Nest 3rd Gen

[Owentp]

So I have my Nest set up. I have 5 wires but not using the yellow wire due to not physically having an AC unit but it is wired to my electric furnace.  I have a pellet stove that heats the main room well but not the back rooms great. I currently use the fan schedule to run my furnace fan only every hour for 15 min to help circulate the warmer air.  

What I want to know is if I connect the yellow wire, will it allow the Nest to identify AC/cooling so I can set it on that to run and my temp, i.e. 72.......will it automatically kick on the fan to run to get to that temp.  It gets around 75 in my main room where my nest is.

[luciaaa]

Hi, @Owentp,

Thank you so much for reaching out to the community. I understand that you want to know if connecting the yellow wire to your Nest thermostat will enable you to set a cooling mode and trigger the fan to run and reach a desired temperature, even though you don't have an AC unit. I’m happy to help!

In this case, if you have a yellow wire, we need to identify to which terminal it was previously connected and verify that it is the wire to turn on the AC. To confirm this information, I would appreciate it if you could share a photo of your previous wiring of your old thermostat and a photo of your control board to verify the wiring configuration. 

Regarding your question, to turn on the AC, you need a physical unit, unless it is an electrical device that provides both. To provide further assistance, please let me know:

Do you have a conventional system or heat pump system?

• Conventional System: Typically consists of two pieces of equipment (furnace and AC).
• Heat Pump: Handles both heating and cooling with a single unit.

This information will help me to provide you with accurate information. Thank you so much for your cooperation. 

Keep me posted.

Best regards,

Ana