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Thinking of selling my Eko for a garn

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Kemer, Feb 24, 2010.

  1. WoodNotOil

    WoodNotOil Minister of Fire

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    From what I have seen most of the gasification boilers use ceramic to take the brunt of the gasser flame (sometimes refered to as "ceramic refractory"). As JimK stated, the Garn gets its high efficiency due to the exceptionally long path the exhaust takes through the high volume of water in the tank. The secondary compustion is not directly in contact with a surface the way most downdraft gassers are. There was a thread on the WoodGun needing refractory replacement more often than other gassers, so perhaps they don't use ceramic refractory?

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  2. jebatty

    jebatty Minister of Fire

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    I also would encourage you to re-think replacing your Eko for a Garn. Both are good boilers with +/- for each. In my opinion advantages to a gasification boiler, like the Eko, with reasonable storage, include:

    1) If you have a closed system, direct interface without a heat exchanger. This will give you about +10F hotter delivered water than the unpressurized Garn with a heat exchanger. An extra 10F in storage is a lot of BTU's: 83,850 if 1000 gallons of storage. Also, if you have baseboard with 180F requirement, the gasification boiler is designed for and excels at continuous high heat output. A Garn with a heat exchanger would have to operate at about 190F to give you 180F water, and that likely means continuous high burn on the Garn, which may not be very efficient.

    2) The Garn moves lots of air through the boiler, and I believe the blower is controlled by a timer. That's great on high burn, but as the wood load burns down, that air continues to carry lots of BTU's up the chimney, and unless you carefully time the burn, that air continues to move even after the Garn has burned nearly and then finally out. I suspect that this could result in loss of considerable BTU's from the Garn tank up the chimney, as the tank transfers heat back to the heat exchanger and out the chimney.

    I believe a gasification boiler, like the Eko, moves much less air in a controlled burn. While in theory the same kind of heat loss may result as the wood load burns down and out, at least in my Tarm, the draft fan automatically shuts down when the smoke box reaches about 210F. There is no ongoing loss of heat from the draft fan continuing to blow, and no loss from storage at all.

    3) Storage with a gasification boiler is flexible, meaning you can easily add as much as you want or need, and you can move the system if you need to because of its smaller and lighter bulk. The Garn is large and heavy, adding storage is not as simple, and moving the Garn could be really difficult.

    4) Upgrade of a gasification boiler is possible, although I doubt any of us want to think about that. But with new wood burning technology becoming available, as with the Frolig and similar, it's not out of the question. Replacing just the gasification boiler, and not the storage, would be quite easy. I certainly would not want to think about upgrading from a Garn due to the large investment, difficulty in moving it, and then investing in and adding storage to a new system.

    5) I think both the Garn and the Eko are about as easy to load, light and operate. Both require wood in the 20-30% M.C. range. The Eko may require smaller splits of shorter length than the Garn, and therefor may take a little more effort in filling the woodshed.

    6) It would be very interesting to obtain side by side comparison of a Garn with a gasification boiler to measure performance on weighed quantities of wood and under similar operating conditions.

    7) Most if not all gasification boilers have a BTU output rating, which may be optimistic and probably is under laboratory conditions. I have not seen a similar rating with a Garn, only a "burn rate." I have seen some percentage numbers provided by Garn on "energy stored," but I have not seen Garn actually put these numbers in black and white as BTU output, and I wonder why. I also suspect that the Garn numbers also may be optimistic and probably under laboratory conditions.

    8) I know little about ongoing maintenance with a Garn, other than I think Garn recommends checking water chemistry twice/year and draining, refilling and retreating the water, if I remember correctly, every 2 years. With my Tarm, after 3 heating seasons, maintenance has included: a) clean chimney once per year (for safety even though chimney is nearly clear); b) brush hx fire tubes 1-2 times per month depending on how much the boiler has been burning; c) remove ash occasionally; d) seal up the boiler from air and moisture during the non-burning summer period; e) one time analysis and water treatment. I have not had to replace/service any boiler parts over the first 3 years of operation.

