The first step to removing your existing thermostat is to turn power off to your heating/cooling system at the circuit breaker box or at the system switch or on your heating /cooling unit.

Next, you must verify that the power has been turned off. To do this go to your thermostat and try raising or lowering the temperature. Many digital thermostats contain backup batteries which makes it a bit difficult in telling if the power is on or off. If you like you can open the thermostat and remove those batteries. Now you should be able to see if there is still power to the actual thermostat itself. You can also listen to see if lowering or raising the thermostat activates your HVAC system or not.

Once you have verified there is no power to your HVAC system itself it is time to remove the front of the old thermostat. While doing this it is very important that you keep the wiring from your HVAC system to the current thermostat because you will want to record exactly how your system is wired so you can duplicate with the new Honeywell Lyric thermostat. At this point with the front cover removed you should now be able to see how your current thermostat is wired. Be on the look out for thick black wires attached with nuts. Chances are if you do have these thick wires with nuts you have a high voltage system and you cannot use the Honeywell Lyric thermostat.

Now, make sure that you have already downloaded the Honeywell Lyric App in the Apple App store or  Google's Play app store. With the Lyric App now open you will locate a option to take a picture of your current wire configuration go ahead and do so. The next phase will be to record your current wiring in the section of the Lyric App by selecting the terminals on your old thermostat that have wires connected to them.

Once all the wires have been recorded, disconnect them from your old thermostat and don't let them fall back into your wall as you will still need them to Install the Lyric thermostat.