In this schematic. Solar Energy is collected by an array made up of Flat-Plate Solar Collectors. The Heat Transfer Fluid, non-toxic glycol, flows through the Dual-Coil Solar Tank. The tank contains the Domestic Hot Water Supply. If there is not enough solar energy to heat the water to the desired temperature, the boiler fires and circulates hot water through the tank's upper coil, insuring constant hot water for the home. In this schematic, the boiler is also providing for a Hydronic Heating System. We have installed many systems of this kind with very favorable results. Using a Wall Hung Boiler, such as a Viessmann Vitodens, and a Single Tank with 2) Heat Exchanger Coils, the installation can be very compact. Typically, in Southern California, systems of this type accomplish about 85% of Domestic Hot Water Production via Solar with the Boiler making up the difference at very high efficiency.