Some suggestions on a "redneck outdoor woodstove" please.

[nanotech]

Hi folks.  

First off, I already have the firebox.  It is an old "Economy" brand (yes, that's the name on the door) wood stove that is about 24 inches wide, 18 inches high, and 30 inches deep.  It has a decent sized door on it that I can fit a normal split chunk of wood through.  It also has a 6 inch chimney mount.

I originally had the idea of making a water jacket (I work at Woodmaster), but after much trial and tribulation have discovered that it is going to be WAY too much work and WAY too much unreliability going that route.  Just too hard for me to get the welds waterproof around the aged and slightly heat-misshapen contours of the firebox.

So what I'm going to do make some things that look kind of like the coils on the back of a refridgerator out of 3/8" soft copper tubing.  Bend it back on itself so it makes a zig-zag shape to go along the side, the top, the other side, then finally the back of the stove.  

This will then have two layers of R-19 unfaced fiberglass insulation covering it, then a sheet metal "house" much like we make the Woodmaster stoves out of to keep it all dry in (and good enough looking that the wife won't tell me to bin it straight away).

All this will be driven by a 1/2hp water pump which will deliver the hot water to my crawlspace where I'm going to mount a pickup truck radiator for the water to flow through and a squirrel cage fan to extract the heat out of it and blow it around the crawlspace to heat my floor (which will in turn heat the rest of the house from the bottom up).

Now, the question for you folks (I'm terrible at fluid dynamics) is that the pump is a 1" (can't remember the gph, Northern Tool's site is partially down right now, link to the exact pump is http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay2?storeId=6970&productId=773



8&R=7738) and I'm going to be running the output through a reducer to go into the 3/8" copper tubing.  This will create a bit of pressure and quite an increase in water velocity.  Hence why I'm making the whole thing (three sides and the top) in a continuous series loop instead of making four separate parralel loops.  But should I?  Do you think about 10-15 passes by the side of the stove will be enough at the velocity it's going to be travelling at to actually collect enough heat energy to actually warm the water up enough?  If it is then I'll run the four sections in parallel and use 1"X1"X3/8" pipe tee's to split it off into the four branches and join it back together again on the output side. But if you folks think it won't have enough time to absorb enough energy, I'll keep it as a single loop.

Please help a misplaced redneck trying to bodge together a homebrewed furnace for himself!!  

I'll see if I can get my camera to take some decent pics in the morning and I'll see if I can't get TurboCAD loaded back up (had to do a format and re-install on the computer) and draw up what I'm trying to do so you get a visual of it instead of just trying to go by my very poor descriptions.......

[John II]

I have been around a few hot-water heating systems in my life, but 1/2 hp seems way to large to me and could run you up a substantial electrical bill if left to run 24/7 ? Most hot-water circulator pumps that I have seen or usually about 1/6 hp. Just my thoughts here.......

Also one time I took a 55 gallon drum and added a barrel stove kit, then wrapped 100' of 3/4" soft copper around it, then placed a shroud over the top to hold the heat down on the top half of the copper tubing. The bottom 1/2 of the tubing essentially received no heating, but the top half was basically covered in tubing. The home was approximately 30 ft X 50 ft with baseboard heat ( 1,500 sq feet. ) I used a 1/6 hp hot water circulation pump with an pressure expansion tank. With hard woods, it heated the house nicely, but with softwoods, it was hard to bring the house up to a comfortable level. Of course we usually left the stove in a dampered off (simmer) setting.

You will need to use a small insulated expansion tank to keep the hot water from expanding and creating leaks in your system. Also a pressure / thermal safety valve is a must.

I believe that my above stove would have functioned much better if I would have had a short piece of sort of a barrel within a barrel to have forced the hot exhaust gasses to have flowed against the side walls of the stove would have greatly helped.

If the flames will follow the contour of the stove sides and top, so that the flames and hot gases are flowing over the inner surface, a lot of heat transfer can take place, but in many stoves, the hot gases will flow primarily though the center of your stove with the gases near the walls of your stove running at much lower temperatures acting as somewhat of an insulator from the heat you really need. So some proper laminar flow techniques of hot gasses would make a big difference.

