With the thermostat bulb closed and the fan switch in the AUTO position, what voltage exists from Terminal R to Terminal G on the Thermostat?

When the thermostat bulb is closed, it indicates that the heating or cooling demand has not been satisfied, but the thermostat is still capable of controlling the fan operation. In a standard HVAC system, the voltage between Terminal R (the power supply terminal) and Terminal G (which controls the fan) is typically 24 volts. This is the standard operating voltage for most low-voltage HVAC controls, including the thermostat and fan circuits.

In the AUTO position, the fan operates only when there is a call for heating or cooling from the system, which means that if there was a request for heat or cooling, the circuit would close and create a pathway that allows the 24 volts to be present at Terminal G. However, since the scenario describes the thermostat bulb as closed, indicating no immediate demand, the voltage between R and G remains at the standard operating voltage of 24 volts, capturing the essence of normal HVAC operations.

Higher voltages like 120 volts or 240 volts are typically not used in direct control circuits for thermostats due to safety and operational standards, as they could pose a hazard if improperly handled. Similarly, 36 volts is not a standard value used in this context for typical residential HVAC systems. Thus, understanding the function of