Furnace Flame Sensor
What is a Furnace Flame Sensor?
The flame sensor is an important safety feature for a gas furnace. The most common type will check right after the gas is burning and safeguard you and your home from dangerous conditions while your gas is burning. The flame sensor is constructed out of metals that will create an electrical current if in the presence of a flame. It is usually meant to shut the product down when not enough burning fuel is detected. A constant flame from the last burner would indicate a reliable burning environment and also that the whole set of burners are getting approximately the very same amount of fuel and air. If no flame is there, any one of the burners inside the group could be burning fuel in an unsafe way. Therefore the system checks for the flame and closes the fuel valve when no flame is detected. Any system can have a false reading, so the control board usually tries to light the burners two more times. If these three times the system delivers the same message that the flame sensor isn’t detecting a flame, the whole furnace is shut down via the control board either for a couple of hours or completely until reset by a service technician. This is called a lockout condition.
When your furnace’s main burners ignite (light up) the flame sensor picks up the heat from the furnace’s main burner sends a signal to the main furnace control board, indicating that it is okay to let the main burner stay on. If the main burners do not ignite, the flame sensor does not send the signal, and the gas valve is shut off.
This device is extremely important to the safety of your family. You do not want it to fail.
We recommend that the flame sensor be replaced every 5 years.
(Cleaning an older sensor should only be a temporary fix.)