Honeywell RTH8500 User Manual page 22

Installing your thermostat
8 Install battery.
Insert the coin cell battery
(included), observing the
correct polarity.
Note:
A correctly inserted
battery will extend about halfway
out of the battery slot on the
thermostat, allowing for easier
removal.
This battery maintains time and
date during power outages. It
does not power the thermostat
(C wire required).
69-2715EF—07
Thermostat interior
20
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