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not your grandpa's garn

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by TCaldwell, Jan 15, 2012.

  1. TCaldwell

    TCaldwell Minister of Fire

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    Here are some pics of my modified garn, o2 controlled. I abandoned the combustion air inlet, fabricated primary and secondary inlets that terminate in the same locations in the firebox. On the other end they are ducted to 4 inch primary and secondary air dampers with belimo modulating actuators. to start from the beginning, the o2 sensor relays feedback to the fluegas analyser converting a signal input to the cybocon ce model free adaptive controller, that calculates and sends a output signal to the belimo actuators/dampers that creates new input for the o2 sensor to transmit. this happens once per second. The desired result is to maintain a setpoint of 7%o2 residual in the fluestream. This is basically how most all o2 controlled boilers operate, just not done with a garn before. It took alot of trial and error, and hundreds of burning hours programming the controller to get robust predictable results. I ran out of picture space, but will post graphs of o2 trending of a stock burn and a o2 controlled burn. I have other mods as well, a tank mix loop that homoginizes the water temp as long as the inducer is on piped with a dirtcal. The garn supply water temp is mixed with a modulating 3 way valve behind the boiler that is next to the flatplate hx in the garn barn that i built this spring by myself.

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  2. Gasifier

    Gasifier Minister of Fire

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    Wow TC. Nice work man. Thanks for sharing. That sounds like you did a lot of work to it. What made you do the modifications to the Garn? Looks like from the number of responses you have so far that everyone was watching the Giants spank the Packers! :ahhh:
  3. heaterman

    heaterman Minister of Fire

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    I've been waiting to see this. Looks like waaaaay too much fun to me. I wish I lived closer to you so I could play with it too.

    Any idea what numbers you're generating for Efficiency and CO?
  4. deerhntr

    deerhntr Member

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    Tom,

    How are things going? Looks good from here.

    Very impressive! Of course I have a couple of questions. Why did you decide to bypass the stock primary combustion inlet?
    Was it not able to provide sufficent fine control to maintain the 7% o2 setpoint, or was it to provide more o2 during the peak of the burn cycle?
    From your pic, the mod for the air inlet is obviously at the door, are you then using the stock inlet as your secondary inlet?

    From your plots, it appears as if you have very good control to the set point.
    What is the theory behind your mod? Is is that by maintaing a constant o2 %, that will maximize the burn and heat transfer during the complete burn cycle? Also that is very interesting how the o2 get starved at the peak of the burn cycle when you burn without control.

    Just a couple more questions. Could you post your pics, larger?
    They come up as thumbnails when selected, and my tired old eyes can't really enjoy the great work you have done. And, is that "heaterman's" garn blanket you have your beast wrapped in?

    By the way, your garn barn looks nice! How much time do you spend in that rocking chair!
  5. Sawyer

    Sawyer Minister of Fire

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    Very nice job Tom, wish I were able to see this in person. I look forward to your graphs. How does the increased O2 effect the flue temperature at peak burn?

    I use Firefox for a browser. I can zoom in on your photos which helps; at 150% level the image is still quite clear.

    If this system lets you use the rocker I need to change my system also!
  6. DaBackBurner

    DaBackBurner Member

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    DANG! Now I have combustion efficiency envy! GREAT work! Looking forward to see the numbers as well.
  7. thecontrolguy

    thecontrolguy Member

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    Hey TC! Nice work. Not meaning to be greedy, or anything, but when you set up that graph you promised, could you (please) put the control output (or damper position) on the graph also? I am interested in how the control programming handles startup, transients such as opening the feed door, and what you do as the O2 sensor degrades or otherwise gets fouled by soot. Is there a software loop for default open-loop control if the sensor is pooped? Cheers and congrats.