    Hope this helps.
  3. Jim K in PA

    Jim K in PA Minister of Fire

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    Jim - with respect to item 7, I think terminology is where the confusion lies. The "burn rate" in a GARN is, in fact, the Btuh output rating. I have calculated the actual heat input to storage countless times, and have not only confirmed the 420k Btuh rating, but have regularly exceeded it. I have well exceeded 450k Btuh in my GARN. As with any solid fueled appliance, the input rating is not linear, whether it's a GARN, TARM, OWB, coal stove, or whatever. With the GARN you can look at your starting and ending temps in the tank, calculate the amount of Btus that went in, and then divide by the period of time that the rise took place to get your rating. Nothing hidden by GARN. Their ratings are conservative.

    As to maintenance, I have yet to clean the heat exchanger tubes (flue) in my GARN, but I suspect I will do so before the 2010/2011 heating season begins this fall. Water testing should be done on all systems, regardless of manufacturer. The 2-year water change recommendation is for particularly poor water sources. The GARN is a very low maintenance unit.

    With respect to the considerations for unpressurized storage, size, and portability, you are right on. However, my FP HX usually gets my approach temp down to 6-8 degrees, but 10 is a good conservative figure to use.
  4. loggie

    loggie New Member

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    I would guess the real world performance of these two units is going to be Quite different. while the eko may get sligtly more out of each piece of wood, the actual BTU output has to be much less than than a garn. While I'm sure these are both fine units The one best suited For a particular installation would depend on the amount of BTU's needed to be stored and the time the owner wants to spend recharging those BTUs.I personally own a 1250 switzer{like a garn only pressurized} and that was the big factor for me to be able to go from 100 deg to 220 with the heating load in the coldest part of the winter in 3 to 4 hours. I do this every day after work .I doubt a eko or tarm could heat that much water in that time .even a eko 80 is rated at 275K BTUs [Is that with kiln dryed 4x4s]what is the BTU output with adverage firewood. I would like to hear what the owners of these units with big storage have to say about recharging time.I think even if you made a constant 250k BTU it will still take 8 hours to bring 2000 gal up 100 deg with no heating load factored in. If it takes 8 hours to charge your storage daily but you do not have 8 hours of free time every day then it won't work well for you. In the end the cost of an 80 series boiler and 1500 or 2000 gal of external storage and the time and parts to put it all together will be close or more than the garn and it will take more of your time everyday doing the same job.That is what I looked at for my install. They are all nice units but some are better suited for some peaple than others.Just my two cents
  5. jebatty

    jebatty Minister of Fire

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    While I don't doubt your experience, I have seen a Garn WHS 3200 in operation, and I'm hopeful that I will have the opportunity to provide some actual information. Based on what I have seen, I am doubtful that the advertised "BTU burn rate" of 950,000 is the output that this unit actually is doing, but there isn't much more that I can say at this time. I also suspect that if the question was put to Garn itself, it would not claim that the actual BTU/H output is the same as the advertised "burn rate." If it was, I think Garn would say BTU/H output rather than burn rate. I haven't seen posts by Garn, and it would be helpful to all of us if Garn would offer more information.
  6. Como

    Como Minister of Fire

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    I have been following this for sometime.

    My impression is that the Garn figures are conservative. I have been corresponding with someone locally who has 2x WHS2000, and he is getting the rated output despite altitude and not having the best wood to burn.

    Cord wood produces its own variables.

    PS The output rating on a Garn is not directly related to burn rate as you are pulling from storage, not the firebox.
  7. jebatty

    jebatty Minister of Fire

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    I dreamed about this last night (my wife says I need to get a life!), thought about how my Tarm (140,000 BTU/H output rating) operates under varying conditions, and also remembered that I saw a Garn brochure that said 97% burn efficiency and 87% energy stored. That last statement might mean that a WHS 2000 rated at 425,000 BTU/H burn rate = 425,000 x 0.97 x 0.87 = 358,660 BTU/H output to storage. Or it might mean 425,000 burn rate x 0.87 = 370,000 BTU/H output to storage. A similar statement, maybe with different percentages, could be made about any wood boiler.

