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Boiler efficiency and wood use

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Downeast Farmer, Jan 20, 2013.

  1. Downeast Farmer

    Downeast Farmer New Member

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    I'm newly here and seeking hard numbers on boiler efficiency as measured by wood use. Has anyone here switched from a conventional wood boiler (Memco, New Yorker, etc.) to a gasification boiler (Garn, Frohling, etc.) and tracked the difference in wood consumption for similar heating loads? Boiler manufacturers make claims about 50% or higher wood savings; does anyone have actual records showing such savings?

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  2. maple1

    maple1 Minister of Fire

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    I'm only half way through my first winter with a gassifier & storage, so it's too early to tell yet. But I still have a lot of wood left. It was around 7.5 cord per year with the old one - I don't expect to halve that, but it's looking like I might be down at least to 5, maybe even close to 4.
  3. flyingcow

    flyingcow Minister of Fire

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    The claim of 50% in savings might be a little high. But you need seasoned wood to run in a gasser. A memco or new yorker will burn whatever you put in it. You could see 25%? gain in wood usage when you compare seasoned wood to green? in a memco/NY boiler.


    I have no experience other than my gasser, but you should look at a solid 30% less wood consumption, more with 2 yr seasoned wood might even push closer to 40%. Plus the coolness factor when you show your buddies your burning wood, and no smoke out of the chimney. For me it's the way to go.
    Taylor Sutherland likes this.
  4. Paver56

    Paver56 Member

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    I went from a new yorker wc-130 to a Froling. I never burned only wood in the new yorker, I used coal and wood. I heat around 4,000sf, all radiant. We built our house 4 yrs ago. It is insulated well. I have had the Froling along with 1500 gallons of unpressurized storage running for about a year now. It had beed a little mild here but this year, heating my water all summer, I used around 5 cord.
    There is no comparison at all between the two. The new yorker, in my opinion was very inneficient. I was basically a slave to it when it was cold out. Being able to burn once every 24-36 hours is great. In the summer I go 7-10 days between fires.
    To answer your origional question, I do not know if it would be a 50% savings in wood consumption, but I think it would be close.
  5. BoilerMan

    BoilerMan Minister of Fire

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    Paver56, I like your sig!

    Downeast, I switched from a NYwc130 to a gasser, had storage before and have been tracking wood consumption. I burned the same well-seasoned wood in the NY as I do in the Attack, and had storage before with the NY. All things being = and I have not been through a whole winter with the Attack yet, but I think it's safe to say 1/3 less wood is a very conservitive number. 50% would be if one really burned their Memco/NY dirty and cold, ie. worst case. If one runs a wood boiler like that, then they may not be a good canidate for a gasser, unless they really want to change their ways. Bottom line: smoke = lost potential heat that would have made it into the water to be used for something useful :) like keeping you warm.

    TS
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  6. hobbyheater

    hobbyheater Minister of Fire

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    pig2.jpg

    My interest with wood boilers started in the late 70s. Our first boiler was like the one pictured above. In one year it burned 22 cords of dry old growth Douglas fir wood that had lots of bark attached. It was also a write-off at the end of that first year as the metal that was not surrounded by water was burnt out and fractured.
    Our second boiler was made in Denmark. A small cast iron sectional down drafter with a triple pass heat exchanger. Its wood consumption was sixteen cords a year. This boiler used the dutch oven concept of a fire box totally surrounded by water. We had to put a tray on the floor underneath it to catch the liquid creosote that would drip out the bottom of the clean out door. I added storage (1046 imperial gallons) to this boiler in hopes of eliminating the creosote on the floor. The creosote now moved from the floor to the chimney. The surprise or prize was that storage dropped its wood consumption to ten cords a year.

    IMGP3685.JPG

    With the creosote problems we were having the second boiler and when we learned of the concept of wood gasification, a Jetstream was soon heating our storage system. Our wood consumption now averages 4 - 4 1/2 cords a year.

