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To Greenwood or not to Greenwood

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Eric Miller, Mar 13, 2008.

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  1. Eric Miller

    Eric Miller New Member

    Joined:
    Feb 27, 2008
    Messages:
    30
    Loc:
    Central MD
    I called my county permits office today to inquire about any regulations in place on wood boilers. I figured I better check now while I'm still in the exploratory phase of this project. I learned that there are no restrictions on the sale or installation of Wood Boilers in Maryland; however, they are illegal to operate. :-S I then called the State Environmental Agency and spoke to the gentleman in charge of overseeing this regulation. He was very helpful, and informed me that I can install a unit if it meets certain state established guidelines for visible emissions and grain loadings (I don't know what the latter means). Anyway, he was aware of Tarm but hadn't heard of EKO but he seemed to think that any decent gasification unit would qualify but they would have to confirm this before I could operate the unit. He also told me that Greenwood boilers have already been approved.

    So it would seem that selecting a Greenwood boiler would give me a shortcut through the regulatory process. I called Greenwood to get some basic pricing information, they are a little more expensive then Tarm or EKO but have 1000 pounds or so of internal ceramic brick for thermal storage so they do not require water storage. I asked and was told that water storage could still be used but eliminating water storage from my system would save about $6000 according to the rough numbers I have for an 800 gallon tank and heat exchangers.

    I am just curious to know what opinion any Greenwood owners have of their systems. I know there are a about a million variables from one system to the next but I'm just trying to get a general idea of how these systems operate. If I went with a Tarm or EKO and water based storage I'm pretty sure it would work out pretty well but I'm a little skeptical about eliminating the water storage. Of course, I have no experience on which to base these assumptions so they are just leaps of intuition on my part.

    So, what are my expectations?
    1) Once a day feeding - During the normal week, I would like my system to be capable of providing heat in the morning for a couple of hours while everyone gets up and ready for work and school. Then the house sits empty for several hours before anyone gets home so no more heat is required until late afternoon and then throughout the evening until bedtime. I really don't want to feed my boiler in the morning; I would prefer just one daily feeding when I get home from work. On the weekends, or other times when we are home and using more heat, I would not mind multiple loadings. It seems the water storage would work out pretty well for what I want. In the evenings, the boiler could heat the house and recharge the storage tank. Then in the morning, the storage tank would provide heat and hot water for showers and keep the house at a moderate temperature during the day until I get home from work to fire up the boiler again.

    2) I would like to generate DHW throughout the entire year. Without the water storage it seems I'd have to run small loads in the Greenwood all the time. With water storage, I was hoping I could skip a few days between firing.

    Also, are the Greenwoods harder to get going from a cold start due to their thermal mass? How do they behave while in bypass, any smoke or other issues? Any special considerations for adding water storage to a Greenwood?

    Thanks again to all.

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  2. Gooserider

    Gooserider Mod Emeritus

    Joined:
    Nov 20, 2006
    Messages:
    6,737
    Loc:
    Northeastern MA (near Lowell)
    If you haven't already done so, use the search engine for posts that might be relevant - I'd search on "Greenwood". I seem to remember complaints about the thermal mass cracking, though it's not clear how big of a problem that is if it happens. I've also heard comments to the effect that regardless of mfgr claims, you still need water storage for best operation..... No personal experience on either claim.

    Gooserider
  3. antos_ketcham

    antos_ketcham Member

    Joined:
    Mar 5, 2008
    Messages:
    155
    Hi Eric -

    I have a Greenwood 100. While I am still on the learning curve, I am very happy with it. It is located 50 feet from my house in a shed. I have no storage and it is not a problem for me. I do have to feed it twice a day when it is cold. If it is high 30's or 40's then once a day is enough. I intend to try to heat my DHW all year and figure with the thermal mass I should only have to do a small fire every other day - we'll see and I'll let you know. As for a cold start being hard - I didn't find that to be the case. The smoke is minimal. It is a good product. Wood in, heat out. Simple controls. The one downside is that Greenwood has poor customer service so make sure your dealer is a solid person to work with and can help you get what you need from the company. PM me if you have more questions.