John II

[nothing to lose]

I think a smaller pump may be in order for this. First I expect it to be a closed loop system so that probably does not need much power. Second closed loop or open either way I dought you are trying for much lift so again not much power needed.

You need volume of water flowing, but it has to flow slow enough to gain heat at the stove and also loose heat at the raditor. So perhaps you do not need a large pump again.

Harbor freight has a really nice looking stainless steel 12Vdc water pump. I plan to buy a couple myself but have not yet. From what I remember about the pump it may be great for something like your system, I think it cost somewhere around $30 or $50.

 I had checked it out pretty well at the store at the time, but that has been awhile.

 I want them for water, used cooking oil, the 35 and 55 gal barrels of alky stuff etc..

If you have a 12V source may be a good pump for you to check out.

Do you really want to heat the crawl space? Depending on your situation, remember animals like to find warm places in winter. I am sure the skunk in my yard would love for me to heat a crawl space here for it, and all those outdoors cats too. Speaking of skunk, someone here posted how to get rid of the smell when sprayed and my dog still has a mild smell after a few baths, I need to look that up again I geuss. Skunk in yard was not a joke.

 For me, it would be better to use some pipe up against the floor for radiated/conduction heating I think then insulate under that and leave the crawl space air stay cold. Also would not need a blower this way or power to run it. May work better than warm air, but it may also cost a bit more to install. Savings in electric may be a plus and nothing to break like blower motors. Only need a water pump.

Heating the water can be done so many ways. Copper tubing on the fire box will probably work well. I have used restaraunt oil here. My plan was to build the fire box and heat exchangers to heat up the oil in a tank, then heat exchangers in the tank to heat the water for the house heating. I can heat oil alot hotter than water and this way when the fire is out I still have lots of heat for a long time. I did not plan to be home much of this winter so I did not build it. Just used the same indoor woodburner we always use that I built years ago.

 If you add some type of thermalmass to hold extra heat like that then you would still have heat after the fire dies out. Many things work well, some better than others, rocks, sand, concrete, water, oil....

 

[gale]

Wouldn't a true Redneck outdoor woodburner, at least have  one 55-gal drum and a requirement to cut through the side of the trailer? sort of like insert the drum through the outside of the trailer, support the drum on cement blocks on the living room carpet, leaving the fire door outside to load the broken pallets from your job.

Sorry, just trying to be funny.  I see one major problem with your idea,  "thermal mass"  the water jacket is the thermal mass for most outdoor heater.  it  holds the heat for hours to up to a day from every burn.  by attaching tudes to the outside, you will only have warm water in that tube while the fire is burning, meaning you will have to continually have to feed the stove, so instead of twice a day loading, it would be more like 24-48 times a day feeding.  I see another problem when one side of the tube is exposed to a surface 600+degrees and the otherside  to less than 100degrees.  

A outside burner is a combination of old boiler technology and a little masonary stove technology.  You build a theraml storing stove and then transfer the heat through water to another location.  The key is the thermal storing part.  Think of your project more like a "Russian" stove, use the little woodburner as the Russian stove's firebox and build a thermal storing unit around that.  The bigger the mass of the storage unit, the longer the heat storage in time.

   Since, you do not want to use water, how about sand.  You could build a simple box around the stove, using steel, fire blocks, etc.  fill it with sand and run your copper tubes through the sand.  The sand should moderate the heat spikes between a hot fire and a burnout , plus hold a heat mass for hours if not days. Theorectically, with enough thermal mass for heat storage, you may actually get your burns down to once a day or even less.

    But, with sand and not water you have another problem.  A water jacket keeps the outside of the stove at 200-220 degrees, roughly the boiling point.  it won't go higher unless you presurize the water.  Sand will try to keep the heat at it's highest point, probaly 500 degrees to 1000 degrees, can your old stove or your copper tubes maintain themself if it is constantly at that temperature?