    I guess I'm looking for either real engineering science or at least pretty good user science to get some hard data and data for an apples/apples comparison with gasification boilers. I have been deceived by anecdotal observations with my Tarm, which is why some real measurements are important. I'm not an engineer, but I have done what I think is pretty good user science with my Tarm. As to the factors below, I have measured BTU/H output and in doing so have measured factors 1 - 7 and 10 or near equivalent.

    Several things jump out at me: 1) what species of wood is being burned, 2) what is the M.C. of that wood; 3) what was the weight of the wood in the test burn; 4) what is the split size/mixture in the burn; 5) is the burn a beginning to end (single load) or is it near continuous feeding to maintain highest burn conditions; 6) how many BTU's/lb for the wood at the specified M.C. and stack temperature; 7) what is the stack temperature; 8) with the Garn, what is the starting tank temperature, and is it uniform top to bottom (no stratification); 9) with the Garn, what is the ending tank temperature and is it uniform top to bottom (no stratification); 10) what is the flow rate through the tank during the test; 11) what is the ambient air temperature and R-rating for the Garn insulation; 12) what is the combustion air input temperature; 13) what is the air relative humidity; 14) how may CFM of combustion air from the draft blower.

    But in the final analysis, it seems to me that the most important factors for a specified BUT/H output rating are: A) what is the heating system return temperature to the boiler; B) what is the supply temperature needed to meet system demand; C) required GPM flow rate at boiler output rating then = supply temp - return temp x 500; D) and to get an accurate rating, since the Garn supplies directly from storage, it would seem that starting uniform, non-stratified tank temperature must equal the heating system return temperature.

    If a WHS 2000 (425,000 BTU/H burn rate) is to be accepted as the output rating, then if the heating system demand is 180F (like for baseboard) and return is 160F (typical standard), then GPM = 42.5. I use the 180F example because that is needed by many of the older heating systems with baseboard, so it meets the real world. The same GPM holds true with a radiant system with 120F supply and 100F return, but I think I can say with confidence that the lower the required supply temperature the easier it is to get a higher BTU/H rating due to increased efficiency in the boiler heat exchanger in transferring heat to the surrounding water, so a boiler at rating X for supply temperature of Y almost certainly has a lower rating if the required supply temperature with the same delta-T is higher than Y.

    Required supply pipe size for 42.5 GPM is 2", and at this flow rate assuming 10 feet of system pump head (which likely is low), a Grundfos 40-50 or larger circulator (or equivalent) is required to provide the flow in the middle of the pump curve.

    Here's where the rubber meet the road. Who has such a setup or equivalent, what is the continuous output performance of the Garn, and what data has been collected to determine the output performance?

    With my Tarm, I have on several occasions logged supply temp, return temp, gpm, and stack temp. I determine gpm by a flowmeter on my system. I find that I can meet or exceed the BTU/H output rating at lower return temperatures over a larger portion of the burn (high delta-T), but that at return temperatures of 160F and higher (lower delta-T), it becomes increasingly difficult to obtain the output rating and I have to maintain a high burn. Also, at lower return temperatures and stack temperature in the 450-470F range, I can obtain the rated output, but as return temperature goes up, I need to increase the burn rate, resulting in stack temperature in the 500-525F range, to meet the rated output. I have some ability to do this by frequent wood loading and also by increasing the draft fan CFM. I have a fixed output circulator, and it should be possible to increase output at higher return temperatures and delta-T less than 20F by moving more water, but I am unable to do that in my system.

    What do you think? Who has a system like that which I described? What data has been collected? Am I off-base?
  8. woodsmaster

    woodsmaster Minister of Fire

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    I'd just like to no if Kemer decided to keep or sell the EKO ?
  9. loggie

    loggie New Member

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    I think there are just too many variables with burning wood to slap a wonder formula on a boiler.while 950k BTUs may be on the high side,maybe not The bottom line is how long it takes to heat the water with a load of firewood.That is the real world output,If it takes 4 hours to bring 2000 gal of water up 100 degrees the boiler must be adverging something like 500k BTUs and may be making 750 at some point during the burn.Without driving yourself crazy or your wife, the bottom line is that a garn "like" boiler will still heat the water much faster than any 250k BTU rated boiler.
  10. Jim K in PA

    Jim K in PA Minister of Fire

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    Jim - It's not just my experience. Many posts by other GARN owners/operators, including Steve (Heaterman) in MN have repeatedly confirmed that the WHS1500/2000 units are conservatively rated as to their energy input. Martin Lunde is very particular about how his product is represented, and although I do not know the specific reason, I am sure there is one for why he chose to refer to the "burn rate" rather than an input rate. By definition, a "rate" is measured over time, otherwise it is a "unit". Even more specifically, this is actually the absorption rate for the storage tank.

