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Garn boiler

edaddyedaddy Member Posts: 4
Need opinion on whether a 
forced induction boiler will work to heat a large in ground pool in michigan.the garn boilers heats and stores 1.2 million btu per burn cycle  not sure what size exchanger to use with it

Comments

  • hot_rodhot_rod Member Posts: 13,737
    Maybe start with a pool boiler calculation.
    Outdoor? Heated year around? Insulated cover? Windbreaks?
    The boiler size will come down to how quickly you want to raise the temperature.
    BTU/hr at full burn would be a good number to know for the Garn to simplify the calculation.

    https://poolresearch.com/pool-heater-size/
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • hot_rodhot_rod Member Posts: 13,737
    I'd probably use the 8 hour burn output number, unless someone is constantly tending and feeding the beast, to keep it at it's highest output.
    So the 2000, looks like a bit over 105,000 BTU/hr. I hope it a small pool :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • edaddyedaddy Member Posts: 4
    Thanks I'm new to trying wood fired boiler, haven't decided but don't want to make a 15k investment that won't cut it
  • ZmanZman Member Posts: 5,948
    I think you need to start by figuring out the heat loss of your pool on the coldest day you will want to heat it as well as the typical day that you will just need to heat it up a bit.

    The storage numbers you quote will help carry the pool over at time when the boiler is not burning. The pool is also a humongous energy storage battery. If you overheat it by a few degrees, it will still be comfortable for a while afterwards

    It takes one BTU to raise the temp of one pound of water one degree Fahrenheit. A gallon of water weighs 8.34 pounds.




    What climate are you in? What season are you heating it in? How big is the pool? What is the cost of the fuels available? What is your time worth stoking the boiler with wood every day or so?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 2,021
    Really the storage of the Garn only helps if the pool has a small heatloss. As has been said, the pool itself is a giant energy store. Unless you are using the Garn for structure heating as well, I'd be more inclined to use a low mass gasification wood boiler. 

    A boiler with build in storage heating a pool, is like using a battery to charge another battery. Charge the battery (pool) with the charger directly. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    ZmanGroundUp
  • edaddyedaddy Member Posts: 4
    I'm planning on using hydronic around pool,and in pool house . I've never had boiler I'm a forced air guy I have the large charmaster but it really is not for this application.i was hoping the garn storage would last while Im at work and can't feed it
  • ZmanZman Member Posts: 5,948
    The mass of the garn will carry you over while at your day job (stoking the garn will be the night job).
    On the flip side, the pool has far more storage buffer than the garn. If you simply let it overshoot it target temp by a few degrees, you will accomplish the same thing.
    I would strongly suggest that you compare the cost of the different fuels available. In many cases, folks install wood burners which are more expensive to purchase and take a tremendous amount of time to feed, only to realize that they could be using another fuel, saving time and money.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • edaddyedaddy Member Posts: 4
    I'm gathering a growing overall opinion is not wood fired heat for large in ground pool. Maybe I'm crazy to stoke the fire vs subsidizing the co.op propane companies.my brother in-law bought a 60k Pontoon and won't fire his pool heater to expensive.i live 20 minutes from lake michigan which is to cold to enjoy all year except to put your toes in .while not getting payed for my time ,saw and all the other costs of wood  it's better than a parade of propane trucks . anyone have a better idea?
    SuperTech
  • ZmanZman Member Posts: 5,948
    This spreadsheet will help you compare costs.
    You might also look at some of the pool specific solar collectors. Not to expensive and put out a great deal of heat. An Air to water heat pump is a common solution as well.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 2,021
    The problem is that a wood gasification boiler is typically (my own personal measurement) 80% efficient. Put that in the calculator. A Garn is a true gasification boiler, and must use good dry wood. Its really a rocket stove, and is akin to a water jacketed Russian fireplace.    Excellent simple robust, just an open system which I'm not a fan of. 

