Abstract: The application discloses improvements in a combination solid-fuel-burning, liquid heating and thermal energy storage apparatus in which a firebox is immersed in a large tank for heating the liquid stored therein and in which an improved flue assembly carries gaseous combustion products from the firebox through the tank liquid to an exhaust stack which has an outlet outside the tank. A blower draws combustion air into the firebox, draws the resulting gaseous combustion products through the flue assembly and provides a forced discharge of said combustion products through the stack outlet. The blower preferably includes a rotary fan in a fan housing which is serially connected in the flue assembly and positioned within the liquid inside the tank to provide a heat exchange housing enhancing the transfer of thermal energy from the combustion products to the surrounding tank liquid and minimizing possible high temperature damage to and excessive wear of the blower parts.