I have two manual doorbells, 1 on the side of the house, 1 at the front, that connect to one mechanical chime box. So there is 1 black wire each going to Front, Trans, and Rear in the box. Can I install a Nest Hello to just the front doorbell and leave the side doorbell as-is? Ultimate goal: ring side doorbell, it rings the mechanical chime; ring front doorbells, it rings mechanical chime AND triggers video in the Nest app
You should be able to do that. The Nest Hello's chime connector gets wired to your mechanical chime, so you'd connect it to your front doorbell's connection in the chime, following the instructions. Initially, we had one Nest Hello just for our front doorbell before adding one for our rear doorbell. If your doorbell has an old transformer, you should check whether it has enough voltage to power the Nest Hello chime connector (https://support.google.com/googlenest/answer/9247132?hl=en). I'm talking about the the wired Nest Hello doorbell; I can't speak to the newer battery Nest doorbell, which seems to have issues.