I have a few somewhat related questions about a closed loop solar thermal system I intend to integrate into my heating system. The heated water is to be fed to an indirect heater for storage then into a tankless boiler, which is already in place. It supplies DHW as well as heat for the radiant floor system through a Taco Xblock heat exchanger. I plan on having three 4x10 flat plate collectors (Max 40,000 BTU/day on a clear day) on a ground mount tilted at 65 degrees. I live in the Pacific Northwest north of Seattle.
I suspect the three 4x10 panels will be overkill during the summer months but was intending to oversize the system so as to optimize the heat collected during the Oct-April heating season as well as make up for any heat loss due to the relatively long piping run from where the collector needs to be located. Was thinking that one of the panels could be covered during the summer months to avoid over heating the system. I plan on putting in a finned radiator heat dump at the collector as a precaution for over heating anyway. Any thoughts?
Since there will be approximately 60' of underground piping from the array to the exterior of the house I was wondering how the line is to be drained when it comes time to replace the glycol. I reckon it will have to be an air purge?
Hot water storage - I am considering a Burnham Allaince AL119SL indirect heater. Is this product a suitable indirect heater for such a system? Is the 119 gallon tank overkill? Better off with the 70 gallon? More storage better for my situation since any heat is also needed for heating season? Also the Burnham literature mentions the AL119SL as having a side mounted heat exchanger coil. But I can find no drawings or schematics of that configuration. Just wondering what that might look like for planning purposes.
Thanks much for any info.