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Thread: Homemade Wood Fired Boiler

  1. #1
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    Homemade Wood Fired Boiler

    I see there is a lot of people wondering how to make their own wood fired pool heater. I live in MA and it can be frustrating playing "superman" jumping into a pool that's less than 75 degrees Fahrenheit. I did it at 50 deg.F! I am an HVAC technician and I will teach you how I am making my "Old #2" vertical water tube boiler.
    Started with a 55gallon metal drum...
    First thing I welded a door on the middle. You can just cut a hole near the bottom too. Next I made a nice cut for the chimney and screwed in some chicken wire over the hole, ever see leaves fly way up in the air on fire? I will be burning lots of brush so this will help. Next I installed 60' of soft copper tubing coiled around the inside wall of the drum at the top. I was planing on giving it legs and weld a solid grate on the bottom but for now it will sit on a grate on a few cinder blocks. This will allow the air to feed it from underneath and easily remove the ash. I still have to make the stack but I will return for pictures of the process and results of the performance. I have read a lot about copper staining the pool but I have an above ground and I am not worried about it. Copper does kill green algae! No more buying algacide!! I will let you know how bad if any the water does get.

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    Re: Homemade Wood Fired Boiler

    Welcome to the forum. YOu may get SOME assist heating your pool with a 55 gallon drum but it won't be much.

    1. The BTU's required to heat the pool are unbelievably high...probably far in excess of what you can exchange with your copper coil

    2. Any small amount you do gain will be lost overnight unless you install a solar cover.

    3. The btu's in leaves and small sticks will never make a dent in your pool temp.

    4. There may not be enough really good firewood in Massachusetts to heat that pool to 80+ when it's 50 outside. My bet is you would burn somewhere around 1/3 cord within 24 hours if you want to make any difference at all. That'll be one heck of a hot fire.

    5. If you do get the fire that hot, you will quickly burn through the thin steel that barrel is made from and it will rust out and you will have to start over.

    6. pH at the correct level will not release copper in the pool so no algicidal effect. If you do get pH low enough where the water is agressive and strips copper from your exchanger, you will have blonds hair turning green and they wont be happy. If you let it continue, the copper may precipitate out onto the pool and equipment and be almost impossible to remove. Copper in pools is simply never a good idea.

    I see there is a lot of people wondering how to make their own wood fired pool heater.
    Not too many. The huge volume of wood required is simply overwhelming....even with a proper system.

    ever see leaves fly way up in the air on fire?
    I did when I was about 12 years old. The fire department was at our house about 10 minutes later.
    Dave S.
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  3. #3
    Senior Member harleysilo's Avatar
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    Re: Homemade Wood Fired Boiler

    Yeah I lpoked at the professional versions of what you Are making, they don't actually generate that much heat, not to mention you would need an unlimited supply of free firewood to make it cheaper than the alternatives. Still interested in watching your project progress cause I thought about doing the same thing.
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    Re: Homemade Wood Fired Boiler

    I live in central MA. Theres not enough wood in all of Worcester county to make dent in trying to keep heat in a pool. Save your energy for something else.

    Seriously, a wood fired boiler wont heat a pool. It takes over 1.5 million btu to heat 15000 gallons 10 degrees. And that's not even counting heat loss as your heating. I don't know how much wood it would take to generate that, but like Dave said, that barrel would melt into a little ball before you got there.
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    Senior Member harleysilo's Avatar
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    Re: Homemade Wood Fired Boiler

    I don't know about destroying the drum with a fire, my dad has a double drum version in his shop for going on 10 years, it's easily 700-800 degrees throughout winter...I should ask him for an accurate temp reading.

    In addition to that we've had a burn barrel with hatchet cuts to the side for years, get the bottom area red hot and don't see any deterioration....
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    Senior Member Lershac's Avatar
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    Re: Homemade Wood Fired Boiler

    Here is a BTU per cord of firewood chart

    You would need cords and cords of wood to effectively heat a pool for any meaningful period of time.

    If heating your house were a match...

    Heating your pool would be a couple of blowtorches.
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    Senior Member Lershac's Avatar
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    Re: Homemade Wood Fired Boiler

    For example I have a 40000 btu heater for the house. My pool heater is 400000 (10x).
    (DIY):16K Gal 20X30 rectangular IG Gunite, w/spa, CCP 520 filter,2 Pentair VS pumps, 400KBTU Pentair gas heater, Heat Pump for cooling, **update5.25.2013** added an intellichem with acid pump that will control existing SWG. My Build Thread Here

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    Re: Homemade Wood Fired Boiler

    First off I have a lot of softwood I usually burn in a 10' bonfire anyway. If I can add anything to the pool I am happy. People on Craigslist are always trying to get rid of it for free. Besides a campfire it's worthless. I know it's not going to produce as hot a flame as hardwood but nobody is going to come take the 9 trees that fell in my yard last October. My pool only gets about 2 hours of sun on a good day. The pool is surrounded by woods. In the hot summer days I am happy if it ever gets to 70-75. So if I can gain 5 degrees I am happy. I plan on burning everyday. As I said, I have to burn a large amount of wood and brush every year. 2.5 acres here having almost 1 acre of woods. Might as well utilize it in the pool.

