Could you provide me with your cat temps at different intervals? I'm having issues with the stove dropping from 1200 to 547 within 45 min of reducing the air. Dealer says it's a draft issue but I'm lost as to the logic.
Yeah, that's not a good temperature. Stove designs vary, but I’d expect all to run between 700 and 1200F in the first few hours of a burn, if the probe is properly located 1.5 inches behind center of face of cat. But that said, I have observed this behavior under several different circumstances:
1. When the cat is plugged with fly ash. If there's a good seal (eg. gasket) around your combustor preventing any exhaust gas path around the outside of the combuster, then a plugged cat is very easy to detect. You'll notice the stove burning very lazy, as if it's on a lower setting, even when the air is set to a very high setting. With my 30 foot chimney, I have observed this behavior several times.
2. When I try to burn wet wood. At low burn rates, the water baking out of the wood is generating steam cool enough to knock the cat out of active reburn. Given the insane amount of rain I have had this summer/fall, I have run into this once or twice this fall, even though I'm burning wood that's seasoned more than 3 years. Simple solution is to burn the stove on a higher setting for long enough to bake sufficient moisture out of the wood, usually at least 30 minutes in my stoves. Just be careful not to lose control of the thing, if you stove doesn't have a limiting thermostat (a'la BK).
3. Poor draft. Simply put, your draft limits how low you can run the stove without stalling it. If you find the cat stalling, mark your air control lever setting (I use small triangles of colored electrical tape as pointers), and try running it a hair higher the next time. The lowest setting at which you can run without stalling is somewhat weather-dependent, you can run lower as it gets colder outside. This is easy to debug with a manometer, if you're much lower than .03" WC, then this is likely your issue.
4. Cat end of life. I just replaced both of my cats, after 3 and 3-1/2 years of use, respectively. The one that I stretched to 3-1/2 years was doing exactly as you describe, falling out of active a little earlier. The new combustor can stay active until I'm down to baseball-sized coals.
There may be other possible causes for your issue, these are just the four I have experienced myself, in 14 years of running cat stoves (or 7 years of running two at a time). Three of the four are pretty easy to determine on your own, the fourth requires a new cat to prove out.
