Coming back to the earlier question on DHW and immersion heater usage. The instructions are all over the place in the Installer Ref guide. pp178 -183 and pp195-196 mainly. I can see why installers just have a standard set up given this complexity…but on the other hand the Daikins are very flexible.
I’ve tried all the settings under 4-03 which defines how the immersion is allowed to operate, the results were very odd and not as described on page 196. I settled for 4-03 = 0 (restricted to disinfection and ‘powerful’) . So the immersion does not operate at all when I am just heating the tank to 44c.
I then looked at the heat up of my system during disinfection;
and saw that it takes an hour to get to the 57c which is the HP max temp. So I set 8-03 to 60 mins (the booster/immersion heater delay). You will see in this picture that the immersion/booster cuts for just 5 mins in after 1 hour. As the HP is still producing a COP of 1.8 (with the outdoor temp at 11c) it makes sense to use the HP up to its maximum in this way. I then trimmed the disinfection target temp to 55c (setting 2-03). Disinfection is not as effective at this lower temp but I never leave the house empty for long periods with the DHW heating still running so the risk is minimal. (if you do encourage legionella by doing the opposite then stick with 60c)