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Does anyone NOT like their Garn? How do you feel about your Garn?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by ThisWarmHouse, Dec 15, 2008.

?

How do you feel about your Garn?

  1. I love it

    22.9%
  2. It’s OK

    5.7%
  3. I hate it

    42.9%
  4. Don’t have one yet but plan on getting one

    28.6%
  5. What’s a Garn?

    0 vote(s)
    0.0%
Thread Status:
Not open for further replies.
  1. Eric Johnson

    Eric Johnson Mod Emeritus

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    I should have mentioned Garnification, who built his own, impressive-looking Garn-style boiler and has been very helpful and supportive of those interested in getting one of their own.

    Helpful Sponsor Ads!





  2. brad068

    brad068 Feeling the Heat

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    Oh, I forgot about you northerners. Do you guys even turn your clocks back up there!? :p

    Did you guys see that in the upper poll there is one voter that HATES his Garn!?! Must be a communist. After all they do like their crude cold war downdrafters. :red:
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    ^^^^Except he has a nasty habit of knocking the Euro downdraft gasifiers.
  4. Sawyer

    Sawyer Minister of Fire

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    Clocks? Googled it, by Wikipedia's definition why would someone want one of those ;-)

    As for the other, definitely KGB!
  5. Tattooz

    Tattooz New Member

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    Hate it....... Yup Hate it......
    Hate that I didnt think of this 20 years ago.......
    GARNS RULE <----- sorry is that a breach????

    STOKE IT........
    [​IMG]
  6. mike1234

    mike1234 New Member

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    I know this could be a highly volatile question, but be gentle, it's just a question.
    Reading this commercial, er I mean thread, I just have to ask, how can a boiler that cost at least (as far as I have been able to tell from your posts) 15,000 to buy and install, (add 15,000 more if you have to build the shed) be something that saves you money? Even if you use less wood than I do by 1/2, it would take about 8 years to pay it off. Let say I pay my wood furnace off in 2, then I am pocketing that money, or buying a cool new chain saw, or a new splitter, or ..., for the 6 years you are still paying off the garn.

    I do understand that you might just prefer the boiler over the furnace as a preference. But do you all have the $$ worked out so that what I said above is not the case? Again be gentle, it's just a question, and I am not questioning your religious beliefs.
  7. brad068

    brad068 Feeling the Heat

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    Alright ,we are going to compare apples toooo... watermelons. Can or are you heating your potable water? Can you heat multiple structures with your furnace? Can you burn your furnace all year to heat potable water? Can you heat your swimming pool? Can you hook up a hot water solar system to your furnace? And does your super jack have at least a 20 year track record?

    For the average guy that only needs to heat one small structure then yes a Garn is probably out of the question, but for the folks that need the btu's these units really show there worth.

    I grew up in a home with a wood furnace and they do get the job done, but having the wood and smoke in the basement and waking up with pasty dry mouth is not something that I was looking forward to in my own home.

    Oh yeah, and I've heard from folks around here that it only cost 10% more to go first class %-P
  8. brad068

    brad068 Feeling the Heat

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    I was just thinking, I wonder if the Yukon super jack is the same furnace that the original super jacks were made by, Jackline. Some of them were little boilers like a horseshoe shape water jacket on top. They were hard to control the heat output and boiled over easy. They were built years ago just north of me and there was another line call Feldon Walker I think. Alot of folks around here had them and then they sold out probably to Yukon.
  9. mike1234

    mike1234 New Member

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    OK, so if you are heating a home & detached shed and pool and .... then the furnace wouldn't even be an option. Good point.
    I like your apple to watermelon comparison, mine does look like an apple next to your watermelon.
    Mine does preheat hot water if I decided to put that option in, but only during the winter, and it's in the garage, no smoke smell in the house.

    BTW I also know that we all invested a certain $$ in our systems, so we will defend our choices to the last dollar. I am not trying to convince you of anything, just enjoying the conversation.

