Changing Temperature Readings from Fahrenheit to Celsius At the controller, the site personnel or technician must select “Settings”. Select “Site Details” Select “Lang/Locale” field and change from “English [en_US}” (Fahrenheit) to “[English [en_CA]” (Celsius) Note: This change is effective only on controllers, not thermostats. TS200 thermostat screens may allow the change but revert immediately if the controller is not set to support the desired display.