Return air ceiling fans type RDV 140 or RDV 90 ideally support the thermal balance of the hall from the roof to the ground. With a continuously variable speed controller, the ceiling fans can be controlled so that draughts in the occupied zone can be reliably avoided. By proportional control of the speed, depending on the temperature differential in the roof area, a maximum heat recirculation effect is achieved. A threshold thermostat switches the fans off automatically if it falls below a configurable minimum temperature. The regulator with selector switch is mounted in the occupied zone; a tuned temperature sensor corresponding to the controller is installed under the roof.