    Not sure about the Yukon history, but no horseshoe shaped thing at the top anymore.
  10. Rick Stanley

    Rick Stanley Feeling the Heat

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    First of all, if I didn't have a lifetime supply of free wood, I wouldn't burn wood at all.

    Further, if I didn't have an existing building to put it into and if I didn't have future plans to heat multiple buildings (drafty old farmhouse with apartment/future apartment in other buildings/greenhouses/future slaughterhouse/food processing facility................a Garn is the last thing I would have bought. Quite honestly, if H. S. Tarm had a bigger unit I'd have gone that route.

    I can burn 1800 gallons of oil a year right here in the house. Depending on the price of oil, the pay back on any boiler would be quite short, especially $4 oil. So, I'd say that Nofossil has the right idea, get the smallest rig that will work for your needs, hook it up right and run it right. Garn is a commercial rig in my opinion.
  11. heaterman

    heaterman Minister of Fire

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    Just an FYI. I know for a fact that the folks at Dectra are seriously contemplating a unit sized for smaller applications. When that may happen is anyone's guess. I would not hold my breath for a couple reasons. Number one is that they are busier than a cat in a dog pound right now. Number two is that while the price point will be lower, I doubt that it will be a lot lower. The only savings in a smaller unit would be from the cost of steel, fabrication and labor would be nearly identical assuming the same design is used and I sure don't want them to mess with that.
  12. jebatty

    jebatty Minister of Fire

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    The Garn website gives good general advice: "It is important to not undersize or oversize any heating appliance." That advice also comes from many forum participants. I will state my conclusion up front.

    Conclusion: The Garn is an impressive wood boiler system which should perform very well when used with a heating load matching its design capabilities. Based on 350,000 BTU burn rate of the smallest Garn unit, it is probable that the Garn is not the best suited for average home heating needs. The average Minnesota home uses between 80-100 million BTU's/yr for heating.* Using 90 million for purposes of example, and assuming 8 months of heating, that works out to 350,000 BTU's/day. I don't know what the Garn efficiency is in transferring burn rate to actual water heated. Assuming 100% (which is not realistic), 64 minutes of burn time would meet the needs of the average Minnesota home on an average day. My system is rated at 140,000 BTU's. Assuming again 100% efficiency (not realistic), 2.5 hours of burn time would meet the similar need. Realistically, it probably would be appropriate to double both of these burn times to approach actual system performance.

    This example highlights the advice to size a system appropriately, as it would appear that a sizable investment on a system to be used about two hours per day, when I am sure the design capacity is for much greater use, would not approach the return on investment for which the system is designed.

    * http://www.state.mn.us/mn/externalDocs/Commerce/Home_Heating_110802040719_Heating.pdf

    Discussion:

    It's really difficult for any person, including Garn owners, to make a good evaluation, unless the person also has direct equivalent experience with other wood boiler systems, including OWB, gasification, etc. That means a side-by-side comparison of the various boilers for Heating System X, for example. If the heating systems are different, the outcomes would be different. My comments are based on Garn published specs for its smallest unit (to make the comparison as closely equivalent as possible to what I now have) + actual experience with the system I purchased and installed.

    Garn was one of the boiler systems I considered before buying another boiler. I was impressed with the integral water storage, but for my application, even the smallest Garn appeared to be oversized, it physically took up too much space (turned out to be not very relevant after I added storage to the system I bought), and it was too heavy for me to handle with the equipment I had available. Initial purchase price and shipping also were out of the range that I was willing to spend.

    Smallest Garn Unit (WHS 1500)
    Physical size: roughly comparable to what I have when 1000 gallon LP storage tank is included in my system.

    Empty weight: very close to what I have, including weight of 1000 gallon tank. I am able to handle my system with my own equipment (1000 lbs boiler + approx 2000 lbs tank), but I cannot handle a single 3500 lb appliance.

