Removing an old device from your Google Home account is easy to do. Here are the steps:
Open the Google Home app on your device.
Select your account.
Select the settings button (the three vertical dots in the upper right corner).
Select Home Control.
Select the device you wish to remove.
Press the trash can icon in the top right corner to remove the device from your account.
Confirm that you would like to remove the device.
And that’s it! You have successfully removed the device from your Google Home account. If you ever need to add it back in, simply follow the same steps but press the ‘+’ sign in order to add it back in.