Abstract: A heating system in which the rpm of the combustion air blower can be selectively decreased by an especially simple and economical arrangement and is achieved by selectively connecting an incandescent plug, utilized for igniting the fuel-mixture only during the starting period, as a series resistor to the electric motor driving the combustion air blower after completion of the starting period. In accordance with a preferred embodiment, connecting of the incandescent plug as a series resistor is produced by way of a relay operated contact and an actuating circuit therefor, a selectively closable switch and a contact of a combustion monitoring thermostat being located in the actuating circuit for controlling activation of the relay operated contact.