Wood Stove Water Heater Experiment - Surprising Results! Part 1

My goal in this video was to build a super efficient off-grid wood-fired hot water heater. I'm fascinated by this concept because of its many applications, from heating homes with in-floor systems to providing hot water for off-grid showers, agriculture, and even hot tubs.
Super Efficient Woodstove Build - • What I Learned Buildin...
Responding to your questions and comments on this video - • Addressing Your Questi...
Comparison to Rocket Stove - • Rocket Stove Water Hea...
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#woodstove #offgrid #waterheater

[@whm304]

Reverse your water flow. Cold in at top, flow down, hot out at bottom. This is known as counter current exchange and extracts the most heat from the flue gas. Great build!!

[@BRZinAhurry]

Had to check this out! Thanks for the pro tip! 🙌

[@BenBrand]

I'm so glad this was already the top comment that I could thumbs up on!

[@stevenfelix6915]

@@BenBrand Same here. This is super important for maximum efficiency. It would be awesome if he could reverse the water flow and compare the different time? Love this!

[@EnglishLevy]

Even though it would be at the expense of thermal dynamics transfer of heat energy, would it be worth trying sans pump and allowing convection to do its thing in current configuration?

[@BenBrand]

@@EnglishLevy maybe if the water barrel was lifted up so its height was the same as the coil. But with it being down below all of the water in the coil will get hot but there would be no wear for it to flow heat wise up since the top tube goes down so far even below the bottom tube before it gets into the barrel. It only takes a very tiny amount of movement to get an order of magnitude more heat so having a very small pump is worth it for sure

[@bluntone2273]

I have no intention of making this contraption but I must compliment the video maker. Clear instructions, no wasted time, no filler, no stupid music. Bravo!

[@mykidsfuture5582]

Exactly. Editor knew EXACTLY what we didn’t need to see and cut it out or sped it up. 👍 Excellent work.

[@1yachtcarpenter]

@@mykidsfuture5582 Nail, head, you know the thing.."Joe By-done" Ret.

[@sunriseboy4837]

Top call!

[@kevinbush4300]

Yep… awesome! Perfect presentation.

[@highplainsdrifter6255]

Best put together video I've seen in ages. Clear and to the point. Just subscribed to your channel. 👍✌️

[@Mr22Jwc22]

Having done this 40 years ago, I can tell you that if you put the copper coil inside the pipe it will be covered with creosote in a few months which will insulate the coils which will keep the coils from heating properly. I put the coils on the outside of the 6" pipe and slipped that inside a piece of 8" pipe with 6" to 8" reducers on both ends of the coils to keep the coils out of the smoke. That worked the best and still gets the water hot enough to burn you. As far as I know it is still working fine. Keep up the good work. Jerry

[@Flexsan]

Could you burn of the creosote by firing it without any water in the loop?

[@GreenhillForge]

copper starts to get soft at around 750f and melts at around 2000f so you probably could get away with it if you really dialed in the fire. I think the only way we'll know for sure is to try it. Maybe after all the testing is done on this first unit I'll have to give it a try...

[@GreenhillForge]

I'll be trying something similar soon so I can test the differences in efficiency of thermal transfer. It's definitely the safer route though.

[@Mr22Jwc22]

@Flexsan, I'm sure you could, but it would difficult because you can't easily control the temp and you can't see the coil. One rule I learned later on was, If at all possible what ever you do try to make it Maintenance Free. Jerry

[@primusolaris7821]

​@GreenhillForgecould you stick a bunch of peltier modules on the upper part of the chimney to generate electricity for the pump? That way it could be truly off grid and it would double as a temperature control system to protect the copper.

[@jChristianGonzález]

Thank you for featuring Proopsy in one of your videos. I took your advice and contacted him for modular homes, and the house have been incredible. Paid slightly less than $29k, and now I’ve paid off my $129k 15 year loan in 8 months. Now totally debt free because I rent it out on Airbnb. Love having no debt for the last 5 months. Thank you Proopsy!

[@craigsudman4556]

Oh man no waisted time, no repeating the same phrase, clear and concise and to the point. A pleasure to watch. Great video thumbs up.

[@sunriseboy4837]

And no bullshit "industrial noise pollution"?! LOL!

[@ebc1f7]

This is how videos should be. I definitely get excited when new videos come out. Always top tier.

[@jerryantaya1266]

No doubt. It's really something you learn to appreciate isn't it 😅

[@sunriseboy4837]

@ Good call.

[@acutedrummer]

we NEED more MEN like you in this world.....oldschool patient go the distance kind of craftsmanship ingenuity and creativity , your an absolute GEM SIR , thank you sooo much for sharing these videos ill pass your channel on hope it grows and grows!

[@thomasjefferson4358]

I calculated that your test setup heated water equivalent to a 5.63 KW electric water heater, or electricity from 16 large (390W) solar panels at peak solar conditions running at roughly 90% efficiency. Compared to commercial gas water heater, it is equivalent to a 24,000 BTU heater running at 80% thermal efficiency. Bottom line, I'm so impressed with your design and applied workmanship. Excellent efficiency of your heat exchanger... you have a natural design sense of a good thermal engineer.

[@markusalan1844]

Wow, very impressive! This video shows about 5% of the actual work you put into this. Hours and hours of planning, sourcing materials, welding, measuring, cutting, grinding, lighting the fire, etc. People like you are what made humanity great. Bravo!

[@longwildernesswalks]

Bro. This was a master class in thermal transfer in practice. I've sat down and thought about this exact creation numerous times. I work in the industrial water treatment industry and have seen thousands of heat exchangers. This was very well done. I've never seen a pipe bent with ice. We've always done it with sand. Great, magnificent work. Bravo!