Just my thoughts.

gale

[jimovonz]

I use a fire as back up heat for my solar hydronic radiant floor heating system. The firebox has two holes punched in the back where a single 1" copper pipe goes in and comes out. The copper pipe is in a simple 'U' shape approx 1 foot long (on its side) with a 1/4" flat steel plate covering it on the inside. The steel plate is for protection against over enthusiastic wood feeding as well as acting as a heat sink. The holes in the firebox are sealed with the same 'goo' you'd use to seal around your flue. If I keep the fire stoked well all day I can rasie the temp in my 500 gal tank by 40degC (averages out around 3kW)

Don't worry about the water in the pipes running too fast. The efficiency of the heat exchanger depends on the temp difference. The greater the difference, the better the efficiency. In fact if the fulid running through the exchanger is turbulant then you also get an efficiency boost. Rather than getting a hot 'slug' of water moving through the pipes, you will be more evenly heating all of the fluid in the system. This may cause a delay in the heat felt at the radiator when the system is started but it does capture the most energy from the fire in the shortest time. The trade off of course is the energy used by the pump (MPPT for hydronic floor heating pump anyone???) My pump varies its speed/flow rate depending on demand but it does max out at 300w which is getting close to 1/2hp.

[nanotech]

I really wish I had talked to you folks BEFORE ordering the pump!!  LOL  It's due to arrive on Tuesday.....

Can these type of pumps be run off of say a light dimmer?  So I could slow it down and in a way limit it from 1/2hp?

Just wondering.

I've also maybe come up with an idea.  I've got an old expansion tank hiding in the woods.  I think I'll dig it out and see if it's still any good and use it for both expansion and storage.  Put it next to the existing one in the bathroom.

I had originally thought of doing radiant floor heating, but I want to heat the entire crawlspace to keep my pipes from freezing as well.  Which they've done three times this year so far.  Both supply and drain.  

And as for animals, the crawlspace is almost completely airtight to the outside.  And with 6 cats inside, not too much worry about critters getting in there from inside the house!!  

I'm not really trying to heat the entire house solely with the woodburner, just take a major portion of the electric heating bill off the top.  Baby steps.  As I can afford a better/bigger system, I'll move towards running completely on wood/RE for heating, but for now I just really need to take a major bite out of the (up to) $500.00 a month for heating.  Not to mention the increased personal energy/motivation due to actually having warm feet instead of taking 20 minutes with a hair dryer at night getting my feet and legs warm enough in bed to go to sleep!!  

[Don Cackleberrycreations]

Hey now I never posted any pics of my old trailor

but that was a real close discription .Also failed to meation the flue made out of old waterheaters welded together.  

You forgot the sun porch built from old sliding glass doors and insulated steel entry doors ( Hey what can I say I have over 400 insulated steel entry doors from a door factory I used to work at  they make great little sheds. Ahh cant forget the pallets

I have roughly 700 or those 4x4s and 2x6 the pallets measure 36"x80" and they do burn good since they are made out of Oak. ) Then I got uptown and bought a nice home built wood stove , double wall construction and 2" square tubing crossing the fire box. added a fan to force heat out from between the double wall and that sucker would heat the trailor a full 24 hours on two loadings  in the coldest weather.

People laughed at my old trailor  but I laughed at their house payments . I gave $800 cash for it and put it on land I owned free and clear. lived in it for 10 years, its currently being disassmbled and recycled . so far Ive recouped $1600 from selling off pieces and scrapping aluminum and copper. Anyone need an an axle or three.

  But Ive stepped up Im no longer  trailor trash just poor white trash now  :-)

[nothing to lose]

"Wouldn't a true Redneck outdoor woodburner, at least have  one 55-gal drum and a requirement to cut through the side of the trailer? sort of like insert the drum through the outside of the trailer, support the drum on cement blocks on the living room carpet, leaving the fire door outside to load the broken pallets from your job."

You have to be very carefull when you put the drum through the wall and it can catch the trailer on fire very easy that way! And why bother going outside to load it if it will be on blocks in the living room anyway??? Just bring in the wood and load it indoors. Now I do have the flue pipe running out the open window behind the wood burner. Open window, take out screen, screw sheet metal to outside of window frame, 6" hole in center for the flue pipe. T on pipe outside (instead of 90 elbow) this way I can take off the coffee can on bottom and clean pipe if needed.

