CC BY 4.0Ihlenburg, MoritzMoritzIhlenburgRéhault, NicolasNicolasRéhaultHerkel, SebastianSebastianHerkelBenndorf, GesaGesaBenndorf2024-05-292024-05-292024Note-ID: 0000A58Ehttps://publica.fraunhofer.de/handle/publica/468946https://doi.org/10.24406/publica-313710.52825/isec.v1i.121710.24406/publica-3137Energy monitoring and performance optimization processes play a significant role in ensuring energy-efficient building operation. However, the current implementation of these processes requires substantial time and effort due to the fragmented and non-digital nature of technical building equipment information. To address these challenges, we demonstrate the application of the PLCont methodology within an ongoing monitoring process in a real building. PLCont utilizes Semantic Web Technologies and established RDF ontologies to describe the control topology. The digital representation of control functions aligns closely with the IEC standard 61131-3, and the PLCont ontology establishes a connection between the topology and the control functions. We compare the conventional approach and the PLCont methodol-ogy using the supply air temperature control of an Air Handling Unit (AHU) as a use case. A graphical user interface built upon the PLCont backend provides a comprehensive represen-tation of the system's functionality. It displays the system topology as a digital HVAC schema, the function code exported from the PLC, time-series data plots, and textual descriptions of implemented functions. We demonstrate how this approach enhances transparency and facil-itates the identification and elimination of faulty system behavior, ultimately contributing to the optimization and energy efficiency of building systems.enBuilding Information Modeling (BIM)DigitizationProgrammable Logic Controller (PLC)Semantic Web Technologies (SWT)conference paper