Thank you OpenEnergyMonitor: Octopus Daikin ASHP monitoring

matt-drummer · 29 October 2023 13:25

Yes that electricity heated something, where the heat went I don’t know. Some in the blip at the beginning? The rest outside?

What about the dip in heat output at about 16.07, I have less heat than electricity.

I have a warranty direct with Daikin for seven years.

What that means, I’m not sure.

I can’t imagine that either Octopus or Daikin want to read negative comments about the product.

Of course, until I know what the problem is, I will reserve judgement.

It is clear that it is not working as it should.

I am assuming that the OEM gear is working properly, I think it is overall as the data agrees with my other sources.

Vinny · 29 October 2023 14:13

the same thing happens with the Daikin that give the expected performance, let’s assume it’s warming up the compressor

Vinny · 29 October 2023 14:40

At this point I think it’s only fair to change the focus from the in house side of things towards the heat pump(Octopus or Daikin).
By not having the expected performance from the DHW as well, it’s clear that even though the radiators don’t seem to be ideally sized, something stops the whole system performing.

If we assume the HP functions properly but for some reason the heat doesn’t get transferred efficiently(air in the top of the heat exchanger) then there’s nothing you can do.
If something is wrong in the heat pump(shortage of gas, elements that control the gas, valves, sensors) that’s clearly nothing you can do, only guessing(enough of that).

3.If everything works well with the HP, whatever it is the issue you will find out from them.

The warranty is there to be used.

Good luck!!

matt-drummer · 29 October 2023 16:27

So I just checked my radiator flow and return temperatures.

Every radiator’s flow is about the same and the difference between the flow and the return on each radiator is between 4c and 5c.

Can I conclude that water is flowing relatively well through each radiator?

marko · 29 October 2023 22:13

Blimey. That’s not an insubstantial amount off preheat vs…none by most others in this weather.

Agree. Look a little later though and it’s back to COP3 ISH in DHW mode which suggests something not mechanically terminal?

Those links are an eye opener on a few counts

Perhaps fan coil mode to force a 5C dT instead of an 8C dT is a deliberate efficiency fudge
These things can kill themselves mechanically (burst their plates) if sensors fail. I wonder if R290 units need to have any more interlocks for safety that would make them more robust too
There have been failures that can cause low COP; some of which are electronic so could be intermittent
These units don’t like low flow temperatures. 35C or up. Interesting but not understood. Why do some units love these and others hate them?

HydroSam · 30 October 2023 09:13

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.

matt-drummer · 30 October 2023 09:38

Thanks, any input is useful.

I expect there are lots of us in similar positions. I’m not saying it’s a problem confined to Octopus but they have been installing a relatively large number of Daikin heat pumps.

The sad thing is, I would imagine that most owners are oblivious to what is going on.

I haven’t experienced sub zero temperatures yet but I have read that Daikin heat pumps are not as good at delivering the rated output at these sort of temperatures, but that is just what I have read.

If that is true, then I doubt my heat pump is over sized.

I don’t think my radiators are too small for the house as I have no trouble heating to 23c when it’s 7c outside at 30c flow temperatures.

I too struggle with pure weather compensation, the house gets too hot and the flow temperature is too low for the heat pump.

So far I can only conclude that the heat pump has a narrow window of operation in terms of efficiency and at the moment I can’t seem to get into that window.

Whatever I do has minimal effect on COP, I can’t destroy it with high flow temperatures and I can’t seem to do better than about 3.3 to 3.4 for heating.

It’s all a bit disappointing.

My trvs are all wide open, I see no value in restricting the heat pump by shutting down radiators.

My radiators are well sized for the rooms and the temperature in each room is in proportion to that designed even if I am running a little warmer overall.

I have Drayton trvs fitted.

I looked at fitting Danfos auto balancing trvs. I downloaded their app and tried to configure my radiators, those I have now and what I plan to change to. The minimum flow temperature I could choose was 40c but even at that it said that their valve was not capable of flowing enough water. That was for K3 radiators at 1200mmm x 600mm. It had no chance with my K3 500mm x 2200mm!

