Combined heat-exchanger and supplemental air circulator for hot-air furnaces

Claim 1

In a forced-circulation air-heating system comprising a conventional fuel-burning hot-air furnace including a hot-air-feed duct system and a cold-air-return duct system, a pipe for conducting flue gases away from said furnace, a first thermostatic switch in and responsive to the temperature of the space to be heated, furnace-connected fuel-supply means controlled by said first thermostatic switch, a relatively high-power motorized blower for forcing air from said return system through said furnace and to said feed system, an air filter in the air-flow path to and through and from said furnace, a second thermostatic switch located in the hot-air portion of said air-flow path for energizing said high-power motorized blower upon a selected rise in furnace air temperature, the improvement comprising: a normally constantly energized relatively low-power motorized blower, and duct means connecting said latter blower so as to force air from said return system into said feed system in bypassing relation to said furnace and its air filter, said duct means including in series therewith a heat-exchanger adapted for good thermal association with said flue-gas pipe, and said heat-exchanger including means for performing an indirect heat exchange between the cold by-pass air and the hot flue gases or combustion products, whereby, the lower-power blower being normally constantly energized during heating periods, a gentle temperature-stratification-reducing air-flow is produced.