When your central heat or air conditioning unit suddenly stops working, you should check to see whether the problem lies with your old thermostat. This is often the case. Replacing the thermostat might initially appear to be a simple task, but once your remove the cover from your thermostat, you might become intimidated by the wires and connections. As long as you pay close attention to where the wires attached to your original thermostat, you can hook up the wiring on your new Honeywell thermostat model RTH111B without mistakes.
Turn off the circuit breaker to your central heating and air conditioning unit. The low-voltage thermostat wires are powered through the main heating and air system in your home. Remove the cover/body from the old thermostat to expose the internal wiring. Confirm the power is off by testing the wires for voltage using a non-contact voltage tester.
Trace each thermostat wire to its terminal screw. Look next to each terminal screw for its identifying letters or numbers. Write each terminal screws' identifier on a small piece of masking tape and wrap the tape around the wire attached to the screw. You might have additional wires that are not attached to the thermostat; do not worry about identifying any loose wires as you will not attach them to the new Honeywell thermostat model RTH111B.
Loosen the wire terminal screws on your old thermostat. Pull the thermostat wires from beneath the thermostat screws.
Remove the screws holding the original thermostat to the wall. Pull the old thermostat from the wall and tape the wires to the wall so they don't fall into the wall cavity.
Thread the wires through the opening in the new Honeywell thermostat. Attach the thermostat's wall plate to the wall with the provided anchors and screws.
Wrap the thermostat wire labeled "Y," "Y1" or "M" around the terminal screw marked with a "Y." Wrap the wire labeled "F" or "G" around the screw marked with a "G." Wrap the wire labeled "W1," "H" or "W" around the screw marked with a "W." Tighten the thermostat terminal screws.
Pay close attention to the terminal screws marked as "Rh" and "Rc." If you only have a wire labeled "R," wrap it around the "Rh" terminal screw. If you have an "R" and an "Rc" wire, use needle-nose pliers to grab the small jumper wire that connects the "Rh" and "Rc" terminals together (on the new thermostat) and pull the jumper wire from beneath the two terminal screws. Wrap the "R" wire around the "Rh" screw and the "Rc" wire around the "Rc" terminal screw. If you have an "R" wire in addition to an "Rh," "4" or "V" wire, wrap the "R" thermostat wire around the "Rc" terminal screw and the "Rh," "4" or "V" wire around the "Rh" terminal. Tighten the "Rh" and the "Rc" terminal screws.
Install batteries into the wall plate, then install the thermostat body onto the wall plate. Turn on the circuit breaker to your central heating and air conditioning unit.