I’m not sure what your 3 medium splits are in comparison to the number required to fill your firebox, but if I’m at less than 20% capacity in any of the stoves I’ve burned, it takes damn near forever for the cat to come up to temp. The two splits I described in my prior post would be at least half gone, before my chimney and cat came up to 500F, the required temp for closing the bypass damper. Three medium splits would do better.
That was my point, there is a limit to this “small fire in a big stove” thing. If you disagree, please send a photo of active secondaries on no more than four toothpicks. [emoji14]
I would need about 10,000 toothpicks to get her up to temp. And it would probably be a big ol nuclear flash. I'n not running a cat, so I cannot give any input regarding a cat stoves needs to achieve & sustain temp. Not a knock on cats, just maybe there is a difference in that area.
3 Medium splits I am guessing is approx 1/3 of a full firebox in my case. But I also use a N-S pyramid style stacking to burn this way. Or, I do 2 N_S & two E-W over top. I do this during shoulder seasons until it is cold enough outside to keep going 24/7. Usually only burning 1x per day in shoulder season. The load also last much longer during shoulder season, as I don't need the amount of heat as I do during the cold spell obviously, and less draw also has an effect on burn time & heat output.
I'm not saying he should go buy the largest stove he can only to burn small fires in it. But he found a larger stove that he can afford. And it can be used efficiently IMO.