Furnace control system and method

#Many furnace systems include a control system that includes sensors, relays and control valves that are used to safely start and operate the furnace system. In operation, the furnace receives a signal to start from a thermostat. The system starts an inducer blower that creates a negative pressure in a collector box of the furnace by drawing air from a combustion air inlet and outputting air through a flue outlet. The system senses the negative pressure and starts a burner assembly in a heat exchanger portion of the system by providing fuel to the burner assembly and igniting the fuel. A blower motor may then start, such that the blower motor receives air flow from a return air duct of a space and outputs the air to the heat exchanger portion of the system. The heated air is output via a supply air duct to heat the space.

#According to one exemplary embodiment, a method for operating a furnace system includes receiving a start instruction at a controller, initiating a start sequence comprising starting an inducer fan operative to induce an air flow through a burner assembly, a heat exchanger portion and a collector portion, determining whether an air pressure in the collector portion is above a first threshold value, starting a furnace ignition sequence including providing fuel to the burner assembly, mixing the fuel with induced air, igniting the fuel and air mixture and starting an ignition timer responsive to determining that the air pressure in the collector portion is above the first threshold value, determining whether the ignition timer has expired, determining whether the air pressure in the collector portion is above a second threshold value responsive to determining that the ignition timer has expired, and stopping the provision of fuel to the burner assembly responsive to determining that the air pressure in the collector portion is not above the second threshold value.

#According to another exemplary embodiment, a furnace system includes an inlet duct communicatively connected to an air source and a burner assembly, a heat exchanger portion communicatively connected to an output of the burner assembly, a collector portion communicatively connected to an output of the heat exchanger assembly, an inducer portion communicatively connected to an output of the collector portion and an exhaust duct, a gas valve communicatively connected to a fuel source and the burner assembly, a first pressure sensor operative to sense a pressure in the collector portion, a second pressure sensor operative to sense a second pressure in the collector portion, and a controller operative to control the gas valve, and the inducer portion, the controller operative to receive a start instruction, initiating a start sequence comprising starting the inducer portion, receive a signal from the first pressure sensor and determine whether the sensed pressure is above a first threshold value, starting a furnace ignition sequence including controlling the gas valve to provide fuel to the burner assembly and starting an ignition timer responsive to determining that an air pressure in the collector portion is above the first threshold value, determining whether the air pressure in the collector portion is above a second threshold value responsive to determining that the ignition timer has expired, and stopping the provision of fuel to the burner assembly by controlling the gas valve responsive to determining that the air pressure in the collector portion is not above the second threshold value.

#The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

#FIG. 1 illustrates an exemplary embodiment of a furnace system.

#FIG. 2 illustrates an alternate exemplary embodiment of a furnace system.

#FIG. 1 illustrates an exemplary embodiment of a furnace system (system) 100. The system 100 includes a return air duct 102 that receives air from a space such as, for example, a residential or commercial structure (not shown). The air is drawn through the return air duct 102 and driven through a heat exchanger portion 104 with a blower fan 107. The air passes through the heat exchanger portion 104, which is heated by a burner assembly 106. The air exits the heat exchanger portion 104 and is output to a supply air duct 108 and sent to the space.

#A controller 110 receives power from a power source 111, and controller 110 may receive signals from a device such as a thermostat 112. The controller 110 includes a logic system that may include, for example, a processor, memory, counters, timers, input devices, output devices and indicators, or other similar electronic circuitry that provides control to the system 100. The controller 110 is operative to control the blower fan 107 and send power and signals to a gas valve assembly 114. The gas valve assembly 114 includes a valve 116 that controls fuel, such as natural gas, received from a fuel source 118 and output to the burner assembly 106. The valve 116 may be controlled by, for example, a solenoid (not shown) that actuates to open the gas valve assembly 114 when power is provided to the solenoid. When the gas valve assembly 114 is opened, fuel is provided to the burner assembly 106.

#The burner assembly 106 receives a flow of air via a burner inlet 119. The air from the burner inlet 119 mixes with the fuel and is ignited by an igniter (not shown) in the burner assembly 106. The product of the combustion exits the burner assembly 106 and is output to a heat exchanger portion 104, which in turn, is output to a collector portion 120. An inducer portion 122 induces a negative pressure in the collector portion 120 and draws the product of the combustion from the collector portion 120 and outputs the product of the combustion via an exhaust duct 124.