Forced-air systems run the fan whenever they're heating or cooling. If your forced air system has a separate fan wire in your Nest thermostat's G terminal, you can run the system fan when it's not heating or cooling. If not, your fan will only run automatically when your system is heating or cooling.
If you have a system with a dedicated fan wire, you can manually turn on the fan with the app or your thermostat, or set a fan schedule. For example, you can set the fan to run all night and automatically turn off in the morning.
Important things to know about fan control
If there's a wire in your thermostat's G terminal
- You can run your system's fan independently of heating or cooling. This allows the fan to run even when heating or cooling isn't active.
- Fan timer can start even if the thermostat is set to Off.
- You can set the fan to run a fixed schedule or manually set it to run. However, your fan can’t start based on schedule if the thermostat is set to Off.
Tip: Fan schedule can't be set to automatically run or switch off when you leave or come home.
- The temperature screen will show a fan icon when your fan is running because of your fan schedule, or if you've turned your fan on manually. Learn about Nest thermostat displays.
If there isn't a wire in your thermostat's G terminal
- The fan can only run while your system is actively heating or cooling.
- Fan control options won't be shown on your thermostat or in the app.
Fan settings enhance comfort and energy efficiency
Longer fan usage may help to even out the temperatures between rooms in your home, but the fan can use a lot of energy and increase your electric bill.
Extended fan usage will increase your system's runtime, which may require you to replace the air filter sooner. To help you know when it's time to replace your system's filter, refer to Air filters and filter reminders.
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