24 June 2014


In order to allow a use of heritage buildings during the cold season heating is needed for a rather long period in Austria. However, the installation of a heating system in
such buildings holds some challenges. A major issue is the required modification of the building structure if a heating system is installed because of historic preservation. That is why
such buildings are most commonly equipped with electric heaters.

This paper deals with an alternative heating system suitable for heritage buildings: Air-to-air heat pumps installed at Castle Rabenstein (Burg Rabenstein) located in Austria. The castle with a gross floor area of ca. 2500 m2 is equipped with several air-to-air heat pumps with variable refrigerant flow and a heating capacity of ca. 500 kW.

For the analysis of possible operation modes a thermal building simulation of a selected area of the castle – which is mainly used for events – was performed by means of TRNSYS.
Different heating strategies were investigated with respect to the heating energy demand for maintaining a comfortable indoor climate. In this context, the reduced room temperature – when no event takes place – and the preheating time in combination with the air supply
temperature of the indoor devices are of special interest.

In order to determine the energy efficiency of the heating system a monitoring concept was established, and the measurement system is in operation since December 2013.