초록 ▼

Furnace combustion in a multi-stage or variable input furnace is controlled by operating the furnace in a high fire mode at furnace start-up until the temperature of the products of combustion, or a temperature corresponding to the products of combustion, equals or exceeds a selected temperature. A

Furnace combustion in a multi-stage or variable input furnace is controlled by operating the furnace in a high fire mode at furnace start-up until the temperature of the products of combustion, or a temperature corresponding to the products of combustion, equals or exceeds a selected temperature. A temperature sensor, preferably a thermostat, is located downstream of the furnace zone of combustion (e.g., in a flue collector box at an outlet from the heat exchanger). The thermostat provides an indication of the products of combustion temperature and has a set point corresponding to the selected temperature. When the products of combustion temperature is less than the selected temperature, the thermostat contacts remain closed. The furnace is operated in the high fire mode while the thermostat contacts remain closed in response to a demand for heating, irrespective of whether the demand is for first stage or second stage heating. When the selected temperature is reached, the thermostat contacts open, thereby allowing the furnace to be operated in either the high fire or in a low fire mode, depending on the level of demand for heating, as indicated by an external room thermostat. By operating the furnace in the high fire mode until the products of combustion temperature reaches a selected temperature (i.e., during cold start-up operation) condensate formation is reduced and room comfort is enhanced by inhibiting air from being supplied to the room at less than a desirable temperature.

대표청구항 ▼

A furnace, comprising: burner means for burning a combustible fuel-air mixture; heat exchanger means in fluid communication with said burner means for receiving products of combustion; fuel supply valve means having at least first and second combustion heat input settings for supplying fuel to said

A furnace, comprising: burner means for burning a combustible fuel-air mixture; heat exchanger means in fluid communication with said burner means for receiving products of combustion; fuel supply valve means having at least first and second combustion heat input settings for supplying fuel to said burner means, said second combustion heat input setting representing a higher rate of combustion than said first combustion heat input setting; combustion air blower means for supplying combustion air to said burner means and for exhausting products of combustion from said furnace; temperature sensing means located downstream of a zone of combustion in the furnace for sensing products of combustion temperature and for providing an indication of the sensed temperature, the zone of combustion being a region of the furnace in which combustion of the fuel-air mixture occurs; and control means responsive to an external demand for heating and to the sensed temperature for controlling rate of combustion in said furnace, said control means being operable to control said fuel supply valve means to operate at said second combustion heat input setting in response to the sensed temperature indicating that a selected temperature condition has not been satisfied, said control means being responsive to the sensed temperature indicating that said selected temperature condition has been satisfied to control said fuel supply valve means to operate at said first combustion heat input setting when the external demand is for a first level of heating and to control said fuel supply valve means to operate at said second combustion heat input setting when the external demand is for a second level of heating, said second level of heating representing a greater demand for heating than said first level of heating.