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Wood Gun vs Econburn

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by heat4steve, Aug 13, 2009.

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  1. PatrickAHS

    PatrickAHS New Member

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    I couldn't agree more. I have to say I have never worked for a company that stands behind its product like AHS does. I personally have been on 25 hour roadtrips to take care of customers who had issues that absolutely had nothing to do with any fault of AHS. Warranty is no good if you won't stand behind it.

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  2. Gooserider

    Gooserider Mod Emeritus

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    Glad to hear that WG stands behind their products Patrick, but I still find some of the website a bit hokey... WG is not alone in this, but I really would like to see WG and the other boiler makers put their manuals online as PDF's so that one can get the "official" answers as to just what the product will need to be installed and keep the code guys happy... (the stove makers do this, why can't the boiler people?) For instance, I know that our local guys tend to follow standard codes, UNLESS the manufacturer says something different in the install manual - thus he would probably prohibit a side vent install unless there were specific directions on it in the manual, in which case it might very well be OK if done to those specs...

    Another item I haven't seen much on, which would need to be in the manual is what the detailed service and cleaning requirements would be, including what sort of space around the unit is required. I know the units have that little ash cyclone thing on the side, but I didn't find any details about where that needs to be placed, and how much room it takes...

    Gooserider
  3. PatrickAHS

    PatrickAHS New Member

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    This will all be fixed soon.
  4. rsettgas

    rsettgas New Member

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    I'm new as a poster here. Looks like a very active forum - congrats. I do occasional wood boiler installs along with my main focus of solar thermal systems and various "conventional" radiant & boiler work.

    I installed a stainless WG for a client a couple years ago, tied into an existing LP boiler system. Don't have much to compare it to, but as others noted, seemed to be pretty well built. WG convinced my client that storage was not needed - I was skeptical. The one lesson learned was that the concept of no-storage does not work for everyone. My client had a well insulated house that even in a 9000+ DD climate did not require heat often enough from the WG to enable the fire to restart as the WG folks had told him it would. Result was that very often, including middle of night (of course), the WG would try to relight, fail, and the forced draft would be blowing cold air through the firebox over a dead fire. As you can imagine, sometimes it took my client a while to realize this was going on - and all the while the WoodGun was cooling itself off. Not a good scene and I'm sure you could rig some sort of override to cut out the forced draft after a certain period with no ignition, but in my mind, you shouldn't have to deal with that.

    This system was in for just the last half of the first heating season, then the owner moved out of town and, sadly, the WG sits drained & unused as the current renter did not want to deal with the potential hassles around repeated fire (re)lighting. Can't say I'd be wild about it either.

    I didn't hear WG's pitch for no-storage first hand, but this experience has added to my skepticism about the concept. I haven't searched this site for previous discussions of no-storage gasification installs, but I'd have to think there have been a few. At this point I'd be clearly on the pro-storage side of the fence.
  5. Piker

    Piker Minister of Fire

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    I cannot speak to every brand in the field, but I can tell you for certain that a downdraft gasser can be run without storage. Do I recommend it? Sure, in most cases it's acceptable... I have yet to have a customer install thermal storage in this neck of the woods... it's something that everyone seems to think is a great idea, but when it comes down to it, they just aren't willing to invest the extra capital to set it up... at least not right away. Is it better to run with storage than without? Absolutly... without a doubt.

    For customers who are running without storage, I always give explicit instructions about how and when to refuel the boiler. It boils down to small hot fires in the upper chamber, and minimizing the length of the burn times when possible to increase efficiency. The idea of being able to shut combustion air off completely has it's merits, but it seems evident that relighting after a long period of time could be an issue, especially if the wood load has been made excessively large in comparison to the heat load in an attempt to achieve long burn times, causing the off cycles to be very long. To me, this sounds like a simple fix... and it goes back to reducing the quantity of wood in the firebox, thus reducing the output of the boiler and forcing us back into that small hot burn again... creating a situation where on/off cycling becomes more frequent and the risk of the fire going completely out becomes less... though with shorter overall burn times.

    Bottom line? Burn times and efficiency are inversely proportional to each other... you just can't have both, at least not on any of the current wood boilers that I have seen. With a standard downdraft, efficiency falls off as you oversize the firebox and increase burn times, though keeping the boiler lit for extended periods of time is not an issue... with a boiler that has the ability to shut combustion air off completely... efficiency is less of an issue but keeping the thing lit becomes the trick.

