A method of heating a liquid, in which heat is transferred from gaseous combustion products to a liquid through a wall, with one side of which this liquid is in contact, and with the other side of which these gaseous combustion products are in contact, where the indicated wall, which forms the heat transfer zone, separates the gas channel , into which these gaseous combustion products are directed, and a belting liquid channel into which the heating liquid is directed, and the specified gaseous combustion products are directed into the aforementioned gas channel, which has at least two distribution screens located coaxially with the gas channel in the heat transfer zone from of gaseous combustion products to the liquid and which have the form of transverse partitions, which are made in such a way that they have an outline similar to the outline of the cross section of the gas channel, and form slit-like openings along the inner surface of the gas channel for the passage of the flow of combustion products, while the area of ​​​​the openings formed by the screens distribution, not less than the area of ​​the outlet opening of the gas channel located after the latter in the direction of the flow of combustion products of the distribution screen.