Cooling the cat

[Ashful]

So, my fourth season is underway, and really my first with a good supply of properly seasoned wood and fully functional ceramic cat combusters. Both stoves are starting up and cruising beautifully on ash and some oak... with one exception.

Usually an hour or more after a reload, and not even particularly large loads, my cat temps seem to go to roughly 1860 - 1900F. Stovetop temp holds a relatively friendly 400F at the hottest spot on the lid, so there is theoretically some room to open primary air a bit.

When the the stove is in this mode, flue pipe temp goes up to 450F (very warm for this stove), and the burn looks and sounds like a damped down back-puffing cycle. Faint roar starts low in a dark firebox, builds over 10 seconds, then a flame show, followed by a second of silence, before repeating. Past attempts to open primary air a bit, to hopefully cool the cat, have lead to this cycle amplifying into full-blown back puffing.

Since I only observe this an hour or more after a reload, I assume it might be doing it on every load, but I'm rarely here to witness.

What might I do better to avoid this? Extending my bake out prior to closing bypass might help, I suppose, but this stove can be a little unruly in bypass.

 

[Diabel]

I get several different types of burns, one of them is excactly what you describe. The funny thing is I can never replicate the same burn twice in a row.

 

[splitoak]

I dont believe any 2 burns are the same...i love lookin in the glass to see what the fire is doing and how its burning and adjust the air accordingly..

 

[Ashful]

Let me be clear that the stove is burning exactly as desired, with the exception of the cat running scary hot. It is not back puffing, although I can easily cause it to do so if I open the air 10% with the cat this hot. If I open the air 50%'ish, I can cool the cat, but at the expense of running up stove-top temperature.

 

[splitoak]

Will it be a different learning curve going from stainless to a ceramic ?..maybe that is the running temp for those..

 

[mellow]

When my cat gets too hot for my comfort I open the bypass a bit or all the way depending on how hot to help cool it off, I rarely touch my air controls.

Mine will get a case of the back puffs if I shut it down to hard, I have to shut my air down in stages to prevent it.

 

[Ashful]

Seems any new cat runs hot in these stoves, splitoak. I had the same troubles with the Steelcats when new, which is why I suspect Condar has a very high failure rate of Steelcats in downdraft cat stoves (namely Jotul and VC). In fact, Condar will not recommend the Steelcat for these stoves, anymore.

I am shutting down in stages, mellow. If closing bypass at t=0, I am lowering air from full to half at 5 minutes, 1/4 at 10 minutes, and closed at 15 minutes.