Hey rdf,
Sorry for the delayed response but thanks for reaching out to the Google Nest Community.
You may take a photo of you can check your wiring and system type by going to Settings > Equipment. From there, you may take a photo and save it for future reference. Also, to know more about the different settings of your Nest thermostat, you may check on this link: https://bit.ly/3y1xFOU
Hope this helps.
Best,
Melba
