Wood stove heat reclaiming unit

Some call them heat exchangers but that is not quite true.
My Earth Stone wood heater did a fair job as manufactured but I knew from past experiences that it could do much better.
I decided since I needed to pull it out of the house and replace the chimney anyway I might as well do a couple of mods to it
First off I wire brushed it down and repainted it in 2 tone Charcoal gray with KBS Extreme temp paint dark on the lower then I made the recovery unit out of a 15 gallon shorty drum by hole sawing 15 holes in the top and bottom and a 3rd disk to put inside to serve as a means to drag the coke build up off the heat tubes then I welded in the 15 1.94" diameter 16 ga tubes then welded the top to the drum with the clean out plate inside and a pull rod to push or pull it back and forth. after I cut a 11" diameter hold in 1 side and an 8" hole in the opposite side I welded a section of an old water filter tank to 1 side then cut an 8" hole in that I formed a piece of 16 ga into an 8" - cylinder and welded that to the dome of the tank this formed an expansion chamber to allow the stove exhaust to spread out exposing more of the tubes to the the heat. then on the now top of the unit I welded a section of 8" chimney pipe and installed a damper which the stove never had before, which had allowed much of the thermal energy to be lost up the chimney then I painted the top of the stove and the added bits with KBS extreme temp light metallic Charcoal gray.
This paint must be heat cured to 350 to 400°f for a minimum of 3 hrs before the stove could be returned to the house otherwise the fumes can be toxic to some people and they smell really bad anyway. So I built a fire in it then as the fire got hotter I stoked the stove completely full of mesquite
Mesquite burns really hot To help trap some of the radiant heat to further assist in the curing of the paint I made a makeshift thermal enclosure by stacking steel garage door [panels all around the stove . With the intake air regulator wide open and the draw damper set at 1/2 I let it bur for several hours probably 3 to 3 1/2 then I opened the door and saw that I could stuff some more wood inside so I added another wheel barrow full and let it burn the rest of the day and into the night. This morning it had gotten down to 33 ° but when I went out and checked on the stove it was still warm
Attachment 20091
Attachment 20092
Attachment 20093
Attachment 20094
Attachment 20095
Attachment 20096
Attachment 20097
Ceiling support jacks made out of pipe and scafold screws to hold the ceramic tile against the transition box until the cement dries.
I screwed lathing to the bottom to the transition box to give the cement something to hold on to
The transition box is 16" sq. and I affixed 2 layers of 1/4" cement backer board on the 4 sides extending almost all the way to the roof the chimney is 8" ID 12" OD triple pipe stainless steel inner pipe
Attachment 20098
Attachment 20099
Attachment 20100
The stove will sit on a 5 ft by 5 ft 4" thick raised concrete slab the fire protection walls are 5 ft high
I screwed 1" firing strips to the walls then added 2 layers of 1/4" cement backer board then covered that with 3/8" thick ceramic tiles with a brick pattern there will be a heat deflecting mantle on top of the fire walls which will be clad in ceramic tiles and later have LED strip lights hidden under them for lighting effect

That's cool. Oops. I mean't hot. Haven't seen that kind of before. It looks neat too.

<!-- BEGIN /var/www/html/homemadetools/protected/modules/zeus/views/tool/postUpdate.php -->
Thanks Frank S! We've added your Wood Stove Heat Recovery Unit to our Heating and Cooling category,
as well as to your builder page: Frank S's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/homemade-wood-stove-heat-recovery-unit"> <img src="/uploads/205804/homemade-wood-stove-heat-recovery-unit.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/homemade-wood-stove-heat-recovery-unit">Wood Stove Heat Recovery Unit</a> <span> by <a href="http://www.homemadetools.net/builder/Frank+S">Frank S</a></span> </div> <div class="tags">tags: <a href='http://www.homemadetools.net/tag/heater'>heater</a> </div> </div> </div> </div>
<!-- END /var/www/html/homemadetools/protected/modules/zeus/views/tool/postUpdate.php -->

Great! I've toyed with the idea of a similar device in the upstairs dryer duct to recover all that nice heat, without the moisture!

For dryers you can make a much smaller unit out of a 2 or 3 gallon metal bucket with thin tubes and a muffin fan to draw the warmed air through but a fan powered by peltiers might work better since it would be powered by the radiant heat and not draw too much cooled air

I could have made a much larger recovery unit for my wood stove but I didn't want to extract all of the thermals from the exhaust and risk loosing the upward draw

Well today was time to re install the wood stove
I have been wanting an excuse to use my Stanley 12 ton hydraulic toe jack for a year
since the stove is a fixed height and the chimney is fully installed the stove had to be raised an inch to force the stove pipe into the receiving part of the transition box to make sure the pipe had a good seal I pushed it up to an inch and a half
Attachment 20134
I think it looks good all I need to do now is to clad the mantle with ceramic tiles and find me one of those really slow turning antique fans to place in the corner behind the stove on the mantle
Attachment 20135

Congratulations Frank S - your Wood Stove Heat Recovery Unit is the Homemade Tool of the Week!