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    Re: Homemade Wood Fired Boiler

    I think you guys are missing the point. I am not trying to go swimming in the middle of march. There are many of us up north that would like some increase in temperature durring our summers whom have more softwood and brush then they know what to do with. My pool gets sun 2 hours out of a day. I see the pool at 75 only if we had a few hot and humid days towards the end of the summer.

  10. #10
    Senior Member Lershac's Avatar
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    Re: Homemade Wood Fired Boiler

    Do what you want, and more power to ya. I have done stuff because I had the idea and others advised me against it for good reason... and it took me doing it and figuring out on my own, that there was a reason they had advised me negatively.

    I really just think it will be an inefficient way to heat your pool, and quite frankly you will tire quickly of feeding it wood. Think about how long it takes to burn a cord of wood. You heater may be 50% efficient, and lets be generous and say your wood/burn material has 18M BTU/cord. so thats 9 million BTU per cord at 50% eff right? In a barrel, lets say you can burn a cord of wood in a week, continuously feeding it wood/stuff. Rounding up thats 60,000 BTU per hour. Thats going to give you for a 10,000 gal pool... a 0.8 degree rise an hour. Now knock off losses due to wind, evaporation, etc... Man you might get half a degree an hour.

    As if that was not enough. To get the flow rates you need you are going to need 1" copper tubing. Have you priced that stuff?

    Good thought, but in my book the numbers just dont pan out. Good luck with your experiment, I sincerely hope I am wrong and you come back and tell me so. Just trying to save you some pain, but it may be fun to make!
    (DIY):16K Gal 20X30 rectangular IG Gunite, w/spa, CCP 520 filter,2 Pentair VS pumps, 400KBTU Pentair gas heater, Heat Pump for cooling, **update5.25.2013** added an intellichem with acid pump that will control existing SWG. My Build Thread Here

  11. #11
    Senior Member Lershac's Avatar
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    Re: Homemade Wood Fired Boiler

    And no lie man, I am a guy who has run a gallon of water from his instant hot water tap (190 deg) and went and dumped it in the hot tub "because I wanted it to heat up faster!" knowing how futile that was, but doing it anyway while my wife and kids laughed at me.
    (DIY):16K Gal 20X30 rectangular IG Gunite, w/spa, CCP 520 filter,2 Pentair VS pumps, 400KBTU Pentair gas heater, Heat Pump for cooling, **update5.25.2013** added an intellichem with acid pump that will control existing SWG. My Build Thread Here

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    Re: Homemade Wood Fired Boiler

    This is a very fun project for me. If I wanted efficiency I would have built it with old steam coils stacked up. I get lots of old stuff free from time to time in my field. I can easily pipe in a oil boiler if btu's were such a concern. I built it using scrap materials besides the copper. I alway have plenty of free wood. I am not talking raking a few branches up in a yard . When I burn every year it's an all day project 10' wide stacked continually on 12-14 different days. Whole trees. Fuel is free, the whole project is less then $100, gives me a way out of massive burning days for nothing but smelling like bonfire, best way getting out of a pool at night is by a fire, cooking marshmallows with the door open, looks cool when people come over, will help keep the bugs away, and overall is just so much fun to make!!

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    Re: Homemade Wood Fired Boiler

    I heat my pool and spa with a Central Boiler Outdoor wood burning furnace. It took some time to get it working properly but I heat my house all winter and hot water and then use it to heat my pool. Have no problem getting the pool to 80+ degrees.
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    Re: Homemade Wood Fired Boiler

    blakeusa,

    How much wood do you burn to do that? Is your pool covered? Do you keep it at 80? How many btu's is your woodstove?
    Dave S.
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    Re: Homemade Wood Fired Boiler

    I think that it is a cool idea! Fun and creative. Do not forget that you can get free pallet scraps that work great for something like this.
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    Re: Homemade Wood Fired Boiler

    A single 60ft copper pipe running like a garden hose will NOT collect and transport enough hot water to make any difference. I would make several coils , or better yet get used car radiators and stack them , then make a manifold and feed each rad with its own supply off pool pump , connecting all discharges back into a return line to pool. This will allow for great flow and absorption of heat produced.

    If you cant get a boat load of water to run through the drum , dont waste the effort.

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