    With fossil fueled burners you have clearly stated "input" and "output" rates, because the fuel is a known and consistent quantity in terms of energy content. The actual "output" of a fossil fuel burner is the energy absorbed by the appliance for distribution. With a wood fired appliance, the fuel is of a highly variable energy content, and therefore a "burn rate" is probably a better term to use. This is especially so with a unit like a GARN that has fully integrated storage, rather than a water jacket which is heated for distribution. I think therein lies the difficulty in how people compare a GARN with just about any other gassifier (with the exception of the Switzter). A gasser has a limited quantity of water to heat, and the burn "rate" must be controlled/limited to some xtent in order to avoid overheating the water jacket. If it cannot be absorbed by the heat load, it must go into storage or be "dumped". With a GARN (and a Switzer, for that matter) the storage tank will absorb copious amounts of heat production up to the boiling point, REGARDLESS of heat load.

    As Dave points out above, a GARN could put out as little as 20k Btuh for a couple days, or 300k Btuh for a couple of hours if you were able to pump the water fast enough. The GARN has a completely variable heat output as a unit, since you draw entirely off of the storage for energy. The firing rate is independent of load, and one of the best features of the GARN. It is also one of the least appreciated characteristics.

    With respect to your experience with the 3200, I would love to see pictures of that beast! I am sure it is subject to the same influences of the fuel source, and perhaps moreso due to the huge volume of the fire box. A 3200 has a firebox that is 3.12 times as large as a 1500/2000. I am not sure how comparable the units are, given their vastly different intended applications.

    A GARN may still not be the right choice for Harry, but only he can determine that.
  11. jebatty

    jebatty Minister of Fire

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    I think we agree on most points. It does seem to me though that the only real measure of output is ability to meet the needs of system demand, not just heating a tank of water. Heating the water tank would be the laboratory measure; meeting system heat demand would be the real world output.

    Perhaps what would be helpful, regardless of the wood boiler, is a system where demand, over an outdoor temperature range, would absorb 100% of the BTU output on the low temperature side and have excess BTU's on the high temperature side. Them, with data on GPM's, system return temperature, and system supply temperature, the real BTU output could be measured. The delta-T combined with the known flow rate would show actual output.
  12. Kemer

    Kemer Member

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    Woodmaster, I sold my EKO in about a week and trying to make up my mind on what to get next.I'm more confused then ever!
  13. Frozen Canuck

    Frozen Canuck Minister of Fire

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    Kemer: Suggest you allow quality & reported customer satisfaction to guide your decision far more than you let price. In my industry & experience those who decide primarily/solely on price usually wind up paying far more in the long run as they repair/replace/upgrade/try to fix problems far more often, they are also burdened with the decreased level of performance & satisfaction that accompanies a poorly designed/thought through/built unit. I am not saying that a Garn is your only choice but it should be on your list if you use quality & reported customer satisfaction as your guide, as should some other units, however I suggest you remove all units that would fit into the same category (quality & reported customer satisfaction) of the one you just sold. Why buy the same problems you just sold. Why not make a list of the units that pass your quality & reported customer satisfaction sniff test, then decide where in that list you can afford to/believe you should purchase, that way you can eliminate a great many units before you ever reach for your wallet. Same should apply in my industry ppl should buy the best quality they can afford not the cheapest they can find, then they could focus on the upgrades they want over time instead of always fixing problems they paid good money for. Makes sense to me.
  14. Jim K in PA

