I have red blue green wire in thermostats, i forgot to click

[157Mclean]

I have red blue green wire in my cooling system. I forgot to click the pic of existing setup. Where will goes the wiring ? 

[laurentbourg · Accepted solution]

It is very hard to give you an accurate answer without a picture of the old thermostat wiring, but try the following it should work:

- Red to Rc or R.
- Blue to Y1 or Y
- Green to G

[157Mclean]

Thanks, which Nest thermostat I should buy 

[laurentbourg]

The Nest thermostat 2020 (the one with the mirrored faceplate) is usually cheaper and should work fine for your use case.