    Firebox: Garn is much larger, and assuming equal quality of wood and equal efficiency of burns, Garn would provide a much longer burn time over what I have; would allow probably for one long, single burn rather than needing to refuel my system under certain circumstances. Ability to burn larger pieces in the Garn is an advantage as it reduces splitting and cutting time. I have seen posts that indicated the Garn can burn higher moisture content wood than the gasifiers should burn. I do not regard this as much of an advantage, if any, for the Garn, as burning increased moisture content wood increases burn inefficiency, potential of creosote formation, and increased smoke, particulate, and aromatic emissions. Future environmental regulations need to be considered if the intent is to burn high moisture content wood.

    Ease of Cleaning/Maintenance: no experience with the Garn and no knowledge. My system is easy and quick to clean; maintenance I know of so far is annual on system shutdown for summer (about 2 hours time).

    Storage: Garn has 1420 and my system has 1055. This is neither an advantage nor a disadvantage, as I could increase my storage to whatever I desired consistent with the capacity of my boiler. I believe my boiler easily could heat 1500 gallons of storage to maximum temp based on how easy it is to heat the 1000 gallons I have.

    BTU burn rate: Garn is 350,000 and mine is 140,000. Each has its +'s and -'s. Garn would bring system up to full temp faster and continue to meet the demands of a much larger heat load than my system would do with equivalent storage. Based on my system's actual capacity to more than meet my heat load needs, my early-on conclusion that the Garn was more boiler than I needed was accurate. I think what is important is to size the boiler to the heat load needed; otherwise, if the boiler is oversized, burn inefficiencies most likely will result; and if undersized, heat needs will not be met.

    Pressurized/Unpressurized: Garn is unpressurized and my system is pressurized. I initially installed my system with a pressurized boiler, hx, and unpressurized storage; since replaced with pressurized storage and system in total. This is a difficult one to state any specific conclusions, as each type of system has advantages and disadvantage. I believe that the Garn integrated open storage system should function very well, and it can be mated to a pressurized heat load with a heat exchanger. A pressurized system in total eliminates the need for the heat exchanger for space heating needs and pretty much eliminates the need to monitor water chemistry after the water is initially treated. I assume the Garn needs periodic water chemistry treatment, much as my old OWB required. This was relatively easy and the chemicals (150 gal open system) were not very expensive, but it was one more maintenance step required.

    Quality: Garn has been around for a long time, as has the manufacturer of my system. I assume both to be of very high quality.

    Support: Based on comments of others, Garn could do better in this area; the manufacturer of my system has received very high user marks on customer support.
  13. ThisWarmHouse

    ThisWarmHouse New Member

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    jbatty,

    Great post. I have personally been trying to think down through some of these same comparisons. Especially regarding a completely pressurized system like the Tarm or Eko with a pressurized storage tank vs. the Garn with the integrated open unpressurized storage. I currently rent but plan to build in the next couple of years and part of my home design will be built around either using a Garn or a system like the Tarm. The thing that attracts me to the Garn is the simplicity. There is so little to go wrong yet it works so well. I don't want to write off alternatives.

    I have a few questions I would love some feedback on.

    1. The Garn's water needs to be periodically tested/treated and a pressurized system doesn't need to be. If you are faithful in testing and treating the Garn's water does either system have an advantage regarding longevity due to the pressurized vs. open system? Are open systems only more susceptible to corrosion when they aren't properly maintained? Why do the Garn open systems seem to last so much longer than other open systems I've seen?

    2. Do the Tarm/Eko systems blow some smoke in your face when you open the door? One of the things I like about the Garn is the way the blower system is designed to not allow the smoke and flames to come out of the door when you open it. I have never experienced a Tarm/Eko system yet. Feedback?

    3. With a Tarm/Eko system with a pressurized storage tank which is likely to go bad first, the storage or the boiler? What is a typical lifespan of one of these systems? I've heard of lots of 20+ year Garns on the field working great. I've heard the Tarms are long lasting but I don't know many specifics.

