The holidays are a busy time for most folks, but as we approach the end of the year, it’s a good idea to have your HVAC professional swing by for a yearly maintenance check on all the components of your home heating system—including the thermocouple.

It’s not a very flashy or imposing device, but if you’re like a lot of homeowners whose furnace relies on a pilot light to start, it’s also a good idea to make sure you understand just what your thermocouple is, and why it’s important. Let’s take a look at what it does, and how it keeps your furnace, your home, and your family safer.

A Thermowhat?

If you have a system that uses a pilot light (rather than an electronic ignition), your system has a safety device called a thermocouple that monitors the condition of your system’s pilot light. The primary component is a metal rod that’s positioned near your pilot light’s flame and connected directly to the gas valve on your furnace.

A properly lit pilot light will heat the rod, which sends a current through the thermocouple and holds your gas line open to feed the furnace. Should your pilot light go out, the voltage drops and the thermocouple automatically closes your gas line.

Safety First: Why Your Thermocouple Matters

For such a tiny blue flame, your pilot light has a big impact on your home’s warmth and safety. The International Association of Certified Home Inspectors warns that, without a pilot light, natural gas can accumulate, unignited, in your furnace and create a dangerous risk of explosion, as well as the potential for carbon monoxide to contaminate the air in your home.

A well-maintained and properly functioning thermocouple helps mitigate these risks by automatically shutting off gas to your furnace when the pilot light is extinguished. Not only does this help prevent gas build-up, but also helps stave off carbon monoxide leaks. It also saves you money by helping to keep wasted gas to a minimum.

Proper Thermocouple Maintenance is a Must

Thermocouples are not intended to last as long as the furnaces in which they’re installed, which means they need to be carefully monitored and replaced as necessary. Their proximity to the flame of the furnace can create a number of issues, including:

  • Shortened lifespan from heat and physical flame damage
  • Accumulation of soot and other debris
  • Component failure, such as wires or an improperly calibrated thermocouple rod

Of the three, the most common issue is a dirty thermocouple, usually caused by dirt, dust and debris accumulating from other parts of the system or a lack of clean air filters. Cleaning and replacing (if necessary) your thermocouple should be part of your annual heating tune-up for best results.

Making sure the thermocouple on your gas-fired furnace is in good working order isn’t just an important part of keeping your system running smoothly this winter—it’s also an essential part of saving money and keeping your family safe.

(If you’re looking for greater efficiency with a smaller footprint, the U.S. Department of Energy recommends upgrading to a medium or high-efficiency system with an electronic ignition— talk to your local HVAC expert to explore the options that are right for your space and budget.)

How Your Thermocouple Keeps Your Furnace Fired Up
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