    Small hot fires are the key to solving most of the issues people have with wood boilers without thermal storage. That and dry wood. If we could all just move away from the "I want 12 hour burn times and I want to do it with green wood" ideas that have been ingrained into our psyche over the past 20 years by slick wood equipment dealers preying on folks' propensity to procrastinate, the world would be a better place. Even if the boilers I sell were good at burning green wood, I would never use that as a selling point... it's counter-productive in the long run, and ultimately costs the customer more time and money.

    One final thought. There are a lot of different wood burning products on the market these days, some good, some not so good... but they ALL have at least three things in common... and that's the inconsistency of the fuel, the inconsistency of the human beings using them, and the need to discover each model's little idiosyncrasies. Burning wood is part science, part artform, and requires some finesse to do properly. I suppose that even the guy burning tires and dead cattle in an outdoor boiler that's almost as big as the house he lives in could be considered art... abstract though it may be. Each product or system out there will operate under a different set of parameters, and each will require a time of "figuring out" and "getting used to."

    cheers
  6. rsettgas

    rsettgas New Member

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    fair enough. working in the solar field I can appreciate the challenge to investing money now in order to "do it right" and save in the long haul.

    and I agree that completely burning small fires is probably the best way to match up with small heating loads if you have no storage. just leads to a bunch of labor that, were it me, I'd probably do everything I could to figure out how to afford some storage so I didn't have to babysit the boiler.
  7. muncybob

    muncybob Minister of Fire

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    Great discussion and interesting reading. It would seem that there is a solution to most problematic matters if the user is willing to make "adjustments" to the user had conceived as the "norm"(smaller more frequent fires, cost of storage, etc.)... I too am skeptical on the idea of no storage but I will be testing this use of the WG this heating season w/o storage due to lack of funds to install a tank. I will be of the mind that storage will still be installed in the near future until proven otherwise...I will post my thoughts on this over the winter.
    Regarding the WG not relighting a fire during low demand times...I'm hoping the adjustable cycle timer on my unit solves that problem. I plan to use the timer only when I have larger loads in the WG due to extended periods of time we may not be at home, but for the most part we plan to burn smaller fires and just make more trips to the basement. Not a big deal for us since my wife works 3rd shift so there is usually somebody home and from what I've read of wood burning newbies (like we will be) there will be a lot of curiosity trips to the boiler anyways!
  8. dogwood

    dogwood Minister of Fire

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    Gooserider, I think Bioheat will email at least their Solo Innova and Froeling manuals if you ask. They did this for me on request. Maybe this site could start a library. It would be better as you suggested if all the companies kept them online. I think I did come across the EKO manual someplace online.

    Mike
  9. Gooserider

    Gooserider Mod Emeritus

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    I know they will, as I have been told as much by them... However that doesn't do much for the next person that comes along, other than having them go through the expense and hassle of mailing manuals to everyone that asks, as opposed to putting them online ONCE per revision as a downloadable file... Back in the bad days of expensive storage, and manual typesetting, this would be a problem, but these days I would be surprised to see anybody producing manuals and other large documents without using electronic tools, and the storage and bandwidth for electronic distribution is approaching free... I know of one ISP that will give you an account with all the tools you need to do a website, unlimited storage, unlimited data transfer, and a bunch of other stuff for $6.95 / month - which is probably on the order of what it would cost BioHeat to mail out ONE set of printed manuals.

    I have found the manuals for both the EKO and PAXO boilers on line at different sites, as well as some of the other boilers - in some cases they are translations of less than stellar quality, but at least there is something on line.

    OTOH, if Hearth.com was to try and create a library, we would have to scan things in from paper, which always gives some quality problems, and is a bit of a headache, plus we would have to deal with the whole issue of copyrights and permissions, etc... I know that Craig has some material posted in the Wiki, but I beleive most of it is for stuff where the company that made it is no longer in business, or is no longer supporting the product and has given permission to post the stuff - though I don't know the details, it's his job not mine...

    My main issue though is that I would like to see all the boiler companies / importers put their manuals online, I think it is an important tool for the consumer, and it is IMHO a useful thing for the companies as well. As a comparison, I have not found ONE currently produced stove that didn't have an online manual available, but currently of the brands I've checked (essentially gasses officially sold in the US) only about half the boiler companies do...

    I know that these days, there are very few major purchases I make where I DON'T look for and download the product manual for the candidates on the "short list" before making a purchase decision - and lack of manuals can often bump a product or vendor off the list...

