Not necessarily. Many thermostats use different lettering to mark wiring terminals. The Lyric app provides a list of the most common markings. Please be sure you've scrolled down in the Lyric app to view the entire list of terminals. If you do not see your terminal listed, please contact the Lyric Technical Support team at 1-800-633-3991 and they will help you determine if the Lyric thermostat will work with your system.