How Does a Thermocouple Work?

Homeowners often express concern about having a natural gas-powered furnace installed in their house. For the most part, these concerns are unwarranted; as long as they receive regular maintenance once a year to see that all of their components are functioning properly, gas furnaces present few health hazards and should work effectively and safely for many years.

One of the ways that the manufacturers of gas furnaces keep their products safe is through a device called the thermocouple. We’ll explain what it is and how it works to keep you safe.

For help with your heating in Salem, OR, contact Comfort Flow Heating today. We will make sure you get the most from your furnace.

The thermocouple

A thermocouple is a device that consists of a pair of strips of metal made from different material. It is installed so that its ends are in the pilot light of the furnace. The thermocouple detects the heat from the pilot light, and should the pilot light go out accidentally, the thermocouple will automatically shut off the gas valve. This prevents unburned gas from flooding into the combustion chamber, where a small spark might cause an explosion.

The thermocouple performs its job through a thermoelectric effect known as the “Seebeck effect,” named after Thomas Johann Seebeck, a German-Estonian physicist who discovered the effect in 1821. Seebeck found that two separate types of metal in proximity to each other will generate electrical voltage in proportion to the heat they sense. The higher the heat around the two metal pieces, the higher the voltage.

The thermocouple in a gas furnace is designed to keep the gas valve open through its electric voltage. If the pilot light goes out, the loss in heat causes the voltage between the two pieces of metal to drop, and this shuts the valve and reduces the combustion risk.

It’s a remarkable feat for so simple and small a device. However, a thermocouple can break, rust, or fall out of place, and this can lead to a potential hazard if the pilot light fails. This is one of the reasons you need to schedule regular preventive maintenance for your gas furnace: technicians will catch failing thermocouples and replace them with the correct unit.

(Some current gas furnaces use a mercury sensor instead of a thermocouple. Your technician will know how to handle potential problems with mercury sensors as well.)

Stay safe this winter with your heating system in Salem, OR: call Comfort Flow Heating and enroll in our maintenance program. We are also ready to help you with repairs, any time of the day or night.