A always fill my firebox full. I have storage, maybe thats why. I fill it full up and burn hot. Rarely does my boiler idle. I heat my storage up to 195* or so. Actually my Tarm holds 5.35 cu. ft. Like I said, most here load twice a day, and burn more than 150 days. I should have mentioned that I heat my domestic h/w with the wood boiler during the winter also.