# My homemade outdoor wood furnace (boiler)



## lapeer20m (Oct 13, 2013)

The old thread disappeared. I waited a week or two hoping it would return.....oh well, i'll start over.

this site is all screwed up and will not allow me to post photos.....i assume it is because of the hack that happened not so long ago...

here is my flickr photostream, in no particular order.....

http://www.flickr.com/photos/[email protected]/

My goal was to build the entire project for under $1K, including installation. So far i'm at about $1,1K.

Bought this old propane tank that was already welded into a crazy huge woodstove.




then i took a welltrol bladder tank and cut the end off. This tank is only about 1/8" thick, while the propane tank is 3/8". I wish the blue tank was thicker, but it's still pretty stout. It was rated for 150 psi. firebox is 119 gallons. I don't know the volume of water that the outside tank holds, somewhere between 50 and 100 i would guess.


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## lapeer20m (Oct 13, 2013)

then i spent hours cutting the end off the propane tank using a five dollar garage sale circular saw and an abrasive blade.










then i welded the "firebox" to the propane tank


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## lapeer20m (Oct 13, 2013)

I used a fire extinguisher with really thick wall for the chimney. It's a co2 bottle rated for 1,200 psi

I cut the hole with a saber saw, which is way past the limit of what the saw is really rated for.


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## lapeer20m (Oct 13, 2013)

they definately won't hire me to weld on submarines anytime soon! 

View attachment 317547


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## lapeer20m (Oct 13, 2013)

first is an older photo showing the inside of the water jacket....




and a photo of a really sweet pile of insulation i scored for FREE!
View attachment 317552


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## lapeer20m (Oct 13, 2013)

had a lot of irons in the fire the past month, like gathering firewood. I'm back to working on the boiler and hope to have it working later this week. 

i estimate i am 10 hours of labor away from test firing the unit which includes installing the boiler in it's final resting place, plumbing pex lines, and the heat exchanger plus the 2 stage thermostat. 

My pex will run above ground through an 18" diameter plastic culvert that will be insulated with material at about R5.0 per inch. 

The boiler itself will be inside a shed which will also hold a face cord of firewood.


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## lapeer20m (Nov 4, 2013)

...


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## lapeer20m (Nov 4, 2013)

this page left blank...


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## lapeer20m (Nov 4, 2013)

This entire project would be easier if i had a shop, or proper metal working tools, or if i actually knew how to weld. It's easy to stick two pieces of metal together, but welding water tight is a different type of skill. I built the boiler outside in my driveway.

I didn't have any 8" pipe laying around, so i decided to cut the ends off a fire extinguisher and use it for the chimney. A CO2 extinguisher is rated for 1,200 psi and is thick wall.

I cut the hole in the blue tank with a cheap jigsaw and a lot of lubrication.


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## lapeer20m (Nov 4, 2013)

After i cut the hole, i welded a foot onto the blue tank and slid it inside the propane tank.






Then i welded the propane tank back together. It had just a couple of million leaks. A couple (days) hours of grinding and re-welding and i had 100% of the leaks fixed on the outside.


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## lapeer20m (Nov 4, 2013)

then i fashioned a "collar" to bridge the gap between the chimney and the propane tank. I made it from the piece i cut off the blue tank. The center i cut with a jig saw, the outside didn't need have as tight a tolerance so i turned up the heat and cut it with my arc welder.












then i welded the collar in place.


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## lapeer20m (Nov 4, 2013)

then i did a little art work on the door






and did my first "test fire"






then i set the boiler into it's final resting place, and covered it with a layer of R-30 insulation. 






instead of burying my pex lines, i opted to run them through an 18" diameter plastic culvert. The very best insulated underground pex is only about R-5. Mine should have an R-value of at least 40. 






For automatic draft control, i built this contraption:











I shot a quick youtube video of the draft control in operation:


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## lapeer20m (Nov 4, 2013)

The boiler has been operational since mid october and has so far been flawless. 

I did install a temperature controller with digital readout that i can see from inside the house. I have been able to go up to 26 hours between filling the firebox, but i'm sure that will change when it actually gets cold. We have been having low temperatures around freezing, with highs in the 40's and 50's. 

I still need to finish insulating the pex lines, and build a shed around the boiler. Hopefully those things will be completed this week.


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## lapeer20m (Nov 9, 2013)

I made really good progress, which is handy because we are already a week into november here in Michigan. It was unseasonably warm as i was able to work outside wearing only jeans and a t-shirt on the 5th of november. 

My pex lines were just laying inside this culvert....






so i crawled inside, using small planks i was able to suspend the pex in the center of the tube. Then i packed the culvert with insulation. The insulation is rated at least R-40, plus the armorflex, plus the plastic culvert itself.

I didn't score any photos of the insulation filled culvert....






I then spray foamed where the culvert meets the house.






Here is where it enters the skeleton of the shed.






Here is the shed mostly built....













I even insulated the gaps inside the shed.






I added more insulation to the boiler. It has a minimum of R-30 all the way around, and more like R-60 or so in some places. 

