Honeywell RTH9580 Wi-Fi User Manual page 10

Installing your thermostat
2 Remove old thermostat faceplate
and leave wires connected.
2a Take a picture of the
wire connections for later
reference.
2b If no wire is connected to
a terminal labeled C or no
C terminal exists on the
old thermostat, view the
Alternate Wiring videos at
wifithermostat.com/videos
Important!
C wire is required
and is the power source for your
thermostat. Without a C wire, your
thermostat will not power up.
69-2809EF—03
C
Terminal
designation
If you have an older thermostat
with a sealed mercury tube, turn
to page 2 for proper disposal
instructions.
8
Note:
You will need a
picture of your wire
connections to wire the
new thermostat.
M33823A