Outside Wood Stove Shop Heater

22,703

129

20

About: Construction worker for under ground utilities. Tinkerer. Welder (I try) electronics geek. Love holiday setups, cars, and building anything

In this instructable i will show you how i made a wood stove heater for my shed. I didnt want to sacrifice the space in the shed for a small wood stove or need to run propane or a flue pipe through the wall or roof. This stove uses a 55 gallon metal drum and steel pipe as a heat exchanger to keep the fire and smoke outside my shop.

Step 1: DISCLAIMER

Making a stove or anything using fire or metal can expose you to hazardous items and chemicals. this is for instructional purposes only. if you choose to make some variation of this heater be sure to understand all elements and hazards involved with such projects. I am not responsible for the actions of others.

Step 2: Materials and Tools

Gather all necessary tools and items you will need to make the heater.


Materials

1 55 Gallon drum stove kit - 50$

1 55 Gallon drum - free

misc steel pieces (searched the scrap bin at a local store)

3" schedule 40 steel pipe - sourced from junk yard

3" pipe 90s - 20$ each at local plumbing supply

1 3" pipe nipple 6" long - 5$

1 4" duct fan - amazon 17$

2 8' pieces of rigid dryer vent/ducting - 15$ each

3/8 rod with nuts and washers

4 large hose clamps (for 4-5 inch pipe) - 1$ each

high temp paint (auto parts store) - 6$

Tools

Drill and bits

Sawzall

Grinder

screw drivers/ sockets

Welder (optional)

plasma cutter (optional)


Personal Protective Equipment (PPE)

Safety glasses / Shield

Leather/cut resistant gloves

Welding mask/shirt (optional)

Step 3: Prep the Drum

** REMEMBER - If your drum is painted or not washed out there could be harmful or flammable vapors inside, or while cutting the patterns out. WEAR YOUR PPE AND RINSE YOUR DRUM!

I recieved mine from a local guy i know who refurbishes drums and i know it was washed out, but it was still painted.

This part is essentially written in the instructions in the barrel kit so I won't be spending much time on it. Take the door piece out of your kit and place it on one end of the drum. then trace the inside edge and mark all drill holes. Cut the door and vent out and drill the holes. Attach with supplied hardware. Do the Same thing for the flue/chimney piece and legs.

Step 4: Prepare the "Heat Exchanger"

In a standard furnace a heat exchanger is essentially a set of tubes where air is moved thru to be warmed up by a source of heat. The idea is to keep the source of heat and exhaust gases seperate from the air that is to be heated.

Here i welded up some pipe i got at a scrap yard together to make a "U" shape. You can use any size pipe you like and get it threaded so no welding is needed as long as the connections are tight. DO NOT USE GALVANIZED PIPE!! Galvenized steel has a coating on it that releases TOXIC fumes when heated/cut/welded.

for this i bought a short pipe nipple, cut it in half and welded it to the end of the scrap pipe from the scrap yard. Alternitively you could buy a 10ft piece and cut it in half and already have the threads on it or use 2 3' pieces and cut off one end for the duct connections.

Step 5: Attach Heat Exchanger to the Drum Stove

After trying to weld the pipe to the sheet metal barrel and failed by burning a hole in it, I decided to to use a piece of 3/8 threaded rod from the hardware store and some washers and nuts to attach the heat exchanger to the drum. My drum had a removable top so at this point cut or drill holes in the top so that the pipes stick out the back. if you used 3 foot pipe sections it doesn't matter how far inside the drum the pipe sits as long as there is about 3-5 inches of pipe sticking out the back to attach the duct to.

Step 6: Burn It Off!! and Paint

At this step before we attach the heat exchanger to something you should be ready to burn off your barrel and heat exchanger pipe. Simply grab some wood and get a roaring fire in the barrel hot enough to melt all paint and mill scale from the barrel and pipe. On my pipe section there was smoke for a short time which I suspect to be mill scale and oils from the steel foundry, this smoke only lasted about 25 minutes. Once it looks like it is clean burn it for another half hour to one hour to make sure. Once this process is done you can use some high heat paint from an auto part store (exhaust manifold) to paint the drum to prevent exterior rust (non contact pyrometer had my barrell temps around 650 at the highest so far). After this, all should be ready to attach to your heat setup.

Step 7: Heater Fan Setup

This is fairly simple, cut a piece of scrap plywood that will fit your opening, in my case it was for the window of my shed that doubles as a shop in the winter. cut 2 4" holes in it for the duct work and fan. install flanges and a fan on one side that blows out toward the heater. I used a jigsaw for this but anything will work. make sure the fan air flow direction is facing out toward the heater. in this picture i just stuck the flex duct in the window and took some readings with a no contact pyrometer and was pleased with the results.

