I’ve been though all the systems on HeatpumpMonitor.org today updating the measured heat demand figures and max outputs of the vaillants under defrost conditions in particular. There are now many more systems with an oversizing factor calculated. Im going to change the term “oversizing factor” to “margin factor” as it seems that the data does support the case for a reasonable margin factor on an accurate heat demand assessment! Having a margin of 1.4x is probably not oversizing but more right sizing (make, model, unit specific caveat).
This is the simple oversizing factor vs performance graph (acknowledging that apparent trends in this graph can be misleading, especially for some makes and model of heat pumps. E.g our experience in the Is an oversized Daikin really a problem? - #18 by TrystanLea thread).
Link to latest data:
https://heatpumpmonitor.org/?chart=1&selected_xaxis=oversizing_factor&minDays=280&selected_color=weighted_average_flow_minus_outside