    Jim K in PA Minister of Fire

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    Jim - I am not sure I follow you 100%, but I think you are combining heat generation with system efficiency. First task is to generate a source of heat energy. That energy then must get distributed to satisfy the heat load. Heating up water in a tank is not a "laboratory measure", at least for me! With a GARN or EKO or Tarm or whatever other heat generating appliance, there is a range of energy output, and a reasonably determinable maximum output. I am not sure, but most other gassers will run at their max output until an upper temp limit is reached, and then they idle (please correct me if this is a misunderstandin). This occurs whether the heat load (heat call) has been satisfied or not. With a GARN, there is no idle time. It is a batch-burn system. You do not reload the firebox until the first batch has been nearly completely burned, if reloading is even necessary. A GARN produces an easily measured amount of heat energy, that is readily converted to a "conversion" rate. I think "input" and "output" are terms that can be misapplied with solid fuel heat generating appliances. A GARN converts heat at a measurable rate. How the heating system then uses that heat energy to meet the demand is a seperate process.

    I am not implying that the efficiency of that process is not relevant to the choice of heating appliance, or the design of the system. In fact it is paramount to both! If you need a constant supply of 180 degree hot water, then a unit that can meet that demand should be chosen. A GARN has a max operating temperature of 200-210 degrees, and that does not give you much dwell time between burns (depending on the load, of course). However, a unit like a Tarm or other continuous burn appliance will need to operate for extended periods of time to maintain the design temperature of the water. Neither a GARN nor a downdraft gasser may be the right solution if constant 180 degree water is required. RE-design of the heat distribution system may be needed in order to better utilise a solid fuel heating appliance, regardless of it's design or method of operation.

    Harold -I understand why you would be confused. :lol: Hang in there.
  15. jebatty

    jebatty Minister of Fire

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    I'm not sure that's what I'm doing, but ...

    I think this hits the nail partially, and we agree. Regardless of the type of wood burning boiler, the purpose is to provide space heating to meet system demand. If a boiler is rated at 425,000 BTU/H and has 1825 gallons of storage (I'm not picking on Garn, put any any boiler name in this equation), if the lowest usable temperature is 150F, if system demand is 250,000 BTU/H, and if the storage is heated to 200F, then usable storage capacity is 761,938 BTU's (1825 x 8.35 x 50), or about 3 hours between burns. And, obviously but importantly, the size of the piping and the circulator need to be sized to move 250,000 BTU/H.

    My other point, though, is this. If a heating system demand is 200,000 BTU/H (pick your number), a person would want to know what size boiler rating the person should buy that could continuously meet a demand of 200,000 BTU/H. A peak or maximum boiler rating is a clue, but due to the wood burn cycle, plus practicality of a person being available to reload the boiler, that maximum is not likely to be attained continuously. It would be really helpful to have a standard other than maximum for a wood burning boiler that would provide better advice to a purchaser in making the purchase decision.

    For example, if maximum output is 300,000 BTU/H, should a person reasonably expect a continuous effective output of, for example, 100,000 BTU/H, or 200,000 BTU/H, or what? Effective output also relates to storage to buffer or store excess BTU's and then release them to the system when boiler output is in the falling range, only to re-store excess BTU's in the high burn stage.

    My final point is that a boiler maximum rating can be very misleading if the maximum output, combined with the storage, can only actually meet a continuous BTU output much less than the maximum rating.

    And by the way, with my Tarm rated at 140,000 BTU/H, I know it can meet that maximum rating for a time at 180 supply and 160 return when the boiler is in high burn, but not for too long a period, and then BTU output starts to fall. My rule of thumb based on experience is average output at about 70-75% of the maximum, with refueling on about a 2-3 hour basis when burning pine. Longer periods between refueling when burning pine result in lower effective continuous output. I have 1000 gal of storage to buffer the high burn to storage and play out the BTU's as boiler output falls.
  16. heaterman

    heaterman Minister of Fire

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    I'm going to chime in here for no other reason than this type of topic garners my interest (pun intended)

