loading
      I wanted to build this heat exchanger to reclaim some of the heat that is lost up the chimney of my wood stove. I use the wood stove to heat my workshop during the winter months . I have seen heat exchanger units available in stores for around $160. Since I'm cheap, and I hate to pay money for things that I think I can build myself,  I set out to create my own heat  exchanger. 

Step 1: Materials and Tools Used

Materials
  1. 2- 12" x 12" pieces of 19 gauge sheet metal
  2. 8- 1-1/4" diameter thin wall steel pipe pieces 11-1/4" long  ( I used Galvanized top rail from chain link fence)
  3. 1- 2-1/2" diameter thin wall steel pipe 11-1/4" long          ( I used Galvanized fence post)
  4. 1- 5 gallon steel bucket , the type that Tar, Asphalt roof coating or Driveway Coating come in.
  5. 2- 6" diameter black steel stove pipe unions
  6. 1 -Can of High Temp Stove Paint
  7. 1-Tube of High-Temp Fireplace Cement
Tools I used
  1. MIG Welder
  2. Bandsaw
  3. Chopsaw
  4. Bench Grinder
  5. Angle Grinder
  6. Rotary Tool
  7. Tin Snips 
  8. Various Drill bits
  9. 1-3/8 " diameter Knockout Punch
Nice execution, especially the price, I try to use as much cheap, free and leftover materials as possible. It's amazing what you can accumulate and trade with friends and selective trash picking. I recently found a sheet if 1/8 copper sheet 4x4' standing out on recycle night!
<p>I have to put this out there since i have not seen anyone post about it but:</p><p>UNDER NO CIRCUMSTANCE SHOULD YOU EVER USE GALVANIZED ANYTHING AROUND HEAT!!!!!!! </p><p>GALVANIZED PIPE WILL RELEASE VERY TOXIC FUMES WHEN HEATED/CUT!!</p><p><a href="https://en.wikipedia.org/wiki/Metal_fume_fever" rel="nofollow">https://en.wikipedia.org/wiki/Metal_fume_fever</a></p><p>please find something else to use.</p>
Hi ak47freak, Thanks for your comment. I love the criticisms I receive from people who havent taken the time to actually read my instructables. Had you read this one completely you would have learned that I removed the galvanized coating (zinc) from the pipes before assembling the unit. Therefore, it poses no health threat to me or my inhabitants. Sure I could have used non-galvanized pipes and saved tge trouble, but instead I used what I had on hand, cut off fence posts left over from another project. It felt good to utilize these scraps and save money. <br>
<p>I strongly suggest you look up the causes of chimney fires before you consider blocking and cooling your flue. </p>
<p>Thanks for your concern, I am not a moron. I have done my research concerning acceptable flue temps. My temps drop by about 100 degrees Farenheit between the inlet and outlet of the exchanger...resulting in flue temps of 350 degrees F and upwards. My chimney cleaning results verify that things are just fine..</p>
<p>Try a product called &quot;Acid Magic&quot; to replace the normal muriatic (HCl). Its buffered (not diluted) and full strength so you can actually have your hands in it safely (well - if you have a cut, you will know it right away). Google and see their website. Its amazing stuff and I have used it to do some heavy duty cleaning I used to use straight HCl for.</p>
<p>ibrewer42, thanks for the info about the buffered acid. I too have used it and felt the burn in the cuts lol</p>
<p>Without proper cleaning, this will cause a chimney fire in short order, and in order to properly clean it one of the end plates has to be removable.<br><br>Which means it has to be gasketed on the removable end to prevent smoke and CO2 from leaking into the &quot;people space&quot;...and there are very few reliable high-temperature gasket materials besides Asbestos.</p>
<p>Absolutely agree. <br><br>Regarding seals we use ceramic rope and thermic cement to seal stoves and flues.</p>
<p>I also agree...as with ANY wood burning chimney, proper cleaning and maintainance is required. I cleaned my exchanger after 2 years of use ( 4 days a week through the winters). There was very little soot present in the unit and about 2 cups of soot from the 15' section of chimney. The flames from my firebox extend up into the exchanger, keeping the inside quite clean.</p>
I apologize if this has been mentioned already (there are a Lot of comments here), but when I read &quot;heat exchanger&quot; my first thought was that the cold air that the stove draws from outside would be heated by the exiting smoke. I would call your device a radiator rather than heat exchanger. (I don't even know if my usage is technically correct, but that would be my gut instinct.) Now this is just a silly distinction, and I wouldn't have bothered mentioning it, but it got me thinking: wouldn't your exchanger be more efficient if it was set up like my description above; that is, if your fan was taking cold air from outside, passing it through the exchanger, and then blowing it into the drafter of the stove?
<p>This one great. Thanks!</p>
