Announcement

Collapse
No announcement yet.

OT: Wood Stove Design

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • George Bulliss
    replied
    I run a Lopi that has the upper tubes for the secondary burn. When shopping for it I was torn between the basic stoves at Tractor supply and the fancy ones at the fireplace stores. The difference in price was considerable. The Lopi heats convectively by means of an outer jacket that air can flow through. This and the secondary air supply all seemed like a lot of hype but I took the chance and am glad I did.

    Compared to the Jotul stove this one replaced, my wood consumption went drastically down. It simply dumps a lot more heat into the house for a given amount of wood. The convective design worked far better than I thought. There is no more getting blasted out of the room, only to find the other parts of the house are still cold. The house is evenly heated and a side benefit to the design is the reduced clearance required, which allowed me to position it closer to the wall. Finally, the secondary combustion feature has made a huge difference on the chimney. I still clean it every year but hardly get anything out of it now. Probably could go several years between cleaning.

    Although more than double the cost to purchase, I've saved far more in money and labor just in the wood savings over the years. The new tech stoves are a huge improvement over the old boxes.

    Leave a comment:


  • A.K. Boomer
    replied
    Sometimes you just can't help let it do it's thing,,, this was an extra dry piece of wood and this is my stove in fully closed mode, this was last night BTW,

    Note the piece of firewood being consumed from the top down, in fact everywhere there's a secondary jet there's a pocket into the wood....

    This was not an ideal situation,

    chucked the wood onto an already raging bed of coals and should have waited about an hour, stove room got up to 84 F...




    Click image for larger version

Name:	DSC06213.jpg
Views:	43
Size:	30.5 KB
ID:	1983341

    Leave a comment:


  • MrWhoopee
    replied
    Originally posted by A.K. Boomer View Post

    Well said but I will add - it's kinda a catch 22 thing, Yes you can even get the lions share of combustion out of your secondary air jets but you have to be careful to not totally smother the main fire either otherwise your kinda defeating the purpose,,, You want to use the secondary air jets in conjunction with the main flame, you want to be able to taper down the main burner but not totally smother it and make it inefficient, Ideally using the secondary air as a "clean up" jet system,,,

    If you let the main burner diminish too much you also run the risk of the whole ball of wax going out in the middle of the night ...

    True.

    On my Buck stove, the primary air control is loosely constructed. Even when the control is completely closed it allows some air in. When I first got it, I "corrected" that by shimming the slide gate so you could actually starve the fire. Then I discovered why it had been built like that. Here's what it looks like when it's settled in for the night.

    Click image for larger version

Name:	20220127_230738[1].jpg
Views:	52
Size:	1.44 MB
ID:	1983282
    Attached Files
    Last edited by MrWhoopee; 01-28-2022, 02:12 AM.

    Leave a comment:


  • CalM
    replied
    Here is one man's improvements. All three sound modifications IMO.

    https://www.youtube.com/watch?v=iGZWx0gwRCo

    Note the DOUBLE LINED fire box, Not a heat extraction fan.

    The stove pipe modification is on the order of those Magic Heat units only DIY. I would NOT care to try to contain a burn through failure of that inner "heat exchanger" 5 inch pipe. Open flue flame out into the room! YIKES!

    eta. Some material like well casing might be a better choice than 5 inch galvanized vent pipe;-)

    I need to look into the heat of transformation for paraffin wax. (I still like the old Cast Iron radiators on my stove! ;-) That thing is pumping LOTS of heat up to the dining room right now. Must be 140F Too hot to leave a hand on for count of 20. All while the return is "chill".
    Last edited by CalM; 01-27-2022, 08:51 PM.

    Leave a comment:


  • Sparky_NY
    replied
    Originally posted by J Tiers View Post
    Yeah, it seems as if you need enough primary air to continue to generate gas to be burned above, or it could go out.. Maybe the stove leaks enough to keep going, the bottom inlet damper does not allow complete closure, or some of the secondary air gets down to the fuel load.
    Yes, newer EPA rated stoves have a stop that limits how far you can close the primary air. I will not close completely.

    Leave a comment:


  • J Tiers
    replied
    Yeah, it seems as if you need enough primary air to continue to generate gas to be burned above, or it could go out.. Maybe the stove leaks enough to keep going, the bottom inlet damper does not allow complete closure, or some of the secondary air gets down to the fuel load.

