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Catalyst vs Non Catalyst

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by ecolbeck, Jan 15, 2012.

  1. Todd

    Todd Minister of Fire

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    Maybe the insulating thingy is more about the baffle on top of the fire box than the sides and bottom? Heat rises and non cats have those insulated baffles to keep the heat in the box longer to help combust the gas and smoke before it escapes up around the baffle? I don't think any cat stoves use ceramic board, fire brick or rock wool blanket up in the baffle area because the cat doesn't need as high of temps to burn the smoke. Maybe that's what they mean by insulating the fire box?

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  2. jharkin

    jharkin Minister of Fire

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    Jeeez... hasn't this one been put to bed already a hundred times over in this very forum?? Cat and non-cat are BOTH great ways to get heat from wood.

    Cat stoves tend to rate slightly higher in absolute efficiency at very low burn rates in lab tests. Noncats tend to rate higher at max heat output and can be more efficient and cleaner at high burn vs a cat at high burn even the catalytic hearth foundations own research says so). non-cats are more tolerant of marginal word and lower maintenance. In the end the best stove really comes down to which fits your needs - both are great.


    BTW This thread is amusing... so full of assumptions an misconceptions so dearly held...

    - That cutaway diagram posted is just a hypothetical stove - it does not mean every stove made is brick lined. Many are not.

    - Firebrick DOES indeed have some insulating value - that's exactly what its designed for, to protect other materials from extreme temps. Without a cat you need to get the firebox gases over 1100F to combust, that would make a plate steel stove turn cherry red, hence the brick lining to slightly insulate the steel shell. Go search firebrick in Wikipedia if you don't believe me.

    - By the way, the ceramic refractory box that some cat stove builders use to house the catalyst has the same purpose.

    - Also the thought insulating materials don't transfer heat is incorrect Every substance with mass transfers heat, insulation value is just a measure of how much it resists heat transfer. The only perfect insulator is a perfect vacuum and that does not exist in reality.
  3. ecolbeck

    ecolbeck New Member

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    Its not "my" view of insulation, its based on what I read on manufacturers websites and sites like hearth.com, woodheat.com, and epa.gov. I was simply simply curious to know if any of the "experts" here at hearth.com had an opinion on insulated fireboxes and their effect on heat transfer into living space. While some respondents have tried to be helpful, one person has treated me to a grumpy diatribe (chill out dude).
  4. HotCoals

    HotCoals Minister of Fire

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    I believe they use the term "insulated" very loosely.
    From what I know they all transfer pretty well.
    Of course steel stoves with a cast iron outer shell take longer to do it..but make up for it at the end.
    Pretty much a non-issue around here from the threads I have seen.
  5. Defiant

    Defiant Vermont Castings Geek

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    Nothing burns more efficient than a properly maintained cat stove.
  6. ecolbeck

    ecolbeck New Member

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    Thank you Jharkin, for a reasoned approach. Based on the pic it looks like you have a sweet old house. How did you insulate it?
    What's funny is that I never had any interest in debating cat vs. non-cat in terms of their relative merits.
  7. chipsoflyin

    chipsoflyin Member

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    Regency puts pumice firebricks in their stoves which reflect heat back into the firebox, this is to help get the the firebox up to temp faster during start up and reload. So in fact they do put insulatieon in some stoves
  8. CTYank

    CTYank Minister of Fire

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    For cleanest burn, the firebrick keeps the firebox temp elevated, typically above 1100 F. You DON'T really want heat transfer there. Then the gases are routed through heat conduction areas of the stove. These can involve surprisingly large conduction area. Then, smokepipe can be involved in significant heat transfer. IMHO, your fundamental assertion is false. You'll find interesting research results in "Woodburner's Encyclopedia" by Jay Shelton, if you can find a copy. It's from circa 1975, so the whole secondary combustion thing was still over the horizon.

