Rheem Manufacturing Company

Lennox Industries Inc.

Dennis R Maiello

Scott Alan Willbanks

Phillip G Brown

Delbert S Christopher

A gas-fired air heating furnace has a modulatable supply air blower and a modulatable gas valve operatively connected to the combustion air heat exchanger burner. A calibration sequence of a microprocessor-based control system is utilized to automatically determine the precise relationship between the gas valve setting and the actual heat transferred by the heat exchanger to air flowing through the furnace by measuring the actual air temperature rise across the heat exchanger obtained using initial calibration settings of the blower and gas valve. The microprocessor uses the results of its calibration sequence to establish an adjustment correlation between the blower and gas valve settings which the microprocessor subsequently utilizes to adjust the flow rates of the blower and the gas valve in a manner maintaining a predetermined, generally constant air temperature rise across the heat exchanger while the furnace alters its overall air heating output rate in response to changing heating demands from the conditioned space served by the furnace.

Fuel-fired modulating furnace calibration apparatus and methods

An electronic two stage furnace controller may be used interchangeably, without modification thereof, with either a single or two stage thermostat to regulate the heating and cooling operation of a two stage heating/cooling furnace to which the controller is connected. The controller is operative to monitor the input it receives from the thermostat, automatically deduce whether the input is from a single stage thermostat or a two stage thermostat, and responsively regulate the operation of the furnace under a corresponding single stage thermostat heating or cooling mode, or a corresponding two stage thermostat heating or cooling mode.

Furnace controller useable, without modification, with either a single

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. In this manner, in addition to providing a wide range of furnace heating output modulation, reliable burner ignition is facilitated and heat exchanger warm-up corrosion is reduced due to the full firing rate start-up of the furnace. Moreover, the incorporation of the two-speed draft inducer fan substantially improves the overall fuel efficiency of the furnace.

Modulating furnace with two-speed draft inducer

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. The NOx reduction members are installed in a parallel relationship on the mounting plate, with their closed ends facing in the same direction, by resiliently deflecting the leg portions of each member toward each other, inserting the outer leg ends in one of the mounting plate hole pairs, and then releasing the legs. With the NOx reduction members secured to the mounting plate in this manner, they are simultaneously inserted closed ends first into their associated combustor tubes, and the mounting plate suitably supported adjacent the combustor tube inlets. The burners are then positioned to inject flames into the combustor tubes with the NOx reduction members positioned therein to operatively intercept the incoming burner flames.

NOX reducing combustor tube insert apparatus

A heat exchanger comprises a clam shell having a first passage, a second passage and a third passage connected sequentially in a plane. A hot collector box made from metal, for example, aluminized steel, in connected to the third passage. A secondary heat exchanger coil is operatively connected to the hot collector box. A second collector box or cold collector box made from plastic is connected to the outlet of the secondary heat exchanger coil. Condensate from the flue and condensate from the cold collector box may be discharged in a common line from the furnace. The clam shell is constructed and arranged to remove about 90%-95% of the energy from the flue products flowing therethrough. The heat exchanger is disposed in a passage between the inlet and the outlet in the housing of a furnace. Air is forced over the heat exchanger, which is disposed in the passage, by a blower in the housing.

Growing community of inventors

Fort Smith, AR, United States of America

Dennis R Maiello