Step 8: Done!

You are now ready to heat! Here is some pyrometer readings from inside the shop and as you can see, the air is plenty warm. I still plan on keeping a carbon monoxide/smoke detector combo in the shop at all times just to make sure i will be safe as well as a fire extinguisher...I do weld and cut in here as well.

Share

    Recommendations

    • DIY Summer Camp Contest

      DIY Summer Camp Contest
    • Games Contest

      Games Contest
    • Backyard Contest

      Backyard Contest

    20 Discussions

    1
    None
    kwhit190211

    6 months ago

    If you cut the section of pipe that you got in 3 pieces, 2 long & 1 short. Then mitered the both ends of the short piece & then mitered 1 end of each of the long pieces you wouldn't need any elbows. Just weld up the mitered ends, together to form your "U". .

    0
    None
    RetiredLE

    Question 7 months ago on Introduction

    How did you support the tubes inside the barrel? Also, the duct motor - was installed to push air through the heater exchanger or suck air out of them? Thanks.

    2 answers
    0
    None
    luposays22RetiredLE

    Answer 7 months ago

    Hi thanks for your comment! Step 5 shows how I attached the front to the barrel. I just bent a piece of threaded rod and used some nuts and washers. The back side simply rests on the sheet steel of the barrel. Also the fan pushes the cold air into the barrel. In past experiences pulling heat past the fan will cause them to fail faster.

    0
    None
    RetiredLEluposays22

    Reply 7 months ago

    Okay thanks. I was hoping you had a pic or a drawing showing how the heat exchanger pipes were supported inside the drum. Also, not sure if you did this or not, but I would recommend lining the bottom of the drum with a layer of sand with a layer of fire brick on top of the sand. It prevents the bottom of the drum from burning through over time. A heavy duty grate placed on top of the fire brick to enhance air flow would also be a good idea. I built a two drum stacked unit like yours some years back and I was able to heat a three bedroom house with attached garage.

    Also, good point regarding the fan duct motor pushing cold air versus pulling hot air to lengthen it's service life.

    Just had another thought.... Enclosing the entire stove versus leaving it sitting out in the weather would also prevent a huge heat loss - which could be directed into the main structure via a box fan or something similar.

    double barrel stove.jpg
    0
    None
    farna

    7 months ago

    Great project, lots of room for improvement though. Most concerns have already been voiced -- insulated duct, better heat exchanger (though that would be hardest to accomplish, having a removable top on the drum would be a necessity for that), using a water system instead of air (wouldn't need a pump -- the heated water would thermosiphon at least a short distance... an old car radiator with electric fan should work well...), a different type of burner, etc. All would require a bigger investment though, so there is a trade-off. Still, if it gets very cold outside you're going to be burning a lot of wood. Insulating the entire drum would be nice. Just building a shed around it would help tremendously, even if uninsulated. Just keeping wind off would help a lot in cold weather. I don't think your fan moves much air. A squirrel cage blower from an old furnace would be more efficient, though harder to mount. Overall you did a great job and accomplished a lot without too much effort -- so don't let the "room for improvement" comments bother you.

    1 reply
    0
    None
    luposays22farna

    Reply 7 months ago

    thanks and yeah i know im in the heating business i had stated on another comment why i went this way and it was just simplicity, i dont leave that stove there all year i hide it in summer and pack it all away. but again as i said, were all here to share ideas and learn from one another and help each other out so id like to see someone build and share theirs and how it works for them because maybe their version of it will work better for others. Keep building on and thanks again for checking it out!

    0
    None
    kleetus92

    7 months ago

    Couple of thoughts... you could pick up some efficiency on your HEX by switching to copper, and or in conjunction with that (use compression fittings not solder) use several smaller pipes vs one big one to get more surface area in the fire box.

    Another option would be to use double wall pipe (or put 4 inch inside 6 inch pipe) for your hot air return... you're going to lose a ton of heat as the outside temperature drops, which will make it progressively harder to get heat into your shop.

    Another option is instead of hot air, why not do a liquid system and a radiator. It doesn't need to be under pressure, or a lot at least, but it would be significantly more efficient than an air to air system.

    Neat project none the less.