<p>Great Work, A friend, with a similar shop, Larger pot bellied wood stove, Made one similar to yours. His was square, 5 x 5 rows of pipes. Made a box to enclose fan, [after using an osolating fan]. In cold Upstate Deer Hunting Season, we could work in shirt sleeves well after sunset. These work so well they should be on every wood burning stove to increase home heat and efficentcy.</p>
<p>Great idea, many thanks!</p>
<p><strong>I like your plan very much. I can see areas for improvement but overall you are on to something.</strong></p><p></p>
<p>I would think using a 10&quot; flu pipe attached to the back, then move the fan to the end of that, would help get the air moving through the center of the exchanger. Also if you made a &quot;funnel&quot; to weld to the center tube that is slightly smaller the the inner diameter of the inner circle of the outer tubes, it would help &quot;catch&quot; the air from the fan and force it through the 2 1/2&quot; pipe while allowing the air through the smaller ones too. As for the thermocouple to control the fan, great idea. I would try to find an old feul oil stove w/fan and use the fan control and fan from that, since most I have seen would turn the fan on after reaching a temperature. I do like the heat exchanger though. Have been thinking of getting one for our stove in our family room. The stove we have puts out 120k BUT's and heats up to 2000 sq ft. It will heat our entire house especially if I turn the furnace blower to &quot;ON&quot; instead of &quot;AUTO&quot;.</p>
From a glance it looks like a steel truck wheel which could probably also be used.
I use a wood stove similar to this to heat my garage that is attached to my house. I was amazed by how much the stove alone helped the entire house by heating the empty space and the attic above that is partially owner above the garage. Ian in the process of building my own exchanger for my stove. I am a welder by trade and have my own welders here in the garage but with the help of my company and some scrap, I modified just a little from this one. I rolled a piece of 18 gauge to 10&quot;. I did use my own left over fencing materials. Thanks for the muriatic acid info btw. I have in the process learned that a metal coffee can fits perfectly over the crimped end of a stovepipe and is easier to weld to the exchanger as well. Also, for those that want to try this project that may not be able to get a hole punch like the one in the instructable, I used an 1-1/4&quot; bi-metal hole saw bit and a die-grinder to make holes the proper size. Thanks for this instructable and the incentive it gave me to use my trade and skill to make my house warmer for my family. I will add pics when my project is finally complete. Thanks again for this idea.
<p>The <br> tube blower heat exchanger will extract more heat from the smoke, but <br>much more heat could be gained, as much as 60%, by burning that smoke in <br> a secondary combustion process. The addition of a &quot;heat drum&quot; secondary <br> combustion chamber and a heated secondary air injection. This is a <br>crude diagram, but I have built a dozen or so by both modifying <br>existing stoves and by building from scratch a double barrel system <br>using barrels for both the primary firebox and and the secondary <br>combustion. Not only is greater heat produced and extracted, but opacity <br> of the smoke out the top of the stack cleared to near zero <br>particulates.</p>
<p>Nice diagram man - I built an outdoor wood furnace using one of those barrel stove kits (https://diybarrelstoveoutdoorfurnace.wordpress.com... and I DEFINITELY NEED TO ADD a secondary combustion system to mine. Your diagram is really cool how it illustrates it. Another guy in one of the forums used square steel stock tubing and welded up a nice cage that has a mounting flange as well as a bunch of small drilled holes. The contraption drastically increased his heat output while also drastically reducing the amt of wood he needs to heat his home. Really awesome, thanks! </p>
<p>Do you have contact info ? I would like to see a finished product and get a quote on you making one and shipping.</p>
<p>Hey man, this project of yours is cool - I love looking at various people's wood burning appliances! Ever think about using one of those small metal buckets that u used for your exchanger for a top-down wood feeding system? That's what I used those buckets for in my stove. I have an instructable on here under my name if you want to check it out, OR just go right to my main web site that has more detail. I build a barrel stove outdoor furnace and some of your techniques kind of reminded me of the stuff I used. Enjoy man, thanks! <br>https://diybarrelstoveoutdoorfurnace.wordpress.com/</p>
Very nice seems like it would help a lot thanks for sharing this
<p>Nicely done! Wondering if there's any way to use a thermoelectric module to power fan(s), so that no AC needed, so it'd be totally self-generating.</p>
