I installed a new cat today and my fireplace stopped backpuffing. I looked at the old cat and was very clean. No plugged holes. Just a few cracks. No creosote buildup. The new cat lit right up fast and stays lit very long. Do you think that when the cat is working properly the smoke is burned assisting in the draft, pulling more through it? Any thoughts?
Changed cat
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I doubt it. The smoke went through the old one the same as the new one. It is just that the new one is burning the smoke better and you are getting more heat from it.
Rockey said:
I believe the combustor manufacturers all discourage using compressed air. They say there is too much risk of blowing the thin coating of catalyst right off the substrate. Most recommend a soft brush and vacuum instead.
This pdf from Condar gives cleaning instructions that are probably universal to all brands: http://www.condar.com/combustorcleaningmanual.pdf.
The main sources of catalyst de-activation are poisoning (lead sulfur and others) and Migration. If the cat gets very hot and stays hot, one will eventually melt the platinum and palladium and they will flow from the places they were deposited in the coating (very tiny amounts well spread out through the matrix) to the point where they agglomerate in larger clumps which have a much smaller surface area that is exposed to the flue gas. I know it doesn't sound logical, but the volume of a sphere is 4/3 * PI * R^3 and the surface area is 4*pi*R^2 so it should be clear that as the radius of the platinum droplet goes up, the ratio of the surface area relating to the volume of catalyst is going down by a factor of R/3 and R is getting bigger the bigger the droplet gets.
For high temperature service, migration and agglomeration is the key factor, while at lower temperature poisoning is the big thing. Sulfates can be burned off at higher temperatures, but other poisons like lead, mercury and other contaminants simply mask the precious metal (they stick to it like glue) so that the surface is not available for assisting in the desired reaction. The only thing to do is to crush the old catalyst and leech out the precious metals and start all over again. Thats what the crooks do who steal catalytic converters from under your car or truck, or at least they sell it to someone who has the sophisticated stuff needed to "mine" the precious metals.
For high temperature service, migration and agglomeration is the key factor, while at lower temperature poisoning is the big thing. Sulfates can be burned off at higher temperatures, but other poisons like lead, mercury and other contaminants simply mask the precious metal (they stick to it like glue) so that the surface is not available for assisting in the desired reaction. The only thing to do is to crush the old catalyst and leech out the precious metals and start all over again. Thats what the crooks do who steal catalytic converters from under your car or truck, or at least they sell it to someone who has the sophisticated stuff needed to "mine" the precious metals.
BrotherBart said:
I think it was the 'it should be clear' bit. Clear enough to those of us who happen to be engineers. But many people just don't follow equations like that in sentences.
I was thinking of getting a "P=MV" bumper sticker, but I don't think it would help stop most people from cutting off truckers. :lol:
JV_Thimble said:
This happens sometimes. Engineers make a joke and everyone quietly leaves the area... :-S
hughmyster said:
Hi Hugh,
To slog back to your original question, I think it may be more than draft that fixed your backpuffing.
If your old cat was worn out, it was allowing unburned smoke into your stove exit and flue, which may have been igniting there and causing the backpuffing.
So a worn cat can allow backpuffing. Good to know!
JV_Thimble said:
I laughed, but that only confirms your point.
Reminds me of Steve Martin's old comedy bit about geek jokes.
Trktrd said:
I bought a condar. How long should a cat last when used properly? When a stove burns clean what is a good rule of thumb on how long to wait to clean the chimney? Dumb it down for me. Im new at this.
Hughmyster, one cleans the chimney whenever it needs cleaning. The only way to know is to inspect it.
We have a cat stove and this is our 4th year for burning it. We've cleaned the chimney one time so fat. However, not many can go that long even with a cat stove. It is more a testament to our very well seasoned wood that we are blessed with. Chimneys still need checking every so often. Ours get checked 2-3 times per season (by habit).
We have a cat stove and this is our 4th year for burning it. We've cleaned the chimney one time so fat. However, not many can go that long even with a cat stove. It is more a testament to our very well seasoned wood that we are blessed with. Chimneys still need checking every so often. Ours get checked 2-3 times per season (by habit).
