User Manual
THR842DUK Wireless
Digital Thermostat
50051983-001 Rev. A
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Contents
About your new thermostat
Appendix
What is a room thermostat? ..................4-5
QUICK START GUIDE............................. 6
Quick reference to controls ....................... 7
In case of difficulty .............................26-29
Warranty information............................... 30
Declarations, disposal & recycling ........... 31
WARNING: This product must be correctly installed and configured to work properly (see
pages 12-23). If you are not experienced in wiring electrical equipment, we recommend
professional installation to avoid possible personal injury or equipment damage.
Operation
TIP: After installation, see the QUICK START GUIDE on page 6 to customise and begin using
your new thermostat right away.
On/off switch ............................................ 8
Heating or cooling control ......................... 9
Temperature control................................ 10
Energy-saving ECO mode ...................... 11
NOTE: This symbol will flash on the screen
when battery power is low. Remove cover and
replace batteries with two fresh AA alkaline
batteries (see page 16).
Installation and setup
®
System installation .................................. 12
Relay box installation .............................. 13
System wiring ....................................14-15
Battery installation & testing ...............16-17
Thermostat installation .......................18-19
System test ............................................ 20
Installer setup ....................................21-25
Copyright © 2010 Honeywell International Inc.
homexperttm by Honeywell is a trademark of Honeywell International Inc. All rights reserved.
3
User Manual
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
What is a room thermostat?
...an explanation for householders
A room thermostat simply switches the heating system on and off as necessary. It works
by sensing the air temperature, switching on the heating when the air temperature falls
below the thermostat setting, and switching it off once this set temperature has been
reached. Turning a room thermostat to a higher setting will not make the room heat up
any faster. How quickly the room heats up depends on the design of the heating system,
for example, the size of boiler and radiators.
Neither does the setting affect how quickly the room cools down. Turning a room thermostat to a lower setting
will result in the room being controlled at a lower temperature, and saves energy.
If your heating system is a boiler with radiators, there will usually be only one room thermostat to control the
whole house. But you can have different temperatures in individual rooms by installing thermostatic radiator
valves (TRVs) on individual radiators. If you don’t have TRVs, you should choose a temperature that is
reasonable for the whole house. If you do have TRVs, you can choose a slightly higher setting to make sure
that even the coldest room is comfortable, then prevent any overheating in other rooms by adjusting the TRVs.
Room thermostats need a free flow of air to sense the temperature, so they must not be covered by curtains
or blocked by furniture. Nearby electric fires, televisions, wall or table lamps may prevent the thermostat from
working properly.
The heating system will not work if a time switch or programmer has switched it off.
The way to set and use your room thermostat is to find the lowest temperature setting that you are
comfortable with, and then leave it alone to do its job. The best way to do this is to set the room thermostat
to a low temperature – say 18°C – and then turn it up by one degree each day until you are comfortable with
the temperature. You won’t have to adjust the thermostat further. Any adjustment above this setting will waste
energy and cost you more money.
4
5
User Manual
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
About your new wireless thermostat
Quick reference
The THR842DUK 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).
Cooling system is
running (see page 9)
ECO mode is on
(see page 11)
QUICK START GUIDE
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 & relay box
(if this has not been done by a professional installer).......................................................... See pages 12-25
2 Select heating (default) or cooling mode ..................................................................................... See page 9
ECO mode countdown
(see page 11)
Heating system is
running (see page 9)
Press to turn ECO mode
on or off (see page 11)
eco
25.0
Indicates display
is showing target
temperature
Press to change
temperature
(see page 10)
°c
Press to turn thermostat
on or off (see page 8)
Current temperature
(or target temperature
when flashing)
3 Set desired indoor temperature ................................................................................................ See page 10
System fault
(see page 27)
Low battery warning
(see page 16 to replace
batteries)
6
Wireless signal
indicator (see
page 26)
Standby symbol appears
when thermostat is off
(see page 8)
7
Operation
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
On/off switch and frost protection
25.0
°c
Heating or cooling control
Press and hold the ON/OFF button as shown at left to turn the
thermostat on or off. When off, the thermostat will never activate the
cooling system, and will activate heating only if necessary to maintain
a minimum indoor temperature of 5º C (frost protection).
