Hi all, looking for advice or ideas on what might have happened, what I might have missed and how to fix it. I’ve got an Octopus installed, 8kw Altherma 3 operating in weather dependant mode. It’s given up adjusting flow temperature based on outside temperature, as if it’s operating in fixed mode. …

[image] DaveB: a massive time commitment Your “idle” time could be months/years, but your “active” time should be small. You have your evidence : now it’s down to the suppliers to give a convincing explanation and close the case to your satisfaction.

Dave, I’ve the same model as you. As many people have said before Daikin’s don’t really like going below 30c flow temp, they get quirky. I was told by a senior Daikin engineer that regardless of settings, once working the heat pump always, always, uses the WDC curve. So I’m puzzled by the comment fr…

Hi Terry, Yes, tried the old turning off and on again but no joy. Below 30 is less efficient but if set to be at 28 it will usually be more like 29 - 30 in reality. I assume this is because of the overshoot. It seems to be doing just about OK but with slighty reduced efficiency like this. 26 (28 - …

Sounds as if your actual heatloss could be as low as 3.5kw. Going back to first principles how is your system configured? Does it have a buffer, do you have a madoka or a third party controller. If you do have a madoka have you tried using it combined with the WDC, I forget the exact settings at the…

Hi Terry, There is a volumiser fitted. The thermostat is the Madoka. I have tried using modulation but it doesn’t really work. I think because, when the WDC was working, the pump was usually trying to run near its minimum when it was 10 or above outside so had nowhere to go to reduce heat and turne…

[image] DaveB: A 9kw model was installed originally but this got swapped after 4 months because it performed poorly. A new survey was carried out before the 8kw was installed but it considerably overstates heat loss. Interested in how you managed to persuade them to change from the poor 9kW t…

Dave, when you say it is ignoring the WDC , what do you mean. You also mention offset, my suggestion would be to ensure the offset is set to zero. Also as I asked before how much radiator capacity do you have. I know @matt-drummer has a lot of radiator capacity and this can sometimes cause him to ha…

Hi Derek, Sorry to hear you’re struggling to get that resolved. I hadn’t settled up, maybe that made it relatively simple but Octopus were very good about dealing with it. I raised concerns about the survey before the installation based on gas usage and the EPC that Octopus arranged but they were a…

Hi Terry, The unit has stopped responding to the WDC so it permanently sits at the same flow temperature, unless I manually change it using the offset feature in the Onecta app or on the MMI. It is not in fixed mode but external temperature changes currently have no effect on flow temperature, whic…

Dave, you may have done this already, but in case you haven’t, Mr AI says; Based on common issues with the Daikin Altherma 3 8kW, especially those installed with smart controls, the issue of the WDC (Weather Dependent Control/Curve) stopping and holding a fixed flow temperature usually points to a …

Daikin Altherma 3 no longer following weather curve

Hardware Heatpump

ColinS (Colin Smith) 19 February 2026 17:46 18

A link to my post when I found this out some time ago…..