My question below is technical and for someone who has experience with solar heating with radiant circuits. Any help in finding an answer or giving me a push in the right direction is appreciated.
I am a green homeowner in NJ designing a solar hot water (DHW) and solar heating system (low temperature radiant) for my home. The low-temperature radiant manifold is a secondary manifold that I would like to use an outdoor reset controller (vary heating circuit radiant temp by outdoor temp) and mixing valve or injection mixing from 2 sources: (1) Solar water storage and (2) my condensing boiler which would be a backup system and heating the remainder of the house as well.
I can find mixing assemblies that use outdoor reset controllers, and I can find differential controllers that can handle two heat sources; however, I am not sure about a controller that does BOTH. For example, lets assume that the solar storage tank is at 80 degrees. The outdoor temp in the day is 56 degrees and the outdoor reset controller calls for 78 degree temperature for low-temp manifold. Because the solar storage tank is at 80 degrees, it should injection mix from heat source #1 - solar storage tank heat exchanger circuit. Then in the evening, the temperature falls to 45 degrees, now the outdoor reset controller requires 82 degrees to meet the heat load of the space. The differential controller should determine that the tank does not have sufficient temp and it should injection mix from heat source #2 - boiler.
Keep in mind that this may be more complex than a simple differential controller - it would be comparing to the outdoor reset desired temperature, not a fixed temperature. I'm not sure if the standard differential controllers would work in this case.
Please advise if there is a differential controller that can do what I need above.
Alexander P. Brown
The P. stands for Plans