    Leave a comment:


  • A.K. Boomer
    replied
    Originally posted by MrWhoopee View Post

    I think you may be misunderstanding secondary combustion, at least as far as the term is used in stove production. There is no additional fuel added, just air. It relies on heating the firebox to a temperature where the unburned gases will spontaneously ignite when oxygen is introduced. My stove relies on natural draw through the secondaries, which are just horizontal pipes with small holes at the top of the firebox. When operating properly, there is no flame at the bottom, the primary air intake control is closed. There is just this ghostly flame floating around the top, with jets of flame emitting from the holes in the pipes. An hour before bed time I load the stove completely and open the primary air. Once the fire is running good and hot, the secondaries will start to fire off with jets of flame. At that point I gradually throttle down the primary air until it is closed. The stove will run all night on the secondaries, producing a hot, clean burn with no smoke.
    Well said but I will add - it's kinda a catch 22 thing, Yes you can even get the lions share of combustion out of your secondary air jets but you have to be careful to not totally smother the main fire either otherwise your kinda defeating the purpose,,, You want to use the secondary air jets in conjunction with the main flame, you want to be able to taper down the main burner but not totally smother it and make it inefficient, Ideally using the secondary air as a "clean up" jet system,,,

    If you let the main burner diminish too much you also run the risk of the whole ball of wax going out in the middle of the night ...

    depends on the type of wood im burning - cedar almost seems to make it's own oxygen lol that's not really the case but it's so burn hungry that it will draw extra hard on the stoves seals and secondary jetting,,, in that case I will do as you describe simply to keep it from getting away from itself... there's never a worry about the main flame getting too low, but even this is dependent on stove design and condition...

    On my stove when im burning hardwood I like to see about a 2/3 main burn to 1/3 clean up, I get it rip roaring, then shut it completely down and let it stabilize, then add just a smidge of main burner air...
    When I do the above it seems the entire stove is in it's happy place and the only time the secondary burn goes out is when the wood is reduced to red hot coals...





    Leave a comment:


  • alanganes
    replied
    Originally posted by darryl View Post

    My last thought for now- is there, or could there be, a device which is a catalyst that would finish combusting the smoke without being consumed itself, something you would build into the stovepipe and basically forget? Perhaps you would pre-heat it electrically, or perhaps use a gas to get it up to temperature so it could then maintain it's temperature after that. Complexity comes back into the system now- and that probably does include maintaining it. Such a catalyst would have to deal with a fairly dirty smoke, and also smoke of different types- including the apparently obligatory burning of milk cartons.
    There is such a catalyst, it is a ceramic honeycomb thing that goes in a chamber between the area where the fire burns and the flue. The catalyst reacts with the flue gas to (gross oversimplification here) make it burn. I believe it works in a manner very similar to an automobile catalytic converter. They have been around for years. They are an alternative to the secondary air type stoves and while I have never owned one I know a few people who have had them and liked them very much.

    lots of reading material here:

    https://www.google.com/search?client...tic+wood+stove

    Leave a comment:


  • MrWhoopee
    replied
    Originally posted by darryl View Post

    I've thought about adding the secondary burner, utilizing propane, but obviously that has to be reliable or you risk blowing the place up. Think about it- you're using wood smoke as your fuel, and that will contaminate everything below your flame. It would seem that the potential is high for clogging up the propane burner. Perhaps there is a design that keeps every part of the propane (or natural gas) system out of the flue except for the flame jets- that would seem to be almost mandatory to me.

    Perhaps secondary burners for this purpose have evolved into efficient and safe devices by now, I don't know. But I'd sure want to look into that- whether there's a design you could copy, or simply purchase. One of my issues is do you have this thing active all night- when the stove is blocked down and set to do little more than smoulder all night?
    I think you may be misunderstanding secondary combustion, at least as far as the term is used in stove production. There is no additional fuel added, just air. It relies on heating the firebox to a temperature where the unburned gases will spontaneously ignite when oxygen is introduced. My stove relies on natural draw through the secondaries, which are just horizontal pipes with small holes at the top of the firebox. When operating properly, there is no flame at the bottom, the primary air intake control is closed. There is just this ghostly flame floating around the top, with jets of flame emitting from the holes in the pipes. An hour before bed time I load the stove completely and open the primary air. Once the fire is running good and hot, the secondaries will start to fire off with jets of flame. At that point I gradually throttle down the primary air until it is closed. The stove will run all night on the secondaries, producing a hot, clean burn with no smoke.

    Leave a comment:


  • J Tiers
    replied
    People do scream about "creosote".

    Thing of it is, if the combustion is complete, there isn't any. Then you can do things to extract more heat from the flue gas.

    You still need to have convection create a "draw" in your chimney, though. I suspect it is cheaper to burn more wood to get the draw, than it is to add some sort of powered forced draft to the system, in terms of total energy cost. But that would need a well controlled study.

    I have a shop-related suggestion, though...... Run the forced draft with a small steam engine you make in your shop, and a operate the boiler from the flue gas heat. If nothing else, it would be a good project. I do not suggest any form of Stirling engine, they just are too much trouble and too little power.

    Leave a comment:


  • A.K. Boomer
    replied
    Click image for larger version  Name:	DSC06188.jpg Views:	0 Size:	34.1 KB ID:	1982916



    Finally got cold around here lately - at least for a few days, not really cold but cold enough to use the stove some even during the day,

    So took a pick tonight of the secondary air burner --- allot of that fuel you see burning at the top part of the stove would normally be going up as unburnt hydrocarbons creating more pollution and also coking up the stove pipes making for unsafe stove pipe fires...

    I do like the wood stove - this time of the year look at it as a kind of work horse of sorts...

    Leave a comment:


  • CalM
    replied
    I've also considered placing a LP gas burner right in the fire box.

    The thinking is that most of the "inefficient" burning is associated with starting and bring a new charge up to temp.

