Honeywell THR840DUK User Manual

User Manual

THR840DUK Digital Thermostat

50051982-001 Rev. A

Contents

homexperttm by Honeywell THR840DUK Digital Thermostat

WARNING: This product must be correctly installed and conﬁgured to work properly (see pages 12-24). If you are not experienced in wiring electrical equipment, we recommend professional installation to avoid possible personal injury or equipment damage.

TIP: After installation, see the QUICK START GUIDE on page 6 to customise and begin using your new thermostat right away.

About your new thermostat

What is a room thermostat? ..................4-5

QUICK START GUIDE ............................. 6

Quick reference to controls ....................... 7

Operation

On/off switch ............................................ 8

Heating or cooling control ......................... 9

Temperature control ................................ 10

Energy-saving ECO mode ......................11

Installation and setup

System installation .................................. 12

Wall bracket installation ..........................13

System wiring ....................................14-17

Battery installation & mounting ................ 18

System test ............................................ 19

Installer setup ....................................20-24

Appendix

In case of difﬁculty .................................. 25

Warranty information ...............................26

Disposal & recycling ................................27

NOTE: This symbol will ﬂash on the screen when battery power is low. Remove cover and replace batteries with two fresh AA alkaline batteries as shown on page 18.

User Manual

What is a room thermostat?

homexperttm by Honeywell THR840DUK Digital 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.

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.

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.

User Manual

homexperttm by Honeywell THR840DUK Digital Thermostat

About your new thermostat

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).

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

(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 reference

Cooling system is running (see page 9)

ECO mode is on (see page 11)

Appears when target temperature is showing

Current temperature (or target temperature when ﬂashing)

System fault (see page 25)

ECO mode countdown (see page 11)

eco

25.0

Low battery warning (see page 18 to replace batteries)

Heating system is running (see page 9)

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)

Standby symbol appears when thermostat is off (see page 8)

Operation

homexperttm by Honeywell THR840DUK Digital Thermostat

On/off switch and frost protection

Press 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 22).

Press and hold to turn on or off

25.0

5.0

System maintains minimum temperature when thermostat is off

Symbol appears when thermostat is off

Heating or cooling control

Press and hold both buttons for 5 seconds

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.

25.0

NOTE: The thermostat will not switch to cooling control unless you enable this feature (see page 22).

Heating changes to cooling

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.

25.0

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