    IMGP3756.JPG

    This picture was taken with the Jetstream firing at full capacity. From burning 22 cords a year to 4 cords per year on average. Thirty years of operating this system has shown some very small issues can alter efficiency and if several of these issues are compounded, efficiency numbers can be greatly effected.
    Taylor Sutherland likes this.
  7. Downeast Farmer

    Downeast Farmer New Member

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    This is my first foray into online posting and I'd have to say it's really great; thanks everyone.
    For most of the last 25 years we heated an old farmhouse on a windy ridge with a Memco boiler and it seemed that our 200-acre woodlot was barely large enough to feed it. Then a couple of years ago we moved into a larger house in town. We now have a Newmac wood furnace with an oil furnace backup and I buy my wood tree length from a local logging outfit ($90 per cord, or thereabouts). I burn from 150 to 300 pounds of wood per day in this Newmac and someone must feed the beast every couple of hours. On those rare days I get the place to 65F I'm treated like visiting royalty. During this fairly average year I will burn about 15 cords of dry maple. Something more efficient seems in order.
    I'm imagining the most efficient system to heat our house for the next 30 years and it seems from what I've read here and elsewhere that such a system would feature a wood boiler with storage and radiant heat. I'm now trying to cost out that system and amortize those costs over 30 years to see if it's worth it; thus the interest in wood savings. I gather 30% savings over a conventional wood boiler (or 40% over my wood furnace) is reasonable.
    The next issue I'll be looking at is the durability of the boiler. Do you guys with your state-of-the-art gassiers feel that you have 30-year boilers? They seem so complicated and component-rich that I wonder if your average farmer could maintain such a boiler for an extended period without a second mortgage. On the other hand, maybe expecting such a long service life from a fairly new technology (the Garn and hobbyheater's Jetstream's boiler excepted) is unreasonable. So, a Garn maybe?
    Is it sensible to design a 30-year wood heating system? What components would your system have? The constraints for me are: 1) no or nearly no fossil fuel use, 2) the minimum use of sustainable fuel, and 3) a system I can maintain (there being no one in my neck of the woods to do it for me).
    (I realize that a major part of this is reducing the heat loss of the house (which is now about 70 BTU/sf and for a number of reasons is unlikely to get much below 30), but that's an issue for another day.
  8. Downeast Farmer

    Downeast Farmer New Member

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    And by the way, hobbyheater, anyone who goes from 22 cords a year to 4.5 is my personal hero. Move to Maine and set up shop as a consultant.
  9. Nofossil

    Nofossil Moderator Emeritus

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    My brother is a fanatic, and has by far the best data I've seen. He weighs his firewood every load and keeps a diary. Here's the bottom line:

    He originally had a traditional indoor boiler, operated at maximum achievable efficiency. He did short daily flat-out burns of well seasoned wood, and added a second heat exchanger to extract heat from the flue gas. He had some heat storage to maintain house temperature between fires. It burned very clean - virtually no creosote or visible smoke. In the pursuit of efficiency, he kept his water jacket way too cool and the boiler eventually rusted out.

    When it died. he built a gasifier out of stainless steel. His wood consumption dropped by 40%.
  10. flyingcow

    flyingcow Minister of Fire

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    Downeast welcome. The gasser's are not complicated. I drive truck. It's easy. To burn with a gasser

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  11. flyingcow

    flyingcow Minister of Fire

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    Oh yeah, I like your red tractor, but I'll raise you a blue one.

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  12. Downeast Farmer

    Downeast Farmer New Member

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    Yes, Flyingcow, blue's nice, too, as are green, orange and gray, all for being so simple, and all of which I've used one time or another. One of my sons did the signature and as he does most of the tractor work I'm grateful for it.

    So, you're not worried about maintaining that Tarm, I take it.
  13. hobbyheater

    hobbyheater Minister of Fire

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    http://lamppakuuma.com/ This furnace has been getting good reviews on Hearth.
  14. hobbyheater

    hobbyheater Minister of Fire

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    IMGP3318.JPG

    What has given the Jetstream its longevity is the fact that it is easy to repair. It is a very simple boiler; one aquastat to control the blower and circulator.

    IMGP3332.JPG

    Refractory repair in progress.

    IMGP3334.JPG

    The refractory repair completed. The refractory nozzle below the air injection pipe is easy to make and can be installed in 15 mins. through the clean-out door at the back. IMGP3338.JPG

    The heat exchanger being moved back into position.
    You have mentioned the name Garn. The Garn boiler is worth consideration. It has a simple system of fire brick in the fire box. The refractory nozzle is simple in construction and looks easy to replace and the company still stocks parts for the boilers that are thirty years old. The boiler comes with ample storage and again is simplistic in design.
    I have never done the math but if you were to add 2000 gallons to some of the other boilers, there would likely not be much difference in price.
  15. 91LMS

    91LMS Member

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    dont want to derail thread but i will put in a vote for a good ole red. she's either on the hay rake or the blower!

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  16. kopeck

    kopeck Minister of Fire

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    There's a lot of variables in wood use. Is it seasoned properly, what kind of wood is it?

    I started using my boiler sometime in mid November and I'm around 2 cords in, maybe a bit shy of that.

