Which T-stat terminals are used when employing a 4-wire setup?

In a 4-wire setup for thermostats, the proper combination of terminals includes R/Rc, W, G, and Y. Each terminal serves a distinct purpose in the operation of the HVAC system.

The R terminal, which can often be denoted as either R or Rc, connects to the power source and provides voltage to the thermostat. The distinction between R and Rc comes into play in some systems where there is a separate transformer for heating and cooling systems.

The W terminal is used for the heating signal, which activates the heating system when the thermostat calls for heat. The G terminal controls the fan operation, allowing for independent fan control. Finally, the Y terminal is responsible for the cooling signal, activating the air conditioning system when cooling is required.

Together, these terminals enable efficient and separate control of heating, cooling, and fan functions in a 4-wire setup. This setup is quite common in modern systems, allowing for better energy management and comfort control in residential HVAC systems.

The other options do not accurately reflect the wiring requirements for a standard 4-wire thermostat.