You can change the frost protection temperature to any level between
5º and 16º C, or turn this feature off so the heating system is never
activated when the thermostat is off (see page 23).
Press and hold
to turn on or off
25.0
°c
25.0
°c
The thermostat is pre-set to control only your heating system. If
installed and set up correctly, it can also be used to control your
cooling system.
To switch between heating and cooling, press and hold the p and q
buttons together until the screen changes.
NOTE: The thermostat will not switch to cooling control unless you
enable this feature (see page 23).
Heating changes to cooling
5.0
System maintains
minimum
temperature when
thermostat is off
Press and hold both buttons for 5 seconds
NOTE: When you change the system, the “Heating” and “Cooling”
symbols will appear for a few seconds, then disappear. Normally, these
symbols appear only when the heating or cooling system is running.
°c
Symbol appears when
thermostat is off
8
9
Operation
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Temperature control
Energy-saving ECO mode
When idle, the thermostat displays the current room temperature.
You can press the p or q buttons at any time to see the “target”
temperature the thermostat is trying to maintain.
Current room temperature
24.0
One button press will display the target temperature, flashing. To
change it, press either button repeatedly, until the display shows
the temperature you want. After a few seconds the display will stop
flashing and change to show the current room temperature.
°c
NOTE: You can use the ECO mode to temporarily override the target
temperature for a specified period of time (see page 11).
Press buttons to display or change target
temperature
25.0
°c
The ECO mode overrides thermostat settings to maintain a different
temperature for 1 to 24 hours. This can be useful to reduce heating or
cooling costs when you are away from home.
Press to enter ECO mode
eco
1hr
Set number of hours
eco
3hr
Change ECO temperature (if needed)
10
2 Press the p or q buttons to set timer (1-24 hours).
While in ECO mode, the screen will alternately display remaining time
and current room temperature. After the timer expires, the thermostat
will resume normal operation. Options:
• Pressthep or q buttons to raise or lower the temporary ECO
temperature if needed.
• PresstheECO button again to cancel ECO mode and resume
normal operation.
NOTE: The default ECO temperature is pre-set to 18º C. To raise or
lower the default temperature, see page 23.
eco
18.0
1 Press the green ECO button to display timer.
°c
11
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
System installation
Install relay box
Installation procedure
The relay box is wired directly to your heating
or cooling equipment. The thermostat
communicates with the relay box using a
wireless RF signal to control the system. Do not
install near metal objects or electronic devices
(TV, sound system, PC, etc.).
1 Install relay box
2 Connect system wiring
3 Activate batteries and install
wireless thermostat
Wireless
thermostat
30 m
etres
1 Make sure electrical power is off.
4 Setup and test system operation
max
. dist
ance
2 Use a screwdriver to release latch and
remove relay box cover.
Relay box
3 Mount relay wall bracket as shown at
left. Install at least 30 cm from any metal
objects such as metal wall boxes and metal
equipment enclosures.
System
wiring
Heating/cooling systems
4 Connect system wiring as shown on pages
14-15, then replace relay box cover.
NOTE: If you are not experienced in equipment installation, we recommend that these
procedures be done by a professional installer.
DISCONNECT ELECTRIC POWER BEFORE INSTALLATION: Can cause electrical shock or
equipment damage.
12
13
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Connect system wiring
Wiring diagrams
Connect wiring from your heating or cooling
equipment to the relay box as shown at left. See
wiring diagrams on page 15 for details.
Burner (direct control)
Combi boiler
Zone valve
Cooling device
1 Make sure electrical power is off.
2 Strip insulation to expose about 6 mm of
bare wire.
