Closed-loop heat-reclaiming system

Claim 1

In a forced-air heating system which includes means for burning fuel to heat air, means for circulating air in proximity to the fuel-burning means to transfer heat therefrom to the air and for circulating the heated air through a heated air duct, a cold-air return duct, a chimney flue for venting gases produced by the burning fuel, and a control system for energizing the fuel-burning means in response to a demand for heat, and for de-energizing the fuel-burning means when the demand is met, the improvement comprising a closed-loop heat-transfer apparatus for reclaiming heat from gases in the chimney flue of the heating system, the heat-transfer apparatus including a first heat-exchanger chamber positioned in series with the chimney flue, the first chamber including a fluid inlet opening and a fluid outlet opening, a coiled conduit positioned interior to the chamber, the conduit having one end connected to the fluid inlet opening and another end connected to the fluid outlet opening, means allowing access to the interior of the first chamber for cleaning and servicing, a second heat-exchanger chamber positioned in series with the cold-air duct, the second chamber including a fluid inlet opening and a fluid outlet opening, means coupling the fluid openings of the first and second chambers to form a closed circulatory loop, a predetermined quantity of heat-transferring fluid contained in the loop, means for circulating the predetermined quantity of fluid through the loop between the first and second chambers to heat the quantity of fluid, transfer the heat therefrom to the cold air in the return duct, and reheat the same quantity of fluid, a temperature-actuated control coupled in the loop in proximity to the fluid outlet opening of the first heat-exchanger chamber to sense maximum temperatures of the fluid, the temperature-actuated control including a high limit control and a low limit control, means electrically connecting the low limit control to the fluid circulating means, the fluid circulating means being activated when the maximum temperature of the fluid exceeds a first predetermined temperature, and means electrically connecting the high limit control to the control system for activating and deactivating the fuel-burning means, heat production by the fuel-burning means being reduced when the maximum temperature of the fluid reaches a second predetermined temperature.