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"Cat stoves do very well with smoldering fires."

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by soupy1957, Sep 24, 2010.

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  1. rdust

    rdust Minister of Fire

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    Lets be fair Dennis, going from the old stove to a new EPA model with or without a CAT you would have saved plenty of wood. :)

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  2. Todd

    Todd Minister of Fire

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    Ok, I'll be fair, since I went from an EPA noncat soapstone to a cat soapstone I've save 1 full cord or wood per year the last 4 years. :cheese: Use to burn 4 cords now it only takes 3.
  3. Patapsco Mike

    Patapsco Mike Feeling the Heat

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    My experience was very similar to Todd's. I went from a very nice, big EPA insert (Avalon Olympic) to the BK Princess. Both great stoves that I would buy again, but I burned a LOT less wood with the BK. The wood savings during shoulder season are most dramatic- I probably burn half as much wood. In mid-winter when I'm running the stove hard the difference in wood used is not as noticeable.

    All I know is at the end of last winter, my first burning the BK, I suddenly realized I would have a lot less wood to split, stack and haul into the house for the rest of my days. That is priceless. There is no question in my mind that the cost of replacing the cat every 5-10 years is more than offset by my savings in wood and manual labor.
  4. jharkin

    jharkin Minister of Fire

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    Soupy,

    I'll agree with all the other respondents here - dont be afraid of a catalyst. They really are not that hard at all once you learn how the stove reacts. The only "trick" if any is learning how to recognize when the cat is warm enough to close down the bypass. 2 ways to do that - the simple way is to get the stove good and hot and then wait a half hour. If you close it down and dont have smoke after 5 minutes your good. The other way is to get a catalyst thermometer and just wait for it to hit 500.

    And yes, if the wood is dry, you have a good coal bed and the cat is hot it is completely OK to see nothing but smoldering in the firebox. Its weird at first but you get used to it. I have seen my stove at times be almost completely dark but the cat chamber thermometer is reading 1500. Thats a happy catalyst :)


    BTW as to complexity, my cat VC actually has fewer controls then our old '79 Resolute that my dad still uses. That think has a damper/bypass and 2 air controls (primary and a secondary for its very early predecessor of a reburn chamber)
  5. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Okay rdust, I'll be very fair. I do expect that I would have decreased the amount of fuel with most EPA stoves. However, read the posts above. Also, I have yet to hear of anyone coming even close to the fuel savings that I have enjoyed. Yes, I have heard of a 1/3 decrease of fuel but so far nobody has matched the results we are getting. I do not know why; I just know it apparently has not happened. I wish it would happen for all of us wood burners. That, I believe, would get even more folks burning wood and saving some of that black gold called oil.

    I do hope that nobody takes my answers concerning the Fireview stove and fuel usage as trying to put down other stoves because that is not my desire. I only post about my experiences and how this particular stove operates. Some have actually wondered if I am employed by Woodstock. Yes, I have been asked that. Well, I suppose I could be if I wanted to! No, I do not intend to. Many of the folks at Woodstock I think did not know what to expect when I showed up for the bbq but yet all were excellent and happy folks. It was a real pleasure meeting them and I hope it was the same for them. I do know I was treated extremely well while there. I was surprised that nobody asked me while I was there why I promoted their company and their stove but that is okay. The only reason I do so is that I enjoy promoting any product and/or company that has a great product and is a great company to deal with. It helps both consumer and seller.

