Advise on homemade OWB

[Beaver State]

Hello, cool site, looking for hints, do/dont and advise prior to starting OWB for new house.

1. Has anybody living on West coast used OWB to heat house/shop/DHW? Do you need as large a unit as people in MI and NY where its below 30 all winter? It rarely gets below 15* here and that is only for a week or so, frost line is 8-12 " not 30....do not want to build overkill and have it idle all the time.

2. I have looked at plans and peoples home builds, not much info other than a few photos. Is there any thread about do's and dont's or what is a waste of time? Any must haves besides a nightlight?

3. not too concerned as I have 85 acres of oak and madrone but efficiency is something to think about, 150-200 gal seems about standard for 1800 sq ft and shop?

Thanks in advance, happy to see that there are other people(freaks as the gf calls me) that actually like cutting trees in the woods and loading it in a truck...happy cutting. Evan

 

[iCreek]

I would not know where to start with building a OWB, but I am sure someone here will be able to give you some advise. Forced air seems to be a plus to keep the fire going, and an ash door would be a great feature also. You might try the 'Search' pulldown and use homemade, lots of other things people make, splitters, stands, trailers, processors, etc., about 640 posts. Good luck and Welcome to the Forum, always glad to see more newbies on the site, and yes some people think we're crazy !!!

 

[Beaver State]

thanks, I did the search and found lots of other great builds(like I need more projects!) but not much on a whole stove. I have looked at several brands but being a mech/fabrictor/gear head, I can stand the thought of not building it myself. I am finishing my house which has 1000 sq ft of radiant heated stamped concrete in main room and I have unlimited oak, madrone and fir on my place but sick of the inside stove mess...not to mention cutting 30+" pieces is half of the cutting. If anybody has built nice OWB I would be very happy to see ideas, flops, must haves etc...steel is too expensive to do it twice. Just built a dedicated wood truck since the really huge madrone is up on a knoll w/4x4 deer trail for access...

 

[cleanburn]

Just watch your building codes where you live, you may not be able to build your own OWF or you may have to meet certain regulations for emissions. For insurance reasons where I live my OWF has to be 50 feet from my house.

 

[Beaver State]

clean burn, I live in rural southern Oregon where we dont even have vehicle inspections. You have to have a cert stove inside the house for ins purposes but nothing about outside anything, they didnt even know what a OWB was. As far as the inspector is concerned, house is heated with instant on propane water heater. Never even asked about all the pex coming up out of the slab! Middle of 85 acres, nobody to file a complaint that wont get eaten by 2 150# dogs before they can make it back to the car. Did I mention I dont worry about theft?
Leaning towards two pieces of pipe 24-36" inside 36-48" for less welding to leak later on down the road and a forced air induction below grate kind of like a Shaver but I think it needs more baffling to make it more efficient on the exhaust side. anybody?

 

[ericjeeper]

I used a 30 inside of a 36

The 30 is 48 inches deep 1/2 inch wall thickness. The 36 is 58 inches deep3/8 wall thickness. These plus 3 pieces of plate steel and you are good to go. hardest part is to be able to get the flue through both pieces without having to lay inside the firebox to weld it up water tight.I welded a stub to the 30 just long enough to protrude out of the 36 yet short enough to be able to drop the 30 down into the 36.
You have to have a means of moving this stuff all around. I used the loader bucket on my tractor. But once I got it all fabbed up I could no longer pick it up.. Therefore you have to have friend with bigger stronger tractor come set it into place.

 

[cleanburn]

Beaverstate, I also live in a state with no real regulations for OWFs. I also live in the middle of nowhere too I don't worry about theft either, its rather nice

My two cents on your build:

Airflow will give you a clean more efficient burn. Watch your secondary and primary airflow. Air under the grates is good, but you also need good secondary for a complete burn.

Baffles to divert air before the flue is also good, it cuts down the smoke and gives better combustion.

Make sure you have a fan, don't go with natural draft....also make sure you have a big enough fan to give you good turbulance which also helps combustion.

I don't personally care for the heat exchangers that are pipes, they are harder to clean and too many of them. I like a simple flue that runs through the water, make the highest surface area flue you can without hindering how you clean your flue. If you can make your flue go through your waterjacket more you are going to be that much more efficient.

