I added this article as I think it may be helpful to people looking to install this product. The model I have fitted is the Google Nest Hello, wired doorbell.
I previously has a battery operated doorbell, powered by 4 x D cells, the batteries dated from at least 20 years ago, more likely 30 and it was powered by 6v. The wire extended from the chime box, all the way to the front door, and a short (press of the bell) would cause the chime to ring.
You will note the Sainsburys batteries, original and still working. Anyhow, this system wasn’t for the the internet age, and I wanted something that was more flexible. I only mention my old system, so you can gauge what may be reused or integrated with the new Nest system.
The Nest doorbell is powered by wire, I wanted something that wasn’t battery-powered as this unit has the option to steam and record 24×7 onto the cloud. The first thing I noticed was the two terminals on the rear of the doorbell, they don’t seem to be marked + or -VE.
That did seem strange, but I read online the unit could be powered from a 12v supply. I connected the Nest to a 12v supply, and my WiFi and sure enough a picture was streaming. Success. Oh not quite. Every time the bell was pushed, the unit would go offline. So I did some further reading and found the unit required 18v AC.
So that would explain why they didnt have + or – on the two connection screws, but maybe not why it worked on 12v DC. In some online articles people has used 12 or 24v DC supplies, but this proved unreliable for me. I assume the bell simply rectified this AC to DC and most likely uses 5v.
So back to Amazon, to order an 18v AC wall wart, as everything I had in my draw was DC. It turns out in the USA typically people run their doorbells on 18 to 24v AC, but then this is the land that uses F and Feet and inches!
In answer to the question what did I reuse from my old system, the answer is nothing, the bell just needed 18v AC via the wires and a WiFI network. When someone presses the bell, my phone beeps and the google mini speaker rings a bell. I understand you can purchase a separate bell, but that is not something I have done.
So in its most basic form, you just need the Nest Hello doorbell and an 18v AC supply. The picture quality seems excellent, and if you pay for the cloud storage it will record 24/7 and keep 60 days of events online. Each time someone pushes the bell you have the option to capture their face (subject to local laws). The phone app then asks if you recognise the person and if you do you can add a name. This is especially good, as next time the person pushes the bell in the house it announces “The postman is at the front door” or “The mother-in-law” and you can ignore and pretend to be out.