Due to delays during the construction of the building, partly caused by the cold winter in 2005, the commissioning of the building had to be done under operating conditions. Immediately after the commissioning the extreme complexity of the requirements for the building controls were observed. Caused by the desired interrelations of the energy fluxes — the waste heat of the chillers for example can be used to heat the building — many conditions have to be accounted for the control strategy. Thereby it was barely possible for the manufacturer of the measurement and control system to use standard components for programming the controllers. A great part of the control strategy had to be programmed without a template. Since there was no time for extensive testing, especially under changing conditions in spring and autumn, the malfunctions have to be corrected during normal operation.

Very soon it became obvious, that the installed cooling power, which was provided only by the absorption chiller, was not sufficient. In the technical plans an additional compression chiller was considered which was not assembled in the beginning because of the stringency of the energy

concept. Furthermore, the absorption chiller did not achieve its designated performance. The inspection of the flow rates showed a lack of flow in the re-cooling unit of the chiller.

In spring 2006 a compression chiller with a capacity of 50 kW for peak load and backup was installed. The cooling tower had been already designed for this additional load. Hence no retrofitting was necessary for the re-cooling. Also the pumps in the re-cooling circuit of the absorption chiller were reinforced. The required flow rate was now reached in this part of the system too.