Abstract: To inhibit internal heat exchanger corrosion, the products of combustion from a standing pilot flame in an induced draft, fuel-fired furnace are prevented from migrating through the heat exchanger during idle periods of the furnace by flowing the products of combustion upwardly through a small vent tube into the outlet section of the draft inducer fan, and then into an external exhaust stack, thereby bypassing the heat exchanger. During operation of the draft inducer fan a negative pressure is maintained within the vent tube, to prevent combustion gas outflow therethrough which might otherwise snuff out the pilot flame, by a venturi structure positioned within the draft inducer fan outlet section adjacent its juncture with the vent tube.

Abstract: A furnace employing a plurality of spaced burners, a carryover tube passing adjacent the burners, a hot surface igniter at one end of the carryover tube, a flame sensor at the other end of the carryover tube and an ignition control for controlling actuation of the hot surface igniter and the flow of combustible gas to the carryover tube and main burners, the ignition control being responsive to the flame sensor.

Abstract: An improved trap assembly for a high efficiency fossil fuel furnace includes a vertical tube closed at its lower end with a condensate inlet immediately above the lower end and a condensate outlet above the inlet. A flue gas inlet is provided at the top end of the tube with a flue gas outlet immediately adjacent thereto. A float with a sealing cap is positioned within the tube and rises in response to the level of condensate to block the flue gas outlet.