Shut off the power to the wall or area where you'll be installing the Intertherm thermostat. Flip the switch on the appropriate circuit breaker to "Off."
Disconnect the old thermostat. Unscrew it from the wall but leave its wires connected momentarily for guidance. Notice where each goes and how they are color-coded before entirely detaching each terminal.
Open up the rear portion of the Intertherm thermostat. Unscrew each terminal and look for the small letters that mark where to place each wire. "R" represents red, "Y" represents yellow, "G" represents green and "W" represents white.
Connect the color-coded wires to the corresponding terminals. Fasten the screws so that they hold the wires firmly in place.
Drill new holes in the wall for the device itself, if necessary. Utilize preexisting holes if possible.
Screw each corner of the thermostat into the wall. Check it to make sure it's secure.
Restore power by flipping the circuit breaker back to the "On" position.