I have an existing closed horizontal loop geothermal heatpump HVAC system using glycol, and an existing solar hot water system also using glycol. The glycol loops are not connected to each other in any way. In the winter when my hot water pre-heat tank is hot enough, the pump to the solar panel stops the flow of glycol to the roof panels, which could otherwise be generating glycol heated above 100 degrees. This happens for a significant portion of the sunlight hours. At the same time (in the winter), my geothermal HVAC is trying to extract heat from at best 55 degree glycol from the ground loops.

Question: Can I install some type of switch connecting the two glycol loops such that; if the water tank is already hot, and if the HVAC is in heating mode, and if the glycol from the roof panels is hotter than the glycol from the ground loops, then the glycol from the roof panels is directed to the heat pump? If this is possible, would this be done by the solar guy or the geothermal guy? Who makes the switch?

Thanks, Kevin