Wow 1st I wan to say thank you for all the information contained in this post im in the process of creating the same thing I was looking to make something like that but did not have any direction on how to get started thanks to you now I to can make one for my wood burning stove thank you its perfect
<p>Im glad you can use some of my ideas to create your own project. Please post a picture when you complete it..</p>
Is that a ramp in the background or a building???
<p>Its a Vert Ramp and a building, I have storage under one side, and a 16' x 32' work shop under the other side</p>
Respectfully, I disagree about ignoring holes and tolerating loose seams. I would recommend as tight a seal as possible on a stove flue if it is used in a modern building.<br> <br> I was privileged as a youth back in the 1970s to meet many older rural people who came of age before WWII and who still used the old tech. My uncle's mother, who was then in her late 80s was born in the 1890s and distrusted electric heaters. She insisted on her potbelly stove right up to the end. The upshot is that I used these old stoves a lot.&nbsp;<br> <br> One of the dangers of pot bellied stoves or any tech burning carbon is that if you get incomplete air flow, you get incomplete combustion which creates carbon monoxide.&nbsp;If you have a stove whose fuel has burnt down to coals and you get an incomplete draft and you have holes, you can leak carbon monoxide. Carbon monoxide is colorless, odor less and its effects subtle.&nbsp;<br> <br> Wood burnt down to coals produces no smoke and even little smell (depending on the wood). It has become charcoal at that point. With an incomplete draft, the hot air produced by the coals isn't being sucked up the flue but is just slowly drifting up it by thermal expansion alone. It won't prefer exiting the chimney over leaking out a hole. Even the slots for lifting the cooking plates become an exit point.&nbsp;<br> <br> In the past, this was rarely a problem because the buildings, even houses, were drafty with lots of natural air exchange. CO or other gases couldn't concentrate easily. These days houses and even work buildings are insulated to the point of being hermetically sealed. Any gasses emitted inside the structure stay there and concentrate especially overnight when no one is opening and closing doors.&nbsp;<br> <br> All technology evolves in an &quot;ecosystem&quot; of other tech. When you move it out of that ecosystem it's associated risk change. Just because a technology has been used safely for decades in one environment doesn't mean it is safe in another.<br> <br> When we put a pot bellied stove in a modern insulated structure we move it out of the well ventilated environment it was designed for and put in it a closed, air recycling environment, we can make them a hazard. Extra care must be taken in their use and maintenance.<br> <br> <br> <br> <br>
<p>plus u 4got 1 thing that it flow down down then upwards as well. u need a small amount of air inflow in to the structure as well.</p>
Good Point and thanks for all of the information. My workshop is definately not air tight, nor is the stove, and Im not spending the night out there while the fire dies down. My risk factors are low, although I am going to take the advice of Greenman48 and install a CO meter to be on the safe side..
If your shop is naturally drafty then there really isn't any risk but carbon monoxide detectors are cheap enough that they should be standard in any environment where carbon is burned for any reason.<br><br>
<p>wat no work gloves.</p>
<p>ok i c now the head. ok heres a thought try filling the void with sand 4 more therm mass soaking?</p>
<p>u need to look at engineer775 channel an look at his water heater set up. </p>
Cool! Great job.
AWESOME IBLE!! <br>TY for sharing Sir. <br> <br>I just had a brain fart. :P <br>is there a way to connect a 2nd fan blade to the center of the blade that is already there?? <br>My thinking is, with the 2nd fan blade, even the center pipe in the heat will put out some heat... <br>or am I out in left field with this? <br> <br>
To be stating the obvious, simply getting black pipe would eliminate the need to deal with the zinc removal. unless the galvanized was free or already on hand.
That supervising head needs to get some glass between him and that arc! And really, given his lack of regard for personal protective equipment, do you really want this guy--well, head--supervising anything around your shop?<br> <br> Seriously though, it's a nice and well documented project. I'd be building something similar right now if I had a metal shop of the magnitude that you do!
LOL, That Head has been hanging around the shop for quite a few years now(14) . He's kind of a shop mascott, by the way, that is not my personal metal shop, just the tool room at work. Thanks for commenting..
