Product Pick of the Week: Furnace Igniters and Flame Sensors

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This week’s Product Pick of the Week has a lot to do with how to keep your home warm this winter season. Your furnace is the least-visited but maybe most important appliance in your household. Check out how your furnace igniters and flame sensors work to keep your home toasty-warm! 

Furnace Igniters

The furnace igniter is exactly how it sounds: it ignites the system with a flame. There are two types of igniters for furnaces, one is a pilot light which is used in older systems and the other is the newer electric hot surface igniters. Systems that rely on the pilot light typically are always lit, but not necessarily ignited. The pilot light will always be on but it does not necessarily mean that the furnace is running. The systems that are newer use electric hot surface igniters and rely on the large amount of heat in a wire with enough electrical resistance that when a current passes through it, it sparks. Short term, hot surface igniters are more dependable than pilot lights, but they do burn out like light bulbs and need more maintenance more often than pilot lights.

Flame Sensor

The flame sensor is part of the safety circuit and it senses the presence of a flame. If the flame goes out but the furnace continues to send fuel, there could be a large, catastrophic explosion. To prevent this, the flame sensor is in charge of sending signals to the central controller, which manages the fuel valves in the furnace. During the initial lighting, the flame sensor is set to an “ignition period” where the reading from the sensor is ignored until there is a large enough flame “sensed”. This ignition period is extremely short to avoid excess gas escaping. After this ignition period, the flame sensor is constantly sending messages to the central controller to assure that the flame is still lit and burning the gas.

In simpler terms, let’s call the furnace an office building. The amount of gas is the amount of people in the building, the doors of the building are the flame and the flame sensor is the security making sure there are not too many people trying to get into the building. In the morning, there is an obvious rush of people coming into the building, so the doors are most likely going to be a lot busier at this time of the day, but security is still sending signals to each other. They are aware of this short “ignition period” or “morning rush”. After the morning rush, security is constantly sending signals to each other to make sure that the doors are functioning correctly and correctly filtering the amount of people who can get into the building at once.

As you can see, the flame sensor is a vital part of the furnace, so it is important that this part functions exceptionally. If you notice that your furnace constantly is shutting off, your flame sensor may be dirty or damaged. You can find some replacement flame sensors here.


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Written By: Madison Jezioro

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