3 Use a screwdriver to loosen terminal screw,
insert wire into slot, then tighten screw.
4 Replace relay box cover, then restore
electrical power.
ABC
Wiring terminals
NOTE: All wiring must comply with IEE
regulations. Keep AC mains supply/load cables
separate from equipment wiring.
2
Terminal screws
NLL
1.5 - 2.5 mm
6 mm max.
14
15
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Activate batteries and test thermostat
Test thermostat (continued from page 16)
Grasp and pull to remove the thermostat cover. Discard the plastic
tab inside to activate the batteries, then test as shown below.
NOTE: This symbol will flash on the screen when battery
power is low. Remove cover and replace batteries with
two fresh AA alkaline batteries.
Remove
tab
5.0
°c
To test the thermostat:
1 Restore electrical power to the relay box.
CO0e
5 Press the q button once.
6 Press and hold the q button until the screen displays TEST. If
the green light on the relay box does not flash, the units are not
“bound” together. See page 28 and follow the instructions to
re-establish wireless communication.
EEse
2 Hold the thermostat 2-3 metres from the relay box.
3 Press and hold the ON/OFF button to turn off the thermostat.
i0se
4 Press and hold the p and q buttons together until the screen
changes as shown at left.
Relay
box
16
17
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Test thermostat location (continued from page 17)
Press
and hold
again
Check
wireless
signal
strength
The wireless thermostat can be mounted in the table stand,
or on a wall. For wall mounting, remove the thermostat cover
and use a screwdriver to separate the thermostat from the
wall bracket as shown at left. Install the wall bracket about
1.2 to 1.5 metres above the floor.
Test signal strength to find a suitable location for the thermostat
before installation.
EEse
55
Install thermostat
While still in Test mode (see pages 16-17), press and hold the q
button until the screen changes as shown, then move the thermostat
and check the screen display until you find a suitable location.
Thermostat
Signal strength:
3
• Donotinstallnearsourcesofhotorcoldair(radiators,
windows, heating or cooling ducts).
0 — 2: No. Move the thermostat to another location.
• Installatleast30cmfrommetalobjects.
3 — 5: Yes. Location is good.
• Installatleast1metreawayfromotherelectronicdevices
(TV, sound system, PC, etc.).
Press and hold the ON/OFF button to stop the test.
Press
and hold
to stop
25.0
Wall
bracket
°c
Table stand
assembly
18
19
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
System test
Installer setup
After installation, you should check to make sure the system is
working properly.
Set temperature to maximum
35.0
°c
2 Press the p button to raise target temperature to maximum
(35°C).
If the system is set up properly, the “heating” symbol should
appear on the thermostat display, the heating system should
begin running, and the green light on the relay box should be on.
Heat should turn on
35.0
1 Check the power supply to make sure the system is on and the
green light on the relay box is off.
°c
25.0
Press and hold both buttons for 5 seconds
i0se
3 To stop the test, press the q button to lower the target
temperature to an appropriate level. The heating system should
turn off and the “heating” symbol on the thermostat screen should
disappear.
To change installer settings:
1 Press and hold the ON/OFF button for 5 seconds.
2 Press and hold the p and q buttons together until the
screen changes.
3 Press the p or q buttons to scroll through functions
quickly until you find one you want to change (see list on
pages 22-23).
4 To change any setting, press the ON/OFF button, then
press the p or q buttons until the correct value is flashing.
0e: 1
Function
20
°c
Installer settings allow you to customise how your system
works. Check the tables on pages 22-24 to see if any settings
need to be changed.
5 Press OFF again to save your choice, then use the p or q
buttons to select another function.
To exit installer setup, press and hold the ON/OFF button
for 5 seconds.