Okay I think I've said enough, feel free to send me a private message if you want to hear more of my rambling

 

[Beaver State]

Clean, I was thinking of splitting forced air to under the box and above the fire to get a good gas burn, another idea was well casing for the stack and dropping it to within 6-10 inches of the bottom of fire box so it will get better swirl and turbulence hopefully helping gas burnoff

 

[bassman]

after buying a brand name unit and seeing how bad it is made I would build my second one but I would do it right and add some stuff!!

I would use 1/8 steel for the firebox but lined with firebrick .

2 or 3 pass firebrick tunnels

blower fan for sure but 3 speed and shut off in case I want to burn without it.

I have seen a simple barrel over a fire work well for a barn setup!!

 

[Beaver State]

Bassman, I am planning on at least 3/8 -1/2 for firebox, havent figured out the brick maze yet, maybe steel baffles? The fan will be on a variable circuit like a dimmer(works great on wood stove) . Had the same thoughts on commercial units, for 8K, you should get more that something that looks like a high school metal shop project....plus I have a complete fab shop w/welders, plasma cutter, break etc...

 

[cleanburn]

Bassman, why firebrick tunnels? You want heat transfer in your flue area....

 

[tawilson]

A friend has an 20 year old wood boiler no longer in use. I'm going to look at it this weekend. It has no shell on it now, I was toying with the idea of turing it into an OWB. I'm a tinknocker so insulating it and enclosing it doesn't scare me.

 

[bassman]

Bassman, why firebrick tunnels? You want heat transfer in your flue area....

I agree but transfer too soon and you get alot of buildup so with a turn or two of firebrick the hot air you end up with is clean so your exchange area stays free of creosote.

I would also go with a smaller firebox that gets superhot unlike my huge firebox that holds alot but the hottest part of the combustion is 12 inches above the exchange area!!

If you or anyone has the area and abbility to work with steel I say build .

Also look into how a blacksmith can make a tiny fire melt steel with a little fuel and some air!!!

as soon as he stops the air the fire dies down to a small flame that is way cooler.

youtube garn and see how well they pull heat from wood.

 

[Beaver State]

sounds like the greenwood model i looked at, full of fire bricks, 3-4 big chunks of madrone and they would be toast! I want steel baffles w/ holes so I dont have to worry about breakage. trying to divide the main fire and secondary burn area, while keeping the fire box to 20 cu ft or less and water cap at 200 gal. working on secondary burn front air feed design fed by draft while the fan blows under fire w/ fan fed from back.

 

[Beaver State]

found a 3' dia .375 thick pipe 3 ft long at metal yard for .60/lb or $190 total. 1/8 or 3/16 4x8 is about $75 plus $10-$20 shear fee for the pieces...wish they had a 42-45" dia pipe!

 

[ericjeeper]

I bopught mine from a pipeline company

They at the time were selling it for 20 dollars a linear foot. he asked me how thick of wall.. I asked how thick they had.. he said up to one inch.. I said half an inch is a plenty. LOL

 

[cleanburn]

Are you going to do stainless?

I suggest it

Just look up some of the larger manufacturers of OWFs or OWB, most of them have the basic design on their websites.

Why re-invent the wheel ya know?

 

[Beaver State]

No stainless, just good ol thick american steel...would think that .375 will take awhile to burn/rust through. My parents bought a fire view in 1970 when we moved here and its only 1/8 but still heating the house every day, should outlast me...lots of complaints on stainless cracking by welds plus its EXPENSIVE!
Pipe has taken(along with all steel) a huge jump in the last year, near 100% increase, plus these guys are not a pipeline co, they are a metal scrap yard so its all $.60 /lb. Best deal around...

 

[cleanburn]

If you plan on doing mild steel make sure you watch your chemicals in your water to make sure you don't rust it out

The stuff you read on stainless isn't correct about cracks in my opinion

 

[Beaver State]

clean, I plan on the corrosion inhibitor although anti freeeze has it in it. I have lots of exp w/ stainless, the problem I see is that it expands at about twice as fast as steel so if everythings not stainless then it will tear itself apart expanding and contracting. There are lots of different stainless alloys ie mixes and some are more flexable than others but it still love to crack at the welds if heated and cooled over and over. No to overlook the price which is 5 times as much if you can find it. Not alot of 3' stainless pipe laying around in So Oregon either.....thanks for the input though:greenchainsaw: