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Posted By Gridlock,
Mar 24, 2010 at 12:31 PM
that must have smelt real good.
I've had cats up to 2000 degrees a few times - every time I did it was more because of the particular wood than any other factor. In some ways, a cat cannot help how hot it gets because if it has a vast amount of fuel (smoke, volatile gases) to burn, it must do so. It is a self-sustaining reaction!
If it becomes a problem, my solution would be larger splits of wood and maybe some less seasoned material - as well as mixing wood species if you find that one species tends to do it more. Each wood species has a different chemical makeup - i.e., some have more coals and some have more gases.
Thanks for the suggestion, Craig. I've been trying all sorts of things, but so far I've been having a tough time achieving a good balance. Last night I tried Gar's technique of trying to move the coals over to once side, and closing the damper immediately after loading. This seemed to work well for a while, but eventually all the wood ignited and I ended up with a similar problem. I had another thing happen yesterday where I had sudden explosive poofs in the firebox. I believe the smoke in the firebox was igniting suddenly. I had the damper closed and the temperature in the CAT chamber rose once again to over 2000 degrees; I actually saw 2250 briefly. I opened the damper and the air control to burn off excess smoke, then closed the damper again, at which point it appeared everything was Ok. Before this happened, I had the air control a bit over 1/3 open, so don't think I was choking it down too much.
I do wonder if this stove is overly touchy and if another CAT stove (like the Woodstock) would be less so.
I had similar experiences with my VC cats. The BK, on the other hand, is extremely predictable and controllable even with a full load of small split pine.
I just read the following sentence in the stove manual:
"Avoid using a full load of very dry wood in the firebox. This may result in continuous very high temperatures in the secondary combustion area and damage the combustor.".
Well, I didn't think my wood was very dry, but maybe that is the case. Any recommendations on a good wood moisture meter?
I've had my cat get away from me a few times and every time it's been a fully loaded fire box, air shut down and no flame action. I found this won't happen if you wait 10-20 minutes to engage and when you do give it some air for 15-30 minutes before turning it down for those longer burns. I was told by the experts that the cat can handle those high temps for short times once in awhile but internal stove temps above 1400 can take it's toll on cast iron parts.
Well, today I've been enjoying a long steady fire without the excessive temperatures. The key seemed to be not to ignite all the wood at once. I pushed all the coals to once side of the box as Gark had suggested, and the wood seems to be burning more slowly from one side to the other with less smoke. Stove-top temperature has been a consistent 550 degrees, and catalytic temps have been ranging between about 1400 and 1700 (I actually am pretty sure the the measured catalytic temperature is reading too high). I just hope I can repeat this!