Auto reignition
Encyclopedia
Auto reignition is a process used in gas burner
s to control ignition devices based on whether a burner flame is lit. This information can be used to stop an ignition device from sparking, which is no longer necessary after the flame is lit. It can also be used to start the sparking device again if the flame goes out while the burner is still supplying gas, for example, from a gust of wind or vibration.
and cooktops use sparking devices to ignite the burner flame. This eliminates the need for a pilot flame, which wastes energy. Most of these sparking device-equipped ranges require the user to control the ignition sparking manually, resulting in a three-step process required to operate the burner:
One implementation of a gas burner with auto reignition senses the electrical conductivity of the flame. This nonzero flame conductivity is because combustion of natural gas
releases enough free electrons to support a small current in air. An electronic circuit then starts or stops the igniter from sparking, based on whether the flame is lit. This reduces the number of steps to turn a burner on from three to one:
This is an elegant solution, compared to detecting flame via a thermocouple
, a photoresistor
or a mercury-filled sensor. No extra components or electrical connections between the sparker electrode and the spark module electronics are required.
This convenience and safety feature is found only (as of June 2009) on higher priced gas ranges and cooktops.
This feature is especially valuable on gas burners with several different short-term users, less likely to bother with or learn multi-step procedures--for example, gas ranges in rental properties, guest houses, or in office kitchens.
Gas burner
A gas burner is a device to generate a flame to heat up products using a gaseous fuel such as acetylene, natural gas or propane. Some burners have an air inlet to mix the fuel gas with air to make a complete combustion...
s to control ignition devices based on whether a burner flame is lit. This information can be used to stop an ignition device from sparking, which is no longer necessary after the flame is lit. It can also be used to start the sparking device again if the flame goes out while the burner is still supplying gas, for example, from a gust of wind or vibration.
Kitchen appliances
Most gas rangesStove
A stove is an enclosed heated space. The term is commonly taken to mean an enclosed space in which fuel is burned to provide heating, either to heat the space in which the stove is situated or to heat the stove itself, and items placed on it...
and cooktops use sparking devices to ignite the burner flame. This eliminates the need for a pilot flame, which wastes energy. Most of these sparking device-equipped ranges require the user to control the ignition sparking manually, resulting in a three-step process required to operate the burner:
- turn burner knob to a position that opens the gas valve and activates the sparking (typically labeled "Lite")
- wait for ignition, typically 0.5 to 2 seconds
- turn burner knob past lite position, to stop the sparking noise and burning out the ignition electrode, to a desired flame intensity
One implementation of a gas burner with auto reignition senses the electrical conductivity of the flame. This nonzero flame conductivity is because combustion of natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
releases enough free electrons to support a small current in air. An electronic circuit then starts or stops the igniter from sparking, based on whether the flame is lit. This reduces the number of steps to turn a burner on from three to one:
- turn knob to a desired flame intensity--while confirming flame ignites
This is an elegant solution, compared to detecting flame via a thermocouple
Thermocouple
A thermocouple is a device consisting of two different conductors that produce a voltage proportional to a temperature difference between either end of the pair of conductors. Thermocouples are a widely used type of temperature sensor for measurement and control and can also be used to convert a...
, a photoresistor
Photoresistor
A photoresistor or light dependent resistor is a resistor whose resistance decreases with increasing incident light intensity. It can also be referred to as a photoconductor or CdS device, from "cadmium sulfide," which is the material from which the device is made and that actually exhibits the...
or a mercury-filled sensor. No extra components or electrical connections between the sparker electrode and the spark module electronics are required.
This convenience and safety feature is found only (as of June 2009) on higher priced gas ranges and cooktops.
The case for requiring auto reignition as a safety feature
Auto reignition lowers the risk of gas leaks:- if a flame goes out during operation, for example, from vibration or a gust of wind
- due to misoperation--a user might not understand the "lite" position must be maintained for about 0.5 to 2 seconds before turning the burner knob on fully. The user might, as a result, turn the burner knob on quickly past the "lite" position without the burning actually igniting and leave the kitchen; thus leaving the gas burner leaking gas into the room.
This feature is especially valuable on gas burners with several different short-term users, less likely to bother with or learn multi-step procedures--for example, gas ranges in rental properties, guest houses, or in office kitchens.