OWB Design Plans

[westyswoods]

Good Morning to all from central Wisconsin. I am looking to build a wood boiler and would like input. Have been researching for the better part of a year while also looking at manufactured. I can not justify paying 6 to 8 k for one. A few points fyi The wood I burn is oak, elm, hickory, locust, cherry, maple and ash.

It will be heating a 2000sq foot shop area with hydronic heat in the floor. This is presently heated with a 100000 btu lpg Dunkirk furnace. Five inch concrete heat sink floor with 2" high density blue board underlayment.

The run from outside to connecting with manifolds in boiler room is 40 ft. Will need to go above ground.

I would like to keep cost below 4k as I will be doing prefab work and some of the welding. Also do not want to build junk.

A few questions?
1. Steel or stainless?
2. What thickness 1/4 or less?
3. Rolled fire chamber or welded?
4. Water cooled door or regular?
5. Line with fire brick on bottom and sides with grate or just grates.
6. Door size and location to fire chamber?
7. Size of fire chamber vs water held are there any ratios or formulas for this?
8. Why does everyone use 8" flues vs 6"

Any and all suggestions and or questions will be appreciated. Does anyone know of good design plans out there?

For those who are heating with LPG look for the price to go up astronomically in the future as there is a consolidation of the industry taking place. Amerigas is going to be the big player.

I hope this post is in the right place as it is my first here. I intend to keep this forum posted on the progress of this process.

Thanks In Advance For The Words Of Wisdom
Westy

[thecfarm]

Welcome to the FF westyswoods.That sounds like a good idea. Just make sure it is legal in your area. Will this be a gasifier type? Will need a blower to drive air into the fire box.My Heatmor has an auger clean out. Has grates down the middle but sand on each side of that. Fire brick go up the sides,I think 6 inches. I have a water cool door.My door is about 18 inches square. Probaly sits up about 8-10 inches form my grates,a guess.

[Gary_C]

Welcome to the FF also. What you are proposing is a good idea, but it may not be practical nor economical. Here is why.

The questions you are asking are good ones and have been debated by manufacturers and others many times. But just on a mathematical standpoint, you have roughly 384 combinations, perhaps more in those eight questions. Even if you got 99 % of the combinations right, you would still have to build 4 stoves or if you were lucky, do extensive rework to get them functional the way you need to have them. So unless you are planning to build them as a business, you will have to eat the cost and the time involved of those protypes.

That's what you are paying the difference in cost for a purchased stove vs. a home made one. The knowledge the manufacturere have gained with multiple prototypes and customer experiences. Plus the efficiency tricks they have learned in their trials.

That's not to say it cannot be done as I know of one guy here that made a number of stoves for some local people. And yes, he had a few problems with his stoves that he had to fix.

And there is the question of efficiency. If you have looked closely at different designs of commercially available stoves, there are certain design features that are used to increase efficiency. And most certainly there are some hidden features not readily seen in those designs that increase the overall efficiency of the stove. And if you don't incorporate those design features that you don't know about, the fuel costs over the years can eat up your initial cost savings in a hurry.

And I haven't even covered corrosion, cracking, leaks, the need for castings, etc.

So I don't really want to discourage you as you could just come up with a fantastic new stove that beats all others on the market. Just wanted to make sure you go into this with your eyes wide open. 

[doctorb]

I do not have the knowledge to consider this project, so you have my admiration.  Welcome to the Forum.

The simplest stove will be of the old traditional design.  It will be a simple firebox surrounded by a water jacket.  No downdraft gassification, no heat exchange design, smokey, and inefficient.  Improvements in those stoves included ash removal systems and better insulation. 

Modern designs are more complex, with fans, solenoids, downdraft combustion, digital controls, and more intricate mechanisms for heat exchange.  If your trying to match those stoves, my hat is off to you.  I don't like to be pessimistic in the face of someone who's embarking on something major, but I think the time involved will overwhelm whatever costs you save.  I worry that you get everything running OK only to have an inaccessible water jacket leak, or some other game-breaking problem, and no one to turn to to fix it but yourself. 

Please keep us posted on your decision and your progress.  A very challenging endeavor!

[beenthere]

Welcome westywoods

Have you been burning wood for heat, and if so, how long?

Good responses to your question, IMO. Hope you will feel free to respond to them and let us know more about where you are at with the development of this design. 

For myself, I like the design of the water heating boiler I have, which is made of rolled and welded 3/16" steel with a 9 gal. waterjacket surrounding the combustion chamber. Has a 6" flue, no bricks or sand, draft damper that is controlled by water temp in the jacket. No blower, no ash pit, no water in the cast iron door. Heat over 2500 sq ft exclusively with wood. Might feel different (more water volume, insulation, etc. ) if it were OWB versus in my basement, but there isn't anything about it I'd like to see different. It is my friend.

[gunman63]

heres a simple one, it works,  easy to  build, built my over 15 years ago, no problems, I burn 4' wood in mine.  Use pipeline pipe if its avalible, my firebox is 3' dia. x 5' long, water jacket, 4' dia. x 6' long.  thickness is 5/8". stove pipe is 6" pipeline pipe. ends are 3/8 flat sheet. firebox  sits on the bottom of the water jacket. forced draft is 2".  no  grating, when its  time to  clean just  shovel out  ashes in the morning, after fire  burns  down,  scrap coals to one side, clean out ashes, repeat for other side,  heats both  house and shop. nothign  fancy, sometimes people  just over think simple.