An interesting build, especially because we don't see wood stove heat recovery units built very frequently on the net, even on dedicated woodburning forums like Hearth.com.

Some nice entries this week: a Drilling Station by Tuomas, a Mill Tram by Captainleeward, a Dovetail Cutter by SteveJustSteve, a Rotary Converter by loyd, a Dial Gauge Chuck Mount by garage nut, a Drill Press Table Repair by Moby Duck, a Foredom Handpiece Hanger by mklotz, a Bench Saw Worktable by markfitz, and a Tool Van Trailer by Frank S.

Frank S - we've added your tool entry to our All Homemade Tool of the Week winners post. And, you'll be receiving a $25 online gift card, in your choice of Amazon, PayPal, or bitcoin. Please PM me your current email address and gift card choice and I'll get it sent over right away.

This is your 4th Homemade Tool of the Week win! Here are all of your winning tools:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/forum/bolt-transport-reciever-hitch-28877#post39268"><img src="https://www.homemadetools.net/uploads/131210/bolt-on-receiver-hitch-2.png" /></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/forum/bolt-transport-reciever-hitch-28877#post39268">Bolt On Receiver Hitch</a> <span> by <a href="/builder/Frank+S">Frank S</a></span> </div> <div class="tags">tags: <a href="https://www.homemadetools.net/tag/portable">portable</a>, <a href="https://www.homemadetools.net/tag/towing">towing</a>, <a href="https://www.homemadetools.net/tag/adjustable">adjustable</a></div> </div> </div> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/forum/d10-dozer-blade-conversion-40314#post57141"><img src="https://www.homemadetools.net/uploads/145623/d10-bulldozer-blade-conversion.jpeg" /></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/forum/d10-dozer-blade-conversion-40314#post57141">D10 Bulldozer Blade Conversion</a> <span> by <a href="/builder/Frank+S">Frank S</a></span> </div> <div class="tags">tags: <a href="https://www.homemadetools.net/tag/blade">blade</a>, <a href="https://www.homemadetools.net/tag/modification">modification</a></div> </div> </div> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/forum/trailer-made-scratch-becomes-boneified-tool-49903#post71491"> <img src="/uploads/155789/trailer-with-cranes.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/forum/trailer-made-scratch-becomes-boneified-tool-49903#post71491">Trailer with Cranes</a> <span> by <a href="https://www.homemadetools.net/builder/Frank+S">Frank S</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/trailer'>trailer</a>, <a href='https://www.homemadetools.net/tag/crane'>crane</a> </div> </div> </div> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/forum/wood-stove-heat-reclaiming-unit-64151#post100865"> <img src="/uploads/205804/homemade-wood-stove-heat-recovery-unit.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/forum/wood-stove-heat-reclaiming-unit-64151#post100865">Wood Stove Heat Recovery Unit</a> <span> by <a href="https://www.homemadetools.net/builder/Frank+S">Frank S</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/heater'>heater</a> </div> </div> </div> </div>

I can truly appreciate this build as I have lived all my life with just wood heat at home (nothing like the radiant heat from a wood stove 😀). My shop has a plate sleel stove in it that could benifit from some rendition of this heat recovery unit. But first it needs insulation! Thanks for showing.

As a side note the panels you used to hold the heat in during the paint cureing jogged my thoughts to the ones that my boss has stacked out back of his shop yard from building his business building. May have to see if he will turn them loose. They would work great for the walls of the car port garage I want to build out of a greenhouse frame I salvaged last spring. The thing was very big for a back yard, back road green house, something like 32x80! All but a few of the rafters failed where the collar tie met the square tube rafters. No heat, too much snow, and not cutting the plastic as a last resort = total collapse. And to light of a frame for that wide a house in this area. What remains of the rafters will make about a 16 foot wide structure. Not enough time in the day.
Eric

I hate my computer these days.
I started to create a reply and the keyboard jumped then wiped out everything I had typed.
So I will create one in word then copy paste and see if that works better.
Any way the heat recovery unit worked well except for a couple of issues which I will address when I build a stove for my workshop and install it there.
I found that I had to maintain a very hot fire in the stove in order to prevent coking or creosote buildup. I used the cleanout disk several times but found that it was a lot of trouble eventually I had to use a slide hammer just to get it to move back and forth so I removed the unit. I wish now that I had flattened the tubes to an oval which would have meant the exhaust gases would have a higher velocity and would have remained hotter until reaching the chimney. There is a fine line between the amount of thermal recovery and maintaining a high enough exit velocity to insure proper combustion has occurred. Different wood has varying amounts of creosote in the unburned exhaust. 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.
After removing the unit, leaving the original straight stack to preserve heat I stacked 250 lbs. of 6 inch ceramic tiles on top of the stove, creating a thermal mass for heat storage. In doing this I found that I could build a medium to large fire of an evening with a small 8 inch fan behind the stove on the mantle and the ceiling fan on low with outside temps falling into the low 20’s or even down to single digits re stoke it once around midnight to keep the front half of the house comfortable so I blocked off the back half since we are only using the back 3 bed rooms for storage anyway I also burned through less than half the amount of wood we were previously using
So there you have an update to the heat recovery unit at its present design there needs to be forced fresh air to create higher combustion temperatures or the tubes need to be oval possibly a combination of both

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 :thumbsup:

Cheers Phil

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.
Attachment 22881

Quote:

---

Originally Posted by Frank S

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.

