Very interesting point. Everything seems right with your reasoning. The thoughts that arise to me are the following:
MartinEau, soleil, le vent[ Parent ]
I put the sketch that our local HVAC guy Eric drew up for me here:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/AddBoiler.htm
It seems like a pretty simple way to go, and he does a lot of radiant floor systems (but no solar ones so far)-- so I think he knows the area well. This is what he is thinking about for his home when he adds solar.
Have not thought a lot about the control, but maybe a two stage thermostat could select solar for the first stage, and then switch to the boiler when the 2nd stage is needed. Heat pumps often have two stage thermostats, so its not uncommon. You would want to have some way to go right to stage two when the solar tank is too cool to provide any heat.
Right on the pump, you should use stainless or bronze. I use a Taco bronze pump -- they offer most of their pumps with a choice of case metal.
GaryGary gary@BuildItSolar.com www.BuildItSolar.com[ Parent ]
Number (1) is just the regular pump in the boiler that circulates water, not an electrically controlled valve as the label says.
So, when you want the boiler to supply heat: energize the boiler pump(1), deenergize the solar tank pump(3). Boiler heated water flows from the boiler, through the floor loops (on left of diagram), and back to the boiler.
When you want heat from the solar tank: energize the solar pump (3), deengergize the boiler pump (1). Water then flows from the solar tank, through pump 3, out through the floor loops, and back to the solar tank via the top line.
Check valve (2) prevents the solar pump from pushing water through the boiler in the wrong direction when in boiler mode. The check built into pump (3) prevents the boiler from pushing water back through pump (3) and into the solar tank in the wrong direction when in solar mode.
Maybe its confusing that the floor loops are not completely shown? The four floor loop lines on the bottom left of the diagram go around and connect to the 4 lines coming into the top left of the diagram.
This paragraph: Check valve (2) prevents the solar pump from pushing water through the boiler in the wrong direction when in boiler mode. The check built into pump (3) prevents the boiler from pushing water back through pump (3) and into the solar tank in the wrong direction when in solar mode.
Should read like this: Check valve (2) prevents the solar pump from pushing water through the boiler in the wrong direction when in SOLAR mode. The check built into pump (3) prevents the boiler from pushing water back through pump (3) and into the solar tank in the wrong direction when in BOILER mode.
Thanks MartinEau, soleil, le vent[ Parent ]