First, Let me suggest that the Zinc That comes off after the ACID Bath, Is Now TOXIC &amp; Baking Soda Has NO Effect on Zinc, After it's been Chemically Altered. <br>Otherwise, You have a Great Project , Glad it worked out for you. <br>To Avoid the Zinc problem in the future, I Suggest you purchase TAIL-PIPING or Muffler Piping from a local suppler, or Get it Cheap at an auto Pick-a-Part Yard. <br>Here's a Trick, Find some Indian Clay in the Ground, wash 7 Filter it so you get Just the Clay &amp; Let it build up until you can fill a 5GAL. Bucket, Keep it moist, Using Sheet Metal Flashing make 2 Round Pipes or tubes, 1' about 20&quot; across &amp; one about 18&quot; <br>Across, Drill Holes in the Lip of the 2 pipes &amp; use 3&quot; Bolts, Washers &amp; nuts, As Spacers for the 2 pipes. Once finished, you should have a pipe Within a Pipe Mold, <br>Now comes the fun part. <br>Setting the Pipe mold on the Ground, ( Note using an old Burlap Feed Sack as a Ground pad) &amp; Fill the space with the Clay. Now Cover it up with a Breathable Screen to keep bugs out &amp; let it dry for a few days. When the ends feel dry, Move the Mold to a Hard Dry Surface &amp; Let it Sun dry a week longer, Then with someone to Help you, Build a Fire big enough to surround the mold( Note or Place it on a Grill &amp; ) Bake it Keeping the fire hot for 12 hours. <br>If All Goes well You'll have a Poor-Mans FIRE-Brick Liner for your Hot-Water-Boiler,, <br>Pot Belly Stove or Backers Oven. <br>Just Wish I had a way of Showing you the Steps. <br>Good Luck.
You can weld galvanized steel safely as long as you use the correct respiratory protection, so it might not have been strictly necessary to remove the zinc (of course, there are plenty of welders who think that &quot;proper respiratory protection&quot; is &quot;keepin' yer melon outta the plume!&quot; but let's not go into that). That said, I don't think that the zinc would be affected by the consistent high temperatures of the stove pipe, but I'm not sure.
Cool Idea....By the way, the purpose of the baking soda is to neutralize the remaining Muriatic acid...So as not to corrode plumbing pipes as it is disposed of..
Pretty nice build! <br> <br>If you would have used something with a larger wall thickness as a housing, I would have recommended to weld some fins to it to increase surface. <br>But I think that won&acute;t work with that bucket and its wall thickness of probably about or less than 1 mm (?!). <br> <br>And in my &quot;very own perception of fluid dynamics&quot; (since I&acute;m not an engineer), it would be more efficient (for the overall air flow through the pipes) to duct the fan and/or make it &quot;pull the air through&quot; to avoid losses due to turbulences on all those edges/protrusions. <br>But my GF who actually &quot;is&quot; a mechanical engineer specialising in thermodynamics says that turbulent flows are best for dissipating heat. Hmmm. I really don&acute;t know. <br>And if you are concerned about overheating the engine of the fan if it &quot;pulls&quot; air, you may extend the motor shaft through the center pipe and install the fan on the other side... <br> <br>An additional approach for maxing out the efficiency of your stove; <br>My neighbour uses an almost similar woodstove and he attached an array of steel pipes to the walls of the burning chamber to increase the surface. Seems to work pretty well (as he says). <br>If you like, I will ask him to take a photo of that build.
These are some good ideas, I was planning on building the original housing out of thicker steel, but then came across the bucket and it seemed to simple, so i used the bucket...a trained welder with better equipment could surely weld some fins on the bucket...I am interested in your neighbors set up, if you do get a picture..
Took a while, but here you are. He also added a &quot;humidifier&quot; on top now :)
Cool.I will have to add some pipes to my stove!. Thanks for the picture.
Switching the fan to a squirrel cage type(like off of a junked van) would solve the problem of the center not getting enough air. for version 2 i would recommend to make it longer and turn it on it's side (so the hot air goes in the little tubes and you blow cold air inside the shell). this way you could make it as long as the vertical rise above the stove. and by forcing air in the top and out the bottom you start differential cooling allowing you to increase efficiency by several times. better yet it wouldn't matter what kind of fan you use as the path is no longer a straight line. so go nuts on fan size. for a better description just google vertical fire tube boiler. Great job.
Thanks, I will check it out

About This Instructable

302,148views

713favorites

License:

Bio: Im just a guy who likes to ride skateboards and enjoys building things that I can use....
More by VertDude:Benchtop Media Blasting Cabinet How to build an Igloo out of snow Woodstove Heat Exchanger 
Add instructable to: