Hydronic systems are systems essentially composed of chillers and fan coils.

Chillers and minichillers are thermal machines which, by exploiting the compression and expansion of the gases used, allow the heat to be removed from the water. Depending on the process and the fluid used in the condensation phase of the refrigerant gas, two categories of chillers or minichillers can be identified: water-cooled and air-cooled.

Hydronic fan coils, also called fan coils, are widely used especially in mixed air/water conditioning systems. In these units the ambient air is taken, filtered to remove coarse dust, and pushed towards the heat exchange coil where it exchanges heat with the water by forced convection and is then expelled. In the case of heating, the heat is withdrawn, in the case of cooling it is released (in this case, dehumidification also takes place).