William Bronson wrote: Can a pump on the primary loop accomplish much the same thing?
Bob Gallamore wrote:Travis, I LOVE your system. I've made a living doing industrial controls and written or modified many PLC programs over the years. There are companies like Automation Direct and Phoenix Contacts that sell very inexpensive PLC components and offer free programming software. My inner geek would love to do something like that. Optimizing PID loops makes my inner geek purr.
I agree that when you ask a system to do too many things there are compromises that mean it doesn't do any of them particularly well. I would much rather have a smaller, dedicated on-demand water heater and pre-heat the water using a solar system. The problem I've read about with solar water heaters is that they sometimes don't get the water hot enough. With a PLC system controlling a couple valves, especially using proportional valves, you could mix pre-heated and cold water going into the on-demand water heater to optimize for the heat rise available in the water heater.
I have some time before I get to the point of putting in radiant heat. It will give me some time to explore doing something like Travis' system.