Honeywell Home DT4 Black Wired Room Thermostat | DT40BT22 On/Off Digital Heating Control

Description

The Honeywell Home DT4 Black Wired Room Thermostat (model DT40BT22) brings a slim, modern design and a large, clear LED segment display to everyday room temperature control. Designed for on-the-wall wired installation, it suits homes and apartments running conventional or combi boilers, heat pumps, and zoned or underfloor heating systems, with a sleek black finish to match contemporary interiors.

At its core is a Fuzzy Logic control algorithm that continually refines heating and cooling response for accurate, stable room temperatures. Backlit, captive touch buttons and an auto-off LED display keep everyday use simple, while a flip-up wiring platform and clear installer/user menus make setup and commissioning straightforward for professionals and homeowners alike.

Black

Colour Finish

24-230V

On/Off Appliance Range

Fuzzy Logic

Control Algorithm

3A / 1A

Switching Capacity

SPDT

Switch Type

5 Year

Manufacturer Warranty

Wired Installation Only

The DT40BT22 is a wired, wall-mounted thermostat for 24-230V on/off appliances such as gas boilers, combi boilers and heat pumps. It is not compatible with 240V electric heating circuits. If a wireless installation is preferred, the equivalent DT4R model is available instead.

Qualified Installation Required

This thermostat switches mains-connected heating and cooling circuits. Wiring and commissioning should be carried out by a qualified electrician or heating installer in line with current UK wiring regulations and the manufacturer's installation instructions.

Installer & User Menus

An installer menu allows configuration of cycle rate, heating/cooling changeover, and upper/lower set point limits to match the connected appliance, while a separate user menu gives the homeowner control over everyday functions - keeping advanced settings protected from accidental changes.

Fuzzy Logic Temperature Control

A self-adjusting Fuzzy Logic algorithm learns how the connected heating or cooling system responds, delivering more accurate room temperature control over time.

Heating & Cooling Modes

Configurable for heating, cooling, or heating and cooling operation, suiting a wide range of system types from simple boiler control to combined heat/cool setups.

Frost Protection in Off Mode

Switching the thermostat to 'Off' activates an integral frost protection setting (minimum 5 °C) to help prevent pipes from freezing during cold weather.

Eco Offset Timing

The Eco Offset function allows a timed temperature offset to be applied automatically during heating and cooling, supporting energy-saving schedules.

Flip-Up Wiring Platform

A flip-up wiring platform speeds up first-fix wiring and simplifies future servicing without needing to remove the thermostat body.

Adjustable LED Display

The LED display brightness is adjustable, improving visibility in a range of ambient lighting conditions, with clear coloured icons indicating heat and cool demand status.

General

Model / MPN

DT40BT22

Product Family

DT4 Wired Room Thermostat

Colour

Black

Installation Type

Wired, wall-mounted

Appliance Compatibility

24-230V on/off: gas boilers, combi boilers, heat pumps

Not Compatible With

240V electric heating circuits

Control & Switching

Control Form

Fuzzy Logic

Heating System Mode

Heating and Cooling (configurable)

Switching Capacity

3A (Resistive), 1A (Inductive)

Switching Type

SPDT

Sensing Element

10k NTC thermistor @ 25 °C

Cycle Rate

Installer-configurable

Display & Operation

Room Temperature Display Range

0 °C to 40 °C

Off Mode Frost Protection

Minimum 5 °C

Eco Offset

Timed temperature offset for heating and cooling

Display

LED segment display with adjustable brightness, auto-off

Controls

Backlit, captive touch buttons

Environmental & Warranty

Shipping/Storage Temperature

-20 °C to 55 °C

Storage Humidity Range

10% to 90%

Warranty

5 years

What systems does the DT4 Black work with?

It's compatible with 24-230V on/off appliances including gas boilers, combi boilers and heat pumps, and also supports zoning, underfloor heating and cooling devices and zone valve applications. It is not suitable for 240V electric heating circuits.

Is this a wired or wireless thermostat?

The DT40BT22 is a wired thermostat for on-the-wall installation. If a wireless setup is preferred, look for the equivalent DT4R model in the same range.

Can this thermostat control both heating and cooling?

Yes, the installer menu allows the mode to be set to heating, cooling, or heating and cooling, so it can be configured to match the connected system.

What happens when the thermostat is switched off?

The 'Off' position includes an integral frost protection setting of at least 5 °C, helping to prevent pipes from freezing even when the heating is deliberately switched off.

How is the thermostat powered?

The wired DT4 model is powered by 2 x AA alkaline batteries for its display and controls, while switching of the heating circuit itself is via the SPDT mains-wired output.

BTU Calculator

BTU & WATT Calculator

Room Dimensions

Length (in m):

Width (in m):

Height (in m):

Room Type

Living Room

Bedroom

Kitchen

Bathroom

Conservatory

Hallway

Glazing Type

Single Glazed

Double Glazed

Triple Glazed

External Walls

0 Wall

1 Wall

2 Walls

3 Walls

4 Walls

Insulation Level

Poor

Average

Good (New Build)

Calculate

Required Heating

0

Watts

0

BTUs