We're working with a 3rd generation Google Nest Thermostat, which is what you should be getting if you buy a new one. Nest has gone to some great lengths to make this a simple install, and while that's certainly true for the most part, you're still wiring up controls for an expensive system that heats and cools your entire home, so it's important to know what you're doing before going in.
Hopefully, before you bought your Nest thermostat you checked the compatibility tool on the Nest website. If not, go ahead and do that before you disturb too much of the box's contents.
Depending on your home's setup, you'll find two additional plates in the box. The metal one is for homes that have the thermostat on an electrical box, while the plate is for covering up the lack of fresh paint behind that old rectangular thermostat.
Now before you go ripping out a bunch of old wires, do two things. First off, shut all the power off for your AC system from the breaker. You'll thank me later when you don't get electrocuted.
Second, take a picture of your existing thermostat and wiring, then make sure to use the handy sticky labels in the installation guidebook to label said wires. You can never have enough references to go back to later.
As with all Nest products, make sure to head into your Nest app and add a new device, then scan that QR code on the back of the thermostat and get going through the setup.
Now for the wiring, which can be tricky. Some thermostats, like mine, have a single row of wires but different labels on top and bottom, which is deceiving if you haven't seen this before. In my case, I've got a heat pump system and needed to follow the wiring letters on the bottom row. Wiring it like the top row will cause the system to blow out hot air instead of cold, and could very well blow a fuse. Not the end of the world, but it's uncomfortable for a while at the very least.
I prefer to trim my cables and re-strip them so that it's got fresh connections to work with. It also helped with the horrible jumbled mess they left in this box when installing the last thermostat.
You'll be wiring up the little plastic disk first. The wires pop right into each port, and the buttons will be fully flat with the frame when they're properly inserted. These are clamps that hold the wires in when inserted and will let go of the wire when the button is pushed further down. Remember that if you need to remove a wire later.
Depending on the wires you had before and what you selected in the Nest app, you may need to put different labels in different places than the previous thermostat had. I found it easiest to split screen the setup diagram and the picture I took of the old thermostat for a better reference. If your phone can't do this you'll just have to swap back and forth.
There's always the possibility that something didn't quite match up in the wiring, despite Nest having a rather good handle on how most systems are wired. Mine, for instance, blew out hot air at first and then blew a fuse. If you find yourself in any of these predicaments, head on over to our quick troubleshooting guide for some ideas on what you could do to fix things up.
Once you're done, make sure the wires are flush with the mounting plate, otherwise, you won't be able to properly click the thermostat into place. Switch the power back on and you should be in business, ready to set up the software portion of this bad boy.
This section is mostly following through the prompts of selecting where you're located, where the thermostat is located, and setting up the WiFi connection. Once you get to the equipment detected section, make sure the wires on the thermostat match up with what you expect on the app. Make sure you select the proper system type so the thermostat knows how to correctly heat and cool the home.
One of the cooler settings is called Eco mode, which will automatically set the temperature while you're out of the house to something higher or lower than would typically be comfortable to spend long amounts of time in. Once you're all done with the prompts you'll be given a key to pair with the app. This security key ensures that no one else can use your thermostat and acts as a two-step verification.