I don’t know what has happened and I have never seen it behave like this before. I haven’t changed anything. There is no back up or booster heater, I don’t even have feeds for them anymore and my Daikin doesn’t have a back up heat anyway. Ignore the room temperature as the sensor is on top of a radiator that I keep forgetting to move.
This is today
And this is normal
Any ideas?
I think it is broken!
It is now really struggling to heat DHW producing less than half the heat it would normally do.
This is yesterdays normal DHW
And this is today (unfortunately I lost data connection at the beginning)
The end of the DHW cycle today is normal, it’s the beginning that it all goes wrong, same as the heating.
Flow rates are normal and I have no loss of water pressure. DHW has been heated to the requested temperature. There are no noises from the heat pump, it is as silent as it usually is with no abnormal vibration.
I don’t know what the problem could be.
Interesting, % carnot definitely too low in that DHW section, though it picked up to 40% towards the end there…
turn it off and back on again?? 
Does that work for heat pumps I wonder?
I’ve been trying to get my head around similar oddities on another system, not a Daikin. Hopefully this is a one off rather than a step change issue on yours, keep us updated.
Thanks Trystan.
Your monitoring system makes it instantly obvious when something is wrong, I’d be lost without it.
The heating is off too.
I know my heat pump inside out and something is wrong.
We’ll see what tomorrow brings.
@TrystanLea I have turned it off at the consumer unit but I am still showing electricity consumption, how come?
Interesting, I wonder if it’s low on refrigerant charge due to a leak?
It crossed my mind Glyn.
I don’t know what the symptoms would be?
The end of the DHW cycle was normal.
But the heat production at the beginning of the DHW cycle was way too low.
The heating is strange, this morning was really bad, it doesn’t look right but it returned to normal after about 20 minutes.
I left the heating running after the DHW cycle and it’s really good with no issues.
I can’t see anything amiss other than excessive electricity consumption on heating this morning and poor heat production in the DHW cycle.
I have no error messages anywhere and no other signs of an issue.
But something is wrong.
Low carnot %, low COP, low heat output, struggling to reach high flow temperatures and nosy outdoor unit would all be symptoms.
As a test, you could set the HP to run at the highest possible flow temperature to see which it can achieve in its current state.
Looking refrigerant is obviously a one-way process, you mention that sometimes it returns to normal, therefore maybe it’s something else? A stuck diverter valve or filter blockage could be a possibility, but the steady flow rate suggests otherwise. No harm in checking the strainer and or mag filter if fitted.
Thanks Glyn,
Well, it got to the high DHW temperatures as normal, it struggled at the beginning of the DHW cycle.
The outdoor unit is virtually silent as normal.
It has been really good on heating today, exceptionally good this afternoon, COP over 7
Flow rates are normal, DHW is a good test, 24 lpm even when performing badly and no change in that during the cycle today, and it is the same as other days.
I’ll see what happens tomorrow.
I can’t contact Octopus/Daikin until Monday in any case.
I have turned it off at the consumer unit and will turn it back on tomorrow.
My data shows it is still using 10W, how can that be?
That’s good to hear, it sounds like it’s back to normal!
Is it fed from multiple circuits? Maybe you just turned off the outdoor or indoor unit?
It’s all off Glyn.
It has a separate supply from my electricity meter installed by Octopus with its own consumer unit in my garage.
It is all off and all the indoor controls are off as they have no electricity supply.
The Madoka (room stat) is off as is the Dakin MMI, both blank screens with no power.
Did this also cut power to the monitoring and the meter(s)? The electric meter(s) won’t able to report 0W if they are switched off, so you may have seen the last reported figure?
Hi Matt. Are there any other fault indications other than those shown in EmonHP? Can we be sure that the heat meter is not giving incorrect readings?
I think you’ve said that the pump is heating rads and DHW satisfactorily.
I have my EmonHP electricity meter directly upstream of the RCBO that feeds the entire heat pump installation. So switching off the RCBO leaves the meter still live and reporting.
Hi Glyn,
The meters are off so they cannot be reporting any use, and I don’t think there is any.
It’s just the main dashboard shows this, I can’t actually see any energy use though, I don’t know where the 10W comes from.
Hi David,
I have no fault indications on the MMI, the Madoka or the Onecta app
The reported electricity use is correct as I have other ways of checking.
The heating was Ok after the first 20 minutes or so yesterday but the first 20 minutes was not normal. Much more electricity was used than I would expect and the heat produced wasn’t enough.
The same was true of the DHW and that is easier to see that something is clearly wrong. The whole cycle took much longer than usual, I guess due to lack of heat at the beginning of the cycle.
We’ll see what happens today.
I have run the heat pump a bit over the last three days.
I don’t have the problem I had on Saturday but something has clearly changed, the heat pump doesn’t get to temperature almost immediately like it did before Saturday.
I have called Octopus and they will arrange a service visit this week.
All I can say is check your filters!
My problem has returned!
I noticed this over the last couple of days, DHW was bad on Thursday but fine yesterday. Heating was bad on initial start on Friday.
This is todays DHW, I noticed the problem, stopped the DHW cycle and started it again 10 minutes later. The restart was as normal.
What is clear is the difference in dT on restart and therefore the heat produced for the electricity consumed.
I will check the filter again tomorrow but I am struggling to see how that would make the return hotter than normal.
Maybe it is a problem with the heat meter, but I find that hard to believe as the problem when heating is a larger than normal electricity use and a lack of heat.
The flow temperatures seem very erratic, are the heat meter sensors ok, or dose the heat pump show similar?
Hi Tony,
The fluctuations in the flow temperature have always been there with my heat pump and the others that I have seen behave the same way.
It is most pronounced when heating in milder weather.
I am running about as low a flow temperature that the heat pump is happy with . I have a permissible overshoot of 4c on my fixed flow temperature and I the heat pump uses this as it needs.
It is a Daikin characteristic as far as I can see.
I can see the flow temperature on the heat pump data and it agrees with the heat meter.
If the problem only existed with DHW I might suspect a problem with the heat meter reporting heat, either air in the system or a fault with the heat meter as the electricity consumption looks normal.
But the issue shows up very badly at the start of a heating run. Not only is there a lack of heat, there is also excessive electricity consumption compared to normal.
This is yesterday’s heating. It stopped itself after 20 minutes or so, just as the flow rate was reducing to normal. It then restarted completely normally 5 minutes later. There is a huge difference in the simulated carnot heat output. It’s not normal for my heat pump, something is wrong.
I’m no expert, but I’d guess something’s up with the refrigerant cycle that isn’t delivering the expected amount of heat. May need to ask Daikin about it.