    Gooserider
  10. Singed Eyebrows

    Singed Eyebrows New Member

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    www.kotly.com has the Atmos manuals online as well as a few others. I'm glad Patrick was able to clear up some of the outstanding Wood Gun issues. Some members are still hesitant to believe a WG can be run without storage not to also mention the no chimney issue. When you understand the WG takes in it's air through a piece of pipe & a motorized flap that has a silicone rubber gasket has the ability to seal the end of the pipe airtite then you also can see that upon sealing the fire dies fast & you don't have the combustion products to deal with that every other boiler & furnace has. I looked at a WG that had the cycle timer & this solved the only other issue WG had & that was relighting. It will be interesting to hear again from MuncieBob as to his results, Randy
  11. Piker

    Piker Minister of Fire

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    I think that is slightly innacurate. While it sounds reasonable that shutting the air off immediately after a burn will prevent combustion products from entering the thie chimney, any time any gasser comes out of an idle state, be it a completely oxygen starved idle state or just an extremely low oxygen idle state, there will be a few moments required to bring the refractories back up to temperature before combustion reaches a high level of efficiency. Without thermal storage, there WILL BE particulates that stick in the stack. Actually, even with thermal storage there will be SOME, though in greatly reduced quantity.

    cheers
  12. Singed Eyebrows

    Singed Eyebrows New Member

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    Hi Piker; I think we are on the same page, though the WG does not shut off air after a burn as you stated, it shuts off during the burn with maybe 3/4 load of wood in it. I should have clarified that the WG does not have the combustion products to deal with in the shut down mode that others do. Upon startup the WG(no storage) may even have more particulates than others. I did not address emissions issues or chimney coating & I would expect that a WG run without storage wouldn't be near as clean as a gasser run flat out into storage as you have stated, Randy
  13. Piker

    Piker Minister of Fire

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    What I meant to say was "shutting the air off immedialty after the high limit on the water jacket has been met." But overall, I would say that we are in agreement.

    cheers
  14. RogerABE

    RogerABE New Member

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    I am happy to have found this conversation thread/topic. I hope the following information is of interest to this group and that it may lead to additional information that can help me.

    Context: I am an engineer in the biomass combustion industry. I am currently working on a feasibility study for installation of a cord wood boiler system into a small, on farm food processing facility. The study is being funded by an agricultural organization and will be published upon completion. AHS Wood Guns and Econoburns, along with other boilers, will be mentioned in the report.

    As many here already know- efficiency numbers are meaningless without a context. Even with a context, efficiency numbers may be misleading if the context does not match real world combustion conditions.

    Econoburns have been tested under the EPA’s voluntary testing program and I have a copy of the publicly available parts of the test results. I do not have test results on the Wood Gun product line (AHS has declined to share them despite repeated requests over a long time frame). I am hoping someone in this group might have more Wood Gun background information they can share as I am trying very hard to impartially evaluate efficiency claims made by each boiler manufacturer.

    Without the data needed to evaluate the Wood Gun’s efficiency claim, the primary recourse left is to attempt to evaluate the context in which that data was initially developed and related outcomes. Here are the details (beyond AHS’s claims) that I have found-
    - Wood Gun was tested by the Arnold Greene Testing Laboratories (AGTL) a long time ago (specific test date not disclosed).
    - Standardized wood boiler testing requirements did not exist in the US at the time of testing. The testing laboratory and manufacturer appear to have been free to select-structure their own efficiency test methods.
    - AGTL’s testing and approval of wood boilers and furnaces included products like the Stelrad wood/coal boiler and the Bryan Outdoor Furnace. I suspect neither of these two products would pass current efficiency standards even if those standards were modified to accommodate them.
    - AGTL’s boiler & solid fuel heating system testing division no longer exists.
    - AGTL specialized in non-destructive testing and that business sector was acquired by another company.
    - AGTL no longer exists.
    - AHS has stated (personal communication) that the company does not plan to have the Wood Gun tested under current EPA standards/methods.

    Econoburn’s Method 28 for OWHH test data shows
    - The boilers were recently tested to the current standardized protocol.
    - Thermal Efficiency at max capacity (162,164 BTU/hr for model 150) is estimated to be 82.1% on a LHV basis. (some calculations based on standard assumptions required)
    - Specific seasonal thermal efficiencies are lower than the efficiency at max capacity- as would be expected for any boiler.

    In short- it is possible to confirm and compare Econoburn’s efficiency claims. Efficiency claims for the Wood Gun can not be currently confirmed or compared and are only provided in sales literature without context. As a result, I agree with Gooserider’s 14aug09 post that stated, “Some of the stuff on the Wood Gun website … strikes me as a bit “snake-oil” flavored.” AHS’s currently stated efficiency number meets this characterization.

    I would appreciate receiving details on AHS’s test results and methodology if anyone happens to have them on file. If nothing else, I hope this message will put some public pressure on AHS to provide the information to properly qualify their efficiency claims and provide the transparency that is in the best interest of potential end users.

