Most smart thermostats today that are Wi-Fi enabled or have a color touch screen may require constant power through a thermostat common wire. This ensures your thermostat has a continuous flow of power to function properly. There may be a few smart thermostat models that don’t require a C wire and can operate with batteries. You should always ensure proper wiring as needed for your HVAC system and corresponding thermostat (with or without a C wire). Check your HVAC system compatibility to see if you need a C wire for your smart thermostat.
This common wire kit eliminates the need to run a new wire throughout your home. Installation is easy. Watch the videos below for more info.
For use with the Sensi Touch Smart Thermostat. The Sensi Smart Thermostat doesn’t require a C wire for most applications.
Does not work with 2-wire systems
![Emerson Sensi smart thermostat](https://cdn11.bigcommerce.com/s-48jto9uofh/product_images/uploaded_images/emerson-sensi-thermostat-78-cooling.png?t=1650045842)
The Sensi™ Smart Thermostat works with HVAC equipment found in most homes and does not require a Common wire (C wire) in most applications. A C wire is only required for heat only, cool only and heat pump systems.
![Emerson Sensi Touch smart thermostat](https://cdn11.bigcommerce.com/s-48jto9uofh/product_images/uploaded_images/st75u-1-black-emerson-sensi-touch-78-cool.png?t=1650045897)
For the Sensi™ Touch Smart Thermostat, all system types require a common wire (C wire).
C wire help made simple.
Do I need a C‑wire?
If you're wondering what a C wire is or how to look for one, you’ve come to the right place. Our step-by-step videos will guide you through the process and answer all your questions.
Basic C wire introduction
Learn about the basics of common wire installation by watching this video. You will also be guided on how-to and when-to connect C wires to thermostats. It also shows three different scenarios to choose which methods works best for you.
Finding and using an unused wire as a C wire
Sensi thermostats require a common wire to complete installation. This video will guide you in checking if you have a common wire, or an unused common wire from your previous thermostat that you can use to install your Sensi thermostat.
Using the G-wire as a C wire
If you can not find an unused wire or common wire, you can also use for fan wire or G-wire as a common wire. This video serve as a second option incommon wire installation.
Installing Common Wire Maker Kit
If there is not an extra unused wire running from the thermostat to the furnace, and using the G-wire as a common wire is not an option, in most cases, installing a Common Wire Maker Kit is the best solution.
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