My homemade outdoor wood furnace (boiler)

[brenndatomu]

Just having firebrick on the bottom and part way up on the sides would help a lot. If you put it the whole way around that would stop too much heat transfer. Just FYI, if one did want to line the whole way around, just look at a brick or stone archway, the key is the keystone.

 

[woodman6666]

This will be a non-pressure boiler like most of the commercial owb. It will be vented to the atmosphere via a ball that sits on top of a pipe. The ball keeps the water from evaporating yet allows any pressure to escape.

The 1/8" wall on the firebox is a concern. However compared to a standard 55 gallon drum, this tank is much more stout. A drum will last at least a few years as a wood stove. The wall on a drum is very thin and is rated for non-pressure applications. My firebox is 1/8" thick, and was rated for 150psi. Will being surrounded by water increase or decrease the life of the firebox? I don't know.

Firebrick is a great idea, but I don't know how to line the top. Any suggestions?

Being surrounded by water will make it last longer. But I agree it is thinner than I would start with stir your ashes daily and never let rain water get in the chimney and run inside.

No on the firebrick all it will do is negate the transfer of heat to the water.
You dont have a lot of room for water there be sure to circulate plenty and draw from a hi spot and return low.

 

[4x4American]

Diggin the project

 

[Patrick62]

So if you were going to use an old Propane tank how do you keep the tank from exploding when cutting it open (torch or blade)? It seems to me that even if you open the valve for a long time there will still be some residual gas in the tank.

Propane boils at -43.6F
Open the valve and ALL the propane in the tank will turn to vapor. Blast it a few times with a compressed air hose and start cutting.
Never mind the extremely strong odor. that is the mercaptan that was added to propane to give it the smell, as propane has no smell all it's own! It is against your better judgement, but trust is needed here.

 

[brenndatomu]

If it were me I'd still purge that baby with some engine exhaust...better safe than WTF, that wasn't supposed to happen!

Oh, and +1 on diggin the project. I love gettin creative with "junk"! And it is especially gratifying when you are done, you can tell the oil (gas?) man to go take a long walk on a short pier!

 

[TheOldBiker]

Firebrick

Good answers, low pressure-ball vent, did not know that.
You would only have to fire brick the bottom anyway, and that would add years to the life of your stove.
Yours with brick on the bottom and being surrounded by water would last a long time, in my opinion.

I built a simple wood stove 33 years ago (copy of the Fisher Stove design) and am still using it in my shop every winter.
The bottom and sides are 1/8" mild steel, the top is 1/4" m.s. I put fire bricks on the bottom only, and it is still sound. The sides are a different story, they are badly warped due to the stove having been cherry red so many times, should have bricked them as well. Although warped, the stove holds together fine, and the front and back are not warped at all.
I cut some replacement sides from 1/4" plate a few years ago, will install them someday, then my grand children will be able to use it 'til they are old.

 

[lapeer20m]

The good news: welding is pretty much finished.

The bad news: I don't have time to work on this project for the next 3 weeks.

I can't post photos from my phone.

Here are some finishing touches

Untitled | Flickr - Photo Sharing!

Here I welded the chimney pipes together.

Untitled | Flickr - Photo Sharing!

Untitled | Flickr - Photo Sharing!

Untitled | Flickr - Photo Sharing!

You may notice there is a backhoe in some of the photos. I don't know how I'd do this project without it. The boiler had to be rotated several times during the assembly process.

Here is the chimney from the inside prior to welding. This was one of the more challenging parts of the project. I had good ventilation, then I had to climb inside and weld while in the confines of the firebox. It was tough when changing rod to get my arms far enough away from the material while maintaining the proper angle.

http://www.flickr.com/photos/84725831@N00/9601437833/in/photostream/

I am excited about lighting a roaring fire inside and flowing water to determine the btu output.

 

[woodman6666]

I see in your pics a Mental Institution are you a resident there? LOL

 

[lapeer20m]

I see in your pics a Mental Institution are you a resident there? LOL

No, lol! Although my wife probably thinks I should be sent to the looney bin for spending days welding and grinding on this project including crawling inside and contorting myself into all sorts of unnatural positions.

The no firearm sign was on the door of the county building. Which brings me to another hobby of mine which is forcing municipalities to remove these types of signs. In Michigan local units of government are prohibited from making any rules regarding the possession of firearms.

But I digress....

 

[lapeer20m]

I didn't do any more work on the boiler, but have been busy doing math.

I found a source that indicated my baseboard radiators give off approximately 600 btu per linear foot at 180*. I have about 125 feet of radiator. Which equals approximately 75k btu.

