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Large Wood burning boiler- which and where to buy, new or ised

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panga
panga Member Posts: 11
I have a hydronic heating system installed on a large greenhouse bank I currently heat with propane. 1.2m btu. 

Would like to install a wood fired boiler, while leaving propane as backup of fire can’t keep up or goes out. 

Any advice on what unit to use and where to source? Economy down, not flush with cash so can’t spend a fortune, but spending a ton on propane and seems like this would pay for it self quickly. Have 60 acres of trees to burn. 

Any advice would be appreciated. 


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  • hot_rod
    hot_rod Member Posts: 22,129
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    A 1.2 million wood boiler would be quite large, any maybe tough to find used. Is that the correct heat load number?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • panga
    panga Member Posts: 11
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    50k sq ft greenhouse bank, we are running 6 200k btu boilers currently to heat it. 

    Wood source could be supplemented by propane on cold nights. So I’m thinking even if wood heat source rating was significantly lower it would be beneficial at cutting that propane bill. 
  • panga
    panga Member Posts: 11
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    PS I need this to be an outdoor unit, feeding in larger chunks of wood would be great, ideally w tractor, but can feed by hand if needed. 

    Any ideas of where to look? 
  • Jamie Hall
    Jamie Hall Member Posts: 23,280
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    Not really. But before you get too far into this, two considerations. First, check your local and state air pollution codes. Some localities are getting rather restrictive on large wood burning boilers and the like. Second, be aware that wood on that scale isn't free, even if you have 60 acres of trees to burn. That acreage, carefully managed, will give you 20 to 60 cords of firewood per year -- no more than that. Taking the low number, that's somewhere around 600 million BTU per year or the equivalent of about 6,000 gallons of propane. That would be enough for that size boiler for about 500 hours of operation. Then, of course, you have to cut the wood, saw it to length, and split it. Probably have to pay someone to do that...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • panga
    panga Member Posts: 11
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    Thanks for the info. We have pretty dense fir and tan oak forests that need to be thinned for fire danger so I see some benefit there. We needed up with 10 cords of blow down last year alone in a winter storm, so eventually you would be correct we will get to that point, but for 5-10 years we are swimming in it. And we have a mini excavator that makes pretty quick work of log processing. But I will look into it along w code. 

    Let me know if anyone has any advice on which boiler, even if only 6-750k btu I think it would be a big help. 

    Thanks 
  • panga
    panga Member Posts: 11
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  • hot_rod
    hot_rod Member Posts: 22,129
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    There are some online wood burner groups Try the “boiler room” at The Hearth. Get in the loop that you are shopping. I’ve seen them on Craigslist also. Ebay?

    Www.hearth.com

    Most all the wood burners sold now have EPA listings, but check to be sure.

    How close are the downwind neighbors🤔
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • panga
    panga Member Posts: 11
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    Thanks I’ll look around see what I can dig up. 
  • leonz
    leonz Member Posts: 1,127
    edited December 2022
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    panga said:

    I have a hydronic heating system installed on a large greenhouse bank I currently heat with propane. 1.2m btu. 


    Would like to install a wood fired boiler, while leaving propane as backup of fire can’t keep up or goes out. 

    Any advice on what unit to use and where to source? Economy down, not flush with cash so can’t spend a fortune, but spending a ton on propane and seems like this would pay for it self quickly. Have 60 acres of trees to burn. 

    Any advice would be appreciated. 


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    Do not waste your money on this or any other outdoor or indoor wood boiler as the opportunity cost is greater than any possible reward.

    You will spend a small fortune installing an outdoor wood boiler like the model you are interested in.

    The way these things are designed is extremely poor as they do not have enough water storage to batch burn wood fuel AND the fire box designs do no one any favors as they are not designed to burn firewood intensely to burn all the smoke.

    You will lose a great deal of heat at idle in the process with the waste smoke going up the stack when the fire is satisfied and the combustion blower is shut down.

    Is there any reason you cannot consider using a coal stoker boiler for the primary heat source?

    You can purchase an outdoor coal stoker boiler from Alternate Heating Systems that can be loaded
    with a farm tractor front end loader and the ash can be shoveled in the bucket from the ash hopper
    that is tilted out to clean it.

    The AHS outdoor and indoor stoker boiler can burn the western coal from the Montana coal fields at a very low cost per ton.

    I would not even consider the GARN 3,000 gallon wood boiler as an option as they require 15% moisture hardwood for fuel and you would be loading it 8-12 times per day.

    For the money invested you would be able to:

    1. invest in a large hoop shed and buy 2 smaller AHS coal gun coal stoker boilers
    2. store large quantities of eastern anthracite pea coal or Montana sub bituminous stoker coal in a dry area undercover on a concrete slab
    3. have a boiler that would be protected from the weather which will make taking care of the stoker and the ash easier to do
    4. you would be able to use surplus bulk milk tanks to store a huge volume of hot water to heat all your green houses with little heat loss
    5. a propane fueled generator wired to sense power loss is all that would be required to protect against power loss protection to power the coal stoker and circulator(s) and the green houses.

    The stoker coal from the surface strip mines in Montana is less expensive than the eastern anthracite coal and can be burned in the AHS coal gun coal stoker boilers.

    The S260 outdoor coal gun is small for your needs but having water storage negates that as the water in a large surplus bulk milk tank is thermal mass/money in the bank.

    You would want to have the belt driven induced combustion fan design for the unit as the electric motor
    will last longer as it rotates at a slower speed to spin the induced draft combustion fan.

    The AHS 1000 coal gun is a possible choice but one of the smaller coal guns like the S 130 or S250, a hoop shed on a concrete slab to store coal and dead ash and a surplus bulk milk tank will be just as cost effective as you want and need to create greater thermal mass per gallon that will have a great deal of residual heat returning to the boiler and surplus bulk milk tank.

    The greater amount of thermal mass you have the easier it is to heat anything.

    You could use an S130 coal gun coal stoker with an indirect drive induced combustion system as an open system with the surplus bulk milk tank or tanks and employ 2 circulators one for the stoker to push water to the surplus bulk milk tank and the second one to push the hot water to the green houses using a plate heat exchanger to keep a greater amount of hot water in the bulk milk tank at all times and allowing the stoker to make 180 degree water around the clock.

    The S130 stoker would require a bit more tending and annual cleaning and uses a 5 inch chimney flue but the hot water output would be greater per pound of coal used than with wood using the Sub Bituminous Coal from Montana.
    gmcinnes
  • leonz
    leonz Member Posts: 1,127
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    I hope we hear from this fellow .
    gmcinnes