HTP’s Versa-Hydro Combined Hydronic Appliance melds hydronic space heating and domestic hot water with complete system control in a single 96%-efficient package. The system consists of a hot water storage tank (55, 80 or 119 gallons), an energy-saving modulating burner assembly attached to the outside bottom of the tank and a space-heating module attached to the tank (at the top) that contains a high-output heat exchanger and a variable-speed pump. A rapid-response system controller modulates water flow from the storage tank and controls output temperatures to save energy. Circle 21