    In my neck of the woods I can buy propane for $1.50/gal. It still costs me twice as much to burn propane than I can burn buy wood. 

    I use a gasification boiler heating storage and a radiant slab. I burn propane in a fire tube mod/con boiler. Pretty much the ideal system for either fuel. Domestic water is heated via 120gallon indirect. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • Jamie HallJamie Hall Member Posts: 13,202
    Just keep in mind that firing a wood boiler -- like firing a wood stove -- can be very satisfying. If you are into the idea. It is also a fair amount of work, not just firing the beast, but stacking the wood (even if you don't cut it yourself) and splitting it (if it doesn't come split). Cost of fuel varies widely -- if you have access to a wood lot and know exactly what you are doing, it's really cheap. 8 or 12 foot firewood delivered is also usually pretty cheap -- but you have to cut it up. Cut to the proper length and split and delivered... now you're into some money.

    Also remember: wood heat is for the young and vigorous... I really enjoyed it myself. 50 years ago...
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
    Solid_Fuel_Man
  • HVACNUTHVACNUT Member Posts: 3,483
    Use the money you save from propane and use it to hire someone to feed the boiler. Seems like all that work would get old real fast. Pools are supposed to be relaxing. 
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 2,021
    Wood is relaxing. 

    Hearing the fuel truck back in the driveway is what raises my blood pressure.....
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    HVACNUTethicalpaul
  • GroundUpGroundUp Member Posts: 1,023
    The Garn is kind of a "need to have basis" item. Wood fired boilers are extremely common in my area and I've been working on them for 15 years but running one my whole life. 99% of applications, there are better wood fired options than the Garn. Remember the Garn needs an insulated shelter and is quite particular with what you feed it. The storage capacity is almost never correct for the heat load so you'll find yourself either overfiring or underfiring it the majority of the time. It was awesome technology 40 years ago but the Garn is little more than a dinosaur now IMO. I'd look into lower mass outdoor units if you're set on burning wood. I heat 6000 sq ft plus DHW in Minnesota with an outdoor unit that only holds 180 gallons of water and I can easily leave for 24 hours at -30F outdoor temps and still have 180 degree water and wood leftover when I get home. With that said, I just bought propane for $.99 yesterday. Despite heating this much area and having 40 acres of oak in my back yard, burning wood realistically only saves me $500 a year in exchange for 100+ hours of manual labor. Sure, it's time I'd probably be laying around anyway, but if one had the option to put those same 100 hours into something like going to work (or even selling the wood), you'd be money ahead indefinitely by buying gas. If I'd penciled it out before dropping this kind of money on my wood boiler system, I never would have done it. Personally I have the option to work infinite hours and those 100 hours a year I spend fooling with that stupid thing would pay for 10 years worth of propane, I'm a self proclaimed idiot.
    Solid_Fuel_Man
  • hot_rodhot_rod Member Posts: 13,737
    Been heating with wood for close to 30 years now, either a wood stove in the living room or a wood fired boiler. At one point I had two boilers and one parlor stove to feed. Much of the lore is gathering splitting and handling the wood, especially if you cut on a crisp fall day
    Looking back at the time and money, it maybe only penciled out on that winter of $3.00 propane prices.
    Dry wood makes a huge difference, a must with gasification type boilers, cut split and stack a year ahead.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 2,021
    I had back surgery 3 years ago.....not a recommended way to take 3 months off......

    Anyhow, that was the first years I didnt heat with wood. With condensing propane boiler and direct piping to a radiant slab, oversized indirect, all low temp. 

    With propane at $1.35/gallon, and figuring wood at $200/cord. It cost me a minimum of $400 more to heat with propane. Reality is, I have less than $100/cord even with all my equipment. 

    I figure I've saved close to $20,000 in real money since I decided to heat with 100% wood. 

    BTW, back surgery was due to cleaning up leaves in the yard. ... should a made those trees firewood!
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
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