    Being a direct sales company does make it a bit harder in some instances for them to make the biq quantity sales because some folks just don't trust direct sales and others never even hear of them. I've seen that here on hearth.com. In some of the PM's and email's I've received from others it is apparent they knew nothing about Woodstock. Fortunately for them they knew enough about me to know that I would give them solid answers and no bull. That is how I have done and will continue to do.
  6. oldspark

    oldspark Guest

    If the efficiently rating of the stoves are pretty much the same cat vs non cat and the fire boxes the same size would not the consumption of the wood for the heat given be the same or so close to call?
  7. Slow1

    Slow1 Minister of Fire

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    You would think so - unless something in the numbers doesn't reflect the actual burning experience. How numbers are calculated and measured compared to so called "real world" situations often times leave quite a gap. I've become convinced that the numbers reported by manufacturers for efficiency are only useful for broad comparisons - so many of them are hardly close to accurate as they are created to meet regulatory requirements. Well, accurate they are - if you are burning 2x4 and 4x4 pieces of lab quality wood in their particular setup on the test bed. I don't do that so the question is how well does the test methodology translate to real world? I have heard a lot of discussions about the hoops that the test folks go through to get particular EPA gph values on a given stove and the optimization of design for that particular test - efficiency tests are likely the same way. Design toward the test to some degree, but then what? Not all stove manufacturers approach it the same way I'm sure, but you get the point.

    Besides the bias in a lab setting, there are other factors as have been pointed out here - the ability to burn lower during shoulder season when less heat is needed could account for less wood burned for some folks - anytime someone over-heats their house they are burning more wood than they need to and if it is avoided then add that to the savings.

    Then of course there is how the user burns it - how much effort is required to get close to 'optimal' efficiency does one stove take vs another? If a particular stove happens to be able to go through a burn cycle untouched and stay closer to optimal efficiency of burn (in more conditions) than another stove (in the real world conditions) then likely it will burn less wood in the long run for the same heat output. I tend to think that it isn't really about the ability to achieve maximum efficiency (in lab or in home) but rather the ease with which one can consistently maintain the highest average efficiency that will reduce overall burn of fuel.

    I don't know - but I suspect that some or all of these factors come into play. Operator habits (from fuel used to loading to fiddling with the stove) ultimately will determine IF the best a stove can get is achieved, but some stoves / stove designs are going to be more tolerant than others and thus more likely to hit closer to optimum on a regular basis.
  8. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Good points Slow1. A case in point is an old thread where it was discussed about how long it takes to get these soapstone stoves up to good heat. Some can do it faster than others (but you can do it too fast too!). For example, one might start with a cold stove and have the cat turned on in 30-40 minutes. For some I recall it taking an hour or so. That says it is fuel and/or the operator.
  9. Battenkiller

    Battenkiller Minister of Fire

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    They aren't the same. Look at Woodstock, for example. All four of their models are using the EPA default of 72% efficiency for a cat stove. It is apparent to me that these were not numbers generated from test data or they wouldn't all be identical. Perhaps these stoves are actually higher in efficiency than the advertised figures? In contrast, the EPA default efficiency for a non-cat (secondary combustion) stove is only 63%.

    It's hard to deny that cat stoves are, in general, more efficient. I've always like the idea behind them, but fell prey to the horror stories. Large industrial manufacturers often use catalysts to increase their yields (i.e. increased efficiency). The same reactions could be forced to completion using heat, pressure, continuous product removal, etc., but the bottom line is that the appropriate catalyst puts the molecules into a better configuration for reactions to occur, so lower energies of activation are needed. That's why cat stoves don't need to achieve 1100ºF to burn off the gases. If the reaction can proceed at 500º instead, there is a much greater chance that more molecules will combine with the oxygen molecules need for complete combustion.

    There are other reasons for reduced wood consumption as well. Burn efficiency is only a part of the equation. Heat transfer efficiency is the part we are all concerned with. The Woodstock stoves have no insulating materials in them. You have to use more energy to get all that stone up to temp, but in the end nothing is lost. The heat comes out steadily and evenly for a longer period of time. Compare that with my VC stove. That thing just blasts the heat out, but that raises the temperature of the room too high. The excess heat is transferred to the outdoors through the walls of my home more rapidly because of this. Then the fire dies down and the stove cools off and I am forced to load it again to keep it warm in here. In effect, I am forced to over-stoke my stove, and this has zero to do with it's actual burn efficiency (which I am convinced is a lot higher in my stove than in many of the old dragons). But Woodstock stoves (and other cats, I'm sure) can maintain their high efficiency at very low burn rates. The Fireview can put out as little as 10,000 BTU/hr and still burn clean. I don't think my stove can do that and still stay lit. I think I'm wasting a lot of wood just keeping it burning clean.

