The invention relates to a volume style assembly type multi-purpose heat interchanger, which comprises a sensor, a casing, an electric heater, a coil pipe, an inner ribbed pipe, and an outer ribbed pipe, a burbling sheet, an upper pipe plate, a combustion chamber, a fastening supporting rack, a condensed water consumption device, and a gas collector. All parts are socket joint-typed, are connected through a rabbet joint, and fastened and positioned through a plurality of threaded rods, a pipe fitting is oppositely connected with the heat interchanger through a sealing element, outer connectors of life hot water tail end, heating tail end, overflow tail end, emptying / water compensation opening and heating belt temperature limit device are arranged on the casing body, the coil pipe, the inner ribbed pipe and the outer ribbed pipe are arranged in the casing body, and the burbling sheets are arranged on the inner ribbed pipe and the outer ribbed pipe; the electric heaters are arranged on the interior part and the exterior part of the casing body, the combustion chamber is arranged at the lower part of the casing body, the upper pipe plate is arranged at the upper part of the casing body, a seal ring and the fastening supporting rack are respectively arranged at the both ends of the upper part of the casing body; the condensed water consumption devices are arranged at the lower parts of the inner ribbed pipe and the outer ribbed pipe. The invention changes the molding method of the traditional small volume type heat interchanger, and has the advantages that the installation and the maintenance are convenient, the thermal efficiency is high, and the operating cost is low, etc.