Ignition control with safeguard function

Abstract

An ignition control and method are provided for overseeing an ignition process on a fuel-fired appliance having a fuel burner, a fuel flow control valve, an ignition source, and a flame detection device. A primary processor initiates the ignition process, monitors the flame status signal and terminates the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following the initiation of the ignition process. A secondary processor monitors the flame status signal independently of the primary processor and terminates the ignition process in the event that the primary processor fails to terminate the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following the initiation of the ignition process. The primary and secondary processors may each have the functional capability to monitor the operation of the other.

1 . An ignition control for controlling an ignition process on a fuel-fired appliance, the appliance having a fuel burner, said ignition control comprising:
 a fuel control valve having an open position in which fuel flows to said burner and a closed position in which fuel flow to said burner is stopped;   an ignition source operatively associated with said burner,   a flame detection device for detecting the presence of a flame at said burner and transmitting a flame status signal indicating flame or no flame;   a controller for overseeing the ignition process of igniting the fuel supplied to said burner, said controller including a primary processor and a secondary processor:   said primary processor having functional capability to operate the ignition device, to monitor the flame status signal from the flame detection device and to terminate the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following an initiation of the ignition process; and   said secondary processor having functional capability to monitor the flame status signal from the flame detection device and to terminate the ignition process in the event that the primary processor does not close the fuel control valve in the presence of a flame status signal indicating no flame after a specified period of time following an initiation of the ignition process.   
     
     
         2 . The ignition control as recited in  claim 1  further comprising said secondary processor having functional capability to monitor the operation of said primary processor. 
     
     
         3 . The ignition control as recited in  claim 1  further comprising said primary processor having functional capability to monitor the operation of said secondary processor. 
     
     
         4 . The ignition control as recited in  claim 3  wherein said secondary processor continuously transmits a status signal to the primary processor. 
     
     
         5 . The ignition control as recited in  claim 1  where each of said primary processor and said secondary processor comprises a microprocessor. 
     
     
         6 . The ignition control as recited in  claim 1  where each of said primary processor and said secondary processor comprises a microcontroller. 
     
     
         7 . The ignition control as recited in  claim 1  wherein each of said primary processor and said secondary processor has functional capability to position the fuel control valve in its closed position to independently terminate the ignition process. 
     
     
         8 . An ignition control for controlling an ignition process on a direct spark ignition gas appliance, the gas appliance having a burner, said ignition control comprising:
 a gas valve having an open position in which gas flows to the burner of the gas appliance and a closed position in which gas flow to the burner of the gas appliance is stopped;   an ignition source operatively associated with the burner of the gas appliance,   a flame detection device operatively associated with the gas appliance for detecting the presence of a flame at the burner and transmitting a flame status signal indicating flame or no flame;   a controller for overseeing the ignition process of igniting the gas supplied to the burner of the gas appliance, said controller including a primary processor and a secondary processor:   said primary processor having functional capability to operate the ignition device, to monitor the flame status signal from the flame detection device and to terminate the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following an initiation of the ignition process; and   said secondary processor having functional capability to monitor the flame status signal from the flame detection device and to terminate the ignition process in the event that the primary processor does not close the gas valve in the presence of a flame status signal indicating no flame after a specified period of time following an initiation of the ignition process.   
     
     
         9 . The ignition control as recited in  claim 8  further comprising said secondary processor having functional capability to monitor the operation of said primary processor. 
     
     
         10 . The ignition control as recited in  claim 8  further comprising said primary processor having functional capability to monitor the operation of said secondary processor. 
     
     
         11 . The ignition control as recited in  claim 10  wherein said secondary processor continuously transmits a status signal to the primary processor. 
     
     
         12 . The ignition control as recited in  claim 8  where each of said primary processor and said secondary processor comprises a microprocessor. 
     
     
         13 . The ignition control as recited in  claim 8  where each of said primary processor and said secondary processor comprises a microcontroller. 
     
     
         14 . The ignition control as recited in  claim 8  wherein each of said primary processor and said secondary processor has functional capability to position the gas valve in its closed position to independently terminate the ignition process. 
     
     
         15 . The ignition control as recited in  claim 8  wherein the gas appliance comprises a gas furnace. 
     
     
         16 . The ignition control as recited in  claim 8  wherein the gas appliance comprises a gas water heater. 
     
     
         17 . The ignition control as recited in  claim 8  wherein the gas appliance comprises a commercial gas cooking apparatus. 
     
     
         18 . A method for overseeing an ignition process on a fuel-fired appliance, the appliance having a fuel burner, a fuel flow control valve, an ignition source operatively associated with the burner, a flame detection device operatively associated with the burner for detecting the presence of a flame at the burner and transmitting a flame status signal indicating flame or no flame; said method comprising the steps of:
 providing a primary processor for initiating the ignition process, for monitoring the flame status signal and for terminating the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following the initiation of the ignition process;   providing a secondary processor for monitoring the flame status signal independently of said primary processor and for terminating the ignition process in the event that said primary processor fails to terminate the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following the initiation of the ignition process.   
     
     
         19 . The method as recited in  claim 18  wherein said secondary processor terminates the ignition process by closing the fuel flow control valve to stop the delivery of fuel to the burner in the event that said primary processor does not close the fuel flow control valve in the presence of a flame status signal indicating no flame after a specified period of time following an initiation of the ignition process. 
     
     
         20 . A method for overseeing an ignition process on a direct spark ignition gas appliance, the gas appliance having a burner, a gas valve, an ignition source operatively associated with the burner of the gas appliance, a flame detection device operatively associated with the gas appliance for detecting the presence of a flame at the burner and transmitting a flame status signal indicating flame or no flame; said method comprising the steps of:
 providing a primary processor for initiating the ignition process, for monitoring the flame status signal and for terminating the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following the initiation of the ignition process;   providing a secondary processor for monitoring the flame status signal independently of said primary processor and for terminating the ignition process in the event that said primary processor fails to terminate the ignition process in the presence of a flame status signal indicating no flame after a specified period of time following the initiation of the ignition process.   
     
     
         21 . The method as recited in  claim 20  wherein said secondary processor terminates the ignition process by closing the gas valve to stop the delivery of gas to the burner in the event that said primary processor does not close the gas valve in the presence of a flame status signal indicating no flame after a specified period of time following an initiation of the ignition process. 
     
     
         22 . The method as recited in  claim 20  wherein the steps of providing a primary processor and of providing a secondary processor comprise providing a primary microprocessor and a secondary microprocessor. 
     
     
         23 . The method as recited in  claim 20  further comprising the step of said secondary processor monitoring the operation of said primary processor. 
     
     
         24 . The method as recited in  claim 20  further comprising the step of said primary processor monitoring the operation of said secondary processor. 
     
     
         25 . The method as recited in  claim 24  further comprising the step of said secondary processor transmitting a status signal to said primary processor whenever said secondary processor is in an active state. 
     
     
         26 . The method as recited in  claim 20  further comprising the step of said secondary processor cycling in sequence through a primary detect mode, an idle mode and a monitor mode. 
     
     
         27 . The method as recited in  claim 26  further characterized in that the secondary processor may move from any of the primary detect mode, the idle mode and the monitor mode directly into a lockout mode.