I have an ECO4 installation.  Grant Aerona 13kW output ASHP driving 14 brand new radiators and all new pipework plus new DHW tank and 10 total (3.6Kwh) solar panels.  The installation and removal of 37 year old oil boiler was completed in 3 days the standard of work was good although much making good of old radiator fixing points required by me.  Handover was perfunctory at best and initially we were running it using the digital wireless room stat which was calling and not calling frequently.  We set it at 20°C.  System has worked fine since install but when temps dropped to around zero living room would not rise above 18°C. The radiator for the sitting room on initial delivery was too big (sat above window ledge) so a smaller one had been fitted.  Called installer and they sent a surveyor, turns out the original survey had reported the size of the window as smaller than it was. He recalculated and said we needed a bigger radiator which was fitted after about 2 week, since when temps have been fine.  On discovering this forum realised we were probably running it incorrectly as the constant on off from room stat never gave the heat pump chance to settle.  Have now opened all the TRV's (except conservatory that would be like heating Norfolk county!) and set thermostat to 30°C so constantly calling. Took my courage in my hand having read the manual and stuff on here had a look at settings as installed which were as follows: Max outgoing water temp in Heating Mode (Tm1) 50°C: Min Outgoings Water Temp in Heating Mode (Tm2)  30°C:  Minimum outdoor air temp corresponding to Max outgoing water temp(Te1) -2°C: Maximum outgoings Air temperature corresponding to maximum (surely that SHOULD be a 'minimum?) outgoings water temp (Te2) 25°C.  This was giving us an indoor temp of 23° plus.  

Adjusted as follows (28/01/2025) Tm1 40: Tm2 28; Te1 -2: Te2 20.  Still slightly too hot. Adjusted (30/01/2025) Tm1 38; Tm2 27; Te 1&2 as before.  Slightly cold now so adjusted (01/02/2025) Tm1 39 everything else as 30/01/25. This is giving 19.5/20°C all over house comfortable for us.  We run the system 24/7 ISH although around 2130 I do set the system back to 18°C using ECO setting on thermostat until the economy 7 kicks in at 0030. As this is 0.06p per unit compared with 0.37p per unit day rate I am quite happy for it to consume a few units heating the property again. By the time we come down it is back to 19.5° so quite happy.  Bedroom is always comfortable. 

I have not had sight of the heat loss calculation for the property but it seems to be working ok. We have an electric AGA which without fail consumes 30 units per night. So taking that out of the equation and background use of approx 6 units per day (I have kept usage records for many years on a spreadsheet so these are accurate figures) the ASHP is consuming around 25 - 40 units per day depending on OAT.  This equates to approx £8 to £15 per day averaging about £10 so January electricity bill will be £300.  Do these figures KWh not costs seem about right. The high figures were when OAT was around -7 overnight. 

The PV panels are doing very little as they are facing East/West (5 each way) and shaded in winter by a higher east /west ridge immediately to the south (where the very low sun is!!!). Come late Feb March they will get a much better sight of the sun. Currently they run the house when ASHP is idle i.e. light, Tele, fridge etc. if the light is good..  

Well that enough from me feel free to comment for my consideration, thank you in advance. Every day is a learning day.  Mark B