It is my intention to share output from my Level 3 kit but before then I would appreciate help in determining if our October 2025 installed Stiebel Eltron HPA-O 10.2 Trend HC 230 heat pump is operating at its best.
Does anyone have the time to look at the data, make observations and raise possible performance questions?
Initial monitoring helpfully revealed that an incorrect controller setting meant that the primary circulating pump was not modulating - corrected on 15 December - but I have no idea if the system has any other control anomalies.
Performance data has been collected as middle England’s outdoor conditions have varied from minus 2°C to plus 7°C but I don’t have the experience to know if the collected data reflect an optimally performing system.
The graphs show a steady 5° flow and return temperature difference, with flow temperatures varying according to external conditions. Indoors, the separately monitored 18°C comfort setting is being maintained with a 16°C setback only during the 16.00-19.00 hrs peak electricity price period. The 50°C DHW switchover is set for the least cost period from 04.00.
It looks like your heat pump is running well. It’s difficult to comment much without knowing some more context e.g property size, calculated heat loss, emitter type, cylinder size etc. Can you submit the system to https://heatpumpmonitor.org/ ?
Initial observations look like space heating is running very efficiently, with a COP of 4+ over the past month.
DHW has only achieved a COP of 2.8. I notice the DHW cycle happens when the tank is still over 40C. The DHW COP will be improved it you wait until the tank is cooler before reheating. But I understand that you want to re-heat the tank during the cheap overnight period (which makes sense. You could consider lowering the DHW set point to 45C, this should still give you sufficient DHW.
System now submitted. DHW divert at 04.00 now set to 45°C.
I should explain that in winter sunshine the house heating is supplemented by the secondary heat input from the solar thermal array (see system diagram and sample day). The mild and sunny conditions this week has meant that the heat pump had no need to run during the day.
