Overview of my homemade hybrid OWB

[cumminstinkerer]

I built my own OWB back in 2010, just a standard box in a box with forced induction. It worked very well but along about this time last year i started wanting to make it more efficient and use less wood. I found a couple sites and started learning a lot. I decided to try and get some secondary burn out of it, knowing full well it would be difficult. I already had an exhaust box in it that forced the exhaust to the very rear before exiting the central flue. I went in below that and added a steel supported firebrick baffle and then routed secondary air inlets along the lower portion of the box from the rear to the front then up to the bottom of the baffle where they turn 90 degrees and run under the baffle with outlet holes. These are connected to my draft fan which also supplies primary air under the entire length of the fire through multiple openings. After visiting with several very helpful folks on here I drilled a small peep hole in my loading door, the peep now remains open after some investigation. After a fair amount of experimenting I found that my secondary tubes needed to be turned to form a vee shape under the baffle, I would then get some secondary flames but not consistent. The air outlets in the secondary tubes started off at 5/32 but it appeared my air velocity was too high, I began drilling the holes out and retesting. I have now settled with them at 3/8 and pointing at approximately 1:00 on the left tube and 11:00 on the right. Now after considerable adjustments to the butterfly valves made into the feed lines for primary and secondary air, one to two minutes into a fresh load the secondary flame lights up and increases in intensity until I have a rolling flame that is from clear color to an incredibly intense bright yellow at the very tips. Once the secondary flame lights the chimney goes completely clear. The only piece of the puzzle left for me at this point other than some final tuning once I get an O2 sensor is my flue temps are somewhat high, I'm running 475-500 surface temps on single wall measured with an IR gun about a foot above the boiler top. I'm in the process of designing a flue tube style HX in hopes of recovering some of this heat and lower flue temps. That however will not be done this year for two reasons, cost and time, and the boiler is my only heat source and therefore cannot shut down at this point to do the install. I am also planning on adding some storage next year, just need to work out the details of where with the wife to make sure and leave her as much storage space in the basement as possible. Thank you to everyone for all the help and just general knowledge sharing I have learned a tremendous amount.

 

[farmer steve]

 

[cumminstinkerer]

Farmer Steve, These darn computer Nazis' at All States Ag Parts wont let me load any of em, and I don't really have any of the actual build, Was in too big of Hurry to get all the build done, was working doing dirt work with my dad running ten and twelve hour days in the dozer then coming back building it at night, had to get it going or it woulda been a cold winter. I do some pics of some of the mods and completed pics of the boiler. I will see if I can weasel them through the firewall and get em on here, And by the way if ya ever call in for parts and get Jason, there is two of us, I'm in De Soto flip me some grief.

 

[cumminstinkerer]

here is a couple of pics I could get to load the one of the inside of the boiler was before I got the secondary air intake tubes all figured out, them and the baffle above them are a clean white grey color now, and just for @Whitespider the can in there is my preferred brand, brewed a little higher in elevation than yours lol, it actually was a spit can the wife said to get rid of and didn't want the critters knocking it over and making a mess so in it went. There has been a few more in there recently since the secondary air got dialed in and man do they burn hot lol. That chimney pic was about two minutes after a fresh load.

 

[cumminstinkerer]

This ones was a few days after the previous chimney pic but she is running full bore about three to four minutes after a fresh load.

 

[cumminstinkerer]

I really wish i could video my secondary burn through the peep hole but i tried it once and it nuked my phone camera, Ill share the two I got but mind you after drilling out the holes in the tubes it is a continuous rolling ball of flames starting off clear at the baffle and rolling back downward turning blue and eventually fading to yellow. It looks like you have one 24" wide oxyacetylene torch tip set at neutral flame pointed down the middle of them two tubes. well shite i cant figure out how to upload a video

 

[cumminstinkerer]

Ok just for a fun update, I got home last night around 6:30 after leaving about 6:15 yesterday morning, House was up to its setpoint of 72*, Boiler was calling for heat but pretty low on fuel down to a small bit of coals. Went inside changed and talked to the wife a bit, got back out and cut a 24"x24"x24" cardboard box a buddy brought out, threw it and two splits in at 6:58, the water temp was 61.3C she took off, Now mind you house is on the thermostat so furnace blows on the HX in the house as needed, and the wife is filling the tub for a bath, which is also drawing on the boiler. The temp controller shut the boiler down at 76*C (on the outside of outlet pipe actual water temp is 185*) at 7:31. I went inside and at 10:00 came out for the night load, still had charred wood left so I threw in eight or nine splits and off to bed. Now it was pretty warm last night 27*F but wind was blowin and it was snowing. At seven this morning still had three charred up logs and good coals, boiler had just shut down from a burn cycle. I'm pretty happy with that all and all.