Abstract: A control system for a combined heating and cooling system connected to the control circuitry therefor, for energizing a fan or other fluid circulating device to circulate fluid and effect thermal transfer of energy therefrom to the spaces being heated in response to energization of the heating and cooling system, and for deenergizing said circulating means a selected time interval after deenergization of said heating and cooling system to effect extraction of thermal energy from the circulating fluid, said control system being operative in the absence of electrical energy or other malfunction to energize fluid circulating device.