    I can offer the following field experience with Garn firing rate/output/btu delivered.
    During the course of construction of the dairy facility during late December through March for "my favorite farmer" we used a single Garn 2000 to supply heat for the pole barn type structure once it was closed in. It was not insulated at all and had tarps covering a 16'x50' "hole" in the north wall. We had two air handlers which were rated at 88,000 btu with 140* water temp running non stop as well as roughly 3600 sq ft of in floor radiant. With the average temp of the building running in the 30-35* range and cement surface temps running in the 75* range I would have to say that the floor was cranking out at least 60tbus per sq ft. This was also continuous output. If you add that all up it comes to about 390,000 btu output from the heat emitters. Bear in mind that most of the time the water temp supplied to the emitters was running from 160-180* so the air handlers were probably producing more on the order of 100K+ and you have an honest 400-420,000 btu continuous load on the Garn.
    Now, during the course of that construction the Garn would regularly raise the water temp in the boiler about 8-10* meaning that around 150-160-Kbtu was being dumped into storage over the course of a burn. Note that I said over the course of a burn, meaning while there was fuel and fire in the firebox. Once the load was consumed and we were working strictly from storage, the water temp of course began to drop at a precipitous rate.
    When you consider and add up the load present and the temp gain in roughly 1900 gallons of storage you can see that the honest btu output to storage was in the neighborhood of 500K on the conservative side. This scenario was repeated 4-5 times a day for 3-1/2 months. There were variables of course that depended on outside ambient temp and wind blowing through the building as is was closed in so those numbers are not cut in stone but they point to the fact that actual output to storage/load was well above the output to storage rating listed by Garn as being 425,000 or there abouts.
    I also have to say that coming from the gas/oil fired side of things the concept of using storage is a little foreign at first. We in that field are used to dealing with a limited range of operating temps and the idea of running a heating system from something that varied from say 120-200* tends to make us think outside the box. The equation introduced by that means that we have to seriously consider the output capability of the heat emitters with reduced (from normal design) water temps. The bottom line is that if the emitters are sized to just barely produce enough heat at 180* then storage is of little use unless you can drive the upper limit to nuclear meltdown levels. Any heating system not able to cope with a meaningful variation in water temp of say at least 50* is a poor candidate for storage based heat regardless of the brand of boiler attached to it. That much is not rocket science and should be obvious to anyone. The main advantage of any storage, not just a Garn type system is being able to use the flywheel of the heated mass to provide heat during the boilers "off" cycle. If that's not possible a person needs to resign themselves to the reality of frequent loading along with firing at a level that matches the current requirements of the system. As we all know, that's extrememly difficult to do without cycling the fire. I also think that everyone who has studied that(cycling the fire) would agree that it's not the best way to attain peak efficiency.
    One other thing regarding the Garn output. It is not dependent on the firing rate. Under the right conditions a person could extract well over a million btu/hour from the storage albeit for a very brief time. Output to the system is limited only by the design of the system and the parameters under which it is operating. Realize of course that those million or so btu's can be replaced at "only" 400-500K per hour, but the fact is that you can dump a huge quantity of heat, from a Garn or any storage for that matter, that far exceeds the actual firing rate very quickly given the right conditions. That is one of the many beauty's of well designed piping and storage.
  17. heaterman

    heaterman Minister of Fire

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  18. heaterman

    heaterman Minister of Fire

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    Some more to your post above.

    (1,2,3&4) Make a huge difference in any boiler which is why the current EPA test makes so little sense.

    (5) That is the only way to logically measure performance.

    (6) will have an effect on overall btu's available in the fuel but does not effect efficiency to a great degree.

    (7) On a Garn it will of course start at existing water temp but usually reach 300-340* within 3-4 minutes of light up. Those are actual verified stack outlet temps. Peak temp may hit 450*+ at the peak of the burn for a brief period depending on how it's loaded.

    8 Stratification is very pronounced in a Garn however during firing the entire tank will turn over within 5-10 minutes of startup and equalize.

    9 Ending tank temp is very uniform from top to bottom due to the mixing effect caused by the location of the HX tubes. Final temp depends on how the user has fired it. There is not aquastat on a Garn.

    (10) Why does flow rate matter? Flow rate + temp drop S-R would have to factored in to arrive at actual output of course.

