Honeywell RTH4300B Guide D'installation page 8

Installation Guide
Did you purchase right thermostat? Count wires to check.
Count the number of wires coming out of the wall and attached to terminals in your
old thermostat. If any of them are attached to a terminal marked "C" or "C1" do not
count that wire in your total.
If the total (not counting C or C1) is 5 wires or less, proceed to the next page. If you
have 6 or more wires, your new thermostat may not be compatible with your system.
Stop installation and call 1-800-468-1502 for advice.
Do you have 6 or more wires? If so, stop now.
You may have purchased the wrong replacement
thermostat.