    Edit: Also, could you indicate what sensor you are using and if it is preheated?
  8. deerhntr

    deerhntr Member

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  9. TCaldwell

    TCaldwell Minister of Fire

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    Sorry for the quick explanations last night, limited time. The garn is first wrapped with 3 inches unfaced fiberglass, used self sticking insulation pins/washers, then 3 inches of closed cell spray foam except for the front and flue area, then a 4 inch layer of metal bldg insulation that has a tough gym-guard scrim covering. The combination seems to work well with no measurable heat radiation. The front of the garn has a 4 inch layer of roxul with duct metal covering. The back of the garn around the flue has a roxul surround covered with sheet metal. I also installed a tank mix loop, installing 2 two inch nipples in tne top of the garn one on either side of the manway cover, the intake is in rear and pulls low from the bottom of the tank and discharges that about 12 inches below water level in the front at a rate of 25gpm only while the inducer is powered. Usally if the front temp gage [old style] reads 180 , five minutes after a start of burn it will drop to 160, keeping the tank temp homoginized as it is being recharged. In the mix loop before the circ I have installed a calefi dirtcal, that is also why i pull the water from the bottom of the tank to pull in any localized debris. The primary and secondary air ducting, of wich due to limited number of pics in the post is the same as the primary shown but in the top of the firebox, same as stock spots. I used a 4 inch round oval aluminized exhaust pipe so I could perforate the air collar without going waterside. the stock combustion air inlet was plated shut thus making the air collar ineffective. I kept stock inducer and still maintain approx 300cfm at ambient air temp. The exhaust tubing came from spin tech automotive. This way i was able to use the nice garn door, but fabricated a more positive latch. Yes the intake mods allow independant control of the primary and secondary air. In principle with a batch burn there is no combustion control, however martin has done a great job of balancing the air and combustor design to be able to accomodate a very clean burn with no moving parts. this comes with it's own burning charachterics as shown with the graph, under aired in the beginning and overaired for the latter part and still maintain one of the cleanest burns available. This curve is dictated by a very fast hot burn, martin's intent. My thought was more to control the combustion to a stiometeric value for wood [7%] throughout the burn, and still maintain a relatively high output. In theory i am retarding the burn at first, relaxing in the middle and forcing at the end by using the stock inducer and not a variable speed setup. The fire starts hot with all primary air, gasification within 3 minutes [1200deg secondary burn temps] then reduces primary and modulates secondary to maintain setpoint, at the end with a o2 level higher than setpoint it closes secondary and all primary burning the coals. This process typically does not go beyond 1800deg in the secondary burn chamber, usally between 1400-1700 for most of the burn, with one turbulator in the last pass flue temps 260-310, the burn seems to last slightly longer also. This flue temp is read from a type k in the first section of class A after the garn. I have a testo portable fluegas analyser that I will measure other fluegas compounds in the next few days and post results. Just a side note, the red line in the o2 controlled graph is damper output with the percentages of the secondary damper represented on the right side of the graph. the secondary damper is closed at beginning and end of burn, the primary damper operates in oposition to the secondary. This shows a high output of 65%, thus the secondary damper is open 65% and the primary is closed 65%, the highs and lows to control vary also on wood species and mc. As complicated as this seems , in the world of combustion control this is a relatively simplistic approach, the froling for example is much more sophisticated and refined, but does not have a 400k btu output. The barn 16x24 took me about 3 months of weekends, with the infloor tubing, Oh I installed a combustion air intake fan with damper in the room that is controlled by the inducer circut.
  10. heaterman

    heaterman Minister of Fire

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    It will be interesting to see how the numbers compare with the test results I have from Garn on a model 2000. The efficiency number they got in the actual dilution tunnel test are at the point that you couldn't go much further without condensing and emissions are very very low. If I can find them I'll post them up here on this thread.
  11. TCaldwell

    TCaldwell Minister of Fire

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    Control guy, the o2 sensor is a bosch lsm11 4 wire wideband industrial sensor, 30watt heater and a 0-1v control signal. The sensor threads into the probe that has particulate screens inside, however before every burn it takes less than a minute to clean it all with compressed air., this makes life predictable for the cybocon ce controller. Russ, thanks for the link. keep the questions coming, as it is too cold to be outside today. the controller has a process value alarm that initiates control at a preset pv
  12. TCaldwell

    TCaldwell Minister of Fire

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    steve, let me know the wood weight and approx makeup so as to keep test simular as possible
  13. skfire

    skfire Feeling the Heat

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    WOW,
    A true MEGARNTRON....or GARNOLING hybrid beast with Intelligence and Brawn.