[@jeroenkoehorst4056]

But this design can't be cleaned. After a few burns you get serious buildup around your copper tubes, essentially insulating the tubes.

[@LuigiRuff]

With the sand? Internal? You can explain to me because I have to do it with a 1 "tube ...​@@jeroenkoehorst4056

[@LuigiRuff]

With the sand? Internal? You can explain to me because I have to do it with a 1 " tube ...

[@henrymoreland8719]

As someone with an imagination , but who struggles to put a shelf up straight, I am continually impressed by the ingenuity and practical ability of folk like yourself. Well done sir.

[@shootermcgavin991]

Came for the experiment- stayed for the haircut. You are awesome- wish you were my neighbor! Best of luck to you !!!

[@wilzacj3297]

A tip of the cap to you sir!! This is a gem of a how-to video complete with real-world testing in the same vid!! The world needs more like you, great build, great explanations, great lighting, great safety demonstration, beautiful countryside too. Consider swapping the direction of cold return water into the top and out the bottom to oppose flow of gases to water. As an aside I really enjoy your power mullet, keep it up you're doing wonderful work here!

[@eadgbefreak]

This the by far the best build video I've ever seen! Well edited, minimal explaining, fast forwarding of the actual cutting/welding scenes and keeping it as simple as possible. Nice work!!! You've earned my sub!

[@JuliusCesar2781]

Honestly, I never ever in my life saw somebody working as fast as you do !😂 Nice !!

[@DormanDiaries]

This was the best most comprehensive video on this subject I’ve seen. Particularly like your thinking with the spacers to expose as much of the surface area of the pipe as possible. Bonza!

[@TannerDulin-j7g]

I have no idea why I ended up here but this has been one hell of a video great job on the build and the video

[@bonkywollocks3078]

Thanks for the warning about the toxicity of the insulation. Thumbs up for that alone. Good man.

[@eliseleonard3477]

This was fun to watch, as I lived for a few years in an entirely wood-heated house in Vermont with a wood cookstove from the 1920’s that had a ‘water jacket’ (pipes in the lining of the firebox). It was attached to a water tank behind it, fed by gravity. Within an hour or so of lighting the stove there would be a supply of hot water for dishes and showers. You could tell how much hot water was left by feeling the tank, which through convection would feel warm to the touch from the top down. You just had to be careful because the hot water could get VERY hot if the stove had been going for a while without using the hot water.

[@willdodd1038]

I can appreciate this greatly! For to heat a wooden hot tub I built a heater very similar to this. For the coil which was of 304 stainless, 5/8” tube, instead of ice, I filled it with salt used 10” and 6” pvc pipe for the mandrel, fabricated a “C” “wrench with a curved pawl at one end of the “C” I fitted with a nylon plastic insert to let it slip and accommodate the radius of the tubing. The wrench had about a 4’ handle welded on, I did my twisting vertically. I put a 6” coil within the 10” coil, with the spring back of the inner coil it also gave me a fairly close clearance. I mounted a “ or 9” Nat.Gas burner under it held vertically spaced with a steel strap frame. For the shroud, again very similar, it was a double “tube” a separated w fiberglass from sheet metal. At the end I found the the greatest efficiency, and the quickest heating time was by flowing maximum volume of water thru the coils. At first I had it plumbed to be one continuous coil but I found it best to separate the bottom and top of both coils and installed a “Y” necked from 5/8” up to 1 1/2” and wound up with a small 1/4 hp transfer pump jst for circulation, then a standard 2 1/2hp swimming pool pump with a strainer basket for heating and to run aeration jets. I regulated the gas valve with a waterbed thermostat (had to tweak that a little). It all worked like a champ for 15 yrs. The 6 1/2’ tub, & heater set up looked great trim with cedar privacy surrounding went with the home when we sold it, heck IT sold the house! Also, instead of a flu, I finally mounted 3/3” discs 6” apart welded to 1/2” rod as a “Heat buffer” and stood it in the center of the inner coil. Very VERY IMPRESSED with you fabricated BREAK !!!

[@ConorFenlon]

This content is the peak of modern civilisation. Incredible.

[@RocVultures]

My folks had a system like this in their house for decades. During the winter, they'd switch to the heat exchanger attached to the woodstove, and use that to heat the house via baseboard hot water heaters. There was a boiler for that system as well, but they'd only use it during shoulder seasons, with the woodstove providing all the house heat during the winter. It was a complicated system, but it really worked great for them.

[@sxcv8131]

This coil build is so satisfying, I would do it the same way. Incredible craftsmanship!

[@undergroundblu]

Love your content mate! One of my favorite subjects paired with your delivery, filming, editing and knowledge all combine to create an awesome clip. Thank you for sharing all the small details. Hopefully one day I'll build myself one of these and will be referring back to your videos. You'll hit 100k+ if you keep this up.

[@douglasthompson2740]

