How to set up your Nest thermostat (3rd gen or earlier) and Nest Thermostat E

• If you installed your Nest thermostat yourself, select Homeowner to answer a few questions about your heating and cooling system.
• Nest Pro has options that only trained professional installers should use for complex systems.
  Warning: Incorrect settings in Pro Setup can cause your HVAC system to malfunction and may damage it.

If your system has a heat pump with an auxiliary heat source, you’ll be asked if your system is dual fuel or single fuel.

If you have a dual fuel system, you will need to have a trained professional set up your thermostat. You can find a trained Nest Pro installer in your area with our online Pro finder.

Learn more about dual fuel

If you have a conventional system installed, your thermostat will ask about the fuel source for your heat and how that heat is delivered. The Nest thermostat uses this information to determine how to control your heating and cooling system.

If you know your fuel source, select it from the list.

Choose I don’t know if you’re not sure. You can always go back later to change your fuel source in the Settings   Equipment menu.

1. Choose O or B
   • ​​The only way to tell for sure if the wire is O or B is to check your heat pump’s manual. Look it up online or contact the manufacturer.
   • Most systems have an O wire, so O is a good choice if you can’t tell.
     Note: If you choose I don’t know, your thermostat will automatically select O.
2. Test your system
   Don’t worry if you made the wrong selection. Your Nest thermostat will ask you to run a system test at the end of setup. Don’t skip this important step and follow the instructions closely.
   • ​​You’ll know that you’ve chosen the right O or B wire if your system behaves normally during the test. 
   • You’ve chosen the wrong wire if your system heats during the cooling test, or cools during the heating test. If you have only heat or only cooling, and you’ve chosen the wrong wire, then your system won’t heat or cool during the test. 
3. Change the setting if needed​
   • If you need to change the O/B wire setting, go back and change the O/B wire setting with your thermostat in Settings   Equipment  Heat Pump.

• Add your thermostat to your account so you can finish setup with the app. When you’re done, you can control it with your phone, change settings remotely, get important notifications, and more.
• You’ll need to be at home near your thermostat to add it to your account. You can’t add it remotely. 
• You’ll also need the latest version of the Nest app. The app will walk you through each step.

Simply follow the Nest app’s instructions to add your thermostat to your account. If the app asks you to scan the QR code, use your phone’s camera.

Troubleshoot QR code scanning

If you have other issues, go to the following article:

Troubleshoot adding a thermostat to your account

How to add your thermostat after installation

Follow these instructions if:

• You want to connect your thermostat to your account after you’ve completed installation and setup. 
• You needed to remove your thermostat from your account for some reason and want to add it back.

1. ​On the Nest app home screen, tap Settings .
2. Tap Add product. The app will switch to a camera view to scan the thermostat’s QR code.
3. To get the QR code, go to your thermostat and press it to open the Quick View menu.
4. Choose Settings .
5. Turn the ring to select Nest app and press to open it.
6. Select QR code. Your thermostat will show you a unique QR code to scan with the app.

Troubleshoot QR code scanning