    4. Are there any major efficiency differences between a Garn and a Tarm type system?

    5. I plan on building a monolithic dome home (super efficient) so I will have really low BTU requirements but with well insulated BTU storage I'm not really concerned with oversizing, in my mind it just means shorter and less frequent burns. Am I incorrect in that thinking? Or are there negatives I should be considering?


    Anyone here had hands on experience with both? What are you impressions of both types of systems? Plus and negatives for each please.
  14. Jim K in PA

    Jim K in PA Minister of Fire

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    Mike - good questions, and if any GARN owners are actually offended by them, then they really did NOT do their homework, and may in fact have made the wrong decision to go with a GARN. With respect to your payback question only, we need to compare apples:apples, along the lines of what Garnification was getting at. Compared to an OWB, the GARN is significantly more expensive in initial cost for the unit, probably close to 75% more. However, that is not an appropriate comparison, IMO. Compared to gassification type stoves, the GARN is also more expensive, probably 40-50% more. However, that does not address the difference in heat storage capacity. Adding in the heat storage tanks and tranfer infrastructure, I think the GARN cost difference will be more in the 15-20% range. I have not done an extensive comparison since my early research, but based on others descriptions of their gassifier+remote storage setups, I think the price differences I describe are fairly close. However, if you must build an entirely new structure that you would NOT otherwise have had to build, that will obviously add more to the total cost. I think your $15k estimate for the cost of the remote building is rather high, since the GARN itself does not need much more than an 8'x16' shed. I think $1500-$2500 additional cost to house the GARN is a reasonable minimum number to add to the analysis.

    So, Payback? As with ANY option, that will be purely an arithmetic exercise. Total the cost of the unit, total the annual cost savings of whatever fuel you are no longer burning, add the annual cost of the wood, and divide the total cost by the total annunal savings minus the annual wood cost, and you have your payback period. For OUR economic calculations, based on $4/gallon oil price as of June 2008, and a 1240 gallon/year oil useage for our house alone, we were looking at a payback period of right around 4 years for our GARN. Of course, that equation is out the window with oil now down in the $2/gallon price range again, so that payback period has now doubled. However, we had to make a tough economic decision at the time of peak oil prices, without the ability to forsee whether prices were going up or down.

    Jim - excellent points, as always. I think the most interesting part of the GARN evaluation process is one of configuration. The physical size and weight of the unit can be, and often is, THE determining factor in it's suitability for a particular application. One would think that form factor would be a secondary consideration after efficiency and operation, but the GARN is an exceptionally large machine.

    With respect to appropriateness to demand, the heat and store system is really the ideal configuration, regardless of what brand combustion unit you choose. Storage capacity solves many issues that apparently are of significant consideration to non-storage equipped gassifier owners, specifically overheating and ability to meet demand over long periods of time without firing. I think that when determine their heat needs and the size and storage capacity of their system, if the GARN exceeds this they discount it as an option. While this is logical, to some extent it eliminates a perfectly viable option. More storage capacity increases time between burns, and higher specific output decreases the time needed to re-charge the tank. What I marvel at is how I quickly can recharge the storage while still meeting my heat load simultaneously.

    I do agree that the GARN is technically and logistically more compatible with a multiple district (building) heat load due to it's size and output capacity. That was one of the key factors in our decision to go with the GARN as I wanted to heat two outbuildings in addition to our house. Forward planning was key to our decision process.

    However, if I lived in a smaller home, with no plans for multiple building heat loads, I would likely have built a small outdoor structure to house a smaller gassifier, and incorporate storage in my house/basement. While the cost would be a little less, that configuration would allow for some flexibility in the installation.

    Good points here in this thread - I hope future wood furnace researchers come across it.
  15. tigermaple

    tigermaple Member

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    The way I figure it the smallest Garn would cost 6-8 grand more than my GW100 installed. That is 40 cords of wood in todays market. More than 4 years of fuel for me plus the wood needs splitting. How much less if any would I burn with a Garn over that 4 years?
    Jeez, 20 grand could get you a GW100 and a 5 acre woodlot plus you could let the wood grow for 4 years adding 30% wood mass.
  16. jebatty

    jebatty Minister of Fire

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    Under the conditions you state, I know of no reason why either type of system would have a material longevity benefit. Everything else being equal, I believe pH maintenance and keeping O2 out of the water are the prime considerations with either system. Acid and oxygen are steel corrosion hogs. Without knowing more about the other open systems you mention, I really can't respond. The only other factor that comes readily to mind is the quality of steel, welds, and construction, all of which also would relate to longevity.

