I have a Daikin Altherma 8KW running on Full WC, which has been running very well for the first 6 weeks of install.
However now the outside temp has hit double numbers the pump just cycles every couple of minutes, I have tried increasing/dectreasing heat curve offset by 2 degrees on the app but this makes little difference
Is there any setting I should be look at to stop this or to make it a sensible time
Many thanks
Mark
Your flow temperature is way too low.
It will never run at that for more than a few minutes.
That heat pump is inefficient below 30c flow temperature compared to above it.
If you want to run that low you could try setting overshoot to 4c if you haven’t already done so.
You can also try limiting the pump speed to give it the best chance of getting going at the lowest flow temperatures.
Daikins go to maximum flow rate for 20 minutes at the start of each heating cycle and this creates lots of heat and a rapidly rising return temperature.
Unless you have truly massive emitters it will never work.
@markr Do you have UFH or Radators? Buffer tank etc?
Mine has been doing the same thing since the temp rose above 10 degrees.
It kicks back in after 5 minutes and draws about 1kW. I’m guessing that’s the compressor and not just the circulation pump?
I’m not sure why Daikin have set such a short delay on the compressor restarts mine seems to try every 5 minutes or so.
Why they don’t just run the circulation pump for a couple of minutes and see what the return is before firing up the compressor I have no idea.
Whilst you have heating switched to on it will try to run.
It does run the circulation pump for about 5 minutes to make sure everything is OK to give it another go.
And that is what it does.
It fails because the start of a heating cycle is aggressive as I described earlier and it is too warm outside, too warm inside and the flow temperature is too low.
It will never work at a really low flow temperature when it is warm outside unless you have huge emitters.
It just generates too much heat and the return temperature rises too quickly.
It is designed to work with the Madoka room control.
You just have to look at your monitoring data and understand it to see where the problems are.
Then work out a way to make it work for you and your home.
It will never just sit there waiting to put in a bit of heat for 10 minutes and then wait 30 minutes and do it again, it is not how it works.
You may be able to do this with a different type of external control, maybe HA or a different room temperature control with a lower hysteresis than the Madoka
But Daikins don’t really like running in short bursts, they are not very efficient like this, particularly the bigger units.
I happen to have a Tado connected to my system alongside the Madoka, I can switch between the three control methods in the MMI.
It does the same when using the Tado.
Have you tried running yours in uderfloor mode with a lower delta T and higher over shoot, I was going to try this next to see if that settles it down at all?
I have tried everything over nearly two years with a Daikin.
But I haven’t had an issue with any of this since May last year.
Mine just runs and runs until I turn it off.
I paid close attention to what was stopping it and eliminated it.
Then I just live with it’s limitations in the way I feel is easiest for us to tolerate.
Your system looks to have been running well at 30°C with a rated emitter output of 20kW.
However, today it’s been cycling like mad, as you show. My guess is that some TRVs or something have shut off parts of the circuit, and it can’t emit the heat. Keep all valves open, and maybe raise the target flow temperature.
How much water is in the system? System volume should be sized so that the system can run at least 15-20 minutes at lowest output to avoid these situations.
Again, I thought that I had my system set to run continuous at a good temperature, however with the increase in outside temperature it has got haywire again.
This is my current chart:
I am running LWT, have a WC of 39°C @ -3 and 25°C @ +21, on the Madoka I have set to -2.
Considering what I need to do now, do I change back to Internal Thermostat (Madoka control) when the temperature increases and back to LWT when the outside temperature decreases?
Increase the WC? Increase or decrease the overshoot on the madoka?
These are the only things I have recently changed so have to assume one of them is not working as it should.
This is very interesting.
I don’t have all the active monitoring so can only look at the Smart meter😂.
But when it’s 11 or 12C that we’re having now it sits at around 250-300W for hours.
Leaving Water Temp is currently 29C.
The house is a nice 21C.
I do have 10 zones of underfloor heating, 4 ensuite towel rads and a 600 X 2800 K2 rad in an annexe - perhaps that is massive enough emitters?
Currently have Delta T of 4 and modulation of 1.
I’m kind of anticipating problems when it’s 14- 15C or more outside.
So, just to see what happens I changed my emitter to underfloor at about ~11AM.
I then dropped the DeltaT to 5 and increased the overshoot to 4.
It seems to have settled down for now.
This is on external control via my Tado at the moment.
I will have to keep an eye on rooms temps to make sure everything stays warm.
If it stays stable I will switch it back to pure WC later, maybe drop the overshoot and increase the DeltaT and see which causes it to start cycling again.
I sometimes see the same behaviour after hot water cycles where the water temp in the volumiser is high compared to the required flow temp for heating but that settles down once the flow temps return to normal.
The Diakin (and many other) start each cycle on maximum output regardless of the reason the last cycle ended. The return water from the radiators will be cool until the complete water content have pass var the heatpump, the heatpump have no visibly of average water temperature in the system.
The thermal mass of the UFH will be helping as the average floor temperature will change slower than the water temperature, also likely the return water temperature will increase before all the water have been past the heatpump.
The volumizer should not be in the circuit when in DHW mode. Normal connect in the return on central heating circuit before it joins the return from DHW circuit.
Yes, most heat pumps start higher and then throttle down.
Between runs it seems the pump keeps running, so it is not that it does not know the correct radiator/return temperature. The return is just immediately rising, which seems to indicate to me there is not enough system volume.
Some of these runs are only 4-5 minutes with average output of about 3000w. Every system should be able to buffer a lot more than that. Adding a volumiser should help.
Hi yes you are correct my mistake. It does make it a bit more confusing that I see this behaviour after a hot water cycle as well.
Sorry late response just rads and a 25l volumizer
Hi sorry been at work with no access to system .
TRVs are all set on setting 5 and circuit is fully open.
You re correct it has been running very well at a low temp, only change is the outside temp,
I did add a positive offset but this did not help apart from get the house to hot for the wife.
Don’t think I could ever achieve that 
