A thermal system for a marine vessel includes a thermal liquid circuit; a pump system for circulating a thermal liquid in the thermal liquid circuit; a number of thermal consumers; and a control device for controlling the pump system. The thermal consumers are arranged in parallel in the thermal liquid circuit, and the thermal consumers are arranged in series with respective Pressure Independent Control Valves (PICVs). A differential pressure sensor is adapted to sense a differential pressure indicative for the differential pressure over a critical one of the Pressure Independent Control Valves, and a signal from the differential pressure sensor is used by the control device as basis for controlling the pump system.