 Takes about 30minutes to an hour to install in late fall, 10-20 minutes to remove in early spring. Far easier to move in and out of the house than a 2 ton Fraklin or such and works great.

 This is not a joke, been used for many years this way, same 55gal barrel, no burnout yet. Durring summer it sits outdoors in rain and weather, it just now starting to get some rust to worry about under/around the flue pipe ring. Still fine for now, next year I may need to fix it or replace the barrel.

 Although it does truely sit on concrete blocks, it has legs. I just did not like it that close to the floor so I raised it on blocks. I made a fire shield for under it of sheet metal and pressed fiberglass board insulation, mutch better than the comercail bought shields and alot cheaper too. The extra fiberglass board was cut to fit the window in 2 pieces with a hole in center for flue pipe and about 1" clearence and this insulates the sheet metal that covers the open window

I have had a couple used comercail wood burners and my friends use those also, I truely like my barrel better than some of those.

In 2000 when it got cold I was not home for a month or more, the wife installed the barrel stove all by herself including carring it in from outside. Try that with most commercail units.

As for pallets, I don't get those, I buy bundles of slabs from the mill that cuts the boards to make pallets though. Does that count

 I have a very different system design I came up with for an outdoor furnace and thermal mass to use the excessive waste heat from a blacksmith and aluminum casting setup. But I got busy with other stuff and travels, and not planning to be home this winter much either I have not built it yet as planned. I geuss this system would not really be much of a redneck system, but I may still used 55gal barrels in it so maybe

[nanotech]

You guys have got me thinking now.

My firebox is rather small.  It MIGHT be able to hold 2 or three fair sized chunks of standard cut & split firewood.  I do think I'm going to be going out to reload it every 2-4 hours.  Instead of trying to bend the tubing into a bunch of successive "S" shapes to get as much contact with the firebox, maybe the idea of a 55 gallon drum on its side would be better.

Then I could just run a continuous wrap-around of the copper tubing like a huge spring!!

That way I could put a HUGE load of wood in at a time and only have to load it once or twice a day.....

Got me rethinking my idea here....

Am I completely turning into a certified redneck now?!?!?!?!

[nothing to lose]

"Am I completely turning into a certified redneck now?!?!?!?"

Getting close.

[coldspot]

Pump-

I'd go for a 12 VDC one myself

And I'd put it in the cold end of the system

Hot water and a plastic pump wouldn't work out

(Just running on about stuff I've never done but

I do have a nifty Liquid Cooled computer and it

has a super powerful 12 VDC pump but was $80.)

I'd also look at some old computer power supply's

fan's for a thermo switch for turning the pump

on only when needed, like when the waters warm enough.

Also a well designed one could run pumpless.

Also a little pond pump 120 VAC might be a thought

at about $5-20.

just my

$0.02

:0

Better get a mirror off solar stuff

and look at back of neck.LOL

[gale]

    Your discription of your stove , genually proves that you are of the  true "redneck" persusion.  The reson for the leaving the firebox door outside is two fold;1) if it was inside, it wouldn't be a outdoor wood burner.  2) Putting it outside gets the kids or the wife out of the trailer to load it while you sit back and watch your favorite NASCAR and/or fishing show.

    Slab wood does count as long as you don't pay for it.

[nothing to lose]

Hmmm, ok, I was thinking the entire thing needed to be outdoor, just the loading door then. I can do that

I don't watch TV so Nascar and fishing shows are out, and I would be too since I build all the fires when I am home, gee I better keep it inside after all.

Woops you lost me on the wood then, I pay about $5 a large bundle, nearly free but not quite.

[Alan Bowen]

Ok, I'm a new guy here.

However I am NOT a new guy to heating with wood!

PALLETS???  All I've used fer the last 29 years.

FREE?? Most of them have been delivered free any time I want them.  

A big ol' semi just backs in and throws them off.

If you are going to build a barrel stove I would like to tell ya about one I had.

It was made from two 35 gallon barrels.  My father-in-law had built it.  The connecting pipe between the barrels was in two pieces.  The free centers from some old terminal spools just weren't tall enough so he used two.

Where he connected the two together he had made a short weld about an inch long then skipped an inch and so on all the way around.  Then he used some kind of stove patch to seal it up.

