Gas Fireplace Thermocouple Vs Thermopile- What Is The Key Difference?

Thermocouples and thermopiles devices are commonly used in home appliances like gas fireplaces and fireplace inserts.

Although both are Thermoelectric devices and convert thermal energy into electrical, the main difference between thermopiles and thermocouples is the individual measurement method.

In a Gas fireplace, Thermopile mainly detects thermal radiation for ensuring its gas burner safety control. On the contrary, Thermocouple acts like a sensor for the pilot gas tube’s gas flow supplies during the pilot light lit up, and the Gas fireplace turns On.

The above explanation might sound a little complicated for some, so read the entire article to understand a gas fireplace thermocouple vs thermopile differences.

About Gas Fireplace Thermocouple:

Initially, Thomas Johann Seebeck discovered the thermoelectric effect resulted after the appearance of Thermocouples in 1821.

According to Seebeck’s discovery, a pair of two different metals wires creates voltage equal to the temperature difference between their junctions.

A thermocouple can consist of two wires or wire legs made of different metals, and their legs are welded together on one end as a junction, where the temperature is measured.  

This generated voltage can be used to detect the temperature. That’s why it is commonly used in modern home appliances such as gas furnaces or fireplaces.

There are different types of thermocouples available for their various applications. Usually, different thermocouples types are selected based on their temperature range and required level sensitivity.

Also, Thermocouples are available in different metals or calibrations combinations such as-

  • Base metal thermocouples with types J, K, T, E, and N (Most Common Calibrations)
  • Nobel metal thermocouples with types R, S, C, and GB (High-Temperature Calibrations)

How Does Gas Fireplace Thermocouple Work?

Since the thermocouple consists of two different metal wires, which join together at one end, heat enters at that end, splits, and travels down each wire separately. Then rejoins and creates thermal electricity. That generated voltage from this electricity delivers an accurate temperature reading between the device ends.

It mainly acts as a temperature measuring sensor or thermally sensitive device used inside the gas furnace or fireplaces to assist the pilot light while keeping the fireplace active and running.

Thermocouple communicates with the gas valve through a subtle electrical pulse, and whenever the gas fireplace pilot light is on, it transfers an electric signal that maintains the gas valve open.

Thermocouples rather work as a fail-safe to hold unburned gas from accumulating, burning, exploding, or causing another type of health risk.

About Gas Fireplace Thermopile:

Mainly it is an electronic instrument, which consists of a series of interconnected thermocouples and alters the thermal power into electrical energy.

The thermopile is also introduced and known as a Power pile. Each of the additional thermocouples is placed in a thermopile to increase the instrument’s capacity to produce more electricity.

For example, if a thermocouple can generate two volts of electricity and if you put four thermocouples into a thermopile, a thermopile will generate eight volts of electricity in total.

That means thermopile’s connection format can produce more outputs than utilizing a single thermocouple. Thermopile measures temperature differences and generates electricity by detecting radiation within an environment.

There two types Thermopiles available, such as-

  • Linear thermopiles (use single detector)
  • Junction thermopiles (use multiple detectors)

How Does Gas Fireplace Thermopile Work?

Since a series of electrodes-connected thermocouples create a thermopile, these thermocouples convert the heat coming from the gas furnace or fireplace into an electrical signal, and the thermopile receives that signal as input.

Then, the thermopile transmits it as the output on another wire or another part of the same wire. These newly generated outputs can be displayed on oscilloscope screens or other devices which can detect temperature change.

When using thermopiles for temperature measurement, both thermopiles and thermocouples should be attached to a wire voltage translating device for temperature reading.

Reportedly, Thermopile voltage outputs are introduced as Seebeck coefficient or Thermoelectric coefficient. Also, they are calculated per kelvin (V/K) or mV/K.

Gas Fireplace Thermocouple Vs Thermopile – What Are the Major Differences?

There are Gas fireplaces available, which come equipped with Thermocouples and other fireplaces are available equipped with the Thermopiles. Even some gas fireplaces are equipped with both Thermocouples and Thermopiles.

Therefore, often consumers or homeowners get confused about which one is better to choose between these available options.

That’s why I wanted to make the task easier by explaining all the differences between the Thermocouples and Thermopiles.

These significant differences will help you understand which type of temperature sensor-equipped gas fireplace will be more beneficial. So have a look here-

FeaturesGas Fireplace ThermocoupleGas Fireplace Thermopile
Consist OfA pair of two different metals wires or wire legs.A series of interconnected or electrodes-connected thermocouples.
Application In Gas FireplaceUtilizes to detect the temperature in fireplaces.Utilizes to create electricity for running the valve. Also, regulate and monitor the temperature when employed by a thermostat.
Production Of Electrical OutputGas Fireplaces with thermopiles produce more electricity.Gas Fireplaces with thermocouples lack sufficient electrical output.
Type Of DeviceThe thermocouple is a contact-based temperature sensor.Thermopile is a non-contact temperature sensor.
Level Of PrecisionDetects radiation with precision and accuracy.Detects radiation with more precision and accuracy than Thermocouple. 
Level Of SensitivityDoes not contain a higher degree of sensitively like ThermopileThermopile delivers the output with a higher degree of sensitivity
Creates MVThermocouple can create around 25 MVThermopile can generate around 750 mv

Frequently Asked Questions (FAQs):

How long does a Gas Fireplace Thermocouple last?

Reportedly, if properly installed and maintained, Thermocouples of the Gas fireplaces can last up to 10 years.

But at the same time, you should note that they can also wear out sooner if used in multifamily units.

How much does it cost to replace a Gas Fireplace thermocouple?

Remember, the exact costing will vary depending on whether the task is performed by a professional technician (highly recommended) or you will do it by yourself.

Still, if you get the replacement task of thermocouple or thermopile done by a professional, the cost will stay between $150 and $250.

How long does a Gas Fireplace thermopile last?

Unfortunately, the Thermopile temperature sensor devices do not come with a specific life expectancy or lasting period.

But thermopiles can easily last for years and even decades only when they are used and maintained accordingly.

Are Thermopiles and Thermocouples interchangeable?

No. Before you plan on replacing the Thermopile with a Thermocouple wait a moment to reconsider. First of all, they are not interchangeable by default.

Typically, A thermopile uses a different type of electrical connection than a thermocouple and produces more electricity than what a thermocouple delivers.

Therefore, when you replace one of them with another one, the requirements will not meet each other. As a result, your device’s gas control will not work correctly.

For further detailed explanation or if you are encountering any troubleshooting issue, which forced you to think about this replacement, visit


Generally, thermocouples and thermopiles are widely used in gas furnaces, fireplaces, and fireplace inserts to produce sufficient power or energy.

Still, it seems like, many gas furnace fireplace or fireplace insert owners get confused between thermocouples and thermopiles since they are not well aware of the significant difference these two have.

That’s why I tried to highlight the detailed comparison between Gas Fireplace Thermocouple vs Thermopile to help them out in today’s article.