I've been doing some thinking about what goes on over the course of a wood fire, and I've started developing a control strategy based on this idea. I've broken the life of a fire into 5 phases, with different strategies for each. Phase 1 - Cold start. Boiler is cold, bypass is open, flue temperature is starting to rise. Turn on tank circulator and wood boiler circulator to flush cold water from the system and get boiler close to storage tank temperature (probably around 120 degrees). Phase 2 - Ramp up to operating temperature. Bypass is closed, boiler is not yet up to temperature. Tank circulator is off. Wood boiler recirc valve is open, and wood circulator is off or low speed. Optional heat loads (hot tub, DHW, storage tank) are off. Phase 3 - Primary heating. Boiler is in operating temperature range. Baseboards, hot tub, and / or domestic hot water need heat. Modulate wood circulator pump speed and optional heat loads to keep outlet temp within target range - near 180 degrees - to maximize baseboard effectiveness. Phase 4 - Storage tank charging. Primary heat loads are satisfied, boiler is still in operating range. Since all boiler output is going to storage tank, modulate pump speed to keep outlet temp just above tank temp (or inlet above 140, as needed). Lower outlet temps result in lower stack temps and increased efficiency. Phase 5 - Scavenging. Fire is out, outlet temp is below storage temp, but boiler still has usable heat. Don't worry about inlet temperature protection. Shut off circulator and wait for combination of demand and usable outlet temperature (140 degrees). Run circulator for five minutes. Repeat until outlet fails to reach 140 after 30 minute wait. Does any of this make sense? Does this represent a dangerous degree of obsession? Any other ideas? I have all of this implemented in code, and I've already tested most of it. I'd be more than glad to try any other ideas. As soon as I run another fire, I'll post a graph.