What Is A Furnace Flame Sensor?

What is a furnace flame sensor?

What Is A Furnace Flame Sensor?

(Last Updated On: June 28, 2017)

Definition of Furnace Flame Sensor

A furnace flame sensor is a specialized safety component that is located inside of the burner assembly of a furnace. It detects and confirms whether or not there is a flame burning inside of the furnace. If no flame is detected, the furnace flame sensor will shut off the furnace in order to avoid a potentially harmful gas leak into the home. This is beneficial in preventing carbon monoxide poisoning to occupants and preventing possible explosions.

How A Furnace Flame Sensor Works

A furnace flame sensor works by detecting the presence of a flame within the furnace. The sensor is a short length of thin metallic rod that creates a small current of electricity in order to confirm there is fire burning within the furnace. As the gas valve opens to begin the combustion process, the current is sent out from the sensor in order to detect the presence of heat from a flame.

If there is a flame detected and all is well with the furnace, heating will continue. However, if the furnace flame sensor does not detect the presence of a flame within 10 seconds of the gas valve opening, it will shut the furnace down. It will attempt this cycle two more times before shutting down the control board and locking out the system. You may be able to reset the furnace yourself, or you may need to call an HVAC technician to reset it. These measures help to keep occupants of the home safe.

Types of Furnace Flame Sensors

Most furnace flame sensors are quite comparable in their function and appearance, although they will vary in their length. There are some models that are straight like a pencil, and others that are shaped like the letter L. There may also be small differences among the porcelain housing of some furnace flame sensors.

Benefits of Furnace Flame Sensors

The biggest benefit of a furnace flame sensor is that it helps to ensure your furnace is not calling for gas without a properly lit flame. This helps to keep anyone within the home safe from harmful gas buildup. It also helps to ensure that the gas is not running without being in use. By preventing the buildup of gas within the home, it can also help to prevent explosions should the home fill with gas and a spark ignite.

Best Practices for Furnace Flame Sensors

One of the biggest problems with furnace flame sensors is that they can sometimes become dirty. This can cause the furnace flame sensor to not function properly. You can tell you have a problem with your furnace flame sensor if the unit cycles before shutting down multiple times. It will eventually lock out, requiring a power restart in order to reset the unit. A furnace flame sensor might also crack, which can also cause your furnace to act up. If your furnace attempts to start up multiple times but ultimately does not run, you may have a problem with your furnace flame sensor.

One of the biggest causes of a dirty furnace flame sensor is not performing regular maintenance on your home’s HVAC system. This is why it’s a good idea to regularly clean your furnace flame sensor and to not skip out on your annual furnace maintenance. While a professional HVAC technician is the best person to perform this task for you, it is something that any moderately handy homeowner can do themselves.

How to Clean a Furnace Flame Sensor

It takes just a few simple steps for a homeowner to clean a furnace flame sensor and get things working normally.

  1. First, you’ll need to shut down the furnace completely.
  2. Next, you’ll need to open the combustion chamber door of your furnace in order to expose the furnace flame sensor.
  3. Remove the furnace flame sensor and remove any rust with a light-grit sandpaper, steel wool, or an emery cloth, before wiping down the metal rod with a paper towel to remove any dust buildup.
  4. Finally, blow off any dust from the furnace’s pilot and electronic igniter before replacing the furnace flame sensor and closing the combustion chamber door.
  5. You can now restart the furnace.

If cleaning the furnace flame sensor does not solve the problem of the furnace not running, you will need to contact a qualified HVAC professional in order to help troubleshoot and fix the issue. While some tasks of furnace maintenance can be completed by a savvy homeowner, it is best to leave larger, more complicated jobs to the professionals.

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