    I don't think it has so much to do with burn efficiency (EPA rating) as it has to do with the fact that a properly sized cat stove can give off just enough heat to do the job over a much longer period of time. If you still feel warm, you won't be refilling your stove as often. Less refills means less wood used. Add in the heat storage ability of 500 pounds of soapstone like in the Woodstock stoves and I think you have a winner.

    I have been thinking long and hard about the Woodstock stoves since I visited the factory, and I am seriously thinking of trying one out in my basement. The time is now as far as their offers go, but I'm kinda broke right now so I may have to wait. Still, it might be worth it for me to buy one through their financing (9.9%) plan, so persuade me to go into debt, I'll love you for it.
  10. oldspark

    oldspark Guest

    I was using the effieienty numbers from the manufactors them selves on the web site so many of the stoves both cat and non cat are over 80%, just trying to compare apples to apples and do not think the soapstone comes into play with my question about the efficienty. It just seems like the two are comparable, I agree with slow about less wood in the shoulder season due to the cat and he seams to think they are more the same when pushing them harder in the winter, I think that makes sense to me if the stoves match up other wise.
  11. Slow1

    Slow1 Minister of Fire

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    Although I would agree that the difference between a cat and non-cat stove in terms of ability to burn clean and efficiently as the stove temps go up (i.e. as the stove is pushed), I am not sure that the difference approaches zero nor would I expect that the curves will remain parallel during the whole burn. I'd love to see real-world numbers to back up any claims but I don't think we'll ever see such things so this is all conjecture in any case. Nice chat for a forum or around a campfire :)

    My reasoning here however is that not the entire burn happens at peak temperatures - thus some part of the burn will be below the key temps where the burn tubes kick in and help burn off things in the non-cat. In the cat stove the cat will remain lit and keep burning off gases for quite some time (as long as it is above 500 or so, and that temp is maintained by the burning action...). Keep in mind that the cat not only burns the smoke but it also helps to burn off other things such as CO which we all know is a by-product of the coaling stage. I have to figure this must contribute some amount of additional heat to the equation.

    And again - we come back to how the stove is burned. As an example I don't get the impression that Backwoods Savage/Dennis burns his FV at full tilt much - rather he seems to run his at a longer, slower burn much of the time. It may well be that in this mode he gets at a peak efficiency for his configuration. That just may not work for everyone - when sizing a stove this may well have to be taken into consideration. Perhaps this is why the FV is officially rated for up to 1600 sqft even though it CAN heat far more (I'm doing something like 2500) but that takes pushing it much harder.
  12. oldspark

    oldspark Guest

    Just the other day I saw a post by begreen or brotherbart that they did not run there non cats for the fires of hell effect any more and it takes less wood so operator has a big part in this and I am sure Dennis knows what he is doing.
  13. branchburner

    branchburner Minister of Fire

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    How do you suppose the average flue temps of a cat compare with a non-cat, in general? (I'm sure a lot of that flue-temp data could be dug up right here on the forum.) I'd assume that if a cat is burning smoke at the lowest possible firebox temps that there would be less overall heat loss up the stack than with a non-cat.
  14. Todd

    Todd Minister of Fire

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    This is what I'm thinking but could be wrong. Manufactures will test and take the highest number they can come up with. Cat stoves are most efficient at lower burns while non cats are more efficient at medium and high burns because they need the higher temps for secondary burn. If you took a cat and non cat stove with the same efficiency and knew how to burn them at their highest efficiency the cat would burn less wood because it's most efficient at a low burn.
  15. Slow1

    Slow1 Minister of Fire

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    My experience is a bit extreme - I went from a downdraft stove that put a LOT of heat up the stack to the FV cat stove. Thus my flue temps fell an amazing amount. I suspect that my experience is not typical in that respect.

