Outdoor wood boilers have become a popular option in the cold country for heating the home.
The advantage is that you keep all the smoke, mess, and fire danger outside and away from the house.
The down side is the cost. A factory made one costs several thousand dollars. We burn wood to save money, thus the spending of several thousand doesn't support that goal.
I will show you how I built mine for almost no cost.

I ran the first one of these all last winter with no problems at all. I didnt buy a single whiff of gas for the whole winter. now I am making this one for a friend

Step 1: The Fire Box

we start with the construction of the fire box. I aquired from a dumpster a large water heater that I am using for my firebox. about 20" to  24" diameter is good. I've found the round firebox works great because the flames play all around the top for good heat transfer.
* First we start with removing the outer cover, insulation, burner assembly from the water heater. all thats left now is the tank.
*Next, I cut out the flue running up the center, and all the pipe fittings, and welded patches over the holes.
* Then, I reused the flue from the center and welded it to the outside of the tank. I welded a plate on the end for pressure testing.
* Now we have to pressure test the tank for leaks. For this, I welded a small pipe fitting in a convenient spot and installed an air valve. this is like a tire valve stem with pipe theads on it. they are used in campers to pressurize the water tank. we only need about 5 psi. with the tank pressurized, I used a thick solution of dishsoap and water in a spray bottle to find the leaks.
<p>OK oil tank found $100, old cast iron radiator had for $50, and massive fan for $25.. time to design the firebox..</p>
Is the firebox still holding up? How many Winter before you think it will burn through?
<p>Yes, the firebox is still holding just fine. I see no indication of trouble, so I guess it will last for a long time yet. </p>
thank you I have wanted to build one forever nows the time
Great! Show us how it turns out.
<p>What about using a 100lb propane cylinder instead of the water heater ?</p>
<p>Any tank will work as long as it is big enough. I think the 100# propane tank might be a bit small in diameter. </p>
Heatmaster SS http://heatmasterss.com also has a how it's made video on their website.
<p>I am about to try this, over the upcoming weeks. so we will see how it goes, i will add pictures as i go </p>
I have to commend the creator of this junk boiler. I just finished building one pretty close to his designs. And it WORKS GREAT!!! thanks again for the idea / post. I had less than $350.00 in the project.
Will this design work with anthracite coal? Besides wood, cheapest fuel in my area
<p>I just don't know. I've never burned coal, and have never seen a stove designed for coal. </p>
i made it and it works great when it works. Dont get me wrong, i no its me somewhere? it keeps getting air locked. I have 180 degree at stove but cold water at duct coil.. ive purged it, put a auto air vent at coil.. ive tried to pressurize it, all with the same results.. Im at my last straw not to mention with the better half also,,shes bout to explode unlike any boiler explosion ever.. lol I need your help please! any advice will be greatly honored. ill answer any questions you may have to the best of my ability... thanks Jeff
<p>Ok, Jeff this is how I work with that. I don't use an auto vent. When I hooked it up initially I fixed it so I could shut a valve and open another to feed water under pressure directly from the garden hose through the coil and then into the tank. </p><p>What I do now is just unhook the coil, and lay it down flat with the hoses still connected, the kick on the circulator pump and it flows the air right on out quick and easy. Hope this helps. </p>
<p>I'm considering modifying this plan to burn wood gas from a DIY gasifier instead of just plain old wood. I'll be sure to post the results of my project after it gets underway.</p>
<p>I'll look forward to seeing your project. </p>
how big is the building your heating, mine is over 2200 sq ft. <br><br>what size pex did you use<br>what size is your heat exchanger<br>how far is the boiler from your house<br>how deep was your trench<br>how big a fuel tank did you use?
<p>I'm heating a little less than 1000 square feet. My friend is heating much more, something like3000 sf I think. Obviously he burns a lot more wood than I do Mine idles most of the time.</p><p> We both used 3/4 &quot; pex. </p><p>My heat exchanger is 18&quot; x 20&quot; three layer.</p><p>My boiler is about 30' from the house, my friends is 75' </p><p>trench is 42&quot; deep as that is the frost level here. </p><p>the outer tank is a standard 275 gallon (US) fuel oil tank. </p>
You should definitely post some recent pics of it now after its all insulated and finished!
Very smart man!...I'm about to start my project...with a custom built firebox. Can't seem to find a water heater any bigger than 16 inches in diameter. I will try to keep pics posted. Thank you again you've been such a big help!
Thank you so much man! Is it still running strong?...if you could make any mods to it what would they be?
<p>Yes, still going strong. I had to patch a leak this year, but otherwise no problems. </p><p>At some point I added an automatic filler for the water. Just a simple float switch connected to a solenoid valve from a dishwasher. </p><p>I really wouldn't change anything. it works great just as is. </p>
What size pump and brand did you use?
