Wood stove heat reclaiming unit

[12bolts]

Its always good to get feedback on big mods like this. Shame it didnt pan out the way you wanted Frank. But kudos to you for posting up a "fail to work as planned" follow up story and not being embarrassed to admit it

Cheers Phil

[Frank S]

I’m never bashful about admitting when things do not pan out exactly as planned.
The heat recovery unit both worked and didn’t work. In some ways it functioned as expected, since there was a significant amount of heat transferred and with a small fan on the mantle that heat was circulated well. Where I failed was in my not taking into consideration that the plenum effect inside of the unit needed 2 things possibly 3, 1 the exhaust from the stove was the same size as the rest of the chimney had this been smaller it might have created a venturi which may have helped to raise the combustion temperatures but a forced air intake would have been better. Another factor is my chimney is right at the recommended height above the peak of the roof the standard minimum is 2 ft to 4 ft mine being at 4 ft, under normal circumstances should be ideal. However the standard does not take into account for low height roofs and nearby obstructions, the peak of my house is barely 13 ft from the ground. I have 2 50 ft tall fruitless mulberry trees with 40 to 50 ft crowns one on the west/ southwest one on the Southeast, each being about 50 ft away from the chimney. To the North again about 50 ft away, I have my temporary tent shop with a peak of 20 ft also to the north I have a wooded area of several acres these create a disruptive laminar flow to the air currents. So even in winter with no leaves the limbs and branches there is still some disruption. What I really need to do is to add another 4 ft of triple pipe to the top of the chimney.
The heat recovery unit had a thermal mass of 50 lbs had it been 3o lbs the convection would have been faster but for a shorter period of time. Had it weighed 100 lbs the heat would have lasted longer, but required an even hotter fire to reduce the creosote buildup. Oval tubes would have had a lower restrictive flow pattern in turn would have reduced the horizontal surface area.
The ceramic tiles offer a couple of advantages that could have helped the recovery unit as well. 1 the 250 lbs. of mass retains heat for longer periods of time offering a stable continuous release the other advantage is being situated right on the top of the stove the combustion heat remains much higher even after the fire has consumed most of the wood. Keeping the damper partially closed slows the consumption even further. The stove is made with a fire brick lining on the bottom and halfway up the sides, a good design but falls short of ideal the ceramic tiles correct this greatly.
I hope this post serves to help others who may be considering doing a similar build in the future.

[Jon]

The introduction of forced air at the fresh air intake would reduce the criticality of maintaining a hot exhaust to insure proper combustion and a complete reduction of materials to ash without creating the creosote residue in the chimney.

a forced air intake would have been better

Can't help but guess at your next modification: adjustable speed blower drawing outside air. I've never had one of these on a woodburner, but I've definitely taken note when I see this as an expensive upgrade option on fancy store-bought woodburners.

[Frank S]

Jon If I were to add forced air intake I would duct it in from outside the house additionally I would want to add thermostatic control this would lead to wanting to convert it to chip, cubes or pellet fed with automatic ash disposal Add in auto ignition and a couple of silent 10" muffin fans above the hallway and registers above the doors to the rooms and I would have a complete central heat wood furnace. It already keeps most of the house more comfortable than my heat pump with the emergency element furnace. But who knows where that wild hair may land next year.

[Jon]

But who knows where that wild hair may land next year.

I'll also add my vote for some nice wall-mounted vintage beefy mechanical dials or controls for the air intake, with audible clicks or tactile feedback indicating movement, and position indicators that are visible across the room. Or even a ship's wheel. No need to bend over awkwardly 1,000 times per year to fiddle with fine-adjusting a dinky little lever or dial.

Pelletizers are rare as homemade tools. It would be interesting to see it done. I also wonder if wood waste like common yard scraps from forested acreage can be made into decent pellets.

[Frank S]

Some people feed their pellet stoves corn, but to me that would be defeating the purpose even if grown on the farm it is consumed the cost of equipment, upkeep, fuel and time would be more than Propane or electricity. Buying pellets unless buying in 1000 lb bags or truckload shipments doesn't work out from an economical standpoint. Between now and next season I plan to come up with a more economical way to harvest stove wood than by using a chainsaw, And anyone chimes in about using an ax I'm way more into the conservation of personal energy than you can possibly imagine.Right now I have at least 50 dead trees that I have knocked down with my back hoe while hauling dirt in the loader bucket, these will be hauled to a central location for processing.
Someone posted an excellent chipper on here a while back I have the materials to build a modified version of it but I want to make mine so it physically reduces the chips to a much smaller size.
If I were to build a pellet making machine. It would probably be more like a fire log machine

[oilblr]

Thank you Frank S for sharing this, it looks wonderful. you seam to have a good head for this.
Ed

[hilerioal@outlook.com]

Great job, Before seeing the front pictures I knew it (wood stove) was a Earth Stove same as mine. It was featured in a TV show "Buying Alaska" by
several 3-4 different episodes. They are great & well made, And will burn all night. I have been looking at several heat exchangers & will probably make my
own version. thanks for the idea AL

[Toolmaker51]

How the _ _ _ _ did I miss this post? I have interest heating the building. It gets cold enough to freeze large pans of water 8" deep...
The plan so far is to get a boiler and run iron radiators. Along with heavy brick walls and 190k something pounds of machinery etc they should help retain radiant heat quite well. There are great variety in boilers; gas, oil, wood, which all seem likely supply exhaust heat that can be tapped as well.

Speaking of unconventional heat sources, a local shop has an interesting feature. Their rotary screw air compressor, dryer, and receiver are all housed inside a small insulated metal garage, butted directly to the shop structure. Two attic style fans pull warmed atmosphere into the shop, louvered to close in the summer when it vents externally.

Another and one I can report unbelievably comfortable is the European ceramic stoves. One house here, built by Germans 130 years ago, is equipped this way. For better details, I offer https://en.wikipedia.org/wiki/Masonry_heater

[hilerioal@outlook.com]

One of the many good features of the earth stoves is they are ready for external pipe heating boilers from the plug on the back. I have original spect. sheet
for that conversion. good luck AL