I had an Earth Stove with a coil in the fire box in 1974 during the oil embargo. The coil consisted of steel 3/4" pipe run in a lateral direction at the back of the vertical wall on the stove. Three runs. The stove was upstairs and the water tank was in the basement so I used a circulating pump to keep the flow going. I was in series with my domestic hot water. Funny thing I didn't expect is I had an oil boiler also in the basement with a coil in it. The wood stove circulating water through it kept the boiler warm. The boiler was shut off since they wouldn't sell oil. It was a baseboard hot water heater. Never had a problem with creosote because I burned a wide open fire once a day for thirty minutes. The uninsulated stove pipe section up to the Metalbestos would glow cherry red in the early morning dark. This kept the coil clean as a whistle and the chimney as well. A friend who was scared of wood heat would only percolate her stove and every month or two she would have to clean the chimney with a resulting five gallon bucket of creosote. I would feel guilty and go check mine every four or five months. I never found any significant build up at all in the five years I ran it. Not only that but firewood was hard to get so you burned what you could lay hands on. The first couple of years I burned green wood, drift wood, all softwoods and still not a problem as long as I burned it hot two or three times a week at least. While it was roaring with the door ajar I would take a thirty minute hot shower to start the day. Never once felt the heat of the water drop although I did not test for numbers. Worked very well for me. Keep in mind this was before the secondary burn and other efficiencies of the modern wood stove. This topic also brings to mind the old fashioned wood cook stove setup. The stove was against the wall which bordered the bathroom so it heated it as well but to our point here there was always a gravity hot water tank mounted on the wall behind the cookstove to provide hot water. A relatively efficient form of wood heat although the other rooms were not well heated and would require a smaller stove to keep the end of the house warm. The bedrooms were upstairs so the rising heat warmed them. Long before well insulated homes and some were mighty drafty but it worked for them. That small coil reverse heating the large boiler pointed at how efficient it was. I was dumbfound when I put in a new boiler (on demand Systems 2000) in 2009 and saw the tiny heat exchanger that it used mounted on top of the boiler casing not even in the fire box!! It was about the size of two cigarette packages yet able to keep a constant flow of hot water going as long as the oil holds out! I would have to look up the efficiency numbers on that which must be amazing. Think of a way to utilize that in your water system. It never sees the fire just the hot water for the baseboards runs a zone through it heating the domestic water for use. So no contamination no electrolysis, no soot or creosote.

[@2Smoke311]

Nice design!! If I may offer a little advice, you may want to change the steel holding the copper tubing in place to a "friendlier" metal like brass, or maybe use copper strapping. Due to a process called Electrolysis, the two metals touching will result in one wearing the other one down over time, causing leaks.

[@winksworks]

Isn't the copper higher on the nobility scale than steel?

[@2Smoke311]

@winksworks No, it isn't. It is a better conductor than almost every other metal, but it will almost always lose the battle when placed too close to other types of material. Especially galvanized pipe.

[@sunriseboy4837]

@ Well spotted!

[@BOSS_DOG]

just add tefgel to contact points.

[@winksworks]

@@BOSS_DOG how do I know you're a seafarer 😂

[@talleyrand2739]

WE had a slow combustion stove on the farm a Carmichael with a wet back,it worked on thermo siphon no pump involved ,if water got to hot had a shepherds type crook vent pipe to let out steam and over flow water to the roof into the guttering and back to the water tanks, the hot water tank was on the roof ,well presented and learned a lot thanks

[@bowesterlund3719]

Super nice work! You can bump the efficiency by reversing the flow in the coil. Inlet at the top and outlet at the bottom. Reverse flow heat exchangers is a more efficient config.

[@David-s3k9h]

Precisely what I was thinking. Deffinately helped my offset head double helix reflux condenser I use to distill "fuel" with.

[@saraadair8362]

Ive been heating house, hot water , and cooking on a woodstove for the last 49 years I love your video , and the way you present the materials and instructions on how to DIY one for ones self. Im unqualifyed to build one myself but if a pre made was for sale Id sure consider buying it, its way better then the stainless steel pipe I got in the firebox of my cookstove. thanks for your sharing

[@navagatingthroughthebeasts2908]

Right 👍

[@asqirl8425]

We live in a travel trailer and do physical labor, we stick framed a bath/sauna house complete w/ a half dozen slider insulated big windows that came our way, w/a wood stove under the clawfoot tub. Your video was top notch! To complete our "rural living in comfort" we use a metal snow shovel to put the coals from the fire in a wheel barrow w/water to make biochar for the garden

[@Dancing_Alone_wRentals]

All that is fascinating. Well done!

[@robertchautardjensen6846]

Nice reminder of a concept that has been around for over a hundred years. It works, my grandfather built one of these over 70 years ago and discussed the concept with me in the 1960's. He used a G cylinder as the sheath and pushed heat into the bottom of the G cylinder from a chip heater and exhausted the smoke through a chimney welded to the top of the G cylinder which was cut away around 200mm from the valve assembly at the top of the G cylinder. Very efficient.

[@zacreed5855]

Your presentation style is so clear and concise, I really appreciate how effectively you're sharing you idea and the thought process along with it. I don't do any welding and was trying to figure out how you were going to manage those standoffs, but cut to fit and weld in place is the absolute best way to go there. Cheers

[@wyoblacksmithtools3097]

Very impressive! Great innovation and design. I am 78 and your video has inspired me to get out to my shop and get something done!!! New subscriber here. Thanks for posting! Jerry

[@patrickjoseph5028]

You are simultaneously condensing your smoke by rapidly transferring its heat to the water … thereby collecting the remaining combustible solids contained in the smoke onto your coil and interior of the box….eventually a chimney fire will happen…..I would suggest keeping the smoke off the coils by having the copper wrapped around a stove pipe that would be easy to clean or be kept creosote free with a higher burn temperature.

[@1kreature]

That's true. There's a balance to be had between how much heat you extract and how much buildup you get. My woodstove is one of those wide ranges and it takes out almost too much heat. 3 years in a row the sweep has not found anything in the pipe but I have to do a cleanout of the stove each year instead or it clogs up!

[@briancarnegie2603]

Yes, and this buildup will happen rapidly in a few hours of burn choking the spacing between the coils and the efficiency will collapse right along with the buildup.

[@dougaltolan3017]

Came looking for this comment. That buildup will also choke the flue, not good for the stove.