    I'm burning a bunch of red maple and poplar, not exactly BTU rich but it's what I have. I figure I'll get through the main heating season on about 4 cord, if I had better wood probably that number would be closer to 3.

    My parent have a house about the same size as mine and a ThermoPride wood furnace and they usually go through about 6 cord. A bit of apples and oranges but that might give you an idea of usage.

    K
  17. kopeck

    kopeck Minister of Fire

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    When's the last it snowed up there? We were suppose to get 3-6" today last night but they swung and missed big time. Other then the snow after Christmas we haven't had anything to speak of down here. I hoping February picks up...

    K
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  18. augercreek

    augercreek Member

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    We are going on our third winter with a Garn 1500 and love it.Most days we fire it just once a day(three loadings)about a wheel barrow of wood.Days like today-20* with wind we will use two loads this evening.Each time you start a burn you must start a fire as there are no coals to restart. It is fired different than a OWB.We heat a 2400sf house,1000sf shop,300sf green house,and domestic water.We burn from September to the end of May.The first year I estimated we used 6 cord less wood than the OWB we had before.Most of our wood is Aspen Black Ash,Alder bushes and what ever else gets in the way of the chain saw.Wood burning is such a variable due to outside temps and type of wood you have.If you have wood like ours you'll twice as much as if you had Oak,volume wise.One thing I would do different would be to get a 2000 Garn as it has more water.If you operate it like the manual says I think it will last a very long time.A friend of mine has had one since 96 and has only changed out the fire bricks once and some of the gaskets and the anode rods.You have your water tested once a year and you're good to go.It is truly smokeless and never any creosote.
    Your brother in Christ Jerry
  19. flyingcow

    flyingcow Minister of Fire

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    No problems. Scrub the tubes when needed. Right now about every 10 to 14 days. In the summer once every month or so. Depends on how dry and how much wood you burn.
  20. flyingcow

    flyingcow Minister of Fire

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    Sundas morning we got 6 to 8 inches. Today it was too cold to snow. I delivered into Portland this am. They were supposed to get 4 to 8 but never saw a flake.
  21. kopeck

    kopeck Minister of Fire

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    NOAA's snow depth map has most of the county between 8-12", which surprised me I thought you folks had more then that on the ground?

    I rolled out of bed thinking I was going to have to shovel this morning. Like you said, not even a flake on the ground. We did get some flurries later on this morning but it's not even a coating.

    K
  22. 91LMS

    91LMS Member

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    got a buddy doing some tower work in portage this week, wasnt a sled or trailer in dean's parking lot.... sad for the economy this late in the season already.
    Taylor Sutherland likes this.
  23. kopeck

    kopeck Minister of Fire

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    Yikes. I stopped in at Norther Outdoors yesterday and they only had 2 or 3 trailers there. They do have some snow though and I saw a fair amount of trailers heading south on 201. The county really counts on that revenue, this is their tourist season.

    K
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  24. 91LMS

    91LMS Member

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    its been quite a while since they had a good year. i remember plenty of seasons we had snow enough to do over 3k w/o trying. they had snow but open water, now its pretty frozen but snow settled a lot. plenty of snow to ride but wondering if folks have backyarditis??? no snow in the backyard so they dont bother to do their winter vacations?
  25. jebatty

    jebatty Minister of Fire

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    So far the only practical way I have found to do this is based on a key assumption: wood moisture content (MC). Plus stack temperature needs to be known and the wood has to be weighed. And if the efficiency of one boiler is to be measured against another, then they both have to be heating the same space under substantially identical conditions.

    For efficiency of one boiler, my Tarm, I have calculated efficiency in terms of btu's to storage as compared to btu's in weighed wood burned, and also efficiency in terms of btuH heat loss as compared to btu's in weighed wood burns. For the first, I have measured efficiency of about 82-84%, and for the second about 88%. My assumptions are that MC = 20% and my measured stack temperature is assumed a constant 400F (although it varies over a burn, from a high of about 450F and then all the way down to fire out and boiler shutdown). Based on this, wood has 6050 btu/lb.

    So, if I burn 100 lbs of wood, my boiler input btu's are 605,000. At 83% efficiency in converting these btu's to stored btu's in my 1000 gal storage tank, the tank temperature would have to rise by about 60F. Since my boiler is in my shop, boiler skin heat and flue to the ceiling, as well as heat loss from plumbing, is also heating the shop. This extra heat increases my measured overall efficiency to about 88% by way of shop heat loss. At this time I cannot account precisely for the remaining 12% of efficiency loss, although I have some ideas.

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