Setting
21
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Installer setup functions
Installer setup functions
** Factory default setting
Function
Description
Setting Options
1: Ot
Minimum boiler on/off time
1 minute **
Options: 1 to 5 minutes
See page 24 for important information
2: Cr
Cycles per hour (CPH)
6 cycles per hour **
Options: 3, 6, 9 or 12
See page 24 for important information
3: Pb
Proportional band width
1.5°C **
Options: 1.5° to 3°C
4: tO
Temperature offset
0: No offset **
Options: +3° to -3°C
5: uL
Maximum temperature allowed
35°C **
Options: 21° to 35°C
6: LL
Minimum temperature allowed
5°C **
Options: 5° to 21°C
Enter Installer Setup (see page 19), then press p or q for access to system settings
Function
Description
Setting Options
7: ES
ECO default temperature
18°C **
Options: 5° to 35°C
8: HC
Heating/Cooling options
0: No central cooling system installed **
1: Allows switching between heating and cooling systems
Thermostat cannot control cooling unless you select 1
9: OS
Frost protection temperature
5°C **
Options: — (none) or 5° to 16°C
10: LC
Loss of communications
instruction
0: Switch relay off **
1: Operate relay 20% on / 80% off
11: FS
RESET TO FACTORY DEFAULT
0: No change
1: Select 1 to restore default settings. All customised
settings will be lost.
NOTE: See descriptions of functions on page 23.
NOTE: See descriptions of functions on page 23.
22
23
Installation and Setup
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Customised settings for your system
Your heating system
Description of functions
Changes required
Setting Options
Standard gas boiler
(<30kW)
None
No change
Zone Valve
None
No change
Oil boiler
Function 1: Ot
Function 2: Cr
Set to 4 minutes
Set to 3 CPH
Thermal actuator
Function 2: Cr
Set to 12 CPH
Electric heating
Function 2: Cr
Set to 12 CPH
Your cooling system
Changes required
Setting Options
Heat pump/air conditioner
Function 1: Ot
Function 2: Cr
Function 8: HC
Set to 4 minutes
Set to 3 CPH
Set to 1
Fan coil
Function 8: HC
Set to 1
Ot Minimum boiler off time: Check proper setting
for your system (see page 24).
LL Minimum temperature: When the q button is
pressed, the thermostat will not allow a target
temperature lower than the minimum you set.
Cr Cycles per hour: Check proper setting for your
system (see page 24).
ES ECO default temperature: This is the default
target temperature when the thermostat is in ECO
mode (see page 11).
Pb Proportional band width: If your heating system
is oversized for your home, you can compensate
by increasing the width of the control proportional
band up to 3°C.
HC Heating/cooling options: When set to 1, the
thermostat can control both heating and cooling
systems (see page 9).
tO Temperature offset: In some cases, the
thermostat must be installed in a location that
does not accurately control temperature for
optimum comfort in other rooms. You can set the
thermostat to compensate for this by adjusting
the offset.
OS Frost protection temperature: Minimum
temperature allowed when the thermostat is off
(see page 8).
LC Loss of communications: Determines how the
system operates if wireless signal is lost between
thermostat and relay box.
uL Maximum temperature: When the p button
is pressed, the thermostat will not allow a target
temperature above the maximum you set.
NOTE: After changing the above settings to accommodate a cooling system, you can switch the thermostat to
control either heating or cooling (see page 10).
24
25
Appendix
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
In case of difficulty
In case of difficulty
Thermostat screen
is blank
• MakesuretwofreshAAalkalinebatteriesareproperlyinstalled(see
page 16).
Heating or cooling
system does not
respond
• Checkthermostatbatteries(seeabove).
• Ifremediesdescribedonpage26cannotresolvetheproblem,the
thermostat may have to be moved. Make sure it is not installed near
sources of hot or cold air (radiators, windows, heating or cooling
ducts).
Desired temperature
cannot be maintained
• Makesureheatingandcoolingsystemshavepower.Checkfusesand
circuit breakers and replace or reset as needed.
If this symbol flashes on the screen during normal operation, a fault has
occurred.
