Condensation heat exchanger

A condensing heat exchanger comprising:

• at least one helically wound tube made of a thermally conductive material and inside which a fluid to be heated;
• can flow,
• a casing inside which the at least one helically wound tube is mounted, —the casing being provided with a gas discharge sleeve, a bottom and a facade, which supports means configured for delivering and/or producing a hot gas inside the casing,
• a deflector which comprises a disk made of thermally insulating material, carried by a sheet metal reinforcement, the deflector being positioned relative to the helically wound tube so as to delimit, with the facade, a combustion chamber,
• wherein the casing comprises a body consisting of a tubular metal ferrule, the tubular metal ferrule having two ends and being closed at one of the two ends by the facade and at the other of the two ends by the bottom,
• wherein the tubular ferrule and the bottom are separate before assembly,
• wherein the bottom is formed in a composite plastic material,
• wherein the tubular metal ferrule has a rear edge which has on at least a part of the circumference of the tubular metal ferrule, a plurality of cutouts delimiting fastening tabs,
• wherein the bottom has at the periphery of the bottom a plurality of fastening slots disposed along at least part of the circumference of the bottom, each fastening slot being dimensioned so as a fastening tab can be inserted therein, each fastening slot being bordered longitudinally by a first longitudinal rib, which protrudes outwardly, and wherein the fastening tab has two folded regions around the first longitudinal rib, so that the ferrule is fastened to the bottom and the helically wound tube is axially stressed at two ends of the helically wound tube between the bottom and the façade.