The DeltaSol MX operates Solar closed loop system with an external heat exchanger contributing to all heating loads. The back up of Space Heating, DHW and Pool heating is provided by a single stage oil/gas Boiler together with Solar loading heating Buffer storage tank. Home distribution incorporates 1 low temp. hydronic space heating circuit (HC1) controlled by floating action 3-way mixing valve with temp. compensation using Outdoor Reset and Indoor temperature Feedback and 1 high temp. space heating zone (forced air Fan Coil unit). The DeltaSol MX provides Warm weather Shutdown (Summer Mode), boiler differential and 7-day programmable Setback control functions for all heating loads. Energy efficient system return flow management is realized by diverting system return water to appropriate temperature layer in Buffer storage tank.