I posted these in another thread:
Hovering over the Hx value shows the following tooltips: (for air-source)
- H1 = Heat pump compressor only
- H2 = Outside unit only
- H3 = Outside unit + Booster and immersion heater (if installed & used)
- H4 = Outside unit + Booster and immersion heater + Central heating pumps & fans
If Legionella is disabled then it will assume immersion isn’t used and bump up to higher boundary.
If you don’t have “Includes booster and immersion heater” ticked, and haven’t disabled legionella, then the system is considered to be H2.