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Thread: Homemade wood boiler?

  1. #1
    Moderator LuJon's Avatar
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    Default Homemade wood boiler?

    I am curious if anyone has built their own wood fired boiler. I don't have any plans to do wood fired heating for my home but I would love to have on to heat my driveway if it could be done reasonably. I am thinking a poured concrete pad with pex tube laid in it to form zones. Obviously the goal would be be able to start a fire rather than do a bunch of shoveling!
    I don't think that a chamber in chamber would be very feasible to fabricate cheaply, I am thinking about a separate fire chamber and water box. The water chamber would be a semi-sealed system with some kind of anti-freeze in it. A circulation pump would be connected to thermostat that would kick it on when the water in the tank hit a preset temp.

    These are just very rough ideas so I would love to see what others have built or hear other ideas!!

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    Member Magnum Man's Avatar
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    Exclamation Be carefull

    Heated contained water even at lower temps below 212 or boiling can still create steam and pressure. Especially if the system has the ability to trap air Dont blow yourself up. I would look into A manufactured certified product for heating your water. Ive been in the hydronic heating buisness for 14 years so I had to give you safety check on this one. Most residential Hydronic systems run at 12 to 20 psi. If your heating device gets out of control for some reason a fellow could end up with a stteam engine. Thats all worst case but just make sure you know what you are doing.

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    I'd like to replicate the boiler unit on one of those Chofu heaters. I have a spare wood stove sitting out in the yard that could be put to use heating a hot-tub if I could figure a simple design.

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    Default I have been working on ideas like that my self

    I had been planing on using an old hot water heater and setting up a by pass before and after the w/h tank. then having a damper control thermistatically controled, by a bi metal spring ,used on auto motive exhaust dampers, or something capable. I have themometers that mount in the tank as well as pressure gauges and switches.
    Safety valves are a must and port them out side.Or in retrospect routed safely with an expansion chamber, to the fire box. This was for water, If I were doing the drive way and house I would use a heat exchanger for the anti freeze ,and route it to the roof for the solar water heater. then with a small circulating pumps in both systems. I already use photovoltic solar power and batteries and run most things on 12 volts,or inverters if I have to. I do this stuff because I can , not because I have to.
    It will always cost something to do the extraordenary, and it helps to plan well beyond what one can initially afoard, but in time, if not forgotten, the whole picture can be realized. Much like putting the tubing in your drive ,before you have the whole system.
    When I lived in snow country We didn't shovel the dirt drive , we packed it down, it was less messy an a lot less slippery. We had no enclines to deal with, so it was easy enough to break down the plow berm and in and out. the only exception was 6' snow fall, then you have to do some serious shoveling , and no one expects you to get to work that day.

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    Moderator Paul H's Avatar
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    I wouldn't want to use water as the fluid running through the driveway tubes. There is bound to be a time the system is allowed to go cold for too long, with too low temps, and the water freezes in your pex tubes. There should be just enough expansion to destroy your driveway.

    I'm also thinking you pay neighborhood kids for quite a few years to shovel the driveway for well under installation costs. Or, you could get a snowblower for much less as well.

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    Member AKDoug's Avatar
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    Price out the glycol required for your system and get back to me It's horribly expensive. You are going to need a pump to move the water and at that point you might as well go with a closed loop system for the driveway with a heat exchanger going to an open system with the wood burner.
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    Moderator LuJon's Avatar
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    Quote Originally Posted by AKDoug View Post
    Price out the glycol required for your system and get back to me It's horribly expensive. You are going to need a pump to move the water and at that point you might as well go with a closed loop system for the driveway with a heat exchanger going to an open system with the wood burner.
    Interesting thought, that would cut back on the amount of fluid in the system! I was thinking about building a permanet concrete base/oven with a barrel over it all plumbed up to the pump and a blow off valve at the top. The heat exchanger idea is a good one, I wonder how you could set it up so it didn't get all crusted over from the smoke but still had good heat transfer...

    On a side note I do have a wheeler and plow that we use (mostly my wife) but it still leaves ice on the ground which is sloped so it makes for an interesting adventure trying to get to the car sometimes

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    Member AKDoug's Avatar
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    You would water jacket the wood side of things. Pump the water through a liquid to liquid heat exchanger with the glycol mix/pump on the other side.
    Bunny Boots and Bearcats: Utility Sled Mayhem

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    Default In theory

    moving salt water does not freeze, am I right ?

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    Moderator Paul H's Avatar
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    Quote Originally Posted by Arleigh View Post
    moving salt water does not freeze, am I right ?
    Wrong.

    When it's cold enough, salt water freezes. I've walked on the Beafort sea.

    At ~ -50 you can through a cup of water in the air, and it'll never hit the ground as it'll flash into ice crystals.

  11. #11

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    Other things to think about:

    Insulation underneath: The amount of heat required to melt the snow will go WAY down if you put some insulation underneath your tubes. If you can do the numbers, you'll learn that you almost can't afford to put tubes in without insulation. heating the ground underneath the driveway is a giant suckfest. I don't know how that would work given the strength required, but there you go.

    Small area: The smaller the area you melt, the less energy (wood) you'll need to melt it. Also the less tubing, glycol, pumping, etc. For instance, you might want to melt just areas for your cars and a narrow area to drive into the driveway vs. the whole thing.

    Timer vs. thermostat: if you were to hook the system up to a boiler at some point its very nice to have a snow melt system on a timer instead of a thermostat. When the snow starts to fly, crank the timer on for thirty minutes to warm up the surface and watch it melt off. You can also have the timer go on and off throughout a day forecast for snow.

    Check with a professional (It ALWAYS pays to check with a professional on these things), but you may need a closed loop glycol system with expansion tank, heat exchanger and pump. The heat exchanger will get its heat either from the air above/around the wood stove (http://www.houseneeds.com/shop/Heati...oilersmain.asp) which may be very inefficient at transferring heat from wood stove to the glycol, or water heated by the wood stove (http://www.builditsolar.com/Experime...ruction.htm#HX) from the coolest web site on solar heating.

    Hopefully you could position a large tank high enough so you wouldn't need a pressurized system and allow the wood stove to heat a big batch of glycol solution and just pump out of the tank, through the coils in your driveway and back into your tank. However, I have no idea if you can do that with glycol/water mix solution.

    I put some pex coils underneath my walkway from garage to house. The pex is cheap, relatively speaking, and even if you screw up the first time the pex is still there, waiting patiently for an improved system. i had a crew prep the surface and lay down the fabric (wire mesh). I surpentined the pex with zip ties, piece of cake, then they came back and poured over it.

    Do this and your wife will be happy, your neighbors will envy you and you can sell your house quicker! When I pour my driveway in 2050 or so, I'll be putting pex where the cars/truck are parked, insulation underneath.

  12. #12

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    I'd use a Hilkoil in the woodstove, if it were me. http://www.hilkoil.com/

    I would also have a mechanical engineer (or at least a good plumber) with experience with heating open slabs review my design before actually building it.

    Let us know if you go for it, sounds interesting. I have been thinking about using a hilkoil in the woodstove in my house and plumbing it out to a fan-coil unit in my shop, but my insurance company doesn't think it's as cool of an idea as I do.

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    A friend of mine built a woodstove with a water jacket to heat the floor of his shop. The jacket holds enough liquid that it wont boil or turn to steam without a serious amount of effort. He used RV antifreeze in the tubes. He also has a large tank on the second level, I think it works in place of a pressure tank.

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