Preassembled pump group for regulation and circulation of fluid at variable temperature. Allows the circulation of the thermal fluid, coming from the primary circuit, by adjusting its temperature by means of a motorized mixing valve. It is used in general heating and radiant panel systems with flow temperature regulation based on room and outside temperature (also called outside or weather or climate compensated control). The group is composed of a pump, flow/return shut-off valves, motorizable mixing valve, flow/return temperature gauges, anti-thermosiphon check valve, thermal insulation. In this group the differential by-pass valve can be installed only externally. The group is reversible (the flow line can be exchanged with the return line).