The door to my firebox is not insulated at this point.


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## lapeer20m (Nov 9, 2013)

and here is my new "log skidder"


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## griff154 (Nov 9, 2013)

I hope you bevled the weld joints. And I would 1 root pass with two stringers of 7018 or 8018. Take your time. I'm a boilermaker and a rushed weld job can spell disater.

Sent from my SCH-I405 using Tapatalk 2


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## bead1099 (Nov 12, 2013)

An ambitious endeavor!


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## H-Ranch (Nov 12, 2013)

Looks like the skidder might need it's own thread!


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## zogger (Nov 12, 2013)

lapeer20m said:


> and here is my new "log skidder"


What izzat thing^^^?? Every boy *needs* one!!!!


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## lapeer20m (Dec 3, 2013)

I just finished installing my sidearm heat exchanger for dhw. 

I'm pretty excited to see how it works.


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## ric5141 (Dec 4, 2013)

Curious what was the approximate cost of this build?


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## lapeer20m (Dec 4, 2013)

Total cost including all material, the tanks, welding rod, pex, insulation, shed, plumbing fittings, heat exchanger, aquastat, 2stage thermostat, wire, lights, etc is about:

$1,700 so far. I'm way over budget, but I simply underestimated how much the install would cost. 

I still need roofing material on the shed and a few small things here and there. But the project is mostly finished.

I estimate I have 200 hours into the project, half of which was metalwork, half was installation.

As a comparison, I spent at least $3k last year for propane.


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## bead1099 (Dec 6, 2013)

Is it throwing heat? How is it working? Very interesting and thanks for sharing!


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## Vermonster (Dec 6, 2013)

That's a pretty original design. Good on you!! Is that a cast iron skillet you're using for the damper??


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## lapeer20m (Dec 6, 2013)

Yes, that's a cast iron pan i'm using for the draft control.

The boiler appears to be working great! It makes more heat than my house can use. At least so far this winter, but we aren't into the really cold temperatures yet. It is almost flawless. I did have 3 separate events where it boiled over, each event occurred when the set point was above 180 degrees F. If i keep the set point below that there are/- no issues. I just ordered a new temperature controller that will turn on the circulator in the house when the boiler reaches 190 degrees presumably keeping the boiler from overheating by dumping the excess heat into my house.

It does a better job heating my house than the existing lpg boiler because the water temp in my cast iron radiators is lower with the owb. Last winter, when the circulator shut off and the radiators were 180-190 degrees, the temperature in the house would continue to climb sometimes 3-5 degrees. That lead to some pretty wild temperature swings.

I tend to put wood in the owb every 12 hours.  I have been able to go 26 hours on a few occasions when the weather was above freezing. I'm a fireman and work 24 hour shifts and the wife is not always available or willing to load the firebox. To get the 24+ hour burn times i have to use hardwood. I've mostly been burning pine, cedar, and poplar on days that i'm home, and save the good stuff for days i work.

Now that it is heating my dhw i'm not using any propane except for the rare occasion.

ETA: I don't think the boiler works so awesome because i'm super smart or know a lot about heating/cooling. It mostly comes down to luck, and the fact that i have a big boiler and relatively small heating demands. I consumed about 1,200 gallons of propane last year, which includes dhw. That averages out to the energy in about 1K pounds of wood per month, every month.


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## lapeer20m (Dec 15, 2013)

Update: 

The boiler has been operational for about 2 months now. We've had temps down as low as 3 degrees F. 

The system works better than I expected. As long as someone feeds it every 12 hours I don't use an once of LPG. My wife's biggest complaint is that the house is too warm. We mostly wear shorts and tee shirts these days. 

If outside temps are above freezing and I pack it full of hardwood I can go 26 hours between feedings. I mostly burn pine poplar and cedar which easily gets me 12 hours burn time. 

We also have nearly unlimited domestic hot water now. 

The only problem is that it occasionally overheats and begins to boil. it seems to happen mostly when I load it before going to work and the house is not calling for heat. I purchased but have yet to install a new temp controller which will override the Tstat and force the circulator for the house to turn on when the water temp reaches 200 degrees. This should cool the boiler by dumping the heat into the house. 

Last year we averaged $400/month in the cold months for propane. Now I'm likely using about $50/month.


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## dave_dj1 (Dec 15, 2013)

It sounds to me like you are letting air in when you don't want it. Is there anything you can do to slow the burn down? Just a thought. It's a nice feeling being independent from the oil and gas companies isn't it?


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## lapeer20m (Dec 15, 2013)

dave_dj1 said:


> It sounds to me like you are letting air in when you don't want it. Is there anything you can do to slow the burn down? Just a thought. It's a nice feeling being independent from the oil and gas companies isn't it?



Yes, I don't have a door gasket. 

If I were to rework my door so as to allow the installation of a gasket that would likely fix my overheating problem. But it's just an occasional problem and the "correct" fix is difficult because the welder and the boiler are nowhere near each other.


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## bead1099 (Dec 15, 2013)

Does it have a stove pipe / chimney damper? A damper on the output makes a big difference too.


