Abstract: A compact, high efficiency heat exchanger for a fuel-fired forced air furnace has horizontally spaced apart inlet and outlet manifold structures which are innerconnected by a horizontally spaced series of vertically serpentined, relatively small diameter flow transfer tubes. Larger diameter inlet flow tubes are positioned beneath the balance of the heat exchanger, extend parallel to the transfer tubes, and have upturned discharge ends connected to the underside of the inlet manifold. The heat exchanger is configured so that its total vertically facing peripheral surface area is considerably larger than its total horizontally facing peripheral surface area, thereby signficantly reducing undesirable outward heat loss through the vertically extending furnace housing side walls upon burner shut off and increasing the overall efficiency rating of the furnace.

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.

Abstract: A fuel-air combustion chamber with improved mounting and thermal distribution features. The combustion chamber is formed with a flange adapted for receiving a plurality of retainer rings therearound for direct securement of the flange to a burner mounting plate adjacent a fuel-air nozzle for generating heat within the combustion chamber. The combustion chamber is also temporarily supported within the furnace housing by a combustible support leg affixed thereto. In this manner, the combustion chamber is supported during shipping and handling by a support leg which is automatically disintegrated during use of the combustion chamber.

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 tubular recuperative heat exchanger structure is mounted in a housing chamber within a fuel-fired condensing furnace in the vertical flow path of supply air being flowed through the housing by a blower. The heat exchanger structure comprises a primary heat exchanger defined by a vertically serpentined series of combustor tubes into open inlet ends of which a series of inshot-type fuel burners flow flames and hot combustion gases, and a secondary heat exchanger formed from a horizontally extending series of finned heat exchanger tubes having inlets in flow communication with the outlets of the combustor tubes and outlets in flow communication with the inlet of a draft inducer fan.

Abstract: A tubular recuperative heat exchanger structure is mounted in a housing chamber within a fuel-fired condensing furnace in the vertical flow path of supply air being flowed through the housing by a blower. The heat exchanger structure comprises a primary heat exchanger defined by a vertically serpentined series of combustor tubes into open inlet ends of which a series of inshot-type fuel burners flow flames and hot combustion gases, and a secondary heat exchanger formed from a horizontally extending series of finned heat exchanger tubes having inlets in flow communication with the outlets of the combustor tubes and outlets in flow communication with the inlet of a draft inducer fan.

Abstract: A fuel-fired, forced air, draft induced heating furnace is provided with NOx reduction apparatus associated with a plurality of combustor tubes forming a portion of its heat exchanger structure. In-shot type fuel burners are spaced apart from and face the open inlet ends of horizontal combustion sections of the combustor tubes. The NOx reduction apparatus includes a plurality of metal mesh tubes having diameters substantially less than the internal diameters of the combustion tubes. Each metal mesh tube is coaxially anchored to and telescopingly over the outlet end of one of the burners and extends therefrom coaxially into the associated combustion tube.

Abstract: A fuel-fired condensing furnace is provided with a specially designed heat exchanger structure having a metal primary section and a plastic secondary or recuperative section. The primary section is defined by a horizontally spaced series of identically sized, vertically serpentined metal combustor tubes adapted to receive a throughflow of a burning fuel-air mixture discharged from the furnace burner section. Each tube has an essentially straight inlet combustion section sized to permit essentially complete combustion therein of the burning fuel-air mixture received by the tube, and a plurality of vertically spaced horizontal heat transfer sections that are horizontally flattened and narrowed to enhance their combustion heat transfer to supply air being forced upwardly through the furnace housing.

Abstract: A fuel-fired forced air condensing furnace has installed therein a recuperative heat exchanger assembly with a primary heat exchange section operative, during furnace operation, to transfer sensible combustion gas heat to air being flowed through the furnace, and a secondary heat exchange section operative to transfer latent combustion gas heat to the air. The secondary heat exchange section includes a finned tube heat exchanger structure extending between spaced apart combustion gas inlet and outlet collector boxes.

Abstract: A fuel-fired, condensing type forced air heating furnace is provided with an improved hot combustion gas-to-air heat exchange system which includes a generally drum-shaped primary heat exchanger having an outlet end connected to a first end of a transfer manifold whose second end is connected the inlet end of a fin-and-tube type secondary heat exchanger which is spaced laterally apart from, faces, and extends generally parallel to the primary heat exchanger. A radial discharge fuel burner end portion is coaxially positioned within an inlet end of the primary heat exchanger and, during furnace operation, a draft inducer fan draws burner combustion gases sequentially through the primary heat exchanger, the transfer manifold and the secondary heat exchanger while air to be heated is flowed externally over these heat transfer elements.

Abstract: A fuel fired, forced air, draft induced heating furnace is provided with NOx reduction apparatus associated with a plurality of combustor tubes forming a portion of its heat exchanger structure. In-shot type fuel burners are spaced apart from and face the open inlet ends of horizontal combustion sections of the combustor tubes. The NOx reduction apparatus includes a plurality of insert members received in inlet end portions of the combustor tubes. Each insert member is formed from a single sheet of metal mesh material and has a hollow, open-ended body portion coaxially received in its associated combustor tube and spaced laterally inwardly from its interior side surface, and a circumferentially spaced plurality of integral, laterally outwardly projecting support rib portions that slidably engage the interior side surface of the combustor tube, thereby automatically maintaining the insert member in a coaxial relationship with the combustor tube regardless of the positional orientation of the tube.

