Abstract: A fuel-fired heating appliance comprises a fuel source, an air source, a chamber in which fuel and air mix, a burner downstream from the mixing chamber, an igniter proximate the burner, a heat exchanger, a blower and a flue pipe. An ambient air inlet may be defined by at least one of the outlet end of the blower and the flue pipe extending between the interior of the flue pipe and an area ambient to the flue pipe. A flow rate of combustion gas may be controlled to a level below a steady-state flow rate during appliance warm-up.

Abstract: A fuel-fired heating appliance comprises a fuel source, an air source, a chamber in which fuel and air mix, a burner downstream from the mixing chamber, an igniter proximate the burner, a heat exchanger, a blower and a flue pipe. An ambient air inlet may be defined by at least one of the outlet end of the blower and the flue pipe extending between the interior of the flue pipe and an area ambient to the flue pipe. A flow rate of combustion gas may be controlled to a level below a steady-state flow rate during appliance warm-up.

Abstract: A fuel-fired heating appliance comprises a fuel source, an air source, a chamber in which fuel and air mix, a burner downstream from the mixing chamber, an igniter proximate the burner, a heat exchanger, a blower and a flue pipe. An ambient air inlet may be defined by at least one of the outlet end of the blower and the flue pipe extending between the interior of the flue pipe and an area ambient to the flue pipe. A flow rate of combustion gas may be controlled to a level below a steady-state flow rate during appliance warm-up.

Abstract: A fuel-fired heating appliance has two fuel flow paths to a burner, each actuatable to a closed state and to an open state. A heat exchanger is in fluid communication with an area proximate the burner. A controller executes the steps: (a) while the first fuel flow path is closed, opening the second flow path; (b) following ignition of fuel flowing from the second flow path, opening the first fuel flow path; and (c) following step (b), closing the second fuel flow path while opening the first fuel flow path.

Abstract: A fuel-fired heating appliance has two fuel flow paths to a burner, each actuatable to a closed state and to an open state. A heat exchanger is in fluid communication with an area proximate the burner. A controller executes the steps: (a) while the first fuel flow path is closed, opening the second flow path; (b) following ignition of fuel flowing from the second flow path, opening the first fuel flow path; and (c) following step (b), closing the second fuel flow path while opening the first fuel flow path.

Abstract: A high-efficiency modulating gas furnace (herein ‘gas furnace’) includes a furnace controller. The gas furnace further includes a gas valve and at least one pressure switch that is coupled to the furnace controller. The electrical contacts of the at least one pressure switch are removed from a series electrical circuit with the gas valve such that the gas furnace operates without de-energizing the gas valve as soon as the electrical contacts of the at least one pressure switch are opened. Further, the furnace controller operates the induced draft blower at or close to a lowest RPM at which the electrical contacts of the at least one pressure switch can be kept closed, which is between a make point RPM at which the electrical contacts of the at least one pressure switch close and a break point RPM at which the electrical contacts of the at least one pressure switch open.

Abstract: A high-efficiency modulating gas furnace (herein ‘gas furnace’) includes a furnace controller. The gas furnace further includes a gas valve and at least one pressure switch that is coupled to the furnace controller. The electrical contacts of the at least one pressure switch are removed from a series electrical circuit with the gas valve such that the gas furnace operates without de-energizing the gas valve as soon as the electrical contacts of the at least one pressure switch are opened. Further, the furnace controller operates the induced draft blower at or close to a lowest RPM at which the electrical contacts of the at least one pressure switch can be kept closed, which is between a make point RPM at which the electrical contacts of the at least one pressure switch close and a break point RPM at which the electrical contacts of the at least one pressure switch open.

Abstract: A fuel-fired heating appliance comprises a burner and a first housing adjacent the burner so that an interior of the first housing receives combustion gasses from combustion at the burner. A heat exchanger defines a second housing with an inlet proximate an outlet of the first housing so that the inlet of the second housing receives combustion gasses from the outlet of the first housing, and wherein the first and second housings attach at an interface. A barrier extends within, and across an interface between, the outlet of the first housing and the inlet of the second housing and defines a thermal resistance that inhibits heat transfer from the combustion gasses to the interface.

Abstract: A fuel-fired heating appliance comprises a fuel source, an air source, a chamber in which fuel and air mix, a burner downstream from the mixing chamber, an igniter proximate the burner, a heat exchanger, a blower and a flue pipe. An ambient air inlet may be defined by at least one of the outlet end of the blower and the flue pipe extending between the interior of the flue pipe and an area ambient to the flue pipe. A flow rate of combustion gas may be controlled to a level below a steady-state flow rate during appliance warm-up.

Abstract: A fuel-fired heating appliance has two fuel flow paths to a burner, each actuatable to a closed state and to an open state. A heat exchanger is in fluid communication with an area proximate the burner. A controller executes the steps: (a) while the first fuel flow path is closed, opening the second flow path; (b) following ignition of fuel flowing from the second flow path, opening the first fuel flow path; and (c) following step (b), closing the second fuel flow path while opening the first fuel flow path.

Abstract: A fuel-fired heating appliance comprises a burner and a first housing adjacent the burner so that an interior of the first housing receives combustion gasses from combustion at the burner. A heat exchanger defines a second housing with an inlet proximate an outlet of the first housing so that the inlet of the second housing receives combustion gasses from the outlet of the first housing, and wherein the first and second housings attach at an interface. A barrier extends within, and across an interface between, the outlet of the first housing and the inlet of the second housing and defines a thermal resistance that inhibits heat transfer from the combustion gasses to the interface.

Abstract: A fuel-fired condensing type air heating furnace is provided with an electronic condensate water level sensing system operative to sense improper outflow of condensate from a collector box portion of the furnace and responsively shut down or prevent operation of the furnace. Condensate probe portions of the system are oriented in a manner such that several air flow orientation of the furnace may be utilized without the necessity of relocating the probes or effecting an re-wiring of the water level sensing system.