Honeywell DT90 User Manual

DT90

DIGITAL ROOM THERMOSTAT

PRODUCT SPECIFICATION SHEET

The new DT90 family of digital room thermostats is a

range of market leading products designed to provide
comfort with economy in modern heating systems.
Its large display and simple button interface make

DT90 extremely easy to use.

Energy efficiency is addressed by state-of-the-art TPI

control performance and an ECO button energy saving

feature.

Applications include control of gas or oil-fired boiler
systems, underfloor heating, electric heating and
zoning systems.

With a modern fresh look that complements any style
of décor, and a range of valued features for users and

installers alike, DT90 sets the standard for simple

environmentally-friendly room thermostats.

FEATURES

• Energy saving TPI control performance

• Advanced self-learning control adapts to the

environment and ensures close temperature
control with minimum energy usage

• Slim modern styling

• Large high contrast display with easy-to-read

characters

• Simple user interface

• Temperature setting procedure eliminates the

risk of accidental setpoint change

• Display shows room temperature, with option

to inquire about setpoint

• 5°C to 35°C setpoint range with 0.5°C

increments

• Temperature set using up or down buttons

• Off/standby button, allowing manual switch off,

with frost protection active

• Adjustable off/standby setpoint 5°C to 16°C or

DT90 can be set to off completely

• Battery powered by 2 x AA (LR6) alkaline cells

• Up to 4 years battery life (minimum 2 years),

with battery low warning

• Simple battery change by unclipping front

cover

• Installer Mode allows the thermostat to be

customised for the application and the needs of
the user

• NVRAM storage of setup parameters, ensuring

these are never lost

• Setpoint limits can be programmed in

• 24…230Vac SPDT potential-free contacts for

simple 2-wire installation

• 8 A resistive, 3 A inductive switch rating

• Surface or switch-box mounting options

• Sensor fault self-diagnostics

• Heat/cool changeover operation mode possible

FEATURES UNIQUE TO DT90E ECO MODEL

• Energy saving ECO button allows user to

change to a lower, energy saving setpoint for a
timed period of their choosing (1…24 hours)

• Display shows countdown of time remaining in

ECO energy saving mode

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CONTROLS / DISPLAY LAYOUT

frost protect indicator heating demand indicator

DT90A

DT90E

DT90 DIGITAL ROOM THERMOSTAT

ECO countdown indicatorECO mode active

temperature display

setpoint indicator

fault indicator

battery low warning

off/standby indicator

SPECIFICATIONS

ELECTRICAL

Power supply : 2 x 1.5V IEC LR6 (AA) Alkaline cells

Battery life : Typically 4 years, minimum 2 years (with

correctly specified alkaline cells)

Battery low
warning

Switch type : SPDT (single pole double throw )

Electrical rating : 230 V, 50…60 Hz, 0.01 A to 8 A

Relay life : 100,000 operations minimum

Wiring : Terminal block capable of accepting

Wiring access : Rear, top and left side

ENVIRONMENTAL & STANDARDS

Operating
temperature
Shipping &
storage
temperature
Humidity : Humidity range 10% to 90% rh, non-

IP class : IP30

Approvals : CE mark, complying with standards

: Display will indicate when battery power

reserve is low. Unit will continue to
function for a minimum of 4 weeks after
the first indication is given

potential free

resistive, 0.1 A to 3 A inductive (0.6pf)

: 24 V, 0…60 Hz, 0.01 A to 8 A resistive,

0.1 A to 3 A inductive (0.6pf)

wires up to 2.5mm²

: 0°C to 40°C

: -20°C to 55°C

condensing

EN60730-1: 2001, EN60730-2-9: 2002
EN55014-1: 2001, EN55014-2: 1997

: WEEE & RoSH compliant

: C-tick

setpoint change buttons

ECO button

off/standby button

ECO mode countdown timer

TEMPERATURE CONTROL

Sensing element : 10K (@25°C ) NTC thermistor

Temperature
setting range

: 5°C to 35°C setpoint range in 0.5°C

increments

Control form : Self-learning TPI Fuzzy Logic algorithm

Proportional
band

Minimum on/off
time

: 1.5°C adjustable up to 3°C in 0.1°C

increments

: 1 minute, adjustable up to 5 min in 1 min

increments

Cycle rate : Adjustable to suit the application 3, 6, 9,

12 cycles per hour

Temperature
control accuracy

: ± 0.5°C (or better) at 20°C, 50% load and

3°C /hour temperature ramp

Frost protection : 5°C when thermostat switched to

off/standby, adjustable 5°C to 16°C

: Frost protection not available in cooling

mode

Positive off : Positive off possible (no frost protection)

by setting in Installer Mode

ECO energy
saving

Fail-safe
operation

: Setpoint default 18°C, adjustable 5°C to

35°C

: If temperature measurement system fails,

unit will continue to operate on the
assumption of a 10% load

METRICS

Dimensions
(unit)
Dimensions
(pack)
Weight (unit) : 165g

Weight (pack) : 192g

: 90 x 92 x 27mm

: 93 x 94 x 46mm

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