[@danielwarren7110]

Same came here to look if anyone had mentioned this, and warn about flue fire. Think although a loss of heat conversation for safety a modified design that be slid over a traditional flue, this would allow a couple of things protecting the coils and the ability to disconnect it and reconnect it to a flue on a fire without the need to remove the original flue, but the butterflies top and bottom would have to be put into the permanent flue not the heat converter, but this would allow the system to be moved between multiple fire places.

[@junkyardjimmyriversiderecy6722]

Yes copper outside of the pipe then insulation and outer pipe will still condense however there is additives that helps prevent this

[@cronocide]

Great stuff, as a heating engineer this idea has been living in my head for the past 20 years 🏆

[@Vikingwerk]

Really nice design, smart way to deal with bending the copper.

[@CommanderCODY05]

You really make me want to build something like this myself. You really explain it amazingly. Thank you so much.

[@nw9353]

Outstanding !!! Clear, to the point, and a pleasure to watch from start to finish.

[@Sithehandyguy-London]

Great video man, very clear and informative. I see some comments about the copper sooting up over time, but you're extracting the most heat with it directly in the flow.

[@GreenhillForge]

Thanks! I've got another design/test video coming out soon

[@robwhite2282]

Dude! That was amazing! Your craftsmanship is outstanding. Your video editing skills are incredible. And to top it all off you own a German Shepherd! Best dogs ever.

[@GreenhillForge]

Thanks! Props to the wife for the editing.

[@MsLittlemare]

I noticed that too! And it’s the German variety I think! What a great breed!

[@Hannbaal666]

It's a pleasure to see a content creator build cool stuff without 50k+ $ of sponsored equipment! you did really well with something almost anyone with a garage could manage to have at home, keep up the good stuff!

[@thebicyclesafaris]

This is so awesome! I have been pondering this concept for years, so excited to see a version of it in action! You are fantastic, and thank you for sharing with all of us!

[@dreamsdocumtru81]

Off grid hot showers you just made off grid truly perfect lol

[@chasbader]

I love this type of content.

[@davevaneable]

I didn't know I needed to watch this, this morning. Fascinated - couldn't turn it off. Great build!

[@ianblack58]

I did a science fair project about efficient energy use and included a hot water heater nearly identical to your design, the teacher said it wouldn’t work so I built a working scale model to prove it. He was an ass so was still sceptical in an ego driven way. I knew he was wrong and I also got me a shinny gold medal for my effort at the fair. So there Mr ………! (No names)

[@I2Speedy4U]

In school I made an ammonia condenser. We generated the ammonia with an ammonia salt and a strong base. The vapor would leave reaction chamber and condense in a stainless steel coil that was immersed in dry ice and acetone. A collection vessel was under the coil that was also immersed in the dry ice solution. Within 15 minutes enough NH3 was collected to add my Li and other necessary ingredients. By lunch the entire science department was in overdrive and eating was the last thing on our minds. Go science!!!

[@ParkerQualityControl]

@@I2Speedy4U that’s an amazing story Jesse!!

[@amyspring3891]

It’s a water heater. Not a hot water heater.

[@ianblack58]

@ well your not wrong

[@greenidguy9292]

@@amyspring3891Lol, right. Why would someone need to heat already hot water??

[@raindogs451]

Generally, I'm not a fan of brazing, but there are a few places it's the best application. Solder will liquify at around 500F. Brazing rod will liquify at 1300+F. When high heat (or fire) is a concern, brazing will liquify at a much higher temp. Great video, Great work. You're a craftsman

[@A.X.76]

I like your build quality and the video was excellent. In Boy Scouts one of our scout masters had a “keg” or a stainless propane tank (not sure which) but it had a coil inside surrounded by water. He heated the water in the tank and the coil water came out the shower head. Metering was just a ball valve. It was awesome!

[@genuismensa]

lmao they also probably know how to make a moonshine still too!

[@A.X.76]

@ what happens at scout camp..stays at scout camp 😁

[@Eduard_Kolesnikov]

I must admit that the video perfectly present the work, masterful work, without any music, no wasted time, perfectly shown in the most informative way.

[@thegary9584]

By adding metric measurements instead of just the imperial…you’re a star mate 🎉🎉

[@Andeving]

Also why is he using Fahrenheit when he lives in UK? (British accent, Tesco bag at 19:07)

[@SuperSpecies]

@@Andeving power outlets too...

[@SuperSpecies]

He does not have a British accent though.

[@km0e69]

Never Never use that 3rd world form of measuring called the metric system

[@ricos1497]

@@Andeving he doesn't have a British accent. Good spot on the Tesco bag though, perhaps he lives in the UK? Or maybe Tesco is a tourist hotspot for the travelling American, and he brought home a souvenir? Either way, it's incredibly useful to provide both imperial and metric. I wish more channels would do so. It amazes me the number of people that use feet and inches in the UK (and farenheit too), and never bother to provide conversion for the viewer/reader. I regularly read articles in the UK press, and on UK TV programs, that state things in feet without conversion. It's bloody annoying, given that anyone that went to school in the UK beyond around 1980 would have been taught in metric. Although, weirdly, I could never fathom (pun intended) a person's height or weight if described in metric, despite weighing food in metric and measuring objects in metric. Kudos to this channel.

[@sennest]

Brilliant, just brilliant! Had a professor of English lit. say that genius is "doing that which is often thought but never done". Thank you very much!🙏🙏😎👍👍

[@advancednutritioninc908]

Excellent Design and Fabrication!! Very Efficient - Well done!

[@kevinrishton1060]

WOW! Great job on the video. Well done love the project! People really don't understand how vulnerable our power grid really is. What you created is great and useful in a multitude of ways!❤

[@Nocrii]

19:15 - I love that scientific representation of temperature by touching your face to it lol

[@GreenhillForge]

figured it was the best way to visually prove how cool it was, lol

[@hotrod500hp]

face is definitely more sensitive then callused work.hands. the viual is a hug to the devise that takes care of you

[@Rob-i9k]

I am very impressed with your build. In fact, you just made me think... in floor off grid heating.