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## H-Ranch (Dec 15, 2013)

lapeer20m said:


> Yes, I don't have a door gasket. If I were to rework my door so as to allow the installation of a gasket that would likely fix my overheating problem. But it's just an occasional problem and the "correct" fix is difficult because the welder and the boiler are nowhere near each other.


A friend of mine used high temperature silicone to fill in the "trough" where a rope gasket would normally be used and he raves about it - seals great, doesn't get hard, no need to replace every other season, etc. If you can shut it down long enough for silicone to cure that may be an option.


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## lapeer20m (Dec 18, 2013)

Apparently my super insulated above ground pex installation is working well. Water temp is about 170 degrees, outside air temp today is about 30 degrees F. No sign of snow melt.


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## Vermonster (Dec 18, 2013)

lapeer20m said:


> Apparently my super insulated above ground pex installation is working well. Water temp is about 170 degrees, outside air temp today is about 30 degrees F. No sign of snow melt.


What kind of longevity do you expect out of your fiber board structure? opcorn:


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## lapeer20m (Dec 18, 2013)

Vermonster said:


> What kind of longevity do you expect out of your fiber board structure? opcorn:



Many decades. 

In the spring i hope to put metal roofing on the shed, as well as paint the walls. 

Rome wasn't built in a day. This fall consisted of a series of "homestead emergencies" which required me to triage on a daily basis and choose which tasks would be completed based on order of importance. Building and installing the boiler was top of the list. Putting a roof on the shed, while still important, was further down on the list.


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## lapeer20m (Jan 8, 2014)

This cold snap has been exciting. It was -13f the other night, which is near record setting. 

I've been using the owb exclusively during the cold snap. I was not able to maintain the 83 degree differential. The house temp fell to 64* but slowly climbed as the outside temp neared zero. 

I would estimate that the owb consumed 400 pounds of wood in 24 hours! That's enough energy to heat the house for more than 2.5 days under normal conditions. 

I spent a lot of time outside helping neighbors and plowing snow. i learned that zero is a lot warmer than -13!


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## dave_dj1 (Jan 8, 2014)

funny how much wood we consume when the temps are in the shi#$%er! LOL
I am burning about 4 days worth in a 36 hour period.
Nice job.


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## 04titanse (Jan 9, 2014)

I have also been quite surprised with how much wood I have been burning. I am using an indoor wood boiler and right now I am burning mostly well seasoned pine, but I have been flying through wood. Between using crappy pine and the very cold temps I am burning 2x's as much as I usually burn. Time to switch to some oak and increase my burn times and consumption. 

Nice work on the boiler. Getting a gasket on that door will make a big difference in overheating. Mine leaks a little and when it gets warm out sometimes I get a little over heating also.


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## millbilly (Jan 26, 2014)

Once your pex supply lines get into the house how is the heat extracted? I have forced air heat, and want to build an owb. I have no clue how these things work. I've been thinking I should start collecting old cast iron radiators. I live in a 1917 sears kit house the 4 cube model. Leaks air like crazy only moved in mid December. Leaks air so bad I'm using $25 a day in fuel oil, I'm dying. I do have an endless supply of wood.


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## dave_dj1 (Jan 26, 2014)

You should forget the radiators and just install a water to air heat exchanger in the plenum of your hot air system.


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## Mike Van (Jan 26, 2014)

Nice job on the boiler, good to see the inventors spirit is alive & well -


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## lapeer20m (Jan 26, 2014)

I have cast iron radiant heat and a standard LPG boiler. My owb connects to the system via a water to water plate heat exchanger. I will try to post a photo of the setup tomorrow.

If you already have forced air heat you can do as others suggest and simply add a water to air heat exchanger to your furnace. It's really just a radiator that has owb water flowing through it.

When there is hot water available and your thermostat calls for heat the furnace fan will run but the burner for your furnace will not fire. 

Btw, I love my owb but I am happy that I have an endless supply of wood as it consumes a lot! 

Last year I averaged $17/day in propane for the season wich is $750 every 6 weeks.

This year I bet it would be closer to $30 or more as its way colder and since jan propane is double the price it was last year.

I'm guessing my propane bill would have been over $5k for this season if I would not have built the owb. 

I've already saved more money in propane than it cost to build and install my boiler and the season is only half over.


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## lapeer20m (Mar 20, 2014)

Update:

Life is good! Spring is in the air! Temps are in the 30's. 
I am back to making a fire once every 30 hours or so. 

When the outdoor temps began to rise, the owb began havin overheating problems again. It has a safety feature that circulates water through all zones in the house when the water temp reaches about 200 degrees f in order to keep the water from boiling. It never boiled but the temp in the house was 80! We had to open windows. 

I took advantage of a warmer day and with no fire in the boiler used rvt silicone to form a door gasket. 

This appears to have fixed the overheating issue once and for all. 

Other than this small glitch, the system has been working great!


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## dave_dj1 (Mar 20, 2014)

That's awesome! Congratulations


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