Germ-free in no time

Challenge

The company thus began developing its “UV-Unit compact” in April 2020. Among other things, the aim was to set the device apart from others already on the market by offering powerful disinfection performance. To achieve this, Howatherm combined high-quality mechanical filters with germ-killing UV-C radiation, a technology that has already been used successfully for the disinfection of water and surfaces for some time. The UV-Unit compact had to be able to automatically adjust its output to the number of people in the room in order to save energy, preserve the service life of the UV-C tubes and operate as quietly as possible. This is made possible by the integration of a CO₂ sensor. A high level of CO₂ indicates that there is a lot of exhaled air in the room and thus a correspondingly high number of aerosols. The UV-Unit compact adjusts the output of the fan to the detected CO₂ level and can add additional UV-C tubes as required, in a total of three stages.

Solution

For control of the mobile system, Howatherm Klimatechnik decided to opt for the easyE4 control relay from Eaton: “We had already used the previous Eaton models, the easy700 and easy800, in other systems, where they were housed in a separate controller box to control the application independently of a higher-level PLC,” explains Martin Brücher, Head of Measurement and Control Technology at Howatherm Klimatechnik. Compared to the previous model, the easyE4 is equipped with significantly more powerful hardware. For maximum flexibility, each easyE4 comes with four digital outputs, four analog/digital inputs with 12 bit resolution, and four fast digital inputs. It can be expanded to a maximum of 188 inputs/outputs by adding up to eleven expansion modules.

When the easyE4 was launched, Brücher took the opportunity to get a feel for the new model via a starter package. In addition to the control relay, the package also included the XV102 touch panel and the necessary software, including application examples of the programming and visualization options. The XV102 display was developed for the visualization and control of applications based on the easyE4 control relay. In order to adapt the display to the price structure of the easyE4 series, unnecessary interfaces have been omitted. If used in combination with the control relay, the display thus enables the implementation of cost-sensitive applications. “Initially, we hadn't planned to use a touch display for the air disinfection devices,” says Brücher. “But once we realized all the possibilities it offered and how easy it was to program, we quickly changed our mind.”

To control the new air disinfection devices, Howatherm uses an easyE4 with an analog expansion module that controls the fan. Brücher: “Since we are using an energy-efficient EC fan, no additional drive electronics are required.” In addition, the easyE4 is connected to a CO2 sensor for monitoring the air quality, to a door contact switch and to the three UV-C tubes. As a result, the performance of the air disinfection device can be automatically adapted to indoor air quality. The control relay adjusts the power of the fan in three stages in line with the detected CO2 level and then switches on additional UV-C tubes as required. “To ensure the longest possible service life of the tubes, we use the easyE4’s integrated operating hours counter,” explains Brücher. “A self-programmed rotation module enables us to utilize the lamps evenly.”

For the programming of the easyE4, Eaton offers the easySoft 7 software, which can be used to create circuit diagrams on a PC or directly on the device. These can first be tested in simulation mode and then documented later. The option to choose from various function blocks, such as data loggers and alarms, makes programming even more efficient. Users have a choice of four different programming languages: the ladder diagram (LD), easy device programming (EDP), structured text (ST) and the function block diagram (FBD). “I really liked these programming options,” says Brücher. In this case, he opted for FBD-based programming: “The controllers we use in our large-scale systems also work with function blocks, hence I feel at home with this programming language.” In addition, he used ST to program some functions for which no modules were available, enabling him to quickly implement a customized program for the UV-Unit compact. “The great advantage of the FBD is its speed,” as Brücher notes. “All I have to do to see the inputs and outputs is to drag the function blocks into the program, and then I can simulate everything at the end.

Since the programming and visualization tools of the easyE4 and the XV102 panel are closely interlinked, Martin Brücher was then able to transfer the project data and variables from the easySoft 7 programming environment directly to the Galileo visualization software. The tool provides a user-friendly visualization interface for efficient application programming. Buttons can thus be superimposed on images and graphics to implement cutting-edge, ergonomic user interfaces. One of the highlights of the UV-Unit compact is the CO2 traffic light programmed by Brücher and his team, which clearly indicates the current level measured by the device – once the light turns red, the CO2 concentration in the room is definitely too high and ventilation should be provided.

Results

Thanks in part to this coordinated control solution and the ease with which the combination of easyE4 and XV102 can be programmed, Howatherm Klimatechnik was able to bring the UV-Unit compact to market after a development period of just five months – including all the necessary purification efficiency tests. The assured availability of the Eaton products from electrical wholesalers was another important factor: Howatherm Klimatechnik procures the devices via Sonepar, which operates three large warehouses and additional regional warehouses across Germany and can usually deliver orders within 24 hours.