Google Nest Thermostat

[Woodland]

I have purchased a Google Nest Thermostat and want to replace a four wire thermostat  that supports an existing forced air heating and cooling system.

Do I now  hook the blue (thermostat) wire up to the Y designated cooling terminal on the nest?

[Markjosephp]

Hello Woodland,

Congratulations on your new Google Nest Thermostat! When it comes to replacing a four-wire thermostat that supports both heating and cooling, the wiring configuration is crucial for proper functionality.

Typically, the blue wire in a thermostat corresponds to the common wire (C), which is used to complete the circuit for the thermostat. However, in your case, you mentioned connecting it to the Y terminal designated for cooling on the Nest Thermostat. The Nest Thermostat usually follows the standard labeling:

• Rh or Rc: Power (24V)
• W: Heating
• Y: Cooling
• G: Fan
• C: Common

If your existing thermostat had a blue wire connected to the cooling terminal, it's likely that the blue wire is acting as the common wire. In this case, you should connect the blue wire to the C terminal on your Nest Thermostat.

Best of luck with your Nest Thermostat installation! If you have any more questions, feel free to ask.

Regards,

Mark

[Woodland]

I have a current four wire thermostat originally installed for heat only.  AC was added and the existing blue wire was used for the cooling unit and connected to the “Y” terminal on the existing thermostat. Can  I now hook this blue wire to the “Y” connection on the Nest?