What is unique about the "C" terminal in HVAC systems?

The "C" terminal, often referred to as the common terminal in HVAC systems, is unique because it is consistently energized with 24VAC. This terminal plays a crucial role in providing a return path for the electrical current in AC systems. It serves as a reference point for the thermostat and other components, ensuring they have the necessary voltage to operate reliably.

In a typical HVAC system, the "C" terminal connects to the transformer that steps down the voltage to 24VAC, allowing the thermostat and other accessories to function correctly. This constant voltage is essential for maintaining the operational integrity of the system, particularly in digital thermostats that require continuous power for precise control and operation.

Understanding the "C" terminal's role is vital for troubleshooting and ensuring that all related components function properly, as it is key to the operation of any thermostat that requires constant power.