• Checkwiring(pages14-15)andsystemconfiguration(pages21-25).
• Pressthebuttonontherelayboxtoilluminatethegreenlightand
temporarily restore system function. This is a manual override which will
not correct the fault; it will only allow the system to provide heat until
the fault is corrected.
• Ifredlightonrelayboxison,thethermostatandrelayboxmayhavelost
communication with each other. Check for metal objects or other devices
that may block or interfere with the wireless signal. Try the test procedures
described on pages 16-20.
• Iftheproblemcannotbecorrected,contactHoneywellCustomerCare
for assistance (see back cover for contact information).
• Ifaboveremediescannotresolvetheproblem,thethermostatmay
have to be moved. Try a location closer to the relay box, or farther
away from interference by metal objects or electronic devices such as
televisions, sound systems, PCs, etc.
26
27
Appendix
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Re-binding procedure
Re-binding procedure (continued from page 28)
If you must replace a wireless thermostat or relay box, the system
will not work until both devices can communicate with each other.
This is called binding. Follow the steps below to re-establish wireless
communication.
1 Hold thermostat about 1 or 2 metres from the relay box, then
press and hold the relay button for 15 seconds.
Press and hold relay box button
Press
and hold
Press
and hold
5.0
i0se
°c
Note: After 5 seconds the red light flashing pattern will change,
but you must hold down the button for at least 15 seconds to
clear previous binding information from memory.
5 Press the p button repeatedly until the display shows “CLr.”
Then press the ON/OFF button to clear previous binding to other
devices.
CL
6 Press the p button again to return to binding mode.
C0nt
7 Press the ON/OFF button again to re-establish wireless
communication with relay box. If successful, the red light on the
relay box will turn off, and the thermostat will return to normal
operation in Off mode a few seconds later.
2 Release the relay button, then press and hold it again for 5
seconds, until the red light flashes evenly (“binding” mode).
3 Release the relay button, then press and hold the thermostat
ON/OFF button to turn off the thermostat.
4 Press and hold the thermostat p and q buttons until the screen
changes as shown at left.
28
Red light
should turn off
25.0
°c
29
Appendix
homexperttm by Honeywell THR842DUK Wireless Digital Thermostat
Limited Warranty
Declarations, disposal and recycling
Honeywell warrants this product for 1 year from date of purchase. We undertake to replace or
repair at our discretion, products should they become defective within 1 year solely as a result
of faulty materials and or workmanship.
Understandably if the product has not been installed or maintained in accordance with
Honeywell’s instructions, has not been used appropriately or if any attempt has been made to
rectify, dismantle or alter the product in any way the warranty will be invalidated.
This product warranty states Honeywell’s entire liability. It does not extend to cover
consequential loss or damage or installation costs arising from a defective product.
If the product is defective, please return it together with a proof of purchase or receipt to the
place of purchase.
Declaration
Honeywell hereby declares that this wireless product is in compliance with the essential
requirements and other relevant provisions of the Radio and Telecommunications Terminal
Equipment (R&TTE) directive, 1999/5/EC.
Disposal and recycling
Batteries and waste electrical products should not be disposed of with household waste.
Please recycle where these facilities exist. Check with your local authority or retailer for
recycling advice.
This does not affect your statutory rights.
If you require further information about this product, call the homexperttm by Honeywell
technical helpline on 0845 604 2893.
Please retain these instructions for future reference.
For a full list of terms and conditions please visit www.homexpertbyhonyewell.com.
© 2010 Honeywell International Inc.
30
31
Need Help?
For assistance with this product please visit www.homexpertbyhoneywell.com, or call
Honeywell Customer Care at 0845 604 2893.
®
Honeywell
The Arnold Centre
Paycocke Road
Basildon, Essex
SS14 3EA
Technical Help Desk: 0845 604 2893
50051983-001 Rev. A
www.homexpertbyhoneywell.com
© 2010 Honeywell International Inc
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