KeithO said:
Holy crap, what a geek.
You were one of those guys I picked on in school who now make tons more money than me.
After I read it a dozen times, it actually made sense and was helpful to the point where I copied and pasted.
Franks, I think you are a very perceptive man. The question is whether you still pick on those guys ?
It was cool in junior school and the girls liked to accompany me on the walk home (more than a couple miles) to talk. But that all stopped in high school.... Geeks were harder to recognize in the military, but it was ultimately all about might there too.. However, I was in the engineering corps and when someone had to "deal" with a piece of unexploded ordinance, or setup 12 claymores every evening, the macho men weren't volunteering, if you know what I mean ??? At least not after the first few blew themselves to smithereens. I was only a section leader (lance corporal) but when you deal with the most dangerous stuff personally, instead of ordering your men to do it they will back you through thick and thin.
My experience has been that for whatever reason, the corporate world (at least here in the midwest in automotive) is extremely hostile to intellectuals. Maybe those relationships and habits built up playing football carry over to the boardroom, I don't know. Rant over...
It was cool in junior school and the girls liked to accompany me on the walk home (more than a couple miles) to talk. But that all stopped in high school.... Geeks were harder to recognize in the military, but it was ultimately all about might there too.. However, I was in the engineering corps and when someone had to "deal" with a piece of unexploded ordinance, or setup 12 claymores every evening, the macho men weren't volunteering, if you know what I mean ??? At least not after the first few blew themselves to smithereens. I was only a section leader (lance corporal) but when you deal with the most dangerous stuff personally, instead of ordering your men to do it they will back you through thick and thin.
My experience has been that for whatever reason, the corporate world (at least here in the midwest in automotive) is extremely hostile to intellectuals. Maybe those relationships and habits built up playing football carry over to the boardroom, I don't know. Rant over...
Backwoods Savage said:
Can the stove be brushed from the bottom? I'm not climbing on the roof. Too steep for me. My chimney is over 30. Feet with 2 slight bends. Also the other question I have is has anyone drilled a small hole in the air assembly plate? I have a 44 elite and there is only one inch of movement on the air assembly between open and close. Its still backpuffing when its all the way closed. It would be easier for me to be able to get the fire going then just move the lever all the way over and not have to worry about it being fully closed or too open .plus that little lever gets to hot and you have to put on gloves and just can't get the right feel of it.
hughmyster, whether one can clean from the bottom depends on the chimney. We have a tee at the bottom so can clean from there. We have a horizontal section but can clean that by opening the top lid on the stove. Not much there though as only some fly ash. But then we don't get much from the chimney either.
I got a cleaning service coming out. Stove is still backpuffing. Im thinking maybe too much creosote buildup in chimney slowing down draft causing backpuffing? Any ideas? When i first got this stove i never had a problem for the first year and a half. Does the type of wood make a difference? Is there such thing as too dry wood?
hughmyster said:
Hi HM,
What stove, chimney, etc?
Would you put it in your signature ("Your Control Panel" up above)
RenovationGeorge said:
44 elite. Air insulated chimney 30 ft. The stove had the option of posi pressure but i did the interior option. I have been trying to figure out why the it has been acting this way. I built this house 3 years ago and the problem is getting progresively worse. Its having those explosions when the air is all the way down and cat ingaged. the smoke exits the door seals and smells up the house.
I put a new cat in. It improved it a little but not enough.Im almost thinking negative pressure? Stack effect?
hughmyster said:
Has it been a year and a half since you had your chimney inspected and cleaned? If so, I'd certainly start there. Otherwise we can discuss other possibilities.
A dirty flue can absolutely cause draft problems on pre-fab units. Has it ever been cleaned? As long as the wood is seasoned, it doesn't matter what kind, some wood takes longer to season than others, but it can't really be too dry. Get that thing cleaned, it can be cleaned from inside, I would, but make sure that they inspect the cap, cleaning from below can push creosote into the cap.hughmyster said:
RenovationGeorge said:
I never had it cleaned. I was told the cat stoves burn clean so they dont need cleaning.
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