    Please note also that, from Jay Shelton's research, metal liners (e.g. cast-iron inside steel stove) have MUCH less effect on heat being transferred out the sides of a stove than firebrick. IOW, they're largely protective/sacrificial, and don't elevate firebox temps.

    Search also for info on "Hill boilers" designed by Prof Richard Hill of U Me back in the '70s, re separation of combustion and heat conduction.

    Okay, time to break new ground.
  9. HotCoals

    HotCoals Minister of Fire

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    You sound like you know what you're talking about.
    In your opinion do you think it's counter productive to run on board blowers on a wood stove?
  10. CTYank

    CTYank Minister of Fire

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    Maybe not, rather just allergic to BS.

    What do you mean by on-board blowers?

    If they'd have the effect of lowering firebox temps, they're likely a bad idea. If they're extracting heat from further downstream in the gas-flow, they might have beneficial effect, BUT only if they don't cool gases enough to reduce draft notably. Cooling those gases can lead also to creosote deposition.

    Whatever the great idea, you've go to test the whole system carefully, over time.
  11. ecolbeck

    ecolbeck New Member

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    JohnB,
    I get what you're saying about heat conducting areas of a stove, and those being different in construction from the firebox. On my Jotul F400 the conducting area is the top plate of the stove where the iron is in direct contact with flue gasses. What I don't get is which assertion of mine you feel is false. Was it "An insulated firebox, while increasing overall efficiency, works against the principle of heat transfer."?
  12. HotCoals

    HotCoals Minister of Fire

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    By on board I mean blowers that came from the factory for that stove.
    The more I think about it the more I shy away from using them.
    I seem to have good air movement throughout my house without them.
    I know my fans lower my stack temps some just being on a short time from experimentation.
    I prefer to not have my stove make creosote.
    I agree with those that talk about blowing colder air from another room into the stove room to move the warmer air around.
    I really think that idea has merit...but I myself don't need to do that..some do.
  13. mtcates

    mtcates Member

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    Most all epa stoves are relatively efficient at extracting heat. If one stove is 10% more efficient than the other that means that instead of 3 cords a winter its now 3.3 cords. Thats not much difference.
  14. CTYank

    CTYank Minister of Fire

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    There it is! The firebox need not have anything to do with heat transfer. Nothing being absolute, there is some transfer through firebrick and iron, and to secondary air preheater. In my firebrick-lined Squirrel, there is significant heat transfer through the sides from the gases that have passed the baffle and are now heating the upper couple of inches of the cast-iron sides. In that stove the gases have to go all the way to the back of the top before doing a 180 about a vertical axis and a 90 up the pipe. They dump a lot of heat, percentage-wise, there, from IR temp readings.

    There are books on the subject, some of which are rigorously done and good-reads. Some are just entertaining. See Amazon.
  15. ecolbeck

    ecolbeck New Member

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    Thankyou JohnB, that makes sense. Here's another couple of questions: why bother to preheat secondary air or any combustion air for that matter? What are some other book titles?
  16. CTYank

    CTYank Minister of Fire

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    Sorry, but that's not true. Firebrick is a serious insulant, for one. To keep temps UP, nothing to do with "steady."

    Take a look at how many of the Danish Rais stoves are designed with fused vermiculite insulating blocks wrapped around the firebox. And relax.
  17. HotCoals

    HotCoals Minister of Fire

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    Interesting that you bring that up.
    I was always under the assumption that colder air holds more oxygen.
    That makes me think a OAK might be a good thing just for that reason.
    But you would think any air coming in a stove could only get as hot as the temp in the stove if it even has a chance to do that.
  18. ecolbeck

    ecolbeck New Member

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    temperature and percent oxygen content in air are not related. Density and temperature are related and so colder air can be thought of as having more of all the gases (including oxygen) per unit of volume (at a given pressure). I would hesitate to say if its enough to make any difference. The only reason I could think of to preheat air is some notion of preventing the firebox from cooling excessively. However, it seems to me that a cursory study of thermodynamics would tell us that that idea is false. Cold air would cool the stove whether its heated in the firebox or preheated from heat from the firebox.
  19. ecolbeck

    ecolbeck New Member

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    I have been contemplating OAK for a long time, not because my house is tight, but because of the idea that the house is cooled by the infiltrating air which replaces the air the stove uses. The question I want answered is how much air is my chimney sucking out of the house when I'm not using the stove or when the stove is cooling off late at night. OAK would prevent the loss of that air and prevent the house from cooling off as much.
  20. HotCoals

