To install a thermostat, first remove the cover plate, then turn off the power to the heating and cooling system. Remove the old thermostat by unscrewing the mounting bolts and label the wires with tape for identification later. Install the new thermostat by connecting the low-voltage wires and attaching the screws. Install batteries, if applicable, and restore power to the heating and cooling system.
While the old thermostat assembly is off, there are a few additional steps to consider. If the wires are short, consider taping them to the wall to avoid having them fall completely into the wall. Otherwise, the wires may be difficult to recover, and they can cause damage to the home. Also, perform a visual check to ensure the wires are in good condition. If they are not, consider replacing them prior to installing the system.
When installing a new thermostat, keep in mind that a previous home or building owner may have incorrectly connected or labeled wires in the past. Therefore, check to confirm that the terminal's colors correspond to the proper connection. The red wire should connect to the "R" terminal and the white to the "W" terminal.
After installing the unit, verify that the thermostat turns on the heating or cooling system. If the set temperature is colder than the room temperature and the unit is on air-conditioning mode, the air should come on.