[Daox]

I'm still debating how exactly I'm going to do this all. I'm all for any input you guys can give.

The solar hot water panels will be a drain back system. This means that the tank will be open to the atmosphere. I was originally thinking of running the floors right off the solar water tank, no heat exchanger. Remember, I'll also have a boiler in the mix here as backup for the solar. So, I'm guessing it'll need to have a stainless heat exchanger and the pumps will need to be bronze or stainless as well.

The other option would be a closed loop / low pressure system for the hydronic heat. It would use a heat exchanger in the solar hot water tank to pickup heat. Using that and oxygen barrier PEX tubing would allow me to avoid the bronze/stainless components.

Yet another option would be to run the boiler on a tiny loop just to heat the solar tank should the temperature drop too low. This would allow me to ensure the boiler never short cycles, but I don't like the idea of keeping the water at X temperature. I'd rather it just vary as the solar provides heat, and just use the boiler when absolutely necessary.