Abstract: A modulating, forced draft, fuel-fired air heating furnace is provided with a two-speed draft inducer fan, and a fuel valve which is fully modulatable between a maximum firing rate and a low firing rate of approximately forty percent thereof. Incorporated into the furnace control system are normally closed low and high fire pressure-electric switches which sense and are sequentially closed by increasingly negative pressure in the draft inducer fan. Upon a call for heat from a thermostat located in the conditioned space served by the furnace, the draft inducer fan is energized at its high speed setting, and a signal is sent to the fuel valve to set it at its full firing rate flow when opened by an ignition switch portion of the control system. The control system functions to open the fuel valve at this maximum flow setting, and permit light-off of the burner, only if (1) both of the low and high fire pressure-electric switches are closed, and (2) the draft inducer fan is operating at its high speed setting.

Abstract: Elongated metal devices are coaxially inserted into, and closely received within, inlet end portions of the heat exchanger combustor tubes of a fuel-fired heating appliance, representatively a forced air heating furnace. The inserted devices function to substantially reduce the NO.sub.x content of the combustion gases ultimately discharged from the furnace by intercepting, dispersing, and thermally quenching the burner flames drawn through the combustor tubes by a draft inducer fan portion of the furnace. Each device is formed by a pair of elongated, generally rectangular slotted metal plate members which are longitudinally overlapped and transversely secured to one another in a manner providing the device with a generally cross-shaped cross section along its length. Elongated slots are formed in the four outer side edges of the device for operational sound reduction purposes. An alternate embodiment of the device is formed by welding together two elongated metal members each having an L-shaped cross section.

Abstract: A fuel-fired air heating furnace is provided with NOx reduction apparatus associated with a plurality of combustor tubes forming a portion of the furnace heat exchanger section. Inshot-type fuel burners are spaced apart from and face the open inlet ends of horizontal combustion sections of the combustor tubes. The NOx reduction apparatus includes a plurality of NOx reduction members formed from a metal rod material, and a mounting plate having a row of spaced apart pairs of mounting holes therein. Each NOx reduction member has an elongated, generally U-shaped configuration, with a closed inner end, an open outer end, and a spaced pair of corrugated leg portions extending between such inner and outer ends.

Abstract: A multiple inshot-type gas burner structure is formed from a pair of facing, intersecured stamper sheet metal plates. A spaced plurality of parallel, rectangularly cross-sectioned burner bodies are defined by facing triangular indentation pairs in the plates and have, at front outlet end portions thereof, side indentations which serve to mix air and gaseous fuel received at rear end portions of the burner bodies, and to divert a portion of the fuel/air mixture into crossover channels intercommunicating front interior portions of the burner bodies. The crossover channels have central arcuate closed portions that cooperate with progressively sized standoff dimples extending between opposite wall portions of the channels to provide an even crossover flame pattern along the outlet slot section of each channel.

Abstract: A high efficiency fuel-fired induced draft condensing furnace is provided with a horizontal vent termination assembly installed in an exterior wall of a building served by the furnace. The vent termination assembly, constructed entirely from PVC plastic pipe and fittings, includes a combustion gas vent pipe connected to the furnace's draft inducer fan outlet, horizontally extending through an opening in the wall, and having an open discharge end positioned outwardly beyond the wall. A larger diameter combustion air inlet pipe circumscribes the vent pipe within the wall opening and forms around the vent pipe an annular combustion air flow passage that is communicated with the furnace combustion air inlet. A coupling member connected to the outer end of the inlet pipe has a diametrically enlarged end portion positioned on the outside surface of the wall, axially inwardly of the outer vent pipe, and forming an annular inlet to the flow passage between the two pipes.

Abstract: A high efficiency fuel-fired condensing furnace is provided with a compact recuperative heat exchanger structure comprising a metal primary heat exchanger positioned above and operatively connected to the inlet side of a secondary heat exchanger formed from a polyetherimide (PEI) plastic material. The primary heat exchanger is formed from a horizontally spaced series of vertically serpentined metal combustor tubes, and the second heat exchanger if formed from horizontally spaced apart injection molded inlet and outlet collector boxes interconnected by a horizontally spaced series of elongated hollow extruded plate members sealingly secured at their opposite ends to the collector boxes with the side edge-to-side edge widths of the hollow plate members being vertically oriented. The outlet ends of the metal tubes are operatively connected to the plastic inlet collector box.

Abstract: An induced draft, fuel-fired upflow furnace is provided with a compact, high efficiency heat exchanger having horizontally spaced apart inlet and outlet manifold structures which are innerconnected by a horizontally spaced series of vertically serpentined, relatively small diameter flow transfer tubes. Larger diameter inlet flow tubes are positioned beneath the balance of the heat exchanger, extend parallel to the transfer tubes, and have upturned discharge ends connected to the underside of the inlet manifold. The heat exchanger is configured so that its total vertically facing peripheral surface area is considerably larger than its total horizontally facing peripheral surface area, thereby significantly reducing undesirable outward heat loss through the vertically extending furnace housing side walls upon burner shut off and increasing the overall efficiency rating of the furnace.