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Hot water storage tank for GW 100

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by antos_ketcham, Mar 5, 2008.

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  1. antos_ketcham

    antos_ketcham Member

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    I have a Greenwood 100. My problem is that it short cycles - I don't think I am pulling enough heat. I have an 1100 square foot log cabin. Short cycling is causing smoke and creosote.

    So my question is - would a 1000 gallon storage tank be in order and where would I get one?

    Any other suggestions?

    Thanks - Pete

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  2. sixroses

    sixroses Member

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    I also have a GW100. has worked really good all winter. I do have 300 gallons of storage because I was tired of boil overs. After some studying and some questions I have have decided to up my storage to nearly 800 gallons. The stove makes so much heat that I have to put it somewhere. I am still deciding on plumbing alternatives. It's 40* outside, my burn times have gone to nearly ten hours. With out 300 gallons, I would have had many small loads. Keep checking the site and asking questions and somebody that really knows will soon answer.
    Steve.
  3. antos_ketcham

    antos_ketcham Member

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    Thanks for that information. I should say that I have been very happy with my Greenwood. My house and my DHW has never been hotter and I haven't burned that much wood - maybe 5 cords since November.

    My issue is the creosote that builds up in the elbow at the bottom and the first section of pipe(single wall) that runs from the elbow to the 8 to 6 reducer. I have had two or three small fires in there. One was hot enough to burn the paint off of the boiler where the elbow attaches!

    I also have much more smoke that I think I should. The boiler never seems to get to run wide open for very long before shutting down.

    I think water storage is the answer so I am hoping someone can tell me where I can order a tank.

    Then again, maybe this is not the problem and I am hoping someone out there has some more ideas for me.

    Pete
  4. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    Welcome aboard Pete.

    I am no engineer, nor do I have storage for my GW100. But I do have some questions, and some opinions :smirk:

    It sounds like your heat load is quite a bit smaller than the capabilities of your unit. When you say it short cycles . . . can you quantify that? The GW is designed to have the damper open and close throughout the load. How long were you getting between loading when you were getting this 'smoke and creosote'? Can you describe the smoke more too? Was it thin white wisps with the damper closed? Or was it smoking with the damper open?

    I don't have storage, and I think some of the guys here that do have it will tell you it is NOT going to increase your efficiency DRAMATICALLY. I bet that it WOULD make burning during Spring and fall much more pleasant though. Couple more questions . . . What do you have the aquastat set at? Is the damper closing fully when it hits the high limit? How full (and what quality wood) are you filling the GW with?

    Jimbo
  5. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    One thing I hate to see is people getting frustrated after having spent a chunk of change on a wood-fired hydronic, so they go and spend MORE MONEY!

    My idea would be to fix the problems first, then decide on laying down more money later.

    1)Have you measured the draft and what is it?
    2)Give us a realistic, objective description of your wood.


    General question . . . . Why are people putting a reducer on these units from 8 to6"??
  6. antos_ketcham

    antos_ketcham Member

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    Thanks Jimbo - let me try to answer your questions.

    1) Short Cycle - the time the damper stays open is very short. The fire gets going and then it shuts right back down - it reaches 180 fast.

    2) I only have to load it twice a day. The smoke is intense and visible for the fist half of the burn cycle.

    3) Smoke when damper is open can be blue and thin or thick and grey/black - depends on outdoor temp. The colder, the bluer the smoke. When it is damped down the smoke is thin, white and wispy generally. Although sometimes it smokes more when shut down.

    4) Aquastat set at 180. Could I go to 190? Will that make the difference a 25 degree one? Could it boil over at 190?

    5) Yes - damper fully closes at high limit.

    6) I am burning good dry hardwood. Only issue is I only have splits this year - not a lot of rounds. When I fill the firebox I fill it half to three quarters full - no more than half way up the door as the manual says.

    hope that helps.

    Pete
  7. antos_ketcham

    antos_ketcham Member

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    Jimbo -

    Honestly - I really don't want to spend more money. But I do want to get the maximum efficiency and cleanliness I can from the Greenwood - this is why I chose it over a traditional OWB.

    That said here are the answers to your questions -

    1) Yes I just had the draft measured - it was a steady 0.5. Maybe I need another section of stack to get the draft higher?

    2) I burn clean, dry hardwood. I don't have a moisture meter (yet) but I stack my wood out in the open with metal roofing on top with the long side of the pile towards the sun. I let my wood season for at least two years if I can. This winter I am using wood that seasoned for 1.5 years. I also have mixed in some kiln dried hardwood from the local mill.

    Pete
  8. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Your heat load is certainly very much smaller than the boiler's output, which is almost certainly causing your problems.

    Storage would work well.

