When it’s time to switch your furnace on for the cool season, you might just turn the heat up and forget about it. But your furnace includes many components that are crucial to heating your home.
Complete Comfort Control, your expert HVAC services in the Hamptons, is here to help you ensure that all the parts of your heating system work as they should. In this blog post, we’ll answer a common question, “How does a flame sensor work on a furnace?”
Why Is a Flame Sensor Important?
The flame sensor is a component in gas furnaces and boilers that switches the furnace off if the pilot light flame dies. Without this safeguard, the pilot light could go out, and the system would still release gas.
Gas leaks can lead to carbon monoxide poisoning, which is very dangerous. The unburned gas also increases the risk of an explosion in the home. This is how furnace flame sensors ensure safe operation.
Furnace Flame Sensor Operation 101
Now, let’s look at how the furnace flame sensor works. Understanding the function of flame sensors in furnaces isn’t difficult. The sensor is a tiny metallic rod with a current of electricity running through it.
When the furnace combustion process begins, a valve opens, and the rod reacts to the heat. Furnace flame sensors work by emitting an electrical current when they feel the warmth. If the sensor doesn’t detect heat from the pilot light, it will shut down the furnace if there’s no flame within 10 seconds.
How does a flame sensor work on a furnace if the pilot light only flickered and came back on? The system will cycle another two times. If it still doesn’t detect firelight, it’ll shut down the system and lock it.
You’ll then either need to reset the unit or call someone to do it for you.
Types of Furnace Flame Sensors
There are two basic categories of flame sensors: optimal readers and bi-metallic strips. Both types start running an electrical current when there’s a flame.
However, the former is usually for industrial units and so can handle a lot more voltage. Therefore, they’re pricy and overkill for the average homeowner.
Your home is more likely to have bi-metallic strips. These use a small voltage current and are more than enough for your needs.
Indications That Your Sensor’s Failing
Considering the flame sensor’s role in the furnace ignition process is to prevent carbon monoxide build-up, it’s important to know the signs that the flame sensor is not working.
If you see the following signs, call us for assistance:
- Your furnace turns on but shuts down seconds later.
- The porcelain that protects the sensor is cracked.
- Soot or other grime covers the surface.
- The metal strip starts to rust, or its tip becomes black.
The average flame sensor lasts around five years.
The Operation and Maintenance of Furnace Flame Sensors
Dirt is one of the leading reasons for failure in these components. When there’s too much grime, the sensor becomes practically useless.
We recommend an annual furnace tune-up to deal with this issue. An experienced technician will first try to clean the flame sensor. If it needs replacing, they’ll let you know.
How Professionals Clean the Furnace Flame Sensor
To clean your flame sensor, HVAC technicians will generally:
- Ask you to switch off the gas and electricity about half an hour before they arrive.
- Find the flame sensor, which is usually at the back of the unit.
- Remove the furnace’s access cover.
- Loosen the sensor from the burner array.
- Disconnect the wiring from the control box and loosen any bolts.
- Remove the sensor from its bracket.
- Lightly sand away the dirt using emery paper. This is a delicate process because scrubbing too hard could damage the sensor.
- Wipe away any residue and soot using a lint-free cloth.
- Reattach the sensor and rewire it.
- Tighten the screws so the unit is properly secure.
- Close the access cover.
- Test the furnace to make sure it’s working properly.
- If the unit doesn’t turn on as it should, it’s time to replace the flame sensor.
The technician may also recommend replacing the sensor if they see signs of corrosion, cracking, or excessive wear and tear.
Contact Us for Help With This Component Today!
Now that we’ve answered, “How does a flame sensor work on a furnace?” you better understand how your furnace works and why furnace maintenance is so important. Do you need some tips for troubleshooting delayed ignition in gas furnaces?
Complete Comfort Control has the expert technicians and experience you need, so call us at 631-910-6702.