Carrier produces a variety of thermostats for the home, some programmable and some non-programmable. The default setting for a Carrier thermostat displays temperature in degrees Fahrenheit, but you can change this to Celsius if you wish. Multiple thermostats are available on Carrier's website.
Open the door on the Comfort Programmable Thermostat and press the "Home" and "Sleep" buttons simultaneously for about three seconds. These buttons are just below the display. Press the "Mode" button on the upper left to change temperature from "F" (Fahrenheit) to "C" (Celsius). When you are finished, press "Done" on the bottom right.
Press and hold the "Mode" button on the top left of the Carrier Non-programmable Large Screen Thermostat for about three seconds. You will see "U1" on the display and the letter "F" in the center. Press the "Up" or "Down" buttons on the right side of the thermostat to change from "F" (Fahrenheit) to "C" (Celsius). When you are finished, press the "Fan" button on the bottom left.
Open the door on the Edge Programmable Thermostat and locate the buttons underneath the heat and cool setpoints; these are on the right side of the bottom row of buttons. Hold these two buttons down simultaneously until the screen displays reset reminders and "01" in the lower right corner. Press the up arrow until "01" changes to "02" with an "F" next to it. Press the bottom-right button underneath the letter "F" until "C" appears. Press the "Done" button and close the door.
Open the door on the Edge Non-Programmable Thermostat and press the "Features" button for about three seconds. The screen will display an "01." Press the up button under the number "01," which will change to "02" with a letter "F" for Fahrenheit next to it. Press the "sleep" button under the "F" and it will start flashing. Then press the up or down button to change the "F" to a "C" for Celsius. Press "Done" and close the door.