[@GreenhillForge]

absolutely

[@justinakapickles3072]

If you added a thin metal pipe in the middle of the coil and fill the coils space with sand. Cleaning would be better and the sand once heated will stay hot long after stove burns out. Might save on fuel

[@Andeving]

Careful with heating sand, it produces silica at high temps. Should be ok near the pipes with the water running through keeping it at max 100C but the edges of the square may reach dangerous temperatures.

[@codypendency9482]

@@Andevinga wood stove only gets to just under 600 degrees the chimney will be way cooler then that and silica is a type of sand and sand doesn’t melt until 1700°c maybe I’m misunderstanding what your saying lol

[@CNCmachiningisfun]

Great video :) . I made one of these, about 30 years ago. While it was only 1% as well built as yours, due to no electricity on my farm, it could easily boil the entire contents of a 180 litre water tank within 3 hours. Yup, the tank was literally vibrating, as the water inside was boiling - - and all without a water pump! Needless to say, I was massively impressed at how well it worked :) .

[@jvin248]

Try using your heat exchanger without the pump, just free flow pipes. Cold inlet at the bottom of the tank, hot fill at the top. You should find the external kettle still heating up because the hottest water rises to the top and automatically pulls in cooler water from the bottom of the tank.

[@GreenhillForge]

That's coming up soon

[@greenwood4020]

BUT, ONLY IF THE TANK IS HIGHER THAN THE COIL. If you want a thermosyphon to work, then the receiving tank needs to be HIGHER than the coil, so the hot water can rise to expand into it. The pipe must slope UP The tank's coldest water at its bottom will also then drop to the bottom of the coil. The pipe must slope Down.

[@johnqpublic9074]

​@greenwood4020 Not true, most early tractors used thermosyphons, the radiator was at the same height as the cooling jacket. The heat rising and cold return allowed circulation.

[@greenwood4020]

@@johnqpublic9074 You are correct. I should have stated the most efficient designs are, as I described. Most model T Fords used the thermosyphon system, but it was susceptible to overheating if worked heavily, but served well for most Model T usage. Many types of water pumps were available as after market accessories.

[@charliemyres5450]

I love your ingenuity with the coil-forming and i am going to share it with my metal-shapers' forum. While it was unnecessary in this experiment; the storage vessel needs an escape vent, so that boiling water can escape. If it can't escape the vessel becomes a bomb and will explode. Be WARNED people have been killed by homemade-hot-water systems. In Western Australia the vent is a tall piece of 1/2" copper pipe, with the top bent into the shape of a shepherd's crook. Boiling water can then fall onto the roof of the house where it is unlikely to burn anyone. Love your movie and your presentation!

[@GreenhillForge]

Thanks! Yeah, a closed system definitely needs some kind of pressure relief. I show my off-grid water jacket wood stove shower system in my next video and its a closed system so it has a built in pressure relief valve.

[@markoperala69420]

thanks for using metric and celsius units, not many american youtubers do these days, THANKS

[@Isaacbp]

So I watched this vid and then went and watched the fireplace build vid and I am just amazed at the efficiency and elegance of how well you designed and built both. The issues that I wouldn't of even considered and then when you mentioned them I imagined complex solutions but then you just "Add a couple of holes" and it works beautifully.

[@nomadicoasis9260]

Your coil will be thickly covered in creosote (less efficient) in 3 weeks or less, and needs to be cleaned. It has the BTU's of coal and will make a fantastic chimney fire... Allowing for cleaning must be part of the design. if your water tank bottom is 2ft. above the top of the coil you don't need a pump. Ask me how I know...

[@zanezip85]

Ok, how…Assuming you tried it w/reverse flow?

[@larryerving4141]

Creosote was the problem that I had when I attempted a similar water heater.

[@nomadicoasis9260]

@ my system produced 4 to 6 litres of creosote every 3 weeks. but It did the job for hot water. easy cleaning must be built into the system.without diligent maintenance it's a chimney fire waiting to happen.

[@nomadicoasis9260]

@ mine had no pump and used thermal circulation. it works just fine.

[@KcCorey]

What energy you have, it's awesome. So well done. As I don't have all the skill sets or tools, I come away understanding how and why. Then I wish I could replicate the projects. Love the little stove. Saw you build it, didn't see the end product working.

[@malefunctionable]

Great project, impressed by the efficiency! And nice editing too, I predict a steady rise in views and subs in the future! I subbed after watching the stove build video and am looking forward to the next! A solution to have a circulation pump also driven by the heat would be amazing, it's such a critical part of the system and would make it pretty mobile. I guess a stirling engine would be too weak🤔 This is going to affect my sleep tonight I'm afraid😂

[@GreenhillForge]

Thanks! I didn't get into this in the video but I'll try to remember to touch on it in the follow up video, but these types of systems can actually be run without a pump. Hot water expands and rises just like hot air does, so if you place the barrel vs the heat exchanger properly the hot water will naturally rise through the copper coil by itself. The only issue with this system is that it might be too hot, meaning the water doesn't move quickly enough to keep the copper from overheating. That's why I added the pump. Maybe after the rocket stove test I'll try taking the pump out and see what happens, at least that way if the copper melts I got the tests done first.

