Furnaces require more than just a burner assembly or heating element; many of them require a thermocouple. It plays an important role in preventing gas from leaking into homes.
What Is a Thermocouple?
A thermocouple is a simple safety device that’s designed to control a furnace’s gas valve in response to the pilot light. It consists of a metal rod with an integrated wire. Thermocouples sense the flame produced by the pilot light. If the thermocouple detects a flame, it will leave the gas valve open. If the thermocouple fails to detect a flame, it will close the gas valve.
The pilot light in a residential furnace is used to ignite gas in the burner assembly. As the furnace’s gas valve releases natural gas, the pilot light will ignite it. The thermocouple is installed directly over the pilot light so that it can determine whether it’s lit.
Furnaces use a thermocouple to protect against gas leaks. If the pilot light goes out, the thermocouple will close the gas valve. Without this device, the gas valve would remain open. Gas would continue to flow out of the gas valve, and the dead pilot light wouldn’t be able to ignite it.
Do All Furnaces Have a Thermocouple?
Not all furnaces have a thermocouple. Only gas furnaces that use a pilot light-based ignition system feature this safety device. Electric furnaces don’t have a thermocouple because they have an electric ignition system.
Many newer gas furnaces don’t have a thermocouple, either. They use an electric ignition system rather than a pilot light-based ignition system, thus eliminating the need for a thermocouple. Your furnace will only have a thermocouple if it runs on gas and uses a pilot light-based ignition system.
Signs of a Bad Thermocouple
If your furnace has a bad thermocouple, you may not be able to turn it on. The thermocouple may completely close the gas valve as a failsafe. Even if the pilot light is lit, the gas valve won’t open.
You can perform a visual inspection of the thermocouple. When thermocouples fail, they may develop cracks or become discolored. A visual inspection alone isn’t always enough to determine whether this device has failed. For a proper diagnosis, you should contact a professional.
If you are experiencing a problem with your air conditioning or heating call us at 512-336-1431 to schedule an appointment. We’ll be glad to come out and take a look at the issue.
1431-183 A/C & Heating proudly serves Round Rock, Georgetown, Cedar Park, Pflugerville, Leander, Liberty Hill, and North Austin.
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