Oil burner

In an oil burner of the air atomising type comprising a combustion chamber provided with means for the supply of atomised oil and means for the supply of combustion air, a fluid chamber surrounding the combustion chamber and arranged to receive heat therefrom and means for removing heated fluid from the fluid chamber and introducing cooler fluid thereto, the improvement comprising a variable speed burner motor for controlling the supply of both oil and combustion air, means for measuring the temperature of the heated fluid leaving the fluid chamber or the temperature difference between heated fluid leaving the fluid chamber and cooler fluid introduced thereto, and a motor speed controller, operatively connected to the burner motor and independent of the composition of the products of combustion in the combustion chamber adapted to receive signals indicative of the measured temperature or temperature difference and vary the speed of the burner motor responsive thereto, whereby the supply of both combustion air and oil is varied dependent only on said temperature or temperture difference, while maintaining substantially unchanged combustion characteristics over the entire output range of the burner.