    As to the Tarm, yes and no. If I follow Tarm's instructions and only open the firebox door after the fuel load has burned down to low coals, then I think I safely can say "no smoke." But often this is not convenient, and I frequently top off the firebox while a burn still is in process. If I'm careful here, I can almost always eliminate smoke of any consequence. But if I'm a little careless, I will get some smoke. For some people, any smoke is too much smoke. It's of no consequence for me.

    There may be many variable at work here. My assumption is that my storage tank, a used LP tank, is of high quality steel, and I see no reason why it should not last for a very long time. Tarm provides a 20 year boiler body warranty, amortized. I'm only in my second season of operation, and all I can say is that so far, it's still "alive."

    Based on manufacturer published data, they appear to be of approximately equal efficiencies. Both seem to have combustion efficiency of 97% or more. Tarm advertises overall efficiency of 75-80%. I have not seen published overall efficiency data for Garn. There may be some engineering differences between them which lead to (assumed small) efficiency differences.

    If you are contemplating buying a wood heating appliance (Garn, Tarm, Eko, etc.) grossly over-rated for your heat load requirements, I think you are spending excess money and your cost/benefit ration will decline. I think the ideal system is one which is firing 100% of the time and modulated to meet a varying heat load demand. Since this is not available for wood, you will be firing the boiler, letting it burn out, and repeating. Each firing has a start-up component when it is burning wood to come up to operating temperature. This is the most inefficient period of the burn. Ideally you would like to minimize these situations, as each is wasting wood heat energy.

    Whether shorter, less frequent burns, will meet your needs depends on how hot you need your water. An in-floor radiant system can operate on a much lower heat of water than will a baseboard system. If you need 160 water, then you will have more frequent burns than if you only need 120 water.

    There is another factor which I think may be relevant. Long periods which allow the firebox to cool so as to permit possible condensation in the firebox should be avoided, as condensation in the firebox plus creosote on the firebox walls = acid = corrosion. So long as the firebox is kept warm enough (by surrounding water in the boiler or otherwise) to prevent condensation, this should not be a problem.
  17. brad068

    brad068 Feeling the Heat

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    I got to throw in my other 2 cents. 1, the garn unit aren't as affected by a power outage as some of the dd's are. You don't need a mixing valve to get the correct return temp, or another circ to remove the heat to storage, and you don't need a overtemp dump or plumb it to siphon heat- simple is better!

    2, these units are so simple. If you break the firebrick you don't need it special from Denmark or Czechoslovakia. you can go downtown and get new ones same with the motor, Graingers,msc,etc. Secondary chamber I can make that myself and I have found a place too. Only think left is the timer, same places. The units have but one door and the majority of the unit and its guts are round- equal expansion few joints= long life

    3, ayuh,.. found a penny. I timed myself the other day and I beat my old record of 6 minutes, did it in 5 3/4's Thats the time it takes me to walk in the door, load, start a fire ( I forgot to tell garn folks this, use cardboard to start your fires works the best), go fill the wheelbarrow and bring it back, check the fire then exit.

