Honeywell RTH8500 Series User Manual page 6

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
C wire is required and
Important!
is the primary power source for
your thermostat. Without a C wire,
your thermostat will not power up.
3 Label wires.
Do not label by wire color.
the supplied sticky tags to label
each wire as you disconnect it.
Label wires according to the old
thermostat terminal designations,
not by wire color.
If no tag matches a
Note:
terminal designation, write the
appropriate letter on a blank
sticky tag.
4 Remove wallplate.
Remove the old wallplate from
the wall after all wires have been
labeled and disconnected.
33-00133ES—01
If you have an older thermostat with a
sealed mercury tube, turn to page ii
for proper disposal instructions.
Terminal
designation
Use
4
C
C
Sticky tag
Blank tags
Terminal
designation