    (11) Being that these are factors influenced by field installation, there is no way to quantify them. Obviously, any storage that is poorly insulated will have a negative effect on overall system performance. Ambient air temps vary widely from being 80*+ in a well insulated enclosed room to freezing conditions in my favorite farmers wood shed.

    (12) In the case of a Garn this would be outdoor ambient plus about 70*it picks up while passing through the storage tank.

    (13) Controllable only under lab conditions and I don't think the DOE AFUE test for gas/oil fired equipment takes them into consideration other than to describe standard test parameters. They are not monitored.

    (14) About 300CFM on a 2000 IIRC. That's from memory so don't take it to the bank.


    Now as to this statement;
    But in the final analysis, it seems to me that the most important factors for a specified BUT/H output rating are: A) what is the heating system return temperature to the boiler; B) what is the supply temperature needed to meet system demand; C) required GPM flow rate at boiler output rating then = supply temp - return temp x 500; D) and to get an accurate rating, since the Garn supplies directly from storage, it would seem that starting uniform, non-stratified tank temperature must equal the heating system return temperature.

    A,B & C allude to how the AFUE test is done. The testing agency or manufacturer will hook a boiler up to return water of 120*, fire the boiler at maximum rate, then adjust the flow rate to acheive an output temp of 140, thus establishing the industry standard 20* differential. The flow rate x the temp drop shows the actual btu output and the efficiency calculated is based on accurate measurement of fuel input be that oil or gas. The huge issue with wood is what is the standard fuel. Obviously the EPA is struggling to come up with a valid criteria for that as witnessed by the sawn, cribbed, kiln dried wood used in the current test which bears about zero relationship to real world experience. Measuring BTU output or efficiency in that way is only applicable if the unit being tested will normally operate under full load, steady state conditions. As you know, this is positively NEVER achieved in the field although a system utilizing storage adequate to absorb an entire load of fuel would come closest.
    As to (D), I'm not following your train of thought there. You could measure absolute output on a Garn only by eliminating the effect of the storage being integral with the firebox and HX and then approximate something along the lines of the AFUE test. Virtually impossible to do as the storage and HX are two parts of the same system.
  19. heaterman

    heaterman Minister of Fire

    Joined:
    Oct 16, 2007
    Messages:
    3,039
    Loc:
    Falmouth, Michigan
    On a Garn or other system using storage large enough to absorb an entire load of wood, it is fairly easy and straight forward to calculate the output and/or firing rate. You begin with a known quantity of water and raise it X number of degrees in X amount of time and thereby establish the firing rate. The only variable with normal storage is stratification in the tank. This is not present in a garn that is being fired.
  20. Kemer

    Kemer Member

    Joined:
    Feb 26, 2008
    Messages:
    213
    Loc:
    Northeast Pa
    Just an update .I did order the 1500 with vertical flue and will be delivered around second week of July.I'm glad I stalled for awhile as it gave me a chance to rethink the location in my attached boiler room.I went with the vertical to avoid any lingering smoke at startup and it made the install so much easier.I think when I'm done I will have a system that I will be very happy with.Thanks for all your help and I will post a picture of my setup when I'm done.Ive asked a lot of questions and I think I've addressed any issues .I'm excitied

    Harry
  21. heaterman

    heaterman Minister of Fire

    Joined:
    Oct 16, 2007
    Messages:
    3,039
    Loc:
    Falmouth, Michigan
    All I can say is that you will probably be very, very happy with your Garn for a very, very long time. I was just at a jobsite north of me and laid my eyes on a pair of Garns that are obviously from the early 80's. They were serial number WHI000029 and WHI000044. Pre 1985 at least. The owner wants me to "give 'em a tune up". They need new gaskets and reaction chambers and that's about it.
  22. Como

    Como Minister of Fire

    Joined:
    Jan 28, 2008
    Messages:
    866
    Loc:
    Colorado
    Just wondering why the install is much easier going vertical, is it a function of the Building it will be situated in?

    On output, for my altitude (just short of 10k) and wood (Pine and Aspen) I was told to de rate by 25%. Which is what I expected.

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