Thermocouple VS Thermopile in Gas Equipment Applications
By Michael Angello – Parts Sales Manager
Thermocouples and thermopiles are critical gas safety devices used in many pieces of gas-heated restaurant equipment. How do they work, why do we use two different safeties, are they interchangeable, and what are their differences, is important information to know about these restaurant equipment parts. These are the questions that have been asked many times, this blog describes their purpose and how they are used in your commercial cooking equipment.
Firstly, it is important to understand the critical nature of thermocouples and thermopiles. They are effectively a safety switch that ensures your gas shuts off if the pilot light is not lit, therefore it prevents unlit gas from filling your kitchen. Both thermocouples and thermopiles operate by making a thermoelectric connection. They take the heat from a flame and convert it to a very small electrical output using dissimilar metals. The thermocouple will generate around 30 millivolts and the thermopile will generate around 300 millivolts. If these numbers look somewhat similar that is because the thermopile is usually around 10 thermocouples tied together most of the time in series but can also be found in parallel. The flame being used is generally a pilot light. The thermocouple will be immersed in the flame and the thermopile will be heated at the tip.
Now that we know they are similar why do we use two different types?
Thermocouple – A thermocouple provides a constant output voltage when immersed in heat. That small electric current is used to hold open an electromagnet, which does not need a large amount to keep it open. The thermocouple controls the flow of gas but is not opening the gas valve itself. When heated gas begins to flow, you will still need a 24-volt circuit to operate the gas valve.
Thermopile – When a thermopile is used the voltage can vary but when heated directly in the flame the voltage becomes constant. There is enough voltage on this to operate a gas valve and physically open the gas valve, so there is no need for a separate power source to open the valve. Each one has its own type of uses designed by the manufacturer.
Finally, what are their differences and are they interchangeable? They are not interchangeable with each other although they are similar, they do two different things in gas-fired systems. Thermocouples are interchangeable with themselves; they are all the same construction but can be manufactured in different lengths. We still suggest replacing it with the OEM-manufactured part but if it is not readily available anyone with the correct length will work. Thermocouples are generally skinny and pointed at the top with a copper tube ending in a threaded connector. Thermopiles are generally wider and will have actual wires leading off the body to screw onto terminals. Thermopiles are also interchangeable with other thermopiles.
One last thing to be aware of is the cost of these items, while a Thermocouple will usually be less than $50 a Thermopile could be $50 and higher.
If you still cannot tell if you have a thermocouple or a thermopile, feel free to give our General Parts Group parts department a call at 1-888-498-1238 and one of our parts specialists will lend a hand.