Home made owb adding baffle and secondary air

[cumminstinkerer]

I have a homemade boiler I built a couple years ago I'm wanting to improve upon. the firebox is 30"x30"x30x2", forced draft under the fire, draft inducer off older he propane furnace, damper in intake pipe after blower controlled by a rotary damper actuator. Top center exit 8" flue with an 8"x2" box extending down from top of fire box the 2" way and from the flue to within 2" of rear wall. I Want to add a baffle below this extending from the rear wall forward approx. 24" and as close to that box as I can get to maintain firebox height. I'm thinking of using 1.5x1.5x1/8" angle making a frame and filling in with firebrick, then bringing air in through the lower front off the same blower but with a manual adjust damper, then up 1/3 the firebox and back to the rear wall the up the rear wall to the bottom of the baffle, then forward along the baffle with holes under the baffle to introduce preheated air. any thoughts or advice would be great. on the current setup if I open the loading a very small amount with the draft fan running I get very intense blue flames along the upper third of the firebox.

 

[TCaldwell]

Your theory is logical, in practice you will have to test and probably make some modifications. Without a portable fluegas analyser to monitor changes it will be difficult to quantify a benefit.

 

[cumminstinkerer]

Your theory is logical, in practice you will have to test and probably make some modifications. Without a portable fluegas analyser to monitor changes it will be difficult to quantify a benefit.

yeah I wish I had one around and that I could shut down and do my mods but the boiler is my only source of heat. it functions really well now, it does smoke some on a fresh load and initially on refire, id like to reduce the smoke some and cut wood usage I really have no idea how much I use as I haven't had it stacked ahead.

 

[cumminstinkerer]

well I got the baffle in it seems to have helped cut wood consumption but ive only had it in for one day. I haven't had a chance to install the secondary air as I ran out of time I'm hoping to catch a couple warm days here in the next couple weeks and put them in. I still have to finalize the design for the secondary tubes as well

 

[cumminstinkerer]

I finally was able to shut down enough to put my secondary air tubes in over the weekend, it did help some to clean it up but I think my air settings are off a bit I get awesome secondary with the loading door cracked open a bit, huge roaring blue flames sounds like a monster propane burner running. with the door shut almost tight it turns to a lazy orange flame. I believe that my primary is driving it to hard, I'm going to try to throttle the primary air down tonight after my wife gets home with the two inch pvc ball valve so I can restrict the primary air flow and be able to adjust it a needed. the secondary and primary feed from the same fan. my primary is wide open and the secondary is wyed into that so it is only getting what air the piping to the primaries cant take, my secondary pipes are 1" black 24 " long with 5/32 holes drilled every one inch in a single row clocked at about 3:30 directly below the baffle. hopefully the secondaries will work better with primaries restricted some I think I am driving it a little hard and blowing too much heat out to fast

 

[warno]

Do you have any pictures of your new set up? I'm looking into getting my OWB running alittle better too.

 

[cumminstinkerer]

no I haven't really taken any pictures but I can try it wont be tonight as I'm going to chiropractor after work. I still haven't got it adjusted just right yet but I'm gaining, I mad a butterfly valve and put in the primary air line last night now I gotta play with getting it all set right but I dropped stack temps by 100* and seems that the wood is lasting way longer

 

[warno]

What flue temps did you have before the mods?

 

[cumminstinkerer]

450* to 500* running between 300* and 350* now, the beast is in my garage, and I had a differnet boiler in there to begin with so my stack comes out of the boiler and 45s then runs the angle to another 45 where it enters the metal bestos then goes vertical out, I'm taking my flue temps right on the point of the first 45 my light off is still not perfect with the door shut but a fairly small bit open and the flame goes pure blue and roars under the baffle I think I might need to drill part of the secondary injection holes out a bit bigger

 

[TCaldwell]

450* to 500* running between 300* and 350* now, the beast is in my garage, and I had a differnet boiler in there to begin with so my stack comes out of the boiler and 45s then runs the angle to another 45 where it enters the metal bestos then goes vertical out, I'm taking my flue temps right on the point of the first 45 my light off is still not perfect with the door shut but a fairly small bit open and the flame goes pure blue and roars under the baffle I think I might need to drill part of the secondary injection holes out a bit bigger

Your lower flue temps are likely from reduced output caused by not enough secondary air. In the beginning of the burn you will need more primary to get the fire going, at high burn dependent on moisture content a good mix might be 50/50, at end of burn,same as the beginning of the burn.

