Skip to content
Available 24/7!  Call or Text Us! 

What is a Thermocouple and How Does it Work With Your Furnace’s Pilot Light?

small_14917801258Earlier this week, we posted a blog about the differences between electronic ignitions and conventional pilot lights. Even though electronic ignitions are becoming more and more common, many St. Louis area homeowners still have furnaces that use conventional pilot lights. If you’re one of those homeowners, you should know about a safety device that’s directly related to your pilot light: the thermocouple. Today we’re going to talk about what a thermocouple is, how it keeps your furnace safe and what can go wrong with this crucial furnace component!

 

What is a thermocouple?

 

A thermocouple is a safety device that’s used to detect whether or not your furnace’s pilot light is lit. It contains a metal rod that is placed very close to your pilot light’s flame. This rod is connected to your furnace’s gas valve.

 

When your pilot light is lit, the heat from the flame sends a voltage through the thermocouple that keeps the gas line open. If the pilot light goes out, the thermocouple will lose its voltage and the gas line to your furnace will be closed.

 

How does a thermocouple make your furnace safer?

 

Your pilot light is responsible for igniting your furnace’s burners. Without it, gas would simply build up in your furnace without actually lighting. This would be very dangerous for two reasons. First, if the pilot light were to turn back on after gas had built up in and around the furnace, it could cause an explosion. Second, excess gas buildup could cause carbon monoxide to get into your home’s air.

 

Because the thermocouple shuts off the gas supply when it doesn’t sense a flame, it prevents your furnace from receiving any gas when the pilot light is out. This restricts gas from building up in your furnace and makes your system much safer because it will prevent explosions and carbon monoxide leaks (discussed above).

 

What can go wrong with your furnace’s thermocouple?

 

There are a couple things that can go wrong with thermocouples that prevent them from operating properly. One of the most common issues is that the thermocouple can get dirty. This will cause the thermocouple to make improper readings, which can shut off the gas supply to your furnace prematurely or prevent gas from reaching your furnace in the first place. In addition, wires can become loose or the thermocouple may need to be recalibrated. Many of these issues can be prevented by changing your air filter and scheduling annual tune-ups.

 

It’s important to note that thermocouples are not designed to last as long as the furnace that they are installed in, so they will need to be replaced periodically. That’s why it’s so important to schedule a furnace tune-up every year so that we can replace your thermocouple as soon as it stops working.

 

If you have any questions about an electronic ignition furnace, or if you’d like a heating system serviced or installed in your home, contact Jerry Kelly, your St. Louis furnace installation and repair contractor. We provide service all over the St. Louis area, including towns like Dardenne Prairie, Des Peres and Frontenac, MO.

 

photo credit: memotec Messtechnik via photopin cc