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User Manual
6
homexpert
tm
by Honeywell THR840DUK Digital Thermostat
7
The THR840DUK is an easy-to-use thermostat designed to maintain a comfortable environment when you
are at home and reduce energy costs when you are away. One touch of the ECO button overrides the normal
temperature to maintain a lower, energy-saving level for a specified period of time (see page 11).
About your new thermostat
Your new thermostat is pre-programmed and ready to go. Just check the steps below and change
settings if needed:
1 Install and set up thermostat
(if this has not been done by a professional installer) ..........................................................See pages 12-24
2 Select heating (default) or cooling mode .....................................................................................See page 9
3 Set desired indoor temperature ................................................................................................See page 10
QUICK START GUIDE
Quick reference
Cooling system is
running (see page 9)
ECO mode countdown
(see page 11)
Heating system is
running (see page 9)
Current temperature
(or target temperature
when flashing)
ECO mode is on
(see page 11)
Press to change
temperature
(see page 10)
Press to turn ECO mode
on or off (see page 11)
Press to turn thermostat
on or off (see page 8)
System fault
(see page 25)
Low battery warning
(see page 18 to replace
batteries)
Standby symbol
appears when
thermostat is off (see
page 8)
25.0
°
c
eco
Appears when
target temperature
is showing