Honeywell RTH8500 Installation Manual page 13

Alternate wiring (conventional systems) About your new thermostat
If labels do not match terminals, connect
wires as shown here (see notes, below).
Remove metal jumper connecting R and
Rc only if you must connect both R and
Rc wires.
If your old thermostat had both R and
RH wires, remove metal jumper. Connect
the R wire to the Rc terminal, and the
RH wire to the R terminal.
If your old thermostat had only 1 C or
C1 wire, connect it to the C terminal. If
your old thermostat had 2 C or C1 wires,
wrap each separately with electrical tape
and do not connect them.
RC
R
W
Y
G
C
Y2
W2

RTH8500
Rc
2
R
2
W
Y
G
C
3
Y2
W2