 

[cumminstinkerer]

ok thank you tccaldwell I will play around some more with it as I get a chance but getting home after dark makes it a little tough to see the exhaust

 

[TCaldwell]

Can you fab up a small stove glass monitoring window to watch the secondary burn so you won't have to disturb the process by opening the door.

 

[cumminstinkerer]

not very easy, I have the door lined with firebrick and I'm not sure if I could get glass to handle being in the door it has warped a fair bit and keeps changing shape. the door is a less than perfect design

 

[cumminstinkerer]

thanks to tcaldwell for some great advice and input, I have managed to achieve secondary ignition, it does however still smoke a very light blue that fades out within about 5-10 feet, it is so faint that it wont even show up in a picture. it does smoke for about five minutes after a fill but I expect that as it takes a bit to get the secondary going, the smoke is not heavy and is way less than before the mods. burn times are running around twelve hours with no issues and it is taking about a third the amount of wood, granted it has been warm but that aside comparing other times when temps were similar before the mods its still at about a third the usage. all and all I'm happy I know a gasser is the way to go but cost for controls is prohibitive at the moment so if I can make this setup perform this well for a couple more years that should allow me to scrounge things up a piece at time for the controls on the gasser, fabbing the actual boiler/burner and those materials are not an issue for me to obtain nor is the fabrication. I built the boiler I am running now with no issues and have several connections when it comes to materials and machines, as well as having a good friend that is an amazing welder (ive seen him tig weld two beer cans together water tight and short of melted paint no sign of the seam) so I'm not worried on that end, I also have a friend that is very good with electronics and computers the actual components involved there are my issue due to cost. thank you to all for the advice and I am always open to more.

 

[cumminstinkerer]

gonna revive this thread, I got all my mods done and finally got all the air set where i think it needs to be. my avatar picture was taken on a morning that was -10 F approximately five minutes after a fresh load of about eight splits that would be three inches on the big side. my flue temps are running about 400-500 on the surface, a load that size on a day like that will run me about six hours with the house at 70 and doing laundry and dishes. my baffle and secondary air tubes are a nice light tan to white. I am pretty happy with it at this point but always gotta play and try to make it better lol. I am going to include a couple of pics, don't mind the crappy look of the boiler or the door latch, improvements are in the works, the old latch broke and that was my quick fix. I'm still working on getting the insulation all done as well. The can in the fire box pic was a chew spitter I need to dispose of, the load in there was 6 mixed pieces of boxelder and red locust put in at 6:20 last night, the picture was taken at ten minutes ten last night with the draft shut down you can kind of see the fire brick baffle and my secondary air tube layout.

 

[cumminstinkerer]

My phone really didn't like the light from the fire so the picture is a bit fuzzy, note that i do not have the chamber lined, the baffle is directly above the air tubes and has a six inch opening at the front the gasses then have to travel around 3 inch by 8 inch box that extends to within to inches of the rear wall to exit out the flue pipe, secondary flame occurs along the under side of the baffle and as the gasses break over the front to travel back down the top side, the upper roof of the fire box that is exposed to water is running a light tan to white just like the baffle.

 

[cumminstinkerer]

oh yes i want to give a shout out to born2burn and TCaldwell and Warno for all there help, Warno check your pm's too.

 

[cumminstinkerer]

I want to try and upload a couple videos of my secondarys but i cant figure out how can someone help, the videos aren't the best my phones camera was just soso now its really bad the heat from the fire cooked the lens.