    HotCoals Minister of Fire

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    Yeah..
    I do know colder"denser" air has a big effect on 2 stroke snowmobile motors.
    If I was jetted for temps around 30f she would run really lean in temps of 0f and below..way lean..but would really haul butt.
    Well this is mostly way over my head and I'm happy with my setup so I'm outa here!
  21. HotCoals

    HotCoals Minister of Fire

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    I dunno.but the draft seems to slow as the flue cools..some say to the point that it can reverse! Dang!
    Seems like you can't win..lol.
  22. Hogwildz

    Hogwildz Minister of Fire

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    Sorry, I live in PA, USA, No Danish stove here. And have yet to hear of PE, Quad, VC, BK, Lopi, Jotul or any others sold here in the states fused with vermiculite or anything else wrapped around the firebox. WHich yes, is what I read the OP as questioning. Doubt he was talking about a Danish stove, but hey again, if he was, then my misunderstanding.


    I been through, over, all around both my Englander and PE, and aside from baffle board, baffle insulation, and fire brick, there is no "Insulation" wrapped around the stove encased between two shells, or magic cover. If I ever move to Denmark or Europe, and use such a stove, then I will concede that they are wrapped in insulation if it in fact is.

    I am relaxed, takes much more than this to get me uptight, and you will know if I am don't worry.
    Have a great night.
  23. Hogwildz

    Hogwildz Minister of Fire

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    Unless you have some type of block off or flapper on the AOK that you would shut during times not using the stove. You may run into the problem of the AOK freezing or the stove & input piping being a big cold cube of steel and pipe. There is a guy on here that fashioned a manual shut off for just that reason.
  24. Hardrockmaple

    Hardrockmaple Feeling the Heat

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    Not to hi jack this thread but I have a cat vs. non cat question. With my DW cat stove I keep it shut down pretty much most of the time (as required), can you run a non cat the same way? I see where someone said you have to get the stove top up to 1100 degrees before shutting it down, that to me is a really high firebox temp. My intent is to replace the old smoke dragon stove in my unfinished, but insulated, basement (1000 sq.ft., wide open with bare concrete floors with a new EPA stove. I want a robust reasonably priced EPA stove, considering a non cat version but am concerned with having to babysit the darned thing. With the smoke dragon it is just fill it up close 'er down and repeat every 8 hours or so. From what I read here that really doesn't seem possible with the secondary burn types.

    Thanks in advance.
  25. ecolbeck

    ecolbeck New Member

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    In my experience, if you are trying for to eek out the longest slowest burn possible, both cat and non cat stoves require some amount of periodic attention. the amount of attention depends on the stove and the quality of wood being burned. I used to have a cat stove which was oversized for the house and I tried to run it at as low a temp as possible. Sometimes however, the catalyst would flame out, requiring the stove to be brought back up to temp. Smoke from the chimney was the flame out indicator that I used. It could have been that the catalyst was near the end of its life span. I currently have a non-catalyst stove. Once they are up to temp these stoves must have flame in the firebox in order to be efficient. If I try to run my stove too low in various conditions it will flame-out and there will be smoke out the chimney. A slight adjustment of the air supply usually cures the problem.
    I only have these issues during the shoulder season when I only need minimal heat from the stove. right now when its -8 out I'm working that stove for everything its worth to get the house back up to temp. right now the only attention the stove needs is more wood and a check to make sure there is no over firing.

    Perhaps a pellet stove would be best if you really want to set it and forget it.

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