That's good and bad. Good because 75kbtu should be easily generated by my boiler. Bad because as water temperature decreases so does btu output of the radiators.
If my water temp is lower I may have a difficult time keeping the house warm on very cold days. If I have 180* water enter the heat exchanger I assume the liquid being heated will be less than 180.

I also did some math on converting gallons of propane burned last year to pounds of wood.

Propane has 91kbtu/gallon
I used about 1,200 gallons last season, (plus one more fillup for summer)

11pounds of dry wood = 1 gal propane
1200 gallons = 13k pounds of wood

A cord of ash weighs approximately 4,237 pounds
A pile of ash 4x4x24 (3 cord) should be equal to about 1,200 gal propane.

I also have a lot of pine, which only weighs about 2,200 pounds per cord.

1,200 gallons would equal a pile of pine 4x4x48 or 6 full cords.

Granted these numbers are approximate, and the overall efficiency of the owb compared to the LPG boiler is a factor. If the owb is only half as efficiemt as the lpg boiler i would need twice as much wood.

 

[woodman6666]

As far as water temp run at least 180 and spin it fast alot of gpm's you will be fine.
AS far as wood usage goes, if you would have cut your inside barrell and added a baffle about 1/3 the way down that is open to the water jacket this would have cut down alot on wood usage but it is another project in itself especially when you are working with round. I know as I have done it a few times. But a real world example a welder that lives close to me wanted to build a owb and came to me and asked me a number of questions and looked at my boiler. He took most of my advice but I remember telling him the most important thing is put that large baffle in and make it protrude to a point lower than your chimney exit is. Well this is the one thing he didnt do and to make a long story short he went through 52 cords of wood last winter, heating a large shop and one house. He is currently trying to figure out how to put the baffle in now but very difficult after the fact. Im not saying you did anything wrong just letting you know that it plays a large role in how much wood you will go thru.

 

[PLAYINWOOD]

This will be a non-pressure boiler like most of the commercial owb. It will be vented to the atmosphere via a ball that sits on top of a pipe. The ball keeps the water from evaporating yet allows any pressure to escape.

The 1/8" wall on the firebox is a concern. However compared to a standard 55 gallon drum, this tank is much more stout. A drum will last at least a few years as a wood stove. The wall on a drum is very thin and is rated for non-pressure applications. My firebox is 1/8" thick, and was rated for 150psi. Will being surrounded by water increase or decrease the life of the firebox? I don't know.

Firebrick is a great idea, but I don't know how to line the top. Any suggestions?

15 years ago when these things were all the rage we were discussing all of the different styles,stainless vs boilerplate, firebrick vs none, because these things were only lasting 5 years or so.
One of the old boy welders filled a paper bag with water, then put an acetylene torch flame to the bag. The bag did not burn ,the water boiled instead.
Lesson learned? if you surround the firebox with water it will dissipate all the heat.

he said if he ever built one,it would be a box within a box,small auger on the bottom surrounded by water on 5 of 6 planes. The door being the 6th plane was never discussed.I see the Heatmor door is jacketed..


a baffle for sure in the firebox

 

[lapeer20m]

15 years ago

he said if he ever built one a box within a box,small auger on the bottom surrounded by water on 5 of 6 planes. The door being the 6th plane was never discussed.I see the Heatmor door is jacketed..

I don't understand what the auger would do, can you please explain this?

 

[lapeer20m]

I do plan to add a non water jacketed baffle. While I am sure that one backed by water would be more efficient, there would be much greater complexity involved, especially with a round firebox. A jacketed door also seems like a great method to capture more heat. Perhaps I'll include both in my next boiler.

I find it unlikely that having a water jacketed baffle would double triple or quintouple the efficiency of the unit, but what do I know?

 

[flashhole]

Anybody got a sketch of the baffle and how it fits to the chamber?

 

[lapeer20m]

Anybody got a sketch of the baffle and how it fits to the chamber?

I think this is a good example of water backed baffle:

Tempower.com

Specifically number 11 on the list.

 

[PLAYINWOOD]

I don't understand what the auger would do, can you please explain this?

ashes

 

[beerman6]

. Well this is the one thing he didnt do and to make a long story short he went through 52 cords of wood last winter, heating a large shop and one

:msp_ohmy:

 

[chaikwa]

One of the old boy welders filled a paper bag with water, then put an acetylene torch flame to the bag. The bag did not burn ,the water boiled instead. Lesson learned? if you surround the firebox with water it will dissipate all the heat.

Okay, I just tried this. Went out in my shop, filled a paper bag with water, (that in itself was a trick!), and held my torch to the bag. Bag immediately caught on fire, water made the torch pop and bang and now I have a shop that smells like a rubbish fire.

I wanna see this 'bag won't burn' trick!

 

[PLAYINWOOD]

try holding a couple inches beneath the bag.