    Thanks,

    Roger
  15. Singed Eyebrows

    Singed Eyebrows New Member

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    Hi Roger; Wouldn't the overall efficiency of any gasser simply be flue gas temperature? This is assuming the boilers radiant losses are not wasted heat & are used as in a basement etc. If this is the case someone could measure a WG gas exit temps. I don't believe that all the efficiency ratings(of the various boilers) are of the percentage of available heat that is put into the water. If I can be of any help with my Atmos (when it's installed) please let me know, Randy PS One of the WG's I saw operating had very high flue gas temps, this was possibly due to burning wet wood as I read somewhere that steam can drive heat out of a wood burner.
  16. Fred61

    Fred61 Minister of Fire

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    The WG has extremely high air flow which IMO would reduce the stack temp and give you a false reading on efficiency. I know because the one I had would actually send still ignited particles out the top of a 15 foot chimney. I suppose it needs that flow because it doesn't have any provision for secondary air injection.
  17. RogerABE

    RogerABE New Member

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    Hi Randy (Singed Eyebrows)-

    In answer to your question "Wouldn’t the overall efficiency of any gasser simply be flue gas temperature?"

    No, flue gas temperature is not a measure of overall efficiency, there are many other variables that need to be known. It is possible to use flue gas temperature as an indicator of a relative change in thermal efficiency (assuming all other variables are constant). Here is one example. Many older wood chip boilers do not have soot blowers. We tell system operators of those systems to watch for their stack temperatures to start climbing as an indication that fly ash has accumulated in the fire tubes and is reducing heat transfer and efficiency. That increase in in temperature is their signal to brush out the fire tubes. Again, that is only a relative change in efficiency- not an absolute measure of efficiency.

    On a more technical note, stack temperature alone doesn't tell us the amount of heat being lost up the flue because it doesn't tell us how much heat is present. We would minimally need to also know the mass of gas going up the flue to determine the # of BTU's going up the stack. An exact measurement would require knowing the composition of the flue gases. As one example, flue gas containing a lot of water vapor may be at the same temperature as another flue gas that does not, but the one containing the water vapor could be taking a lot more energy up the stack.

    At the risk of really complicating things- let's take another tangent to a system that has too little combustion air (sub stoichiometric). If the wood in the firebox is at a temperature that the wood is being volatized into a combustible gas, then stack temperature alone won't tell us that the gas we could be burning is being lost up the stack due to a lack of oxygen to convert that gas to available heat.

    Bottom line- stack temperature MAY (under certain conditions) indicate a relative change in efficiency, but it doesn't tell us absolute efficiency. The best way to determine efficiency is to look at available energy into the system vs energy captured to the heat load. Even then, manufacturers can play games with the specifications (i.e. LHV vs HHV efficiency numbers) to mask what will happen in a real world application. Hope that helps Randy.

    Roger
  18. Singed Eyebrows

    Singed Eyebrows New Member

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    Hi Roger; I can understand some of what you said. If you know the amount of btu's available in the wood you load into the furnace & this can be figured reasonaby close & you know the btu's that are going up the chimney doesn't this give you overall efficiency? The btu's going into the chimney is not only temp as I mentioned it is also cfm as Fred pointed out. I read in a number of previous posts people saying that if only we had an engineer on this forum, well now we have one, it's good to have you here, Randy
  19. RogerABE

    RogerABE New Member

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    Randy- If, and that's a big IF, we know flue gas temperature, the mass flow rate of the flue gases, and the gas composition of the flue gas, then yes, efficiency (ignoring jacket losses) can be determined if you know the input conditions too. However, (you knew that word was coming, didn't you) a single measurement or set of measurements during a short portion of the burn cycle isn't sufficient.

    It is much easier to measure heat flow in the hydronic loop than to measure the heat flow in the flue because there are fewer variables and the variables are easier to characterize. Measuring heat extraction in the hydronic loop requires 3 sensors (supply temp, return temp and flow rate). Many more sensors are required for the stack. Gas flow profiles in the stack may not be well defined, so multiple temperature sensors are required (cross sectional area or chord sampling). The flue gas sampling protocols and instrumentation are more complex and much more expensive.

    Mass fuel flow into a batch fired boiler doesn't happen, so current test lab procedures measure mass loss instead by placing the boiler on a scale and watch the weight decrease as fuel is burned.

    Think of it as a three variable system- if we know (measure) two, we can calculate the third. Flue gas is the hardest to measure accurately, so I'd rather calculate it if given the option. Roger
  20. Singed Eyebrows

    Singed Eyebrows New Member

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    Hi Roger; After I posted I realized it's more complicated than I first thought. I thought about putting the boiler on a scale & even then seems to be a can of worms. I don't envy you on this one, Randy
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