How to Wire a Honeywell RCT8100A

Power off your furnace. Do not work on an active furnace.

Take the old thermostat off of the wall, but leave the wires attached. Most thermostats will have labeled screws to which the wires attach. Place a piece of electrical tape around each wire and write the letter of the screw on that wire. If there are unattached wires, tape over the bare metal.

Remove the screws holding the wires in place. Hold on to the wires to prevent them falling back into the wall.

Loosen the screws for the terminals on the Honeywell RCT8100A thermostat. Insert the bare metal of the wire into the terminal with the matching label. Tighten the screw.

Match a wire labeled "F" to terminal "G." Match a wire labeled "Y1" or "M" to terminal "Y." Match a wire labeled "W1" or "H" to terminal "W." Match a wire labeled "Rc" or "R" to terminal "Rc." Match a wire labeled "R," "Rh," "4" or "V" to terminal "Rh." Note, if you have more than one of the "R," "Rc" or "Rh" wires, remove the jumper between the two terminals. If there is only one, attach it to the terminal labeled "Rh." Leave wires labeled "C," "X" or "B" disconnected.

Place the jumper on the back of the thermostat into position "HG" for a gas or oil furnace and into position "HE" for an electric furnace.

Install batteries and mount the thermostat to the wall with the mounting holes. Switch the furnace on and test the features of the Honeywell RCT8100A thermostat.