When I had burned out my first stove, (It wasn't built tough enough for hot pallet fires) Pa gave me that home built stove.  That first year it didn't seem to be as good as my old stove, but we got through the winter.

The next fall, right after I had lit the first fire, I noticed how dirty the stove was.  I grabbed a brush and was trying to clean off some of the dust before it got too hot for the brush.  I bumped that furnace patch and it all fell off.

NOW,,,,,  I had 1/8" by 1" openings spaced an inch apart all the way around that connecting pipe.  The top barrel all of a sudden came ALIVE!!!!

Unburned gasses that had been going up the chimney were now getting fresh air and burning.  The top barrel from then on always burned hotter then the bottom barrel.

After the "conversion" If one of those barrels got red hot it would be the top one way before the bottom one.  (time to turn the fire down)

I used WAY less firewood that winter too.  I used that stove for about ten years then it was getting pretty tired.  I ran into a gteat deal on an airtight All Nighter Grizzley about the same time so it has been heating my house for the last 15 years.

Still burning pallets though.

Alan

[gale]

Have you ever considered how eco-friendly and how ingenuieous a true redneck is. Those tree- huggers from California, just simply not compete, they have nothing on a redneck from the eastern midwest to the deep south.  A Redneck will reuse, conserve, or recycle anything. They have never saw something that someone tossed into a dumpster that they could not find another use for , and they have the fortitude to go into that dumpster to get that treasure. They see every tree, scrap piece of wood, or even a old shed as a posible source of heat. They will live in houses and trailers long after a "normal" person will condemn it to the landfill or as a tear down, which is so more eco-freindly than building a new house. They understand that a little sweat, is worth more than most things that you can buy in a store. They drive older cars, which is more eco-freindly than building a new hybred.

   I local example, a old farmstead was suddenly surrounded by houses.  on this farmstead was a old chicken coop, which was in good condition, but could no longer be used as a chicken coop.  The grandfather was resigned to have the local fire dept burn it down as training, a huge eco-tragedy.  The grandson convinces the grandfather to let him move his family of 5 into the old coop.  He swaps out the old fan vents with windows he got from his job at the house trailer factory, puts in a wood stove.  He took carpet scraps from work and pieced together a floor covering,  he burnt pallet, wood srap, and other wood he scrounged from work.  He worked part-time for a couple contractors, and was able to save from the dumpster, a complete bathroom set, kitchen cabinates, old beds, light fixtures, etc.

   Between his two jobs, I believe he ended paying almost nothing for everything in his house.  But on the eco-freindly side, he was a genius, he recycled everthing, he saved tons and tons from rotting in a landfill.

   Of course he lived in a chicken coop, the county health dept, really did not like it much.  His wife really did not like it much.

[nothing to lose]

Hmmm, I may fit that pretty well other than the chicken coop part.

Actually I like that point of view.

Yes how much polution would be caused by building me a new ECO friendly car every 3-5 years? All those parts cause much polution to produce and ship, assemble and ship etc..

And destroying the 10-20year old cars I drive now creates polution also. Hard to think that my 87 Cougar is a classic 19 years old soon to be antique at 20 years

Ticks me off all the nice old farm houses I see when traveling, empty and abandoned, and a new expensive trailer house right beside it. Should have spent that $30,000 or $50,000 fixing up the nice real house instead of buying a trailer most often. That nice real house would have been going up in value while the trailer house will fall in value over the years. Sometimes a house may not be worth fixing, most the time that's not the problem though.

[lfabich]

New here and am interested in the DIY wood boiler concept. My idea is to build my wood stove in a contained area.  Cement house, metal. Perhaps a 100 gallon tank welded into a 500 gallon tank so it is sealed up.   Open the top of the large tank horizontally and put in sand as a heat sink to surround the wood stove and flue.  In this sand would be  pex pipe rather than copper. The type that is used in concrete for heat exchange. Cheaper and able to withstand heat. How much is something I need to experiment.  Also I was thinking I would, before I put in the pipe put in sand and read the temps in certian areas around the stove to see where would be the opitmum area to coil the tubes without getting too hot on a hot burn.  The large sand mass would hold heat for some time. Could insulate the inside wall.   The tubeing will bend as I need it as I bury with sand.  Am interested on any commment about this idea.  Thanks in advance.

