Comparison of different testing methods for gas fired domestic boiler efficiency determination

As the Energy Performance of Buildings Directive is being implemented throughout the European Union, a clear need for certification of boiler and domestic heating devices has arisen. Several ‘Notified Bodies’ exist, spread around the different member states. They are acting as the notified body of that member state and focus on local certification. A boiler manufacturer has its equipment tested according to the ‘Boiler Efficiency directive 92/42/EC’. Recently, tests done by several notified bodies in sequence on an identical unit of a manufacturer showed that results could differ depending on which notified body performed the test.In cooperation with ‘Technigas’ (Notified Body in Belgium) a detailed study was done of the measurement setup and devices for determining boiler efficiencies. Several aspects were studied: measurement devices (absolute or differential types), their location within the test setup (focussing on accuracy and their overall impact on the result) and the measurement strategy (measuring on the primary or the secondary water side). The study was performed for both full load and part load scenarios of a gas fired domestic boiler (smaller than 70 kW [4]).The results clearly indicate that temperature measurements arecritical for assessing boiler efficiency. Secondly the test setup using secondary circuit measurements should be preferred. Tests were performed at ‘Technigas’ on different setups in order to validate the findings.

► Labelling of boiler is now obliged by European standards.
► Error propagation is analysed for different methods of boiler performance testing.
► Secondary water side measurement with separate calibration of has highest quality.
► A sensitivity analysis showed that the water temperatures are important factors.