A thermopile is a series of thermocouples connected in sequence to generate electrical current when exposed to a temperature difference. In HVAC systems, thermopiles are commonly used in gas furnaces and water heaters to power the gas valve without requiring external electricity. A single thermopile can generate 25 to 30 millivolts under normal operating conditions.
Technical Specifications
Thermopiles consist of multiple junctions of dissimilar metals arranged to maximize voltage output. Standard residential thermopiles produce approximately 750 to 900 millivolts at full temperature differential. They typically require a 50-degree Fahrenheit temperature difference between the hot and cold junctions to operate effectively.
HVAC Applications
Thermopiles serve as pilot safety devices in standing pilot furnaces, generating enough current to hold open the main gas valve through a solenoid. When the pilot light extinguishes, voltage drops and the valve closes automatically, preventing gas leaks. This fail-safe mechanism has been standard in furnace design for decades, making thermopiles essential safety components in traditional gas heating systems.