---

Quote:

---

Originally Posted by Frank S

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.

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.

Quote:

---

Originally Posted by Frank S

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.

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

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

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

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

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

For an industrial application I would want to design my heating unit to be at the minimum a tri fuel unit IE gas Oil & organic such as wood pellets or chips. with forced air combustion automatic ash removal the unit would also have an exhaust gas re-combustion chamber with massive thermal mass forced air convection I imagine that I would construct the combustion chamber out of Inconel or the modern equivalent with integral boiler tubes for radiant circulation heating.
There are many secondary heat sources associated in a machine / fabrication facility such as the heat from welding or from the electric motors running the machines.
Vent hoods over welding stations should be able to serve a secondary purpose. They are primarily thought of as a means to removing the fumes but they can also provide a significant amount of passive heating which can easily become passively active by the addition of small thermally powered fans.
Cooling a facility can be more problematic than heating but the total thermal mass helps there as well.

The only stoves I've run across are small, some had water jackets.
My fervent hope is low-pressure water in iron radiators will be satisfactory. Natural gas and a secondary combustible fuel, to avoid petroleum if possible. I've collected a couple thousand pounds of iron radiators; estimating the surface area of them in comparison to a very large local house [~10,000 sq. ft.]. They'll be on shelves above the floor, near ceiling height. My 6500 sq. ft and 16' flat ceiling need 375k. It will be drywall, with blown insulation. The joists are 8" so at least R19+, windows are glass blocks, so it's sealed decently.
I don't have cooling other than large shop fans. The loading doors are on 3 sides, summer's tolerable.

placing them high up off the floor near the ceiling id going to be great providing that is where you are working wearing your anti gravity boots.
Sorry thermal dynamics 101 heat rises.
the other side of that coin is having them at floor level they are the most in the way objects in the world. Impossible to keep an area clean around them and if they are near any machine that generates swarf they act like huge chip collection repositories.
Ideally using long finned tubes placed about 3 ft off the floor and having a shelf over them works best
Using the cast iron radiators if they were mounted at about 8 ft high from the floor with a bright surfaced deflector behind and above them and smallish muffin type fans https://www.amazon.com/Achla-Designs.../dp/B001FXVJ1U
behind them or better yet under them forcing a low volume air flow up and around them, the deflector which would be behind and above , plus if louvers were horizontally mounted in front these would direct the air flow down and out.
Heated air almost needs to be moved by convection for best results but a gentle push greatly aids the areas to be covered. drawing the colder air upwards to the radiators will help a lot as well.
Anything that can be done to move the cold stagnant air near the floor to force it to be absorbed with the heated air also helps

I had all but forgotten about this thread as with many I have started only reminded of it just today by someone thanking me for a post in it.
Let me make an update while the heat reclaiming chamber I made functioned admirably the first winter I used it I later removed it for reasons of difficulty in cleaning of the many passage ways. the cleaning plate I had in it really needed some modifications but as the unit was welded up solid the only way to do this would have been to cut it open make the mods then weld it back up.
However with a hot enough fire the soot would not form on the surfaces and previously deposited soot would eventually be expelled this was hardly possible to do in my house as even on the days that winter that dropped into the single digits due to the amount of reclaimed useable heat available we never were able to build a large extremely hot fire for long enough periods of time or often enough to maintain a decent enough draw velocity which would pull the flames fare enough into the chamber to help with the cleaning. Smaller fires were more than sufeincent to heat nearly the entire 1850 sq ft of the house while not making the living room so unbearably hot. on one day where the temps did not rise above the mid teens we actually had many of the windows and the kitchen door open for a good part of the day because the heater had brought the living room temp to over 100°f and the kitchen to 90°f. For that reason and reasons that it wasn't very aesthetically pleasing
The following winter after removing the chamber I placed about 300 lbs. of ceramic tiles on the top of the stove to serve as thermal mass I still have to watch how large of a fire I build in the thing and not even think about building a fire in the mornings if the outside temps are going to rise into the 50s or better the thermal mass will still radiate enough heat to last until the outside warms up.
I saved the chamber to eventually install in my more than 6000 sq ft work shop but the heater I plan to construct to go under it may possibly be a tri fuel IE wood, oil, or propane