US Patent 10145583 Heating apparatus

Heating apparatus includes an air inlet, a plurality of air outlets, an impeller, a motor for rotating the impeller to draw air through the air inlet, a user interface for allowing a user to select a rotational speed of the motor from a user selectable range of values, and a plurality of heater assemblies each comprising at least one positive temperature coefficient (PTC) heating element for heating air passing from the air inlet to a respective air outlet. The magnitude of a current drawn by the heater assemblies is detected, and the rotational speed of the motor is controlled independently from the rotational speed selected by the user depending on a characteristic of the current drawn by the heater assemblies.