    1 reply
    0
    None
    luposays22kleetus92

    Reply 7 months ago

    cost vs efficiency. yes dual wall pipe or just simply wrap that heated return in insulation would work well. you could even use kaowool and wrap the wood stove in it to keep more heat in. I have a hydronic heating unit i picked up from a demoed building but the price for a 1in or even 3/4 copper pipe coil was way more expensive then just using a hot air unit. I had seen designs for a wood fired hot water heater that i was once going to build for our hunting cabin up north where we dont have the amenities of home i.e. power and plumbing. this unit can easily be adapted to do both by simply removing the back where the pipes stick out and wrapping copper around the steel pipe inside for the future. another reason i skipped the liquid unit was purchasing glycol for the system was another big expense, plain old antifreeze wasnt going to cut it. if someone has the stuff on hand to do it by all means thats why were all here to share and learn from each other.

    0
    None
    gingergirl64

    Question 7 months ago on Introduction

    Would you mind if I posted the link to this instrucable on an Off-grid and Homesteading Facebook page? Others have posted photos of these, but yours in a nice set of directions on how to build one. Yours also is a bit more inclined toward the necessary PPE for the build. Just out of curiosity, do you have a carbon monoxide detector in your shop?

    1 answer
    0
    None
    Daelke

    7 months ago

    Excellent idea! These days I don't need something like this but in the past it would have been very helpful. I found your idea to very entertaining. Thank you for taking the time to post it here.

    0
    None
    DmitryP2

    7 months ago

    You can try to modify this: https://www.instructables.com/id/Samara-Gasifier-...

    You need to coil heating channel in top side section, and maybe remove diaphragm, using the lowest wrap of heating pipe as hot air flow deflector (see double wall wood gasifier stoves made from cans).

    Advantages are low fuel consumptions comparing to classical metal stoves, compactness, it does not need a chimney, and you can cook atop of this like stove still heating your workshop or glasshouse.

    0
    None
    sageclouddancer

    7 months ago

    could you do this with a rocket stove instead it uses less wood to heat with?

    1 reply
    0
    None
    zooms.oomssageclouddancer

    Reply 7 months ago

    You have two options with a rocket stove.

    1) make a pocket rocket (no big thermal mass) with a heat exchanger inside like this. I've even seen hot water heaters like that.

    2) have a thermal mass with both your exhaust pipe and heat exchanger pipe going through it next to each other.

    0
    None
    uncle reamus

    7 months ago

    This is right on time. Me and the old lady will be closing tomorrow morning on our new house, well our 118 year old house. It has a 32x32 foot barn that i will park my truck in becuase the 10 x 20 garage, i have to fold the mirrors just to get inside of. So my plan is to turn the garage into a work shop. Here in Ohio it gets down into the teens, not horridly cold but cold enough.

    0
    None
    gm280

    8 months ago

    I like your project. I have a 24' by 36' shop and each year I think about how I am going to heat it. Presently I use a K1 kerosene heater inside. And while that works well, I'd really like to keep the heater part outside and pipe in only the heat. So I have to reread your post and think now. Thumbs Up

    2 replies
    0
    None
    wkovigm280

    Reply 7 months ago

    in your case there's at least one company that makes "add on" barrel kits for these stoves too. Vogelzang is one and available through tractor supply. the bottom barrel is used for the fire and the one (or two) you put on top are strictly heat chambers that you can make into heat exchangers like this project. every barrel you add is close to another 50,000 btu of heat scavenged from the same fire

    0
    None
    luposays22gm280

    Reply 8 months ago

    free heat is the best heat! if i left something out just message me i am happy to help! in my situation i built this because a commercially bough furnace was not cost effective and i couldnt spare the space for a wood stove or pellet or other fuel fired appliance

    0
    None
    KonnerS3

    8 months ago

    What size is your shop and what are your outside winter temps? How well has it worked to bring the shop up to a comfortable temp?

    1 reply
    0
    None
    luposays22KonnerS3

    Reply 8 months ago

    my shop is a 10x20 shed made from standard building materials and is not insulated. Here in New England it can get close to 0*F and sometimes below. Last January we had a hard cold snap and were in the negatives for a few weeks straight, along with impressive snow totals. I used the heater for the repair and maintenance of my lawn tractor as well as snowblower repairs. Without insulation and using a small propane infrared heater to take the initial chill out while the stove warmed up, it was around 60*F when it was real cold or i forgot to put more wood in it. if it were in the 15F-25F range without a howling wind, easily 70-75*F. I dont find a need to insulate my shop/shed as i am out there once or twice a week, usually, but i have some moving blankets i hang up to make some barriers if im working on something for a few days in a row.