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 do want to include immersion, then you probably want to include both the electrical and heat input. This requires knowing how many watts are going into the immersion and adding it to the power and energy feeds. Be aware that this will drop the COP, and will be at a disadvantage when compared to other H4 systems that never use the immersion.
Personally, I think it’s best to exclude the immersion entirely, as it’s not pertinent to the performance of the heat pump.