Honeywell RTH8500 Series User Manual page 8

Installing your thermostat
The Wi-Fi thermostat requires a C wire to operate. The C, or common, wire
Important!
brings 24 VAC power to the thermostat. Many older mechanical or battery operated
thermostats do not require a C wire. If you don't have a C wire, try:
• Looking for an unused wire that is pushed into the wall. Connect that wire to C and
check that it is connected to the 24 VAC common at your heating/cooling system.
Check the video section at wifithermostat.com
Not all heating/cooling systems label the 24 VAC common C. Check your system
Note:
manual or contact the manufacturer to find out which terminal is the 24 VAC common.
View the Alternate Wiring videos at wifithermostat.com/videos
Wiring
For
conventional
conditioner), see page 6. See "Glossary" on page 27 for further definition.
For a
heat pump
definition.
Wiring (conventional system)
7A Wire the Wi-Fi thermostat to your conventional system.
a Starting with the C Wire, match the sticky tag on the
wire to the terminal labels.
You must have a C wire. See page 6.
b Loosen screw, insert wire on inside edge of
terminal, then tighten screw.
c Verify wire is firmly secured by gently pulling
on wire.
d Repeat steps a–c for all other wires.
e Push any excess wire back into the wall
opening after all wires are installed.
f Continue to page 9.
Labels don't match?
wiring key on page 7.
33-00133ES—01
heating/cooling systems (natural gas, oil or electric furnace, air
system, see page 7. See "Glossary" on page 27 for further
See alternate
E/AUX
Note:
application might be different
than the wiring from above.
6
Remove metal jumper
if you have both
only
R and RC wires
HEAT PUMP
CONVENTIONAL
RC
Y2
L
W
W2
K
K
The wiring for your
RC
R R
O/B
Y Y
G G
C C