Turn off power to the HVAC system at the breaker
Remove the old thermostat cover
Take a photo of the existing wiring
Label each wire by its terminal letter
Remove the old thermostat base
Check the new thermostat’s wiring diagram
Match each labeled wire to the correct terminal
Connect the wires to the new thermostat base
Mount the new thermostat base to the wall
Attach the thermostat display or cover
Restore power at the breaker
Follow the thermostat setup instructions
Test heating and cooling operation