B. New Member

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    Here is a drawing I made up a while ago to try to explain things the way I have come to understand them.
    [​IMG]

    The option in the center would be the Tarm just turned upside down, I know people who will argue that that is not a true gasification because the gas really never stops burning between the point where it is created and the secondary combustion chamber.
    There does not seem to be any widely recognized definition of gasifying burner so marketing departments use the word to their advantage whenever they can.
  12. tuolumne

    tuolumne New Member

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    If this is the definition of gasification, I do not believe I've seen a boiler coresponding to the 3rd drawing. The Eko has a "nozzle" separating the burning chamber from the gasification chamber, but this appears to be just a plenum as with the Tarm and Greenwood. The Rohor model looks like traditional wood boilers. The Garn looks good, but the heat output from the smallest unit is more than 6 times what I need. It seems that with such a small heat load, I should be looking more for a boiler that is easy to light and keep going, easy to keep clean and with good longevity, rather than efficiency. Any thoughts?
  13. slowzuki

    slowzuki Feeling the Heat

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    I'd say with a small heat load you need to look for those features but you should be thinking some type of storage. I'm using an 800 gal tank with my system and arguable my 6 inch thick slab too. If the boiler can't reach a nice hot steady state burn, the advertised efficiency will never be reached. So storage is important to soak up this heat.
  14. alfio

    alfio New Member

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    witch tarm model are you looking at , there's is the same tech. as the eko the wood load is on the top chamber just like the eko. I'm not sugesting that one is better then the other but that the design are similar has for the rohor, greenwood if you look carefully you would see that there the same boiler design has is the adobe boiler . the eko ,tarm and there is one american made model that worth looking at , tha's alternative energy corp. from Pennsylvania they have a gasification model also very promising design. the last three are what i consider gasification boiler .
  15. alfio

    alfio New Member

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    just remembered sum thing , the boiler from alternative energy is capable of burning pellets in it , by changing the ceramic chamber separators .

    just thought i'd let you know .
  16. webbie

    webbie Seasoned Moderator Staff Member

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    Although it was initially thought that wood gasifiers would idle when in the "off" mode, real world experiences has shown that this creates a number of very corrosive compounds which greatly shorten the life of the boiler vessel. In fact, certain companies such as Eshland Wood Gun may have went out of business due to these premature failures.

    From my experience with Tarm, an important factor is climate and heat load. We had less boilers failing in the northern climes, but folks who used them in the summer for DHW and on low output constantly did see premature failure of the steel - usually starting as pinholes.
  17. alfio

    alfio New Member

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    correction ; it's not alternative energy, but Alternate heating systems inc. sorry :red:
  18. tuolumne

    tuolumne New Member

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    Thanks all. These manufacturers all like to say burning green wood and idleing is fine but it defies common sense. Not knowing where to go beyond the specs etc, I began to look at the weights of the units thinking that for storage/longegivity or whatever the heavy weights may do better. Most models weighed in around 900-1000 lbs. The Orlan Eko is an 85 kBTU boiler and weighed in at 1250 lbs. Also, this boiler is only 85 kBTU/hr which means more high temp burns for our small heat load. The Greenwood is an astonishing 2400 lbs or ceramic hulk. Looking closer at their specs, Greenwood does not actually mention gasification, but rather a superheated firebox created by injecting air. Now I'm leaning towards the Eko and very confused. The Eko is also by far the cheapest....5k vs. 6-8k if my memory serves. I had previously looked at the Alternate Heating systems boiler and it looks good. Then again, Tarm has been in business for a long time and is more local to VT.
  19. keyman512us

    keyman512us Member

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    The 85K/hr might not sound like much...but you would be surprised just what it will heat!

    The question you have to ask yourself are how often are you willing to load it? A boiler is work no matter what model you go with....take all factors into consideration...you are on the right track.

    Ideally with boilers...regardless of what the manufacuters say, IMHO, the best set-up is to let it do it's job...burn the wood, make the hot water and then go from there (storage)...

    From my own personal experience (with a boiler)...I will say one thing: It's a lot easier to build a larger, hotter, fire...than to try to build a smaller, longer burning one...

    Just keep in mind...smaller, hotter fires usually equal a cleaner burn....very important with boilers.
  20. alfio

    alfio New Member

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    Hi, tuolumne; just taught of sum thing , if your going to invest on a storage tank , i think you can even go with a up draft model , like energy king's , and since you going to run it hot and store the heat , I'm guessing that it will burn just as clean as any other, at a better price , more like $3500 compared to 6 to 8k. taught I'd give an other alternative . I know those grassfires are high priced, thats why i event bought one my self .
  21. slowzuki

    slowzuki Feeling the Heat

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    An energy king is not efficient and clean burning like a gasifier type. It is updraft but is completely water jacketed for low combustion chamber temps giving smoke. So no it won't burn as clean as any others.

    Some of the gasifiers will burn green wood ok. The fire in the primary chamber is only to heat the wood enough to gasify it to burn it in the 2nd chamber. The chamber design in some trys to limit the gasification zone to a small area and uses the cool water walls to keep the load from gasifiying too fast. Most downdrafts are like this. They will need dry wood to get the process started and can burn somewhat green wood once up to temp.

    Updraft units subject the whole fuel load to pretty darn high temp loads and can gasify wet wood with ease once up to temp. In this sense they are really just an advanced boiler rather than a gasifier. You could refractory line an old school model like an energy king and get similar clean burns with some secordary air work etc.
  22. alfio

    alfio New Member

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    slowzuki ; if I'm not mistaking the gasifier's, at least all the ones i have seen, are also water jacketed .I been told that that design is more efficient , because more of the heat is captured by the water .
  23. Eric Johnson

    Eric Johnson Mod Emeritus

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    Craig: The old Eshland is now being manufactured by Alternative Energy Systems (or whatever it's called now) in Pennsylvania. Interestingly enough, it has a stainless steel firebox (and maybe hx tubes) as well as a cyclone to take particulates from smoke. Strange. They're supposed to have one here at the show in Bangor, so I'll check it out and let you know what's up.

    Also, there's a mfg in western NY that makes a conventional gasifier like the Tarm or EKO. But it's about $2,000 more expensive, and the warranty (according to the website) dosen't apply if you install it yourself. I did learn from their sales rep that in NYS there's no sales tax if you are putting in a primary heat source. There's also a $400 tax credit for installing a high efficiency boiler, which gasifiers all appear to be (80% overall efficiency +).

    The EKO is somewhat cheaper than the Tarm, but not by a significant amount. You have to shop around and buy in the offseason to get a Tarm at the right price. Cozyheat.net sells EKOs for the lowest priced, IME. I'm planning to buy an EKO 60 this summer.

    For all the reasons mentioned, I think hot water storage is the way to go with a gasifier. Way more flexibility.
  24. alfio

    alfio New Member

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    HI Eric; are you talking about thermo-control heating systems.
  25. slowzuki

    slowzuki Feeling the Heat

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    Not exactly, the water jacket is in the fuel area to slow the combustion down. It gets very creosote covered they as the gasification process, before it is burned in the nozzle, makes all kinds of tars and nasty stuff. These are what is burning in the ceramic/refractory area of combustion.

    After the combustion area then the heat is extracted by another water jacket or heat exchanger.

    Without a ceramic/refractory insulated area, you can almost certainly say right now it is a dirty boiler. All the design work these boilers have in them is in that area to mix air with the tars and burn it cleanly in that hot refractory zone.

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