State-of-the-art office building air conditioning
Hybrid VRF system for the company headquarters of Aucotec AG
Isernhagen near HanoverModern office buildings differ from traditional office complexes in their functional openness and communication-promoting design. For the modernly designed new headquarters of the Aucotec AG software company, a cooling and heating solution had to be found to meet the requirements of the multifunctional building.
Requirements for heating and air conditioning technology
Since 1985, Aucotec AG has been developing engineering software for the entire life cycle of machines, plants, and mobile systems. Its corporate philosophy: “We recognise that maximum efficiency can only be achieved through networking and interdisciplinary cooperation.” This key aspect was also to be implemented in the new building in Hanover. In addition to the office and conference rooms and the reception area, the communicative concept also included leisure rooms and lounges. Correspondingly, the requirements were wide-ranging: an air-conditioning technology for cooling and heating that is barely visible, very quiet, smart to operate, draught-free, and with maximum energy efficiency – involving a lean construction process.
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- Cooling and heating
- Quiet, draught-free operation
- Highest energy efficiency
- Visually discreet
- Smart control system
- Lean construction process
Which solution did Aucotec AG opt for?
Hybrid VRF SystemFor the demands of modern office buildings
A Mitsubishi Electric City Multi seriesHybrid VRF System (HVRF)was implemented as the heating and air-conditioning solution for simultaneous heating and cooling with heat recovery. The 2-pipe system combines the advantages of a direct evaporation system with those of a water-based system that uses water instead of refrigerant as the sole transport medium in the building itself.
The Hybrid VRF system was developed specifically to meet the demands of modern building architecture. The technology is based on the City Multi VRF R2 heat pump system from Mitsubishi Electric and consists of a City Multi VRF outdoor unit, a Hybrid BC controller (HBC) and special indoor units equipped with a water coil. A total of six hybrid VRF outdoor units with a cooling output of 400 kW and a heating output of 450 kW are installed on one roof. They feed the refrigerant via branch lines to six HBC controllers which are located on the individual floors either in the suspended ceilings or in a plant room for visible installation. From there, they supply the indoor units with the required heating or cooling output.
The HBC controllers are responsible for heat exchange between the refrigerant-based outdoor circuits and the water-based indoor circuits with the indoor units. All pipes leading through the building transport water. Refrigerant is only present in the pipes from the outdoor units to the HBC controllers.
Requirement: cooling and heating
Each individual indoor unit can be operated independently in heating or cooling mode. Heat extracted from the rooms requiring cooling is used elsewhere in the building for heating other rooms and areas.
Requirement: energy efficiency
The Hybrid VRF system was developed specifically to meet the demands of modern building architecture with high efficiency requirements. Heat recovery allows energy savings of up to 40 % compared to conventional units with two separate systems for heating and cooling. Hybrid VRF systems are characterised not only by their reduced refrigerant quantities, but also by their high energy efficiency. Hybrid VRF systems can therefore make a decisive contribution to fulfilling current and, at best, future guidelines for modern, sustainable constructions. Its strengths come to the fore in the context of green buildings as well as LEED, BREEAM and DGNB certifications.
Requirement: discreet look
Two pipes with a very small cross-section run through the building to each indoor unit, so that the Hybrid VRF system requires very little space. To gain as much ceiling height as possible, the pipes running from the HBC controller to the indoor units are not routed through the suspended ceilings. Instead, they are installed in the raised floor or in the screed together with the lines. The concealed installation of the pipework in the concrete floor also reduced the number of ducts leading through different fire safety zones, as escape and rescue routes often need to be crossed when pipes are installed in the suspended ceilings in the traditional way. This was much to the delight of both the architect and the building contractor, as the use of this air-conditioning system enabled an even better and more open architecture.
Requirement: quiet, draught-free operation
All pipes leading through the building transport water. Refrigerant is only present in the pipes from the outdoor units to the HBC controllers. Thanks to the water-based distribution, the hybrid system offers the advantage of operating at higher system temperatures than a refrigerant-based system. This results in much more pleasant air conditioning with very smooth temperature transition and virtually no draughts, noticeably increasing climate comfort. The water in the indoor circuit of the hybrid VRF systems also ensures a particularly quiet operation of the indoor units.
Requirement: smart control system
A modern office building also deserves a state-of-the-art control system. The air-conditioning equipment is fully controlled via the Remote Monitoring Interface (RMI) with consumption data analysis for the individual building units. The cloud-based software solution for visualised control and supervision as well as permanent monitoring of air-conditioning systems via smartphone apps or web browsers allow individual employees to set a custom temperature from their workplace via the user interface of their computer. The specialist trade company also has the option of remotely accessing the system at any time to provide optimum support.
Another great advantage:The specialist company in charge – here RKS Klimaservice GmbH – can centrally manage the air-conditioning system and analyse the consumption and energy data. This allows them to view any operating errors or failures remotely at any time and, if necessary, rectify them remotely. The RMI is connected to a Mitsubishi Electric EW-50E central control unit via a router.
Requirement: lean construction process
Design and installation of the 2-pipe system is very flexible and much more straightforward than for a chiller plus an additional heat generator with four pipes. For example, no additional pumps, tanks or switch valves are required in the Hybrid VRF system. With the 2-pipe system, there are significantly fewer connection points in the piping network. This ultimately reduces potential leaks and makes the system more reliable and less maintenance-intensive.
The key points
Summary- The construction of the new headquarters of Aucotec AG imposes high requirements on the technical building equipment: The air conditioning of the building should be quiet, comfortable, safe and energy-efficient.
- A City Multi Hybrid VRF system from Mitsubishi Electric was installed as the heating and air-conditioning solution for simultaneous heating and cooling with heat recovery.
- The 2-pipe system combines the advantages of a direct evaporation system with those of a water-based system that uses water instead of refrigerant as the sole transport medium in the building itself.
- It thus optimally meets the building contractor’s requirements and is particularly economical and environmentally friendly thanks to its heat recovery function.