Len

[lfabich]

Posted this above but thought it might be better at the end.  Sorry.

New here and am interested in the DIY wood boiler concept. My idea is to build my wood stove in a contained area.  Cement house, metal. Perhaps a 100 gallon tank welded into a 500 gallon tank so it is sealed up.   Open the top of the large tank horizontally and put in sand as a heat sink to surround the wood stove and flue.  In this sand would be  pex pipe rather than copper. The type that is used in concrete for heat exchange. Cheaper and able to withstand heat. How much is something I need to experiment.  Also I was thinking I would, before I put in the pipe put in sand and read the temps in certian areas around the stove to see where would be the opitmum area to coil the tubes without getting too hot on a hot burn.  The large sand mass would hold heat for some time. Could insulate the inside wall.   The tubeing will bend as I need it as I bury with sand.  Am interested on any commment about this idea.  Thanks in advance.

Len

[Vince]

Since, you do not want to use water, how about sand.  You could build a simple box around the stove, using steel, fire blocks, etc.  fill it with sand and run your copper tubes through the sand.  The sand should moderate the heat spikes between a hot fire and a burnout , plus hold a heat mass for hours if not days. Theorectically, with enough thermal mass for heat storage, you may actually get your burns down to once a day or even less.

But, with sand and not water you have another problem.  A water jacket keeps the outside of the stove at 200-220 degrees, roughly the boiling point.  it won't go higher unless you presurize the water.  Sand will try to keep the heat at it's highest point, probaly 500 degrees to 1000 degrees, can your old stove or your copper tubes maintain themself if it is constantly at that temperature?

Dang, I was thinking of doing just that, surrounding a wood burner I already have with sand outside. I had no idea the temperatures could get that high. This also presents the problem of the water or whatever liquids turning to steam if they're not moving fast enough.

Perhaps there would be a simple and inexpensive way to somehow surround the woodstove with some water, then surround that with sand ?

[gale]

   A well-built stove should easily handle the heat.

   The current outdoor wood-burner was and is designed for a simple purpose.  It is to have a wood burner and be able to locate it outside the house.  A simple design change, increasing the fuel load and limiting the air supply,  has reduced the need to load the stove down to twice a day for most stoves.  There is huge room for improvement.

   The most obvious area for improvement is heat storage.  Looking at probaly the most efficient wood stove, the Russian stove or massonary stove, it produces a very even heat with a very small fuel load.  I was in the Ukraine a few years ago,and toured a 100 year old village, in each and every house/cottage was a massive "Russian" stove,  from literally burning a small armful of twigs once per day, they were able to heat the entire cottage for the day and have enough heat to cook all day.  The key was thermal mass.  The firebox was only 1foot by 1foot by 2 foot, but the stove weighed tons, literally had enough stone, cement, sand , and mud to fill a large tri-axle dump truck.  Once all this earth got hot, it stayed hot, the little fire did not actually heat the stove to temperature, but instead maintained the temperature of the stove.

   Looking at solar-water heating systems,  they are able to raise the temperature of the water in the system to 120- 150F only, but are able to use that heat to heat a house for days or even weeks, the key is the amount of water and/or the size of heat sink of the system, once again the thermal mass.  I believe that I read about a system on this board about a person using his concrete floor in his basement as his thermal mass.  He ran tubes through a foot thick concrete floor and heated this by a solar-water unit, from this he is able to keep his house warm for over a week, with out additional heat from the solar unit.

   Locally, We have a fellow using a 1000gal solar heat sink with his outdoor wood stove.  The old heat sink is a tank filled with pebble sized stone and water.  He burns his wood stove only once every couple days, to heat the heat sink, then he uses a heat exchanger and underfloor heating to heat his house.  I don't know if it is more efficent, but it beats the biggest problem I have with a outdoor wood-burner,  I am not always there twice a day to feed the stove, and on Sunday morning when it is -5F, I don't want to put on my long-johns to go feed the stove.

    I didn't answer any questions, but I did give you more to think about.