[@malefunctionable]

@GreenhillForge Yeah, I've seen a few projects without a pump, but it does seem to be very finicky to get to circulate fast enough, and then it could become somewhat of a safety issue. The principle would be the same(opposite) as a fluid cooling system, my knowledge limits to engines and such where there's always a pump, I wonder if systems without pumps are used elsewere🤔

[@GreenhillForge]

@@malefunctionable Yeah, thermosiphons are passive heat exchanging systems and they're used in at least a few things I can think of. Biggest one being rooftop solar hot water systems. But I can't think of any that come anywhere near the kind of temps in solid fuel burning systems. A lot easier and safer if you're topping out at like 140F instead of 1200F.

[@GreenhillForge]

Just occured that a simple steam engine could work really well and would also sync up well with the system. The hotter it gets the faster the pump would run. Maybe I'll try building one...

[@comaktinyhomes]

@GreenhillForge Do it!

[@archangelcharlie]

I love that there’s essentially no wrong way of doing this as long as it achieves the same outcome , but we’re watching such a innovative method

[@bobhoward9016]

Heres an idea, using excess solar energy. Once your battery has reached full charge, diverting the excess into a heating element and filling the contraption with sand. Solar electric water heater.

[@beatdrive741]

Heating elements are HEAVYYY loads, wouldn’t work imo. Google Solar PV-T panels mate, a much better solution I think.

[@kensmith5694]

@beatdrive741 His idea is a good one. Once the batteries are full and you have already paid for the panels, you are best off to find some other use for the energy. The panels are selected for changing the batteries on the worst days of the year so most of the time there is excess. Heating elements come in all wattage levels.

[@beatdrive741]

@@kensmith5694 it isn’t efficient in the slightest, there are better approaches that already exist. Sure it could work but you’ll end up with an overly complicated installation that gives you very small amounts of warm water. Lower the wattage, lower the capability. For something as crucial as hot water availability you want simplicity really where possible. If you want to use the excess energy you’d honestly be better off storing it elsewhere as potential energy. Another battery, or pumped water storage or something.

[@kensmith5694]

@beatdrive741 Storing energy as heat is fine. I see no point in further discussion

[@beatdrive741]

@@kensmith5694 sure thing, you can but it’s simply inefficient in a multitude of ways. Ultimately it boils down to what problem are you trying to solve. Maybe there’s an edge case where it works but I’m not seeing it..

[@CM-sm6rs]

Tradesmen are the salt of everyday life. You, sir, are an artist at your craft. Absolutely have a new follower! Wonderful video, well done, great direction and teaching.

[@rdmckeever7645]

Interesting idea. Won't the copper cause rapid galvanic corrosion of the iron and collect creosote rapidly as the smoke passes over the water cooled copper? Maybe 5/16" stainless brake line or 3/8" stainless wort chiller coil tubing would be safer?

[@chasbader]

For galvanic corrosion to occur, the metallic junction must be in the presence of an electrolyte.

[@jefflebowski3784]

Good design, good execution and nicely described - clear and to the point with no bs. Great video. As others have commented reversing the water flow should increase efficiency.

[@LyleAshbaugh]

Nobody needs a hot water heater, we need cold water heaters 😜

[@Reviloj]

It’s because people don’t like going to the ATM. They like going to the ATM machine.

[@c56cameo]

Came to say the same If the water is already hot it doesn't need a heater

[@PeapickerTheGreat]

@@Reviloj to enter their PIN number

[@mysticdavestarotmachinesho5093]

Made me laugh. smile and grin.

[@RobertSiedentopf-nn8pn]

Nice job

[@oldschoolcars3318]

First view of your work. Excellent! I have done hybrid wood heat and sun maxx evac tube solar hot water and heating systems. I used their 264 gallon tank with a 60 tube array and a therma-coil brand coil inside the wood stove. In pennsylvania winters you only need a coil perhaps 1/5 the size of the one you have made (about 60 -70" of 3/4"" pipe). The stove unit is stainless and is connected to copper piping wit dielectric unions. The feed and return lines are dumped into a coil in the tank with three coils in it. A second coil in the tank goes to the solar loop which has a 5 ft section of copper baseboard heat in parallel with it. A solar controller or a plc control both loops allowing you to use the baseboard heater as a heat dump if needed. The third coil in the tank feeds the hydronic radiant system and a separate domestic hot water tank. Looking forward to exploring more of your videos.

[@craigkennedy9968]

You made a critical mistake that inhibited the performance This comes from the energy experts in the HVAC industry, it is called Pre-Heating. The cold water inlet should be at the top, closest to the end terminals if the flue. When you look at the Copper tubing, a section of that copper, say 1" length. It will conduct heat at a specific rate, drawing heat away from the flue and transfer that heat through the heat of conduction to the water. Since that Heat Transfer is limited, you are considering Temperature Rise. Since the heat closest to the stove is hotter than it is by the termination of the flue, you want the most heat transfer as possible. If your inlet water is at the farthest point, it absorbs heat, and as it runs through that Copper Pipe, it will be exposed to hotter temps. You are literally Pre-Heating the water before it gets to the Hottest portion of the Flue, where it will absorb the most heat. Additional benefit is that the resistance of the water to the Pump will be reduced, resulting in a more efficient pump operation with less stress on the motor. Your Heat Rise will likely improve by 25-50°. Another improvement to your setup would be to add your heat exchanger as a bypass to a primary flue, with the damper installed above a tee, where the air would go into a tee when primary flue passage is closed off. This would minimize flue gases exposed to the heat exchanger unless needed by simply closing the damper. Basically, close the damper to turn on the hot water heater.

[@nomadicoasis9260]

The inlet pipe at the top is best for a pumped system, backwards for a thermal only circulation system. The water rising when heated makes the pump work harder, not less. I like your bypass idea... Mine use-to boil off every once in a while... I plumed for that, and it would have been irrelevant except the standard blow off valves are not rated for repeated use and tend to leak after 2-3 times.