    However, I can tell you that last year during the cold periods - Jan/Feb when it was below freezing I regularly would have ice form on my chimney cap. When I would do my reloads (particularly in the morning) I would hear it break off and fall. I don't think I'm losing much excess heat up the stack here - any less and I'm afraid it could affect my draft.
  16. Todd

    Todd Minister of Fire

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    That's something I've looked into and it seems that the cats burn a little lower stack temps. I know I noticed lower stack temps since I went to a cat stove. Blaze King flue temps are so low they recommend a certain amount of vertical pipe before any horizontal run.
  17. Flatbedford

    Flatbedford Minister of Fire

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    With regard to heat up the flue. I know that when I reload my Fireview with the bypass open, the double wall pipe gets too hot to touch. After only a few minutes with the cat engaged, the pipe cools enough that I can hold my hand on it. The stove temp goes way up and the flew temp goes down. Does a non cat EPA stove do the same thing? Before the Fireview we had and old Franklin smoke dragon so I can't compare.
  18. Patapsco Mike

    Patapsco Mike Feeling the Heat

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    Yes, for the given amount of heat, but the difference is illustrated in the title of this post. Cat stoves can run very efficiently with a smoldering fire. Non-cats can't.

    I run a smoldering fire for nearly all of shoulder season. This allows me to burn a load of wood for maybe 50% longer than I could in my non-cat (12 or even 14 hours as opposed to 6 or 8- or- burning just two or three logs for 8 hours which was not possible with my non-cat). With my old stove, I'd go through way more wood and I would have to throw a window open once in a while or let the stove go out during the day to keep my house from getting too warm. Now, I just turn down the thermostat on the stove and dial down the heat output.

    Overall I'm getting maybe about the same amount of heat per amount of wood, but I'm able to dial down the BTU output of the stove while maintaining peak efficiency. This is the magic of the cat.

    When you in mid-winter, running full-out, burn times in a cat are better but the difference in amount of wood used is not nearly as significant.
  19. oldspark

    oldspark Guest

    Yes they do but to what extent compared to a cat stove I would think less, the stove top is hotter on a non cat than the stack except for start up and reload.
  20. Flatbedford

    Flatbedford Minister of Fire

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    My stove top is always hotter than the pipe. Just the pipe is much cooler with cat engaged.
  21. oldspark

    oldspark Guest

    Even on start up with out the cat engaged?
  22. Flatbedford

    Flatbedford Minister of Fire

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    Not sure about that now that I think about it. I just don't remember. I'll have to get back to you on that in about 6 weeks or so.
  23. Todd

    Todd Minister of Fire

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    When i'm in the bypass mode my stack temps can sore into the red if I don't watch the amount of air I give it. The stove top lags behind until you engage the cat then the stove top climbs while the stack drops. Cruising 500-650 stove top relates to about 240-300 external stack temp about 20" up for me.
  24. Slow1

    Slow1 Minister of Fire

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    On first light of a cold stove - not in my house. Those top stones do take more time to heat up than my single wall stove pipe, even with a top-down fire. But once things get going the pipe will generally remain cooler than the stove top.

    During the constant heating time and re-loading from coals I would have to say the same is true again - the stove pipe will heat up first, then the stones on top catch up. However then it is a bit faster as I'll engage the cat as soon as the pipe hits 400 and the stove top will get there mighty quickly while the stove pipe will fall down at the same time.

    Overall while the stove is in operation the top will remain warmer than the pipe the vast majority of the time though.
  25. rdust

    rdust Minister of Fire

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    I can see that. I'd guess you saved most of it during the shoulder seasons? If I remember right Dennis went from 6 cords a year to 3 with the CAT stove. So even using your 1 cord savings Dennis would have still cut his use pretty significantly. :)
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