Units for the temperature regulation of a fluid (water) to the users via a primary fluid (steam, superheated water, or diathermic oil) and through the use of heat exchangers. By exploiting an existing primary fluid distribution line, they allow for automatic and precise temperature regulation of a second fluid (water) to the users. Electronically controlled by a microprocessor system, they are equipped with a user circuit circulation pump, expansion vessel, level regulation, automatic loading system, power panel, control panel, high-efficiency heat exchangers, and certified control and safety systems. Available in versions for design temperatures up to 200°C and power outputs up to 5 MW.