[@chasbader]

Basically what you described is what is known as a counterflow heat exchanger. What is in the video is a thermosiphon. If you have an adequate pump, then thermosiphon isn't required. Counterflow designs can be very efficient! Would be a simple mod and a great follow-up video.

[@craigkennedy9968]

​@@chasbaderwe Pre-Heating the air of 90% condensing gas and oil furnaces. It pulls so much heat out of the flue gases that it condenses the moisture from those gases. Due to the acidity, and the moisture, we can not use a metal flue for them, we have to use PVC, and account for removal of those condensate. Extremely efficient.

[@nomadicoasis9260]

With respect to your factually accurate and clearly written description. Your talking like your living on grid and not rationing every watt of solar energy. ie the pump. using a pump when thermal siphoning will do the job is scandalous! not unreasonable or erational mind you. the coil caking up with hard or sticky creosote is a maintenance "nightmare" and a chimney fire waiting to happen. ultimate efficiency must needs take a back seat to maintenance and safety. this guy did a great job on fabricating and thinking of maintenance. that being said I would not be cleaning that design in my house as it would be a terrific mess every 3 weeks. It may end your marriage if you have one. I would not build one fire to heat my house and another to heat the water,extra labour. so that's a problem. In case you sense a extra bit of passion here that would be because I came by it honestly. (long explanation, not relevant to the facts) creosote is an insulator and hostile to energy transfer efficiency. not that that is in any way a problem, up till week 3. then the system works poorly and safety is threatened.then you clean it. a good set up takes 45 minutes to an hour from lighting the fire, after that you risk a boil over an have to deal with the problem of steam. or an explosion take your pick. I know it's counter intuitive but your striving for mediocrity here. the best system is a water jacket around the flue (1/4" of water ) and for the love of all that is holy plumb it so that every last bubble floats to the top and harmlessly blows out the steam rated blow off valve, just like o'll Moby Dick. the water jacket allows you to use a chimney brush in a few minutes.easy. if the water jacket is to efficient the steam rated valve takes care of that. just make sure the steam and water eject in a harmless direction. one more thing there is a magic line 2 feet above the coil were hot water will not go below. make sure the bottom of the tank is above that. or use a pump- be a heretic I don't care. Jared

[@AlexM-nx5bp]

You're at about 19,600 BTU/ HR based on your start / stop and total time. Awesome. Working on a coil system to feed in floor radiant for an office shed build coming up. Love your video!

[@cdmChase1]

You dont need the water pump. When the water heats, it'll push it around with convection. But! I suppose it'll push it around quicker just saying it'll still work without it. Great video, mate 👍🏻

[@AntonCode]

I bet the exchanger would work horizontally so long as the chimney was insulated and tall enough to create draw. As for the combustible buildup everyone is talking about, a complete burn would definitely help, either with high heat + gasifier second stage or a catalyst. And your build is such that you can do a complete disassembly and clean which is amazing. Fantastic job and excellent video editing

[@whiterabbit2786]

That was awesome. I have no idea how the algorithm delivered me. But I'm glad I watched it. You put a lot of work into that project.

[@kenoguy10]

Maybe a steel pipe inside a steel pipe "water jacket" with turbulator fins welded on for heat exchanger inside an insulated flue pipe might be a way to address problems of creosote and avoiding dissimilar metals issues. Also it would be good to be done in a way to be able to remove the water jacket/heat exchanger assembly from the flue pipe for cleaning/maintenance. I like this... Very interesting. This is a very well done video. Looks like something I'd like to have for water heat storage (large tanks/barrels/IBC totes) in a greenhouse so tropical plants can be grown in winter here in southwest Missouri. Thanks to others for info about reverse flow efficiency increase... You learn something new every day!!!! Subscribed... and 👍

[@aaronfurman8208]

Dude, the mullet, well, I can admit, it through me at first, but I have to say, you're an absolute genius! Awesome work. Seriously.

[@LupenTheThird]

You are a master mate. Is a shame you don't have more people following you.

[@vicweast]

Great content for a project I was considering to heat an indoor pool and poorhouse in Winter. Smart work... Thanks!

[@ubergroupinc]

I was thinking that if this coil was hooked up to a sauna stove, you could get sauna and a hot tub from the same wood!! Amazing videos!!

[@jaccurtis5789]

Brilliantly done, very impressed by the efficiency. By my estimations that’s around 5.7kW to heat up that much water and about 85% heat recovery, can’t get much better than that :)

[@dannetko4982]

Great video! I was going to mention the counter current concept but I see someone beat me to it. The reason that is better is because you get maximum heat exchange when there is maximum difference between the hot gases and the water. Also another person mentioned creosote build up, a major engineering hurdle when dealing with burning wood. The previous commentator gives one approach to the solution. If you can figure out how to install your tubing to have constant contact with the outside of the flue, that works best. Another approach to this would ber to have the heat exchanger inside the flue, but come up with a built in internal creasote cleaning mechanism. It would have to be religiously used frequently enough to not build up to much. Another very fun engineering project would be to elliminate the creasote by focusing on the design of the stove itself. You need to add a secondary combustion chamber with a separate, preheated, controlled combustion air intake. I built one that resulted in a pure blue flame in the 2ndary combustion chamber and no visible smoke coming out of the flue. That indicated an almost perfect combustion with almost no creosote to condense out on the exchanger surfaces. Have fun!

[@GreenhillForge]

I disscused counterflow in the follow up comments video

[@Pdfflyer1]

I completely agree with the design which you have proposed and you do have a hand in great videography, and I do appreciate the fact that it’s a very short video based on the fact that information without any accompanying music. A better suggestion, even than what your design is would be to convert a single wall, wood stove to become a double wall, wood stove with a water jacket. It’s even the heated with the cold in at the top and the warm out the bottom.

