Honeywell DT70 Series

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The DT70 digital thermostats are designed for ON/OFF

control of the valve, or the valve and fan in 2-pipe fan-

coil applications and also one-stage compressors in

DX-type equipment.

The thermostat operates an on/off valve to provide

control at the desired setpoint temperature.

Fan-coil thermostat models are available with constant

or cycled fan operation, and have a three-speed fan

selector switch with low, medium and high settings.

The fan can also be controlled from the thermostat. In

some cases it is wired to run continuously, and can be

switched off with the system ON/OFF switch.

Heat/cool changeover operation is also possible on all

versions. This function can be accomplished by

changing the Heat/Cool parameter in SETUP mode.

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•

Elegant styling with digital display makes

thermostat well harmonised with any interior

decoration of office or hotel

•

Digital display of room ambient temperature, with

display of user selected setpoint on demand

•

Push button adjustment of setpoint

•

Push button setting of Heat/Cool changeover

•

Switches allow manual control of system operation

and fan speed

•

Thermostat mounts directly onto a wall, a standard

65mm junction box (hole pitch 60mm) or a

85mm junction box

•

Ability to set minimum relay off-times (heating or

cooling) for applications requiring compressor short-

cycle protection (0~10min.)

•

Ability to set control-off-times for applications

requiring starting-time reservation (0~24hr.)

•

Ability to display temperature sensor failure for

easier troubleshooting

•

EEPROM permanently retains user settings in the

event of power loss

•

Suitable for use with Honeywell VC4000/VC6000

series and V4043/V4044 valves and compressor

starters/relays up to 2A full load rating

Contents

Application ………………………………………………… 1

Features …………………………………………………… 1

Specifications ……………………………………………... 2

Installation …………………………………………………. 3

Wiring diagram ……………………………………………. 4~5

Operation ………………………………………………….. 6

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The Honeywell DT70 Series Digital Fan-Coil Thermostats are designed for ON/OFF control of valves and fans in 2-pipe fan-coil applications, as well as single-stage compressors in DX-type equipment. These thermostats regulate an on/off valve to maintain a desired setpoint temperature.

Function Description:

The DT70 series thermostats provide temperature control for fan-coil and air-conditioning systems. They are capable of controlling the fan in either a constant or cycled operation mode, offering three fan speed settings (low, medium, high) via a selector switch. Heat/cool changeover operation is supported across all versions and can be configured in SETUP mode. The device displays the room's ambient temperature and, on demand, the user-selected setpoint. Push buttons allow for easy adjustment of the setpoint and selection of heat/cool changeover. Manual control of system operation and fan speed is also possible via dedicated switches.

Important Technical Specifications:

Setpoint Range: 5°C to 35°C, adjustable in 0.5°C increments.
Differential: 1°C maximum (0.5°C typical).
Thermostat Switch: 1 S.P.D.T. relay.
Control Performance: ON/OFF control.
Electrical Ratings: 4(2) A, 220 V~, 12A inrush. Suitable for loads such as fans, zone valves, and relays.
Operational Life: Greater than 100,000 cycles for thermostat contacts at 220 V~; greater than 10,000 operations for all manually operated switches.
Supply Voltage: Vac±10%, 50/60Hz (models available for 110V and 220V).
Wiring: 7 or 9 screw-in terminals, accepting 18-26AWG wires.
Enclosure: Plastic 2-piece housing (front cover, rear cover).
Dimensions: 76 x 125 x 30mm (W x H x D).
Operating Temperature Range: 5°C to 45°C.
Shipping and Storage Temperature Range: -20°C to 55°C.
Humidity Range: 5% to 95% RH, non-condensing at 26°C.
Mounting: Directly onto a wall or standard 65x65mm (hole pitch 60mm) or 85x85mm junction box. Mounting screws are supplied.
Compatibility: Suitable for use with Honeywell VC4000/VC6000 series and V4043/V4044 valves, and compressor starters/relays up to 2A full load rating.

Usage Features:

Elegant Design: Digital display and modern styling blend well with office or hotel interiors.
Setpoint Adjustment: Easy push-button adjustment of temperature setpoint.
Heat/Cool Changeover: Push-button setting for switching between heating and cooling modes.
Fan Control: Manual control of fan speed (low, medium, high) via a selector switch. Fan can be constant or cycled.
Minimum Relay Off-Time: Adjustable setting (0-10 minutes) to prevent short-cycling of compressors, protecting the equipment.
Control-Off-Times: Ability to set control-off-times (0-24 hours) for applications requiring starting-time reservation.
EEPROM Retention: User settings are permanently retained in EEPROM even during power loss.
Display Biasing: Room temperature display can be biased by -1°C or -2°C for calibration.
System Switch: Controls power to the thermostat and fan-coil equipment. In the off position, terminal four is powered to close the VC4000/VC6000 valve (DT70-F002ET, F012ET models only).

Maintenance Features:

Temperature Sensor Failure Display: The device can display temperature sensor failure, aiding in easier troubleshooting.
Installer Setup Mode: Provides access to advanced settings for configuration, including cooling/heating changeover, minimum relay off-time, room temperature display biasing, and output timer settings.
Power Loss Handling: During timer counting, if power is lost or the system switch is off, the timer setting is canceled, preventing unintended operation after power restoration.