What is a Thermopile?

Two stove devices help you understand your stove's temperature: a thermocouple and a thermopile. Which type you have will depend on the make and model of your stove.

In a previous article, we discussed what a thermocouple is, but what about a thermopile?

This article breaks down what a thermopile is, when it should be replaced, and how to replace it.

What is a Thermopile?

Like a thermocouple, a thermopile is a device that uses heat that is then converted into electricity. In fact, it is multiple thermocouples put together, typically five or more.

With more thermocouples in one device, your thermopile allows for greater voltage, resulting in more precise radiation identification within the unit and more accurate readings. It can also produce enough electricity to create and detect higher temperatures. The output is so high that it can even work with a separate thermostat and operate a gas valve for added heat increases. These last two traits are what thermopiles are used for most often.

Where is a Thermopile in a Gas or Wood Stove

The thermopile is usually near the pilot since it ignites gas or wood pellets. The electrical potential difference between the junctions increases when heat is increased inside the stove or fireplace. This voltage increase can ignite pellets, spark an igniter, and operate a gas valve or thermostat.

How Does a Thermopile Work?

As we mentioned, a thermopile consists of multiple thermocouples wired together in series. A thermocouple is made of two metals joined at one end. When the junction of the two metals is heated, it creates a voltage between the free ends of the metals. (For more information on this, see our article devoted to thermocouples.)

The voltage created by each thermocouple in a thermopile is added together. This means that the more thermocouples there are in a thermopile, the higher the voltage it can create. Thermopiles typically have between 5 or more thermocouples and can have a voltage output in the 100s of mV, whereas a single thermocouple ranges between 8 and 30 mV.

How to Know if Your Thermopile is Working Correctly?

Like thermocouples, thermopiles can wear out and need to be replaced. Here's how you can check yours and know when it's time for a new one.

One way to tell if it may need replacing is if the temperature readings are inaccurate or, in the case of a gas fireplace, if the pilot light won't work continuously. Take a look at the pilot light. If the pilot is also flickering or yellow, that's a sign that the thermopile isn't working properly.

You can check the electrical output with a multimeter. To do this, turn off your stove, disconnect the power, and ensure the thermostat is in the off position. Then, place the volt meter probes on the TP and the THTP terminals (the screws). A good thermopile with the main burner off should read with a minimum of 325 mV with the main burner off. With the burner on, it should read at least 110mV.

How to Replace Your Thermopile

Replacing a thermopile is a fairly straightforward process that you can do at home. First, you'll need to purchase a new thermopile (make sure to get the right one for your stove). Then, follow these steps:

• First, turn off your stove by unplugging the electricity from the wall.
• Remove the back panel that provides access to the gas valve and the thermopile. You will spot the thermopile when you see the two wires labeled TP and THTP.
• Remove the wires from the TP and THTP sections and pull out the thermopile.
• Replace the old thermopile with the new one, repeating the same process in reverse.

Your Answer for Greater Heat Readings and Output

Your thermopile is a highly accurate and powerful device to give you maximum heat and reliable temperatures. By checking the pilot light to ensure it is blue and by doing periodic voltage testing of your device when questions about performance arise, you can get the best performance from your fireplace.