3. Device description and purpose

The DT240 is a multifunctional digital electronic thermostat with an LCD display, used for controlling heating and cooling processes. Its regulation range is from -55 to +255 °C. The thermostat is controlled by a microcontroller, ensuring an accuracy of ± 1 °C across the entire operating range. As a temperature sensor, the thermostat uses an NTC resistor, with the specific measurement range depending on the type of connected NTC resistor/sensor (see Temperature sensor resistance table). Its differential is adjustable from 0.1 to 10 °C. It is powered by an alternating voltage between 100 V and 250 V, at a frequency of 50 or 60 Hz.

The thermostat housing is 2 DIN modules wide, i.e., 36 mm, and is designed for quick installation on a standard 35 mm DIN rail. Due to the ability to select and connect up to 11 different types of NTC sensors, this thermostat is an ideal choice when existing equipment needs to be replaced with new.

NTC sensors with values of: 10, 12, 15, 16.7, 33, 47, 50, and 100 kΩ / 25°C can be used. Additionally, the thermostat incorporates digital noise filtering, ensuring accurate temperature measurement even if the temperature sensor cable is laid near power cables, up to a length of 100 m.

One of the more important features of this thermostat is the high permissible load of the voltage-free switching contact of the main output relay, up to 25 A, which in many cases eliminates the need for an additional electromagnetic contactor. The thermostat also has an additional auxiliary electronic relay with a switching capacity of 1 A / 250 V~, which can be used as an alarm output.

Alarms can be triggered by: sensor temperature open circuit or short circuit, or temperature too low or too high, accompanied by an audible signal and the alarm cause displayed on the thermostat screen.

In addition to thermostat operating mode, the DT240 can also operate in manual and time-based mode. The manual mode is useful when testing a heating or cooling installation without the need for specific temperature conditions at the time of installation and commissioning. In time mode, the DT240 behaves as a time relay with adjustable on/off times and/or for the main electromechanical and/or auxiliary electronic output relay. Times can be set in the range of 1 minute to 10 hours. This operating mode can be useful in the event of NTC sensor damage, ensuring that the operation of the regulated heating or cooling process is not interrupted.

For greater safety and a wider range of applications, the DT240 thermostat employs galvanic isolation of the NTC temperature sensor circuit, and the thermostat is designed and tested to withstand overvoltages exceeding 4 kV.

The high-resolution, highly visible multi-colour LCD screen displays numerous numerical and textual data and symbols, enabling simple setup, providing extensive information, and ensuring correct use of the thermostat.

To ensure the DT240 thermostat remains easy to use despite its many features, a brief explanation is provided for each function. This is accessed by activating the  symbol, which leads to help text displayed on the thermostat screen.

The DT240 thermostat offers a multilingual user interface, with the following languages available for selection: English, German, Croatian, Polish, Hungarian, Bosnian, Serbian (Cyrillic script), and Korean.

The thermostat housing is printed with manufacturer details, serial number, CE mark, and a terminal block diagram, which facilitates correct wiring.