<p>I used a TACO model 007 1/25 hp circulator pump</p><p><a href="http://www.supplyhouse.com/Taco-007-F5-007-Cast-Iron-Circulator-1-25-HP-1983000-p" rel="nofollow">http://www.supplyhouse.com/Taco-007-F5-007-Cast-Iron-Circulator-1-25-HP-1983000-p</a></p>
What aquastat are you using ?
Ok thanks!!!
<p>this one would be a good choice</p><p><a href="http://www.supplyhouse.com/Honeywell-L6006A1012-High-or-Low-Limit-Circulator-Aquastat-100-240F-range-5-30F-Adj-Differential-10466000-p" rel="nofollow">http://www.supplyhouse.com/Honeywell-L6006A1012-High-or-Low-Limit-Circulator-Aquastat-100-240F-range-5-30F-Adj-Differential-10466000-p</a></p>
What size hot water heater did you use
<p>It was either 80 or 100 gallon water heater. One that large is hard to find normally, but any tank will do this is about that size. </p>
<p>Thank you for this plan. I made this and so far it works great. One thing about the air tight welding, it can be a pain.Do your best to make it air tight by welding but in the end dont worry about the pin holes. I kept chasing pin holes time after time, I would fix one and another would pop up. I got tired of this and thought of giving up.I did some research and found some boiler sealer, I think it is made by Gunk. The sealer sealed everything up in no time with no leaks. Welding air tight is better Im sure but dont give up if you have pin holes you cant get there is relief. Thanks again for the plan.</p>
<p>Thanks for the suggestion, backcreek. I'm a fairly experienced welder, but I still had to chase a few leaks. It's a drag. </p>
<p>Yeah I figured you were experienced. I was just puttin that out there for others who might find it overwhelming. Thanks again.</p>
Nice build. Wondering if the damper closes off completely or allows some combustion air through?
<p>the damper pretty much closes completely, but being hand made it leaks a little. probably the door seal leaks a little too. It would be easy to add an adjustable stop screw if you found it necessary. </p>
that makes sense. thanks<br>
<p>Hi I have been doing alot of research on wood furnaces approx how many cords of wood would your design use on an average winter , looks great and shows good hoping to hear from you </p><p>carey </p>
<p>Of course it depends on the winter, and how much house you are heating, how well insulated etc. I think last winter I used about 5 cords. It was a long cold winter and my place is not especially well insulated. </p>
<p>Dude this is awesome, you think if I tackle some like this and get stuck in the process I could possibly get some assistance from you either by e-mail or phone I have been wanting one of these but are extremely expensive, and thank's for posting this bright design</p>
Yes, I'm always happy to help. the hardest part of this project was welding everything water tight. If you can do that, the rest is easy.
<p>re: torch + fuel oil tank. </p><p>I've heard of a couple cases of oil tanks (used motor oil?) blowing up when they were welded on. Perhaps there was a wee bit o' gasoline in the oil? Anywho, when i've cut steel barrels, I've filled em with h2o first. Inert gas is another option. Nitrogen, co2, etc. A hunk o' dry ice would work. Let it turn into gas.</p>
<p>That's always worth caution. I knew that these tanks contained only fuel oil since I personally removed them from the basement and drain the fuel oil out of them. </p><p>With all the plugs removed and knowing that the fuel oil is slow burning I felt safe in just letting it burn out. </p><p>You of course should use your own best judgement to secure your own safety.</p>
<p>Love this post! Have welding skills and a $750, bill for 200 gallons of propane as motivation to start this project. Was wondering if you only support the firebox by welding it to your fuel tank on the end that sticks out? Was also wondering if you'd be willing to give me some email support if i needed it?</p>
<p>Yes, the only support for the fire box is around the front where it's welded in, and the smoke pipe in the rear also supports it. It might be a good idea to add legs under the back end of it, but I couldn't figure an easy way to put them on with no access. </p><p>I'm not any expert on this, but would be happy to help you with my experiences. </p><p>e mail <a href="mailto:the.inventor64@yahoo.com" rel="nofollow">the.inventor64@yahoo.com</a></p>
<p>outstanding! How has it done this winter? Do you get 12 hours out of a load of wood in the box? searching around for &quot;junk&quot; to build mine!</p><p>Just sent you an email to touch base</p>
Wow, what a great job, congratulations.
And thank for the captions in video!
Love it, plan on doing my own similar project someday, have a seen a few similar projects on youtube, you should do a quick video presentation and throw it up there, yours looks a lot nicer than most of them on youtube, seems to better utilize the existing heating cooling system parts!
Ok, so I've made a couple video slide shows. Hope they are ok.
Thanks, I just might do the video. I haven't posted anything to youtube yet, but was thinking about trying it out. I have to give a lot of credit to my neighbor who built one a few years before i did. I utilized a lot of his experience to make mine better.
Always gotta give credit to our predecessors! When I make mine I will utilize concepts from all those who made them before me, gotta love the internet allowing us to share all the knowledge!

About This Instructable




Bio: I'm just an all around tinkerer inventor. I work with just about any type of material.
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