Everything You Need To Know About Furnace Flame Sensors

As winter rolls around, you’ll be using your heater much more frequently, which means preventative care is essential at your facility. Your furnace is a potentially dangerous component of the HVAC system. Without proper safety checks in place, your furnace can have undetected gas leaks or fires that cause catastrophic damage to your facility. 


That is why it is essential to take care of your furnace’s flame sensor before and during the winter months. This guide will help you learn more about this all-too-important component, and how to prevent it from having issues at critical moments. 


What is a flame sensor?


The flame sensor, located inside the burner assembly, is a sensor that detects flames inside the unit. If a flame is detected, the sensor will signal to shut off the furnace entirely to prevent fires and leaks of carbon monoxide. This is one of the most critical safety components of your entire HVAC system. In older systems, a different type of flame sensor called a thermocouple is present. This serves the same purpose but uses different technology to detect flames and turn off the furnace. 


How to tell if your flame sensor is working properly.


Flame sensors can eventually stop working, especially if they are from an older system. If you have an older HVAC unit, your HVAC technician will look for these signs that your sensor may not be working anymore: 


  • The furnace burners will turn on but shut off immediately after
  • The flame sensor is covered in ash or dust (which signals it’s time for cleaning)
  • The tip of the flame sensor is black
  • The casing is cracked or pieces are falling off


Flame sensor maintenance.


Luckily, unless the sensor needs to be replaced, this component has a fairly simple maintenance plan. Your HVAC technician may periodically clean and test it, but otherwise, your flame sensor should last 15 to 30 years with minimal maintenance. You may have to replace it once throughout your building ownership or management, but it’s unlikely to cause you too many problems. 


If you haven’t had an HVAC maintenance check in a while, call MaintenX for a simple tune-up before firing up the furnace. It could save your facility from a fire or gas leak, and help you save on emergency repairs.

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