    Another! penny... I 've seen a tarm unit in action and I got to say the firebox is small. Think it was a solo 60 or something. My fingers would be all brusied up if I had to put wood in a door that small. But then again your throwing in twigs (not leaving anything for the birds to make nesting out of). I do split up my wood but not that small and it seems to burn it just fine.
  18. jebatty

    jebatty Minister of Fire

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    Correct statement that Garn takes larger wood pieces than, for example, Tarm. The Tarm is designed essentially to burn small splits (4-5" diameter) up to 20" long (18" works better). There will be more splitting and cutting with a Tarm than with Garn. I did mention this in my first long post above.
  19. sdrobertson

    sdrobertson Minister of Fire

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    I haven't gotten in on this one yet so here I go - I enjoy trying to build something with my own hands and I like to scrounge things to try and do my work as cheap as possible so I can spend the rest of my money on the kids. This being said, I'll buy new most of the time as I'm limited on my scroungeing time. I went with the EKO because: 1. It was "used" but never fired so a deal. 2. I had access to propane tanks for storage. 3. My father has one and I new the quality. 4. I read about but had never actually seen a Garn. 5. Others but minor.

    I have roughly $7000.00 into my system and even though I haven't priced it I'm guessing that's over half of a GARN. This doesn't include the pole building or insulation as I would need both for either unit. I would never direct anyone to not purchase a GARN as I see absolutely no down side to them. They are a beautiful boiler and I would love to own one as they are incredible simple and efficient. I own a S-10 4x4 but would love a diesel one ton 4 door 4x4 long bed(w/plow).
  20. heaterman

    heaterman Minister of Fire

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    I want to hear from the guy who voted that he hates his Garn. What in particular is the problem?
  21. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Properly-maintained, either system should last decades.

    Garns tend to last longer than other open systems (eg, outdoor wood boilers) primarily because folks actually maintain the water quality. Many OWB's see little if any water treatment.

    That said, I am aware of some Garns leaking due to bad water, so proper treatment really must be followed. That could be seen as a disadvantage, although even closed systems should have their water monitored (they are just less likely to have problems).

    The Eko and the Tarm/Scandtec Solo Plus series can release smoke. The Tarm Solo Innova and the Fröling are both induced-draft like the Garn, and include smoke extraction passages, so smoke release is similar to or less than what you would see with a Garn.

    Depends upon the tanks that are used. Folks building systems using salvaged tanks (propane or other) may be taking a gamble with what the condition of the tank actually is. I've even heard of folks using used fuel oil tanks for pressurized storage - which is certainly do-able, but I think it's safe to say that such tanks will fail much sooner than the boiler, in most cases.

    The tanks that Tarm sells are ASME-rated pressure vessels, designed to handle pressures (125PSI, if I recall correctly) far in excess of what we use in typical heating systems. They are actually expansion tanks designed for commercial systems, so they are designed to operate with water and air in them, creating a corrosive environment, and still provide reasonable longevity. So it's safe to say that they are made of some very thick, high quality steel, and will last many decades in normal use. I don't even install isolation valves on them, because the odds of a tank failing are trivially-low, and I'd say that the valve is more likely to fail than the tank.

    I believe that Garn lists an efficiency on the order of 75%. The Tarm/Scandtec Solo Plus series generally provides an efficiency on the order of 80%, the Tarm Solo Innova should be around 85%, and the Fröling provides a rated efficiency in excess of 90%.

    So, the Garn is the lowest among those, in combustion efficiency (presuming that the others are all installed with storage, to be comparable). Of course, none of the other units being discussed are in the same output class as the Garn units, so it's really an apples to oranges comparison - most boilers in the same size range as the Garn will post similar numbers.

    First step in sizing is to determine the heat load (peak and average) of your structure, and to decide how long you want to go between burns (during peak and average conditions). Then design the radiation in order to determine the minimum water temp which will allow proper operation. Use that number, or 120-degrees (whichever is higher), and determine how many gallons of water you need in order to supply the given load for the given between-burn interval.

    Once you know how large a tank you need, then you can see what system will be appropriate. If you figure that you need 600 gallons, then even a WHS1500 might be a wee bit excessive. If you need 1200 gallons, jumping up to a WHS1500 might not be that crazy.

    Assuming that you are sizing a separate tank and boiler, you size the tank to the above conditions, then size the boiler based upon realistic tank re-heating. The boiler size in a storage situation is not related to the heat load - it is related to the tank size.

