Which two terminals are used to test the fan center relay for 24 volts?

In a typical heating and cooling system, the fan center relay is a crucial component that controls the operation of the fan. To test the fan center relay for 24 volts, you need to check the voltage between the terminals designated as "R" (power) and "C" (common).

Terminal "R" is connected to the transformer and provides the 24-volt power supply necessary for the operation of various components in the HVAC system, including the fan center relay. Terminal "C" serves as a return path for the power. When measuring voltage across these two terminals, if you have a reading of approximately 24 volts, it indicates that the circuit is functioning properly and that the fan center relay can be energized when needed.

Other terminal combinations like "X" and "Y," "A" and "B," or "1" and "2" may serve specific functions within the system, but they do not represent the main power and common connections needed to test the voltage at the fan center relay effectively. Understanding the significance of terminals "R" and "C" is essential for technicians to diagnose and service HVAC systems accurately.