    So, Turn up the HEAT, with gas.

    Never a frustrated lack of kindling. Works with any sort of fuel wood. and if located at the back of a log wood stove, would serve to put a bit of KICK into what smoke there might be and get it to burn clean. A "multi-fuel Hybrid.

    Plus, when a fella was lazy, or run out of wood in the wood box. (Lazy again ;-) just strike up the gas! Not much different than a kitchen oven.;-)

    someday.... if I ever really need to.

    Leave a comment:


  • CalM
    replied
    Well, To blame the Red Devil compound for your chimney fire is misplaced. The Red Devil is merely a chemical conversion to harden, em brittle creosote formations as an aid to either falling down or being brushed out. (Or being caught up in the flue gas and carried away. The "fire" was a result of previous build up and the intensity of the fire you had at the time the compound was dosed into the fire box.

    Propane burners are as simple as a metal tube with a few holes in it. The mixing valve and chamber can easily be kept outside of any "dirty area".

    https://external-content.duckduckgo....JPG&f=1&nofb=1

    On the final point. " flue gas Scrubbers" are well evolved technologies. There are different iterations depending on the fuel.
    There is a "biomass" power generating station up state. No real smoke is ever evident. Still, uninvited visitors are not allowed, even in the ash dump.

    clean burn tech.
    https://www.fao.org/3/t0512e/T0512e0a.htm
    Last edited by CalM; 01-11-2022, 07:15 PM.

    Leave a comment:


  • darryl
    replied
    I don't have much to add here, as I am not an expert on anything. But I did burn wood for heat for a lot of years, and I've had my share of 'incidents'. One was when I fired up an old stove in a house I'd just moved into. Long story short, I should have pulled all the pipes for cleaning, and to have access to the chimney also for cleaning. I didn't do that. I used something called Red Devil to clean the pipes, and to save myself a lot of messy work. Nearly burned the house down- I don't know why it didn't.

    But that brings up the issue of secondary combustion. The Red Devil obviously caused the build-up in the pipes to combust, and I had tossed a second tablespoon of it into the stove after the first tablespoon didn't seem to be doing anything after an hour or so. At any rate, I suppose you'd have to call that secondary combustion. Whether the products exiting the chimney were any cleaner I can't say- there was a steady stream of sparks and some were still glowing as they fell onto the roof. Had the system been cleared decently to begin with, I would not have had that problem- but I don't know if this compound would have created more pollution than the simple burning of wood would have.

    I've thought about adding the secondary burner, utilizing propane, but obviously that has to be reliable or you risk blowing the place up. Think about it- you're using wood smoke as your fuel, and that will contaminate everything below your flame. It would seem that the potential is high for clogging up the propane burner. Perhaps there is a design that keeps every part of the propane (or natural gas) system out of the flue except for the flame jets- that would seem to be almost mandatory to me.

    Perhaps secondary burners for this purpose have evolved into efficient and safe devices by now, I don't know. But I'd sure want to look into that- whether there's a design you could copy, or simply purchase. One of my issues is do you have this thing active all night- when the stove is blocked down and set to do little more than smoulder all night?

    My last thought for now- is there, or could there be, a device which is a catalyst that would finish combusting the smoke without being consumed itself, something you would build into the stovepipe and basically forget? Perhaps you would pre-heat it electrically, or perhaps use a gas to get it up to temperature so it could then maintain it's temperature after that. Complexity comes back into the system now- and that probably does include maintaining it. Such a catalyst would have to deal with a fairly dirty smoke, and also smoke of different types- including the apparently obligatory burning of milk cartons.

    And this does bring up another issue, that of dealing with waste. We either burn waste, or bury it. Either way the final products end up in the atmosphere- either right away as you burn it, or years later as it decomposes underground. The question here is, can you burn something so efficiently that you reduce the polluting component (s) to the absolute minimum- anything you put into such a device gets reduced to the cleanest it could be? Whether wood smoke, or household garbage of every type- the more completely it burns, the more heat you could get to use, and the least pollution you would release to the environment. And on this note- can you arrange for the final gaseous product to include itself in the production of a solid lump of 'waste' instead of being released to the atmosphere? Say, the slow but steady production of another, potentially useful, material?

    Leave a comment:


  • jdunmyer
    replied

    The other complaint is something I cannot do anything about - it's just a simple brick lined stove and has to be emptied by letting the fire go out and hand scooping the ashes,,, if you ever had a grate type stove you will know how much of a hassle this is in comparison ---- they are so handy, you can shake the grates some to clean them while the stove is burning - pull a pan out and empty in a safe place outside if you want,,,, they are the ultimate stove "workhorse" as they never eve need to take a break,,,
    When I used the barrel stove, I built a rake and a shovel for cleaning the ashes. Rake the coals towards the rear, shovel out ashes, then rake the coals towards the front and add wood. Mind you, I left a bed of ashes, perhaps 3" or 4" deep, never cleaning it out completely. It wasn't necessary to shut the stove down completely, just do it when the fire is low, like first thing in the morning.

    Leave a comment:

Working...
X