Add-on boiler

摘要

Disclosed is an add-on boiler that has an insulated cover covering a housing that carries a finned heat-recovery coil. The add-on boiler is mounted on the casing of a heating device to heat water in the coil with heat transferred by conduction and radiation. The insulated cover maintains the heated water in the coil at a high temperature to prevent the internal operating temperature of the heating device from dropping below the critical temperature at which creosote forms from the flue gases.