When installing a new digital thermostat there are a couple of things to figure out. Is your home a single zone thermostat or a multi zone thermostat? If you have one furnace and one central air unit, that would be a single zone. If you have more than one furnace or air unit you would have multi zones in your home. Older homes may only have two thermostat wires, so you may have to install a new thermostat wire. Accomplishing this is not a big job, and would take a licensed electrician about an hour.
THINGS YOU WILL NEED
Needle nose pliers
Disconnect the power to the furnace using the emergency cut off switch, or the main breaker. Proceed to the thermostat, and twist off the outer cover of the thermostat. Loosen the two screws holding the thermostat to the wall, and turn thermostat until the thermostat is loose from the wall.
Loosen the screws on the back of the thermostat that are holding the wires in place. Be sure to mark which zones the wires were connected to. Tape all the wires to the wall. Doing this, will not let them fall inside your wall. We do not want to remove or cut sheetrock to get them back out of the wall.
Using the new thermostat, you will need to line up with the old holes from the previous thermostat. Follow the enclosed directions for wiring the wires to the according terminals. You will have at least 3 wires for the digital style thermostat; a black one and a white one. These will turn the furnace on and off. The third wire will power the thermostat.
Snap the new thermostat cover into place. When it lights up you will need to follow the prompts to set the temperatures. For instance; when you wake up, leave to work, when you return home from work, and when you go to bed.
Mount the out door sensor at this time using a drill. You will want to turn this on while standing next to the thermostat to make sure it registers. This is a battery device that will tell you what the temperatures are outside, and read them back to the thermostat inside your home. Place the bracket around the sensor, and place on the north side of your home. Make sure it is above the snow line if you have snow where you live.