[@GreenhillForge]

thanks! I showed my off grid water jacket shower in the following video. check it out if you'd like

[@carlcrossgrove9009]

Incredible build, I will be very interested in the rocket stove test! If you're dreaming of the wood-fired hot tub, that is not only a much simpler, more primitive build, I think it's already commercially available, so keep an eye out.

[@scizorunleashed]

This was great to watch, I can see so much potential with this setup. I imagine having the water outputting into a separate tank would be great for quick showers. Very tempted to do something like this at my field.

[@GreenhillForge]

I have a water jacket wood stove shower in my garden area that I show in my next video

[@gordonmcconachie2492]

I thank that's a super heat exchanger if the hot air flow is nice and slow that certainly a splendid innovation , your design should put the big heat recovery business out of business 😊

[@VictorInChains]

We have a whole house (300sq. meter) heated by a single fire place this way, Italie works great. The installation is more sophisticated since it coexists with gas heating and sanitary heats water too but the principle is the same. Good work, nice video 😊

[@johnquarles3305]

Really great stuff brother. couple upgrades if heating speed is the metric - 1) how you make your fire, wood type (combine fast and slow burning woods), way you cut the wood will make a massive difference on heat/time 2) volume of woodstove relative to volume of wood/burning material relative to inside air, relative to air flute or outflow oulling out air on the top after the coil is of interest but a bit above my backyard physics level - touched upon that with flutes but thought i'd mention, a huge woodstove might work faster with same amount of wood, or perhaps an even smaller space with same amount of wood, maybe this is an easy physics q. 3) run a separate pipe underground first, could potentially pre heat the water (depending on waters starting temp vs. ground temp vs. volume of pipes underground) seen in common geo heating or 'air pipes' for greenhouse. - i'm looking into this for both sauna and hot waters. much love from VA

[@pietrocuni]

I’m really impressed! That’s what I call a QUALITY video! Subscribed! Greetings from Italy! 🇮🇹 ❤️

[@GreenhillForge]

Thanks very much! Where in in Italy? I was born in Naples and my family is originally from Luca

[@pietrocuni]

@ ohhh wow! Those are beautiful cities! Naples and Lucca! I’m from Cesena, a medieval city near Bologna!

[@GreenhillForge]

@@pietrocuni Wow, looks really beautiful there!

[@timothywhieldon1971]

NEXT LEVEL. 10/10 job. personally i would make a smaller coil out of 3/8 and 1/4 for inner coils. A neighbor of mine from back int he day did this but more of a boiler than a coil... strait pipes vs coils.... and he bragged about his wood stove was so efficient that there was only at max a 50*F temp difference of heat of the water (boiling) and the exhaust. He heated his radiant floor, water heater, and garage with this.

[@johns.1940]

i wasn't that impressed til I saw you split that 1/2 bar stock with a cut off disc! That's what experience teaches. Nice work!

[@Shmerpy]

Very nice vid! If you raised the tank up it would thermosyphon, then you wouldn''t need the pump. I built a system with a HW jacket in the woodstove and a solar HW heater on a roof, then moved my tank upstairs so everything thermosyphoned into it, plus the tank had the usual two electric elements. Worked great. The plumbing store guys thought I was nuts though...

[@fredrickncube4528]

Mind blowing skills and efficiency in your craft 👌 🙌 👏

[@stefanthalen5932]

Man, you don't mess around! And what a cool shop!

[@lynettearkin8194]

I was an engineer on yachts and the heat exchangers all use counter flow. Think of the temps of the hot air being cooled and water being heated. To get most transfer of energy the cooled air at the top will have temp difference to water at the top before water is warmed. As warm water flows down it is headed toward warmest air which still gives more temp transfer.😊

[@GreenhillForge]

If you want you can check this video out where I go over why I intentionally didn't use counterflow (and some other things) kzbin.info/www/bejne/poHCY3RrjMmpp8k

[@nooneknows6060]

Nicely done! I recommend that if possible you keep the water supply higher than the heating coil. That will help ensure that water is always in the coils, and you could also eliminate the pump so a power source won’t be needed.

[@danielbuckner2167]

I built a self standing hot tub for an event off grid. The "tub" was a 20' pool filled with about 4 feet of water. I used 50' of 1/2" copper pipe coiled inside a steel barrel. A small door at the bottom of the barrel to feed wood and a flue pipe out the top and two small holes for the copper to go in and back out. I put a cheap circulation pump on the input side and the outfeed went to a hose that went to center bottom of the above ground pool. It seemed to not work well at first as there was so much water but after a few hours it was almost too hot to get in! I used a long 2x4 across the center over the pool with a tarp to help limit heat loss. Once the pool was hot the tarp was taken off and we had to let the fire in the barrel die down and it needed very little wood and worked well. Because of the huge mass of the water, once the tarp was on it even stayed warm overnight!

[@erico7430]

Very cool to make such efficient use of wood as a water heating source, great craftsmanship. Can't help but think that for a hot tube that perhaps a pellet stove would allow more long term consistent heating.

[@l0I0I0I0]

Nice!. Congrads! You could use it to heat a dumptruck full of burried and insulated sand pit to heat a barn or building. Or perhaps hook up a duel source geothermal heat pump to the sand pit or water reseviour to efficiently heat your home on the coldest of days.

[@JonasMarcinko]

Great video great contraption! One thing I learned having the the copper inside the fire place or flue is that it condenses really quickly and builds a lot of soot and char around it. Which then doesn’t transfer the heat as well. One way to clean it is empty the water out and burn a really hot fire to burn off the carbon buildup.