[martyinmi]

Welcome Westy-
1. I'd go with steel.
2. 1/4" seems to be about right for proper heat transfer and longevity
3. Round has many inherent design quality's that lend themselves to a more efficient and longer lasting boiler.
4. I've built 2 OWB's with water cooled doors and wish I hadn't. The doors are hard to insulate as well as the lines feeding them.
5. Line with firebrick on bottom and sides with grate.
6. Bigger doors are harder to keep sealed and harder to keep from warping. We've made them as big as 24"- overkill in my book.
7. A 36"-42" round(maybe 4-5 ft. long?) inside a 48"-60" round(maybe 5-6 ft. long?) outside is a popular design. See gunman's specs.
8. I've never built one with a 8". If you were heating in excess of 5000 ft., that would probably be the way to go.

9. Weld inside and out wherever possible.
10. Design air intake with over/under air. Force-feed with fan as opposed to gravity.
11. Make any heat transfer areas as easy to clean as possible.
12. Check with your zoning board to make sure that you'll be able to use one that's not EPA phase 2 certified. Rumor has it that here in Mi we will only be able purchase EPA models by the end of next year. Then they will begin the force-phasing-out of the non compliant ones in the coming years.
13. Everyone on this site loves pictures!

[mrcaptainbob]

Sounds neat, Guman63. Any pics?

[Tom_Averwater]

I would use the plans for the Seton boiler. It is a water tube boiler with refractory panels for the firebox .

[westyswoods]

Thanks to all for the responses. A few answer to some of the questions.

It is legal and I've been burning wood in both house and shops for twenty plus years. I have looked a Heatmore amd several other brands, like some ideas of all but do have some problems with the high tech stuff being developed.

This is what I do, make things it is in the blood, as my father was a self educated research and design engineer for some of the larger industrial corps in the Beloit area. Believe me my eyes are more than wide open as I've never developed anything which has not taken several redos and more work than one originally plans. Just the way it is. Thanks for the heads up.

I am looking to most likely produce at least two or three more with modifications as I go.

Not sure as to gasification question yet I have heard both pros and cons. One of the concerns I have is the long term structual integrity of the steel and welds with this gasification. I look at as much like the free standing catalytic wood burners. I had two and both warped due to excessive heat. Also talked to several others with same problems. Need more info on the issue.

I sure see the point of larger doors being more suspectable to warping although the Heatmore has a water cooled door, I am leaning against as the extra labor and pieces just spell more to break down the road.

I do like the idea of protecting the lower sides and steel with sand and fire brick.

Have a friend who built his own and one of his mistakes was not having the bottom of the door opening high enough above fire level. Which brings me to another thought, of making a loading cradle which can be put into firebox on a rail system and dumped or lower onto fire.

I like the feedback much appreciated and keep the suggestions and questions coming as I will keep the members posted.

BTW sorry for the misplacement of this original post.

Westyswoods
Westy

[thecfarm]

Make the sheet metal a little big longer where the feed door is,than have an outer door. One door for the firebox and an exterior door. On my Heatmor there is a small shelf. Real handy to keep gloves there and a gallon of bar and chain to use the next day. I also dry my gloves there too. Keep it simple too. I have no electronic devices on mine. Just Honeywell controllers that can be bought anywheres. The blowers are the only dealer item. I would check out any and all OWB. I would see someone filling their OWB before I bought one and I would stop and spend a few minutes asking about it.

[shelbycharger400]

their is a reason why EVERYTHING is going electronic....  its to keep the industry people busy!
everything usto be mechanical, funny now it uses a computer to do the same job

i did some research on owd,   i couldnt get past the price,  it would take 8 to 10 years to break even on the deal.  my 1800 sq 1960 house is poorly insulated, i have a ton of windows too.  winter i go through $1600 in propane..at  1.80 to 2.50 a gal
This year  i got the wood stove in ( been splittin wood for 3 years)
Anyway,  the upper plate in the fire box, needs to be a bunch of v 's or w's , you get the picture, to give you more surface area, personally id have the whole firebox sides wider at the top then the bottom.
firebox in the middle, with water able to circulate all 4 sides ..,  front...just sheet steel in 1/4 plate uninsulated
firebox needs to be tig welded inside and out.  as well as the water jacket, then slip the firebox into the waterjacket and weld the outside . the firebox would have standoffs to hold it up inside..theirs no way you could hold it.   then exhaust comes out the back, and steel plate it.          most of the stoves on the market have as about as much insulation as your indoor water heater, 2 inches of foam.    tin is easy to install, as is callin up a guy with the spray foam truck.
you could put a grate in it, and a lower ash pan.   as far as the dampner.   id do like my parents indoor 1970's woodstove.  their is a 4 inch disk on the door,  that screws in and out, a baffel that looks like a shoe box on the inside .
you will still need a pump to move the water ( put it in your  house) and the pipeing, heat exchanger in the ductwork, something to trigger the fan to come on ect.
shure...its not as efficient as a over engineered 8k  + new computer controled... but ya know what... less moving parts equal cost savings in the long run

biggest thing i noticed on people with thier owd.. is a lot of them are really really belching the smoke.
my woodstove here.. if its a hot fire, very little smokey smoke, a cold fire/cold draft,  or wet wood...belches the smoke.
and i redid all my door and glass seals, as well as put a seal on between the dampener pan and the bottom of my stove, they never had one their factory.   i always pull the dampner nearly all the way shut after a lot of coals form.  (works awsome for a 1980s stove, its a defiance masters choice)

also, do note.. dont make hard 90 degree cuts in the steel plate ANYWHERE, radius cut, or drill the corners before you cut. this will help prevent the stress cracks.   if you cut the door out of the front plate, you still can reuse the cut out, just put in 1/8 in x 1 1/4 around the cut out inside,  you can leave a lip so the door shuts against it, or you can make the door oversize and put a glue on fiber glass seal, or have a 1/2 in or 3/4 in steel door made and mill out the slot for a rope seal.

[Piston]

Welcome to the forum Westy, sounds like a great project and we'll all be interested in your progress. 

Are you planning on using any type of insulation?