Read the Instructions
Before you begin, read the manufacturer's instructions that were sent with the thermostat. These pages will guide you by step-by-step instructions on how to install the device before you begin.
Turn Off Power
Before doing any electrical work, shut off the power. In this case, the circuit feeding the furnace controls the power to the thermostat. Go to the breaker or fuse panel and turn the breaker off or fuse out.
Remove Old Thermostat
Take the face plate off of the old thermostat and remove the mounting screws. This will expose the thermostat base. Carefully remove the wires from the thermostat base. Mark down on a piece of paper which color wire goes to what terminal. It should be red to "R" for power, white to "C" for common, blue to "Y" for cool, and green to "G" for fan. Be sure to tie the wires together so that they don't fall into the wall.
Thermostat Base Removal
Remove the old base by removing the mounting screws. These may be screwed into plastic anchors. These mounts probably won't work with the new thermostat.
Install New Thermostat Base
In order to install the new base, you'll need to install the new mounting hardware. Usually the manufacturer will send some plastic anchors. With a drill bit slightly smaller than the anchor, drill the holes for the new base. It's a good idea to level the thermostat for looks.
Wire The New Thermostat
Using the paper that you wrote the wire colors on, connect the wires accordingly to the new thermostat. Remember, each color goes on only one terminal screw.
Attach The New Thermostat
Now attach the new thermostat to the base and install the cover. Depending on the model, this may be mounted with screws.
Turn Power On
The final step is to turn the power back on and test the thermostat. Check to see if the thermostat is functioning properly. It's just that simple!
- Be sure to tie the thermostat wire back so it doesn't fall down inside of the wall.
- Take note of the wire colors and the marked terminals they are connected to. This is important for reconnecting.
What You Need
- Wire Strippers
- Scratch Awl (for making a hole in the drywall for the new plastic anchors)