Identify Wires You Will Not Use - Honeywell RTH4300B Installation Manual

RTH4300B Programmable Thermostat

Identify wires you will not use

If any wires are not attached to terminals in your old thermostat, do not connect them
to your new thermostat.
If a wire is attached to a terminal marked "C" or "C1," disconnect it. You will not
connect it to your new thermostat.
Wrap the bare metal ends of each unused wire with electrical tape, so it cannot touch
and short out other wires.
Do not use unconnected wires.
Do not use C or C1 wire.