Most systems have a simple single speed fan. They can be either on or off. But in rare cases, a system's fan speed can be controlled by a thermostat. This lets you change how much air the fan pushes through your system’s vents to warm or cool your home.
- The Nest Learning Thermostat is compatible with system fans that have one, two, or three speeds.
- The Google Nest Thermostat E is only compatible with single speed system fans.
- Variable speed fans, high voltage forced air systems with fans, and proprietary systems with fans, aren't compatible with either the Nest Learning Thermostat or the Nest Thermostat E.
Multi-speed systems and the Nest Learning Thermostat
The Nest Learning Thermostat is compatible with most systems that have a single 24 volt fan wire. The most common labels for these wires are G or G1. Use our compatibility checker to help determine if you can install a Nest thermostat in your home.
If your system has more than one fan wire, you’ll need to contact a Nest Pro to have your Nest thermostat installed. Some systems that need to be installed by a Nest Pro include systems with G2, G3, GM, or GH wires.
Important: Installing a Nest Learning Thermostat to control a multi-speed fan can be complicated, and incorrect settings can damage your system, your Nest thermostat or both. We strongly recommend Nest Pro installation for all multi-speed fan systems with more than one fan wire. Your system will need to be controlled with 24 volt wires and your Nest thermostat must have software version 5.6 or later.
How the Nest Learning Thermostat works with multi-speed fans
Your thermostat will work a little differently if you have a single fan wire or if you have several.
If you have a multi-speed fan with a single 24 volt wire, the speed of your fan is not controlled by your thermostat. Instead your fan’s speed is programmed into the HVAC equipment’s control board. This means you’ll be able to use your Nest Learning Thermostat to adjust the temperature and turn your fan on or off, but you won’t be able to control your fan speed.
If you have more than one fan wire installed, your Nest Learning Thermostat will determine your fan speed automatically, or you can select a speed in your settings menu.