From Refrigerant Cycle to Product Testing: Fostering Innovation in Heat Pump Controllers through Real-Life Testing
At the EU policy level, it is discussed to revise the test method for heat pumps within the framework of the EU Energy Labelling regulation for central space heating appliances. The proposed change aims to replace current stationary measurements (component testing), conducted according to EN 14511:2022 and requiring manufacturer support to force steady-state operation, with a load-based testing approach (product testing) known as the compensation method. The new compensation testing method couples a building model to hydronic test benches to emulate a realistic response of the hydronic system, resulting in dynamic operating behavior. The heat pump is assessed in its normal operating mode, without any additional inputs from the manufacturer, paving the way towards independent testing and rating. The resulting evaluation parameter (COP) accounts for the efficiency of the refrigerant cycle, the backup heater, and the heat pump controller, which is closer to reality than steady-state measurements. Moreover, this method is technologically neutral and enables a level playing field for all technologies, including future compressor-less heat pumps. While the emulator was already introduced in the literature, this work introduces new features of the method designed to test dynamic hydronic flow characteristics. Specifically, it incorporates a perfect hydraulic switch to allow variable flow rates of the heat pump within one test point. The target parameter (setpoint) of the method is the average heat flow provided by the heat pump. This allows the manufacturer to resolve the tradeoff between mass flow and supply temperature in a system-specific manner. The method is performed with different heat pumps in several laboratories to prove reproducibility. Implementing the proposed load-based test via future Energy Labelling regulations will incentivize better controls through more representative testing, allow for a fair comparison of different products and technologies, and enable independent market surveillance.