    My HUMBLE Congrats and sincere admiration!!!!

    Scott
  14. bioman

    bioman Burning Hunk

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    Why didn't garn think of that ? you pay big money for a boiler and you'd think it would run properly.
  15. Como

    Como Minister of Fire

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    I think it is going to take me several hours to work through this.

    Just a quick question, why did you use Roxul only on the front? I would have thought it would be ideal all the way around.
  16. TCaldwell

    TCaldwell Minister of Fire

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    David, with all the bungs, cleanout ports, air collar and loading door, it didnt leave much room left, not as effective but more convenient.
  17. DaBackBurner

    DaBackBurner Member

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    I wasn't going to comment I was just going to let it go, but for me some reason I can't...You pay alot of money for alot of things, and thankfully we have people that think they can improve things, so they give 'er a go. I applaud those people, their inquiring minds and am thankful for them. Without them we might as well put on a smock, grab a rock and try and kill that saber-tooth tiger. I for one am glad for the guy who invented the spear. Sorry, I didn't mean to muddle this thread up, maybe I should just go split some wood..with a hammer.
  18. Como

    Como Minister of Fire

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    Did you use the Roxul you can get from Lowes or the specialty product for Boilers?
  19. heaterman

    heaterman Minister of Fire

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    In a money is no object world, Garn would be more than happy to sell you a factory made boiler like that. Unfortunately, they have to work on this planet and within the boundaries prescribed by the people that buy them so peak technology is traded for a substantial reduction in cost. ;)
  20. Como

    Como Minister of Fire

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    One of the reasons I went with Garn is that it is simple by design.

    I admire people who want to do this to eek out a few percentage points of extra efficiency, but from my perspective I have lots of things that can and do go wrong as it is, I would rather burn a bit more wood.
  21. TCaldwell

    TCaldwell Minister of Fire

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    David, the big box roxul is fine.
    Da Back, You could consider me a anomalie about this stuff, it all started because i got tierd of hearing the oil boiler, and my wife and family are understanding. They all began to refer to the project as the other woman. Not suprisingly most vendors thought the project was admirable, and interesting but most unwilling to really help because of being a homeowner not with a engineering background and also not proctor&gamble;. The real truth in proving came with actually trying and watching results. Otherwise i never would have been exposed to isolation transformers, ground loops, control signals, o2, pid and on. After all this I would like to think my modifications are improvements, but in reality the gains are small with respect to money and time invested, and alot of extra liability for commercial viability as heaterman stated. With that said thankyou all for the compliments and ongoing support.
  22. ewdudley

    ewdudley Minister of Fire

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    Small indeed, not counting Hack Value!

    [From wikipedia:]

    Hack value

    Hack value is the notion used by hackers to express that something is worth doing or is interesting. This is something that hackers often feel intuitively about a problem or solution; the feeling approaches the mystical for some.

    An aspect of hack value is performing feats for the sake of showing that they can be done, even if others think it is difficult. Using things in a unique way outside their intended purpose is often perceived as having hack value. Examples are using a dot matrix impact printer to produce musical notes, using a flatbed scanner to take ultra-high-resolution photographs or using an optical mouse as barcode reader.

    A solution or feat has hack value if it is done in a way that has finesse, cleverness or brilliance. So creativity is an important part of the meaning.
  23. heaterman

    heaterman Minister of Fire

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    Anomaly......I like that. Funny thing is probably 90% of the people in the US figure that any person who cuts and burns wood to heat their home is an anomaly. We be an anomalous bunch for sure.

    I for one get quite a kick out of your project Tom. More power to ya is all I can say. What model pump did you wind up going with for the "blender".
  24. heaterman

    heaterman Minister of Fire

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    Yep! That's Tom. An anomalous hacker. :)

    That project has hack value that is off the charts.

    And I mean that in a most complimentary way.
  25. TCaldwell

    TCaldwell Minister of Fire

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    Well, i see i am not alone

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