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.

Abstract: A circulating fluid that is heated by a number of gas-fired burner assemblies is used to heat a space either through a hot water system or a forced air heating system. Each burner assembly includes a housing with a heat exchanger mounted therein and a gas burner for heating the fluid which flows through the heat exchanger. The heat exchangers are connected in parallel in a closed loop forced circulation system. A microprocessor based thermostat control compares the temperature in the space heated by the air with a reference temperature. Dependent upon the magnitude of the difference between the temperatures, one or more of the burner assemblies are energized. The burner assemblies are sized such that during most of the heating season only a fraction of the burner assemblies are used.