My stove manual says: You can get an indication of whether the catalysts are working by comparing the amount of smoke leaving the chimney when the smoke is going through the combustor and catalyst light-off has been achieved, to the amount of smoke leaving the chimney when the smoke is not routed through the combustors (bypass mode). I find this difficult. Conditions have to be perfect to observe chimney smoke before and after the catalyst lever is pulled. Overcast skies, wind, way the wood is burning, etc all effect visible smoke out my chimney. Would observing the catalysts glowing red also confirm the catalysts are functioning properly? I mean, is it possible for them to glow red but NOT be functioning properly? Cause it's way easier for me to kneel down and see if they're glowing.
If the cat is glowing I don't see how it could not be working...unless you have overfired the stove and the whole thing is about to melt down! The trick with looking at the chimney is learning to tell the difference between steam and smoke...steam tends to dissipate within 5-10' of the chimney, smoke tends to trail off much longer.
Monadnock Monster, You're right; it isn't always easy to tell just by looking at the chimney. Looking at the cat is also a good indication of the cat working. However, some cats are not easily seen just by looking into the stove. The Absolute Steel I have can only be seen if you open the top panel of the stove, and if you do that, you're letting fumes into the house. The best indication of the cat doing it's job is the temp guages. Usually one on the flue about 12 to 15 inches up from the stove top. Then a second one on the stove top. Before the cat is engaged you'll see the flue temp rise, as all the heat is going out the flue, along with the smoke. The Stove Top Temp is most likely less hot then the flue. Then, once the fire gets going well the STT maybe between 300'F and 400'F and it's time to engage the cat. Once the cat is engaged shortly after that you should see the flue temp being to decrease. Also, you will see the Stove Top Temp increase in heat. I'm not sure what Skeeter's message is saying. I have heard that the cat may be working without being red or orange, but if you're seeing a red cat, then it's working, and you should see high STT and low, about 300' F flue temp.
Thanks for all this, Old Hippie! In my setup, I don't have access to the flue, so monitoring temps there isn't possible. With STT, the soapstone doesn't register a difference, honestly. I can fire the thing up to 500* with or without the cat. My stove has a cat probe to measure temp, but that's for the bypass and doesn't really change (that I can tell) after I've engaged it. So that leaves me looking at the cats, or looking at the emissions. And most times I look up at emissions, I can't see anything, even just after I've started a fire in a cold stove. Maybe I need glasses.
Thanks! But I usually can't see anything up there, even after lighting a fresh fire in a cold stove. I CAN however easily see the cats, and I assume if they're glowing red the sucker is working like it should. Right? And interesting what you wrote about steam... I've heard a byproduct of the chemical reaction in the cats is water.... so that water boils off and can be visible out the chimney???? Or is it moisture in the wood?
A cat probe should increase in temp after engaging the cat by closing the bypass,. especially if you also dial down the primary air. (That'll decrease primary fire, leading to more half-burnt gases and smoke, which is fuel for the cat.) If it stays the same or decreases the cat might be not working well Every burning of carbon fuels means carbohydrates+oxygen gives CO2 (if combustion is complete, this is where the carbon atoms end up) and water (this is where the hydrogen atoms from the carboHYDRATE end up -caps not meant to offend only to emphasize). And wood is never dry, as in zero percent water. So water always comes out of a chimney. It it's cold enough that can be steam. But generally (in cold, dry winter weather) steam appears a few inches from the chimney and disappears a few feet away. Just like your breath. Smoke is visible directly at the cap and does not dissolve but dilutes. I once did a back of the envelope calculation on this,.that I copy here: Perfectly dry wood contains about 6% (by weight) hydrogen - that hydrogen is part of the cellulose etc, not the water in there. When burning that hydrogen combines with oxygen to make water. Oxygen is heavier than hydrogen, and water is H2O, and this results in a pound of dry (!) wood producing about (more than!) half a pound of water! So you put a 40 lbs load of wood in there, you get (adding pounds of oxygen gas drawn from the air of your home) ~21 lbs of water - going out the stack. Even if the wood is perfectly dry! Add to that your 6 pounds of water that was contained between the wood fibers, and there you have your steam source: 27 lbs of water from a 15% wet 40 lbs load of wood.
And just to put this another way, 27 lbs water is almost 3.25 gallons! No wonder wood over 20% MC doesn't burn worth a hoot!
Yeah. And we all know how much energy it takes (in this case from the fire that would otherwise heat your home) to boil and evaporate water...
Pretty dang cool. I never really considered what happened to the moisture in the wood, and never would have guessed it'd be visible steam out the stack. I'll definitely pay more attention to that going forward. BUT, at my house and with my chimney, it's difficult for me to observe emissions. SO, if a cat is glowing red, does that confirm it's working properly? Google says a cat is good for ~12,000 hours, which is a bit nebulous. As best I can tell, that's about three or four seasons for me. As I approach that point, can I simply observe to see if they're glowing, and when they stop glowing, know I need to replace them?
If it's glowing, it works imo. But if it's not glowing it doesn't mean it doesn't work. It needs to be about 500 F to start working and 500 F doesn't emit enough visible light for a human to see. 12,000 hrs is about right. Seasons is more nebulous because they run from September to April or from November to March or so.... You'll have to estimate how many hours you burn in a season...
A glowing cat does not confirm it’s “working” just like a non glowing cat does not confirm it is dead. At high settings a mostly dead cat can glow but will quickly drop out and not work at lower settings. It can be mostly dead. Many of us run these things at low output all the time so the cat can be totally junk unless you crank it way up and then it glows and sorta works but we don’t run car stoves for high output.
Somehow this isn't surprising. So how do you know if the cat's dead, assuming there isn't physical degradation? Flu temps, as referenced by old hippie up there ^^?
Smoke from the flue is my biggest clue. No, it’s not steam! The need to use higher stove settings for the same amount of output is second and this comes with reduced burn times. Junk accumulation on the face of the cat is another clue. Even a mostly dead cat can still do a little bit of work when you burn the heck out of the primary fire but that’s useless. They lose the bottom end first and that’s where the magic happens.