    I don't have direct experience with Garns yet (ie, I have never installed one), but they have a good reputation. I wouldn't hesitate to specify one for an appropriate situation, although I should put a caveat on there that I really only think there is much use for the WHS2000 - below that, I would likely specify a Tarm- or Fröling-based coupled with appropriate storage tanks (possibly sourced from Dectra if on the large side, since they do supply bare tanks without the boiler guts). It's in the 2000-gallon and larger systems where I think the Garn really has its niche.

    Joe
  22. jklingel

    jklingel Feeling the Heat

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    WarmHouse: I don't see your post as commercial at all. Anyone brave enough to ask to (potentially) be ripped to pieces publicly should be commended. I've read all the responses, and some very good points were brought up, so I am glad this thread exists. I am looking real hard at a Garn, and don't feel the "physically too big" is a valid point if a person is going to add a storage tank to his/her smaller boiler. Two separate items eat up a lot of floor space and pipes/valves.... I can't yet comment on the "over-size is fine, it just means fewer firings" because I don't have a wood boiler yet, and that is one issue I have wondered about. As I see it, most boilers in most situations should have storage, so you either have it in your boiler or next to it. I did ask the new Garn dealer up here if a slightly smaller Garn was perhaps in the works, but I have not as yet heard back. My gut feeling is to want a boiler just a tad smaller than the Garn 1500, but that is only a gut. As for cost, I have not priced a Garn yet, but an Econoburn (I think it was) will cost me $12K and a Tarm about $10K. Add storage and plumbing, and that will probably be relatively close to a Garn; no? Dunno. So, you guys keep firing away and I'll keep reading. Thanks for the thoughts.
  23. jebatty

    jebatty Minister of Fire

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    Northern MN
    Joe - a major difference between your input and some by others, including myself, is your experience in the field. I always read your comments with interest.

    This point is pure logic and I need to remember it. The caveat is the situation where the storage itself is undersized, which may occur for a variety of reasons, including space available.

    You and I may be using different terminology but talking the same point. I understand combustion efficiency to be different from boiler efficiency. The first relates purely to combustion, and I think all of the gasification boilers are within 1% or so on this, ranging between 97-99%. The second relates to efficiency in transferring the combustion heat to the water (my use of the term "boiler efficiency"). I think this is what your efficiency numbers relate to.
  24. mike1234

    mike1234 New Member

    Joined:
    Dec 5, 2008
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    Loc:
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    Let's talk about this 95 - 97% efficiency rating. I have a 95% rated propane furnace, which has PVC intake and PVC exhaust. 5% of the heat is lost up the chimney, so PVC is appropriate. I am fairly sure no wood burning appliance would say that PVC for the exhaust is OK, way too much heat goes up that chimney, in fact to keep the chimney clean it needs to be about 300 or so, right?
    Given those facts, how can a wood boiler/furnace/insert/ anything be 95% efficient if that much heat is going up the chimney, and not into your home? Just seems like these numbers are a little optimistic.

    I have learned a lot about boilers in this thread, if I had more than 1 building to heat, and if I had 15,000, and if I was a much better plumber than I am (I hate plumbing repairs, 1 repair leads to 4 more problems and repairs) then I think it would be better, yes I said better than my wood furnace. 1 building, no plumbing, in my situation I think the furnace was right for me.

    If I was shopping right now for a method of wood heat, this thread would be more help then most of the research I did when I was shopping. (I didn't find hearth.com until after I purchased my furnace).

    Someday, when I travel east and north of here, I'd sure like to see some of these boilers you have all installed in operation.
  25. jebatty

    jebatty Minister of Fire

    Joined:
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    For gasification boilers, this is combustion efficiency, meaning this % of energy in the wood that is combusted (turned into heat). It is not the amount of heat combusted transferred to water. I assume your propane appliance is rated on heat generated transferred to your system. Do you have info on raw propane btu's actually combusted?

    Example for wood gasification boiler: 98% combustion efficiency x 80% heat transfer efficiency = 78% overall efficiency.
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