The economizer is intended for reduction of the boiler heat losses during heat transfer of flue gases of the heat carrier which returns from the heating system to a boiler. This product is completed with a flue damper. Economizers come without insulation. Thermal insulation: the outside of the cylinder is covered with basalt insulation and sheathed with a protective screen. Insulation of the economizer is performed after installation works, together with thermal insulation of boiler room pipelines.