project: smart thermostat – nest and hive

Nest with the unofficial home-made stand – the official version of this plastic shape is £35

The Google nest thermostat or its Hive equivalent are items which I’d be happy to pay for rather than make. A first reason is that we rely too much on warmth, and a second reason is that it’s a premium product with software that makes setting a schedule almost a pleasure. You can change any setting with the software on the web, mobile app or the device itself. The system learns and keeps a record of your energy use. One could make such a device with two relays but for once I’m impressed with the value it adds. For example, the app on your phone can know whether you’re away or driving home and can set the heating accordingly – thus you do not heat an empty home.

Adding a smart thermostat to Home Assistant

Until recently you could sign up for a nest developer account, collect some credentials to allow you to suck all the data into Home Assistant. I did that and I’ve listed what’s available below. Other brands of thermostat provide similar functions. See Home Assistant thermostats

This is Home Assistant’s thermostat card – easy and fast to control if you’re away from home. I don’t need this simply because the actual thermostat is to hand anyway. However it’s available to adjust via a Home Assistant automation should you need more or less heating.
Here you see the set target and actual room temperatures of two nest thermostats. I spotted the odd target temperature settings during the night and corrected that.
This shows all of the parameters available when you connect via the Nest Developer API. Thank Google that this is closed to new accounts

Installing nest differently

Having seen many nest thermostat installations on youtube, I couldn’t see why the nest heatlink (below) needed to be near the heating wiring box. I had a traditional programmer on a hall wall behind which were all four wires for the heatlink. (There was a live, neutral plus the two hot water and radiator control wires). I considered it better to have the actual Nest thermostat in a living room rather than a hall. So the heatlink went in the hall to cover the holes left by the old programmer.

This heatlink also has a permanent 12v supply that I will one day use for some other device.

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