    Or you could increase your heat load by opening all the windows, but I don't think that's a good idea! :)

    The size of storage tank that will work best for you depends upon the particulars of your house. The biggest factor is an accurate heat loss calculation, and information about the existing radiation (for example, if baseboard, how long?). That determines what water temperature "swing" your tank can see while still heating the house, which ends up determining how many hours of run-time you will get from a given tank size.

    Joe
  9. Nofossil

    Nofossil Moderator Emeritus

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    On my EKO, I had good results by restricting the fan inlet to reduce the 'burn rate'. That allowed me to match the boiler output more closely to my heat load. Don't know if there's an equivalent solution in your case.

    Is there any chance that your circulator is undersized or that there's some flow restriction? That would cause short cycling even when there's and unsatisfied heat load.
  10. sparke

    sparke Minister of Fire

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    As you know these units do not like split wood!! My unit burns rounds very cleanly but it does not burn splits cleanly for the first hour of the cycle. As a matter of fact I would rather burn green rounds then dry splits!! I am not sure the GW burns green wood (no pun intended) as well as the Greenfire. I suspect it is the airflow from the grate that makes the biggest difference...
  11. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    Just to follow up on three good comments above . . .

    1)When it short cycles, is it supplying your residence with all the requested heat? If not, maybe som HX problems and/or circ sizing issues.
    2)Have you tried small loads? My observation is that 8 hour loads burn the best. From the sounds of your heat load, you probably only need two small layers of wood on a coal bed. I doubt you need to even approach the mid point of the door.

    Now, having said all that, You shouldn't be 'smoking' if your wood is as good as you describe. I use wood that is lower quality than you, and my general observation is that after one damper open cycle, the GW will not smoke more tha 30 sec when the damper re-opens.

    I would suggest avoiding the kiln-dried stuff for a while and observe the smoke quotient. I have always found that dimensional lumber will smoke like a freight train. My WAG is that it is cause by a very poor fuel/air ratio.

    Jimbo
  12. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Poor air/fuel ratio (since the dimensional tends to have higher surface area than unsplit cordwood), and too dry. Some water is needed in order to moderate the combustion, just like some octane is needed in gasoline.

    Since your guess has been confirmed, it is not officially a SWAG.

    Joe
  13. antos_ketcham

    antos_ketcham Member

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    Just to clarify quickly - the kiln dried I am using is not dimensional it is kiln dried hard wood splits.

    Pete
  14. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    There are a number of ways to make the GW smoke . . .

    If you're burning seasoned hardwood (Oak is perfect, followed by apple, hard maple and ash) that is seasoned, you've eliminated one reason.
    Running at too low a temp is another, but if you're burning 170-190*, that's not the problem
    Letting as/coals build up over the air inlets is another, but this usually means you can't get any heat outa' it.
    Too much fuel, especially too much surface area, will cause smoke too, but this should only happen early in the burn . . .

    Oh!! The surest way to make her smoke is to put Aspen in it :roll:
  15. DKerley

    DKerley New Member

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    Hi Pete,

    I am in a similar situation to you. I have a GW200 which is oversized for my heat load when our outside air temperatures start getting near the freezing point. I too am looking at storage as an option and have posted a thread on that issue. The learning curve for operating my greenwood has been very steep. Our wood in the Yukon is S**t - Beetle killed spruce and Pine. Low BTU's - high pitch content. I did some time lapse photography during the night to attempt to understand how the greenwood cycles. If you have a camera capable of doing that, it is very interesting. Feel free to PM me should you want me to share any results of my research. I believe that Sthilwoody has storage on his GW100.

    I think that we need to start a new subcategory of "Boiler Room"for the "greenwood support group". This is where us Greenwood owners could find solace in knowing that we are not alone in our attempts to operate our greenwoods as the sales brochure suggests - no ash, no smoke, no creosote.

    Cheers,
  16. antos_ketcham

    antos_ketcham Member

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    So do you think I should set my aquastat to 190? Any downside to this?

    Pete
  17. Eric Johnson

    Eric Johnson Mod Emeritus

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    Yeah, but it’s a pretty sharp looking brochure, you gotta give them that. Beautiful women and everything.
  18. antos_ketcham

    antos_ketcham Member

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    Glad to hear the Yukon checking in. While your wood may not be good btu wise, you do live in a beautiful province.

    I will PM you regarding your research.

    Agreed on the Greenwood support forum - how do we get that going?

    Pete
  19. antos_ketcham

    antos_ketcham Member

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    Hi Eric -

    I saw that you were looking to get a Greenwood at the NE Expo in VT this spring. The dealer I bought it from lives "just down the road" from Essex in St. George. I'm sure he'd come. He's been a CB dealer for years and is switching over to Greenwood as of the new regs. going into effect.

    Pete
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