To replace a two-wire manual thermostat, purchase a battery operated two-wire digital thermostat, remove the old unit and replace it with the new one. Installation takes only a few minutes.Continue Reading
Most digital thermostats use a third wire that provides power from the home's electrical supply. If the third wire is not already in place, a battery-powered model is a good option. Replacing the two-wire unit with a standard digital thermostat involves running power from the electrical panel to the thermostat, usually requiring the services of an electrician or HVAC professional.
Turn off the circuit breaker that powers the furnace to prevent damage. Remove the cover from the manual thermostat. Locate and remove the screws that hold it to the wall. Loosen the screws that hold the wires in place and remove the wires from the thermostat. Tape the wires to the wall so they do not slip through the hole. Contact your local waste disposal company about recycling the old thermostat, which is likely to contain mercury.
Attach the two wires to the corresponding terminals on the new thermostat. Attach the new unit to the wall in place of the old one. Install the battery and place the cover on the thermostat. Follow the manufacturer's directions for setting the new unit.