    Pete
  4. DKerley

    DKerley New Member

    Joined:
    Jan 27, 2008
    Messages:
    75
    Loc:
    Yukon, Canada
    Hi Eric,

    I run a GW 200 for my heating needs in the North. So far, as others have mentioned, it has been a bit of a learning curve. The unit is well made and contrary to what others have said, I have had decent support from Greenwood.

    At the moment, I do not have storage but I am considering it for the shoulder seasons when it is too warm for the GW to run 24/7. In order for the GW to operate efficiently you need to be able to pull off enough BTU's per hour to prevent it from idling for too long or short cycling. On the 200, they say a minimum of 50K BTUH.

    My only issue to date has been the excessive build up of creosote and fly ash on the heat transfer tubes and the associated loss of efficiency. This has been the fault of the wood and operator more so than the design. My wood has been comprised of beetle killed spruce and pine which both have a lot of pitch. The design limitation on the GW200 is the lack of easy access to the rear transfer tubes for cleaning.

    I personally don't like having to light fires. Running it 24/7 keeps the refractory nice and hot which may be why I have had only limited amounts of cracking in the ceramic and apparently, does not affect the performance at all.

    The GW200 is located inside my attached garage. This is extremely convenient when I have to load wood and it is -40 outside. The added benefit is that it heats the garage for free. Smoke from the loading door can be an issue if you open it up to look at your fire constantly. Our procedure at home is to turn on the draft inducer and open the garage door prior to opening the loading door. This prevents an accumulation of smoke which is otherwise possible.

    Another factor to consider before you get the Greenwood is the size of wood that you have available. The GW likes large un-split logs best. It will burn smaller but the wood load does not last as long. I love loading 24" long by 16"D into the 200. One piece of crappy spruce will last 6-8 hours depending on the outside temperature and heat demand. With the 200 I can load in about 100 lbs of spruce and have it last 8-10 hours while it is between -30 and -40.

    The jury is still out regarding wood consumption. So far my consumption has been a lot higher than expected. This, I think, is a result of having poor wood and also being oversized for my present heating requirements.

    Would I buy another Greenwood? At this point I would say yes but at the same time, if I were planning on solar DHW in the off season and had to have storage for that, I may consider one of the other gasifiers.
  5. antos_ketcham

    antos_ketcham Member

    Joined:
    Mar 5, 2008
    Messages:
    155
    I wonder Doug if the level of customer service increases the closer you get to Greenwood HQ's time zone? In all seriousness, another couple points I'd add Eric are:

    1) I too have not experienced the cracking of the refractory. I have two places I need to fill with the replacement cement but this is where the sides and back come together. I have had part of the seams between the two open up. No big deal.

    2) I am burning good dry hardwood and I have the issue of creosote and ash on the transfer tubes as well. I can't get at the back ones, but I keep what I can reach brushed off. A little hassle but not bad.

    3) Would I buy one again. At this point I would say yes. One of the main appeals to me was that the GW is a clean burning unit that doesn't need water storage - I just don't have the room. We live in a 1000 sq foot cabin and I need every square inch of my basement for other purposes.

    4) If I had to look at a second unit at this point I might check out the EKO. If I was doing it all over again, I might have picked up one of the new EPA approved OWB's - only because then I wouldn't have had to build a shed to house my boiler.

    Doug - do you know how many BTU's an hour I need to be pulling from a 100 to prevent short cycling?

    Thanks.

    Pete
  6. muleman51

    muleman51 Member

    Joined:
    Feb 18, 2008
    Messages:
    230
    Loc:
    SE Minnesota
    My $.02, not worth more, from using a GW type (adobe) for 4 months is that you will need storage to make these work efficiently. You will have $10000 tied up, at least, before you get everything working satisfactorily. That is something they don't want you to know. Would I buy this type again, probably not , although I am stuck now, I would most likely go with a garn type or at least something that can be used with a minimum amount of fooling with. Told you it wasn't worth $.02.
  7. DKerley

    DKerley New Member

    Joined:
    Jan 27, 2008
    Messages:
    75
    Loc:
    Yukon, Canada
    Pete,

    I have heard two different numbers. The first was from Greenwood themselves of 50K out of the GW200 that works out to 25% of the rated BTUH. The other number I heard is from my installer whom is considering becoming the dealer for Greenwood in the Yukon. He said that he was told about 30%. So both numbers are pretty close.
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