Igniter failure detection assemblies for furnaces, and corresponding methods of detecting igniter failure

Abstract

Exemplary embodiments are provided of igniter failure detection assemblies for furnaces. In an exemplary embodiment, an igniter failure detection assembly includes a hot surface igniter, an igniter relay coupled to the hot surface igniter, a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor and hot surface igniter, and a controller configured to detect a voltage at the node and determine whether a fault condition of the hot surface igniter exists based on the detected voltage at the node. A detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter. Example methods of detecting an igniter fault condition are also disclosed.

What is claimed is: 
     
         1 . An igniter failure detection assembly for a furnace, the igniter failure detection assembly comprising:
 a hot surface igniter adapted to, in response to receiving a current, heat up to ignite a combustible gas of the furnace;   an igniter relay coupled to the hot surface igniter, the igniter relay adapted to selectively supply a current to the hot surface igniter based on a state of the igniter relay;   a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor, and the hot surface igniter; and   a controller configured to detect a voltage at the node and determine whether a fault condition of the hot surface igniter exists based on the detected voltage at the node, wherein a detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter.   
     
     
         2 . The igniter failure detection assembly of  claim 1 , further comprising a flame sensor adapted to sense a presence or absence of a flame generated in response to ignition of the combustible gas by the hot surface igniter. 
     
     
         3 . The igniter failure detection assembly of  claim 2 , wherein the controller is coupled to the flame sensor and is configured to detect the presence or absence of a flame via the flame sensor. 
     
     
         4 . The igniter failure detection assembly of  claim 3 , wherein the controller is configured to determine whether the fault condition of the hot surface igniter exists in response to detection of the absence of a flame after the start of a combustion process of the furnace. 
     
     
         5 . The igniter failure detection assembly of  claim 4 , wherein the controller is configured to, when the controller detects an absence of a flame and the detected node voltage corresponds to the normal operation resistance value of the hot surface igniter, determine a fault condition of the igniter relay. 
     
     
         6 . The igniter failure detection assembly of  claim 1 , wherein the resistance value of the hot surface igniter is less than about fifty ohms. 
     
     
         7 . The igniter failure detection assembly of  claim 1 , wherein the resistance value of the resistor is greater than about fifty ohms. 
     
     
         8 . The igniter failure detection assembly of  claim 7 , wherein the resistance value of the resistor is greater than or equal to about 500 thousand ohms. 
     
     
         9 . The igniter failure detection assembly of  claim 1 , wherein the igniter relay is coupled to a line voltage input and is adapted to selectively supply the line voltage input to the hot surface igniter based on the state of the igniter relay. 
     
     
         10 . The igniter failure detection assembly of  claim 9 , wherein the line voltage input is approximately 110 volts alternating current (VAC). 
     
     
         11 . The igniter failure detection assembly of  claim 9 , further comprising:
 an inducer relay coupled between the line voltage input and the igniter relay; and   a second resistor coupled in parallel with the igniter relay, the second resistor having a substantially similar resistance value as the resistor coupled in parallel with the hot surface igniter.   
     
     
         12 . The igniter failure detection assembly of  claim 11 , wherein, when a status of the igniter relay is set to off, the controller is configured to:
 when the detected node voltage is equal to about half of the line voltage input, determine a fault condition of the hot surface igniter;   when the detected node voltage is about equal to the line voltage input, determine the igniter relay is stuck in a closed position; and   when the detected node voltage is about zero, determine a normal operation condition of the hot surface igniter and the igniter relay.   
     
     
         13 . The igniter failure detection assembly of  claim 11 , wherein, when a status of the igniter relay is set to on, the controller is configured to:
 when the detected node voltage is equal to about half of the line voltage input, determine a fault condition of the hot surface igniter and that the igniter relay is stuck in an open position; and   when the detected node voltage is about zero, determine the igniter relay is stuck in an open position.   
     
     
         14 . The igniter failure detection assembly of  claim 1 , further comprising a conditioning circuit coupled between the node and the controller to adjust the detected node voltage within a range suitable for the microcontroller input. 
     
     
         15 . An HVAC system including a furnace having the igniter failure detection assembly of  claim 1 , wherein the controller comprises a furnace controller of the furnace. 
     
     
         16 . A method of detecting a fault condition of a furnace igniter assembly, the furnace igniter assembly including a hot surface igniter adapted to heat up to ignite a combustible gas of the furnace, an igniter relay coupled to the hot surface igniter to selectively supply a current to the hot surface igniter based on a state of the igniter relay, and a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor and the hot surface igniter, the method comprising:
 initiating a combustion process of the furnace;   detecting a voltage at the node defined between the igniter relay, the resistor and the hot surface igniter; and   determining whether a fault condition of the hot surface igniter exists based on the detected voltage at the node, wherein a detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter.   
     
     
         17 . The method of  claim 16 , further comprising sensing a presence or absence of a flame generated in response to ignition of the combustible gas by the hot surface igniter, and determining whether the fault condition of the hot surface igniter exists in response to detection of the absence of a flame after the start of the combustion process of the furnace. 
     
     
         18 . The method of  claim 17 , further comprising, when an absence of a flame is detected after the start of the combustion process of the furnace and the detected node voltage corresponds to the normal operation resistance value of the hot surface igniter, determining that a fault condition of the igniter relay exists. 
     
     
         19 . The method of  claim 16 , wherein the resistance value of the hot surface igniter is less than about fifty ohms and the resistance value of the resistor is greater than about fifty ohms. 
     
     
         20 . The method of  claim 16 , wherein the furnace igniter assembly further includes an inducer relay coupled to the igniter relay and a second resistor coupled in parallel with the igniter relay, and the second resistor has a resistance value that is substantially the same as the resistance value of the resistor coupled in parallel with the hot surface igniter, the method further comprising:
 determining whether a fault condition of the igniter relay exists based on the detected node voltage of the node defined between the hot surface igniter and the igniter relay.