A thermal system includes a Rankine cycle heat recovery device including a Rankine circuit having a first heat exchanger, an expander, a condenser, and a first pump. A cooling device having a cooling circuit that includes a second heat exchanger, a second pump, and a third heat exchanger with a device to be cooled. The thermal system comprises a device for regulating the pressure in the Rankine circuit and includes an enclosure delimiting a space and housing a movable part separating the space into first and second chambers. The first chamber communicates with the Rankine circuit and the second chamber communicates with the cooling circuit.