Just wanted to drop in and say this is a really interesting thread. I have another Daikin on the Heat Pump monitor list, the Altherma 11.2kw in Farnham, Surrey, so will be experiencing similar outside conditions to the other Hampshire Daikin’s mentioned above. Mine is the other R410a Atherma monobloc.
What has been discussed here over the last few weeks is similar to the journey I’ve been on over the last 2 1/2 years. I was one of the participants in the OVO/BEIS electrification of heat trial. My first installer was eventually kicked off the scheme (and MCS), my system was then nursed back to health by another installer who was parachuted in, but they only had scope to improve some of the pipework.
Over this time for heating, I have removed the fixed-flow rate, tried pure weather compensation (house gets too hot), low LWT with the Daikin controller modulation, higher LWT with Daikin controller modulating. I seem to be settling on a min LWT of 35C at 13C (generally the temp the house needs heating) and a max of 40C at -5C outside. The house was warm enough during the -8C we had last winter, with the heat pump gently ticking over outputting 5kw all day (another sign the pump is over-sized).
I too have similar conclusions, the heat pump is over-sized for my house, the radiators are probably too small in some rooms. And the radiators need further balancing still. I think my pipework is less than ideal, there are several branches and plastic has been used in places, however with a low heat requirement I should be able to make it work. ‘Cheap’ city plumbing TRV and locksheilds were used and I am really struggling to balance the system, if anyone has a recommendation for improving the radiator valves please share. Only one TRV in my bedroom is actually used, so I don’t really need TRV’s.
I don’t want to take over this thread though, so if you have ideas my own chat is here
Thanks again for documenting all this, I’ve found it a really interesting read.