Whether they would actually work or not I don’t know. They are not expensive, about £30 each.

I have some plastic pipe but I can’t see any flow problems, my radiators are all roughly the same temperature and all seem to be flowing water with a difference between the flow and return of each one of 4c to 5c.

I should have my thermal imaging camera later and I will be able to check how they fill.

If I can eliminate any problems with my radiators I should be able to concentrate on getting the best out of the heat pump and/or working out what is wrong with it.

If my heat pump really does have such a narrow window of operation then I will start to feel like it has been mis-sold.

marko · 30 October 2023 11:02

You will not be able to use the pressure independent presettable danfoss TRVs. Those are intended for large heating systems that experience a wide range of differential pressure and operate at large (20-30C) deltaT between supply and return.

If your rads really are pretty much equal in deltaT then your existing setup may not be terribly out of balance…

We could do the math if it got to a steady state at a decently high flow temperature. The room also needs you be at a known temperature and without drafts though. (you can’t open windows too reduce it to 20C because that introduces extra air movement which will increase radiator output)

You can also try the heat meter balancing version.

pump on all rads open. Note flow rate.
switch off one rad, not flowrate, switch on again

Repeat until you see the effect of turning off each rad by the difference in flowrate between everything and one less. Compare against what it should be by math.

That isn’t perfect (shutting off flow to one will reduce pipework pressure drops and increase flow to others; especially on branched systems with marginal pipe sizing; less so on manifold type systems) but will pickup gross imbalance.

matt-drummer · 30 October 2023 11:08

Hi Marko,

Thank you again.

Yes, I dismissed those trvs straight away as unsuitable.

I cannot see any major issues with the balance as it is now and I intend to change most of the radiators in the next couple of weeks so I am not going to spend too much time on this now.

matt-drummer · 30 October 2023 14:11

No preheat or warming up the compressor for the first run of the day here. It was warmer outside on Saturday afternoon than it was this morning and the heat pump had already bee running. Maybe it is something it does to prepare for a DHW cycle., who knows!

HydroSam · 30 October 2023 17:56

I think it is a pre-heat thing when the pump goes from standby to full loading. On my display I get a small icon depicting when this happens. Daikin refer to it in the manual as Hot Start Mode active. That’s all the details they provide in my manual.

matt-drummer · 30 October 2023 18:13

Thanks Sam,

It did something during/before my DHW on Saturday.

It did not do it this morning even though it was colder and the load this morning was much higher than Saturday, 3 and a bit kW on Saturday, 11kW this morning.

It doesn’t make sense to me.

matt-drummer · 30 October 2023 19:42

Time to display my ignorance and stupidity again!

I have been looking at some other heat pumps for a few minutes.

So my house might be good or bad in terms of heat loss and my radiators may be good or bad too.

But the heat going into my house is the heat it needs at the room temperature I have set.

My heat pump is achieving that room temperature.

So if my house needs 3.3kW of heat at this moment that is the same as any other house taking 3.3kW of heat.

Is that correct?

If so, my heat pump is is consuming 1kw of electricity to produce 3.3kW of heat why are some other similar sized heat pumps only consuming 500w to do the same job and why are some other similar sized heat pumps producing 6+kW of heat whilst using the same amount of electricity as mine?

Logically I come to the conclusion that my heat pump is either defective or badly designed?

I know this is stating the obvious but my heat pump is either consuming too much electricity for the heat produced or it is not producing enough heat for the electricity consumed, I can’t see any other explanation.

I have also taken account of my flow temperature, increasing it or lowering it makes no appreciable difference, if anything lower flow temperatures make it worse.

Is there any other plausible explanation?

I have tried it for a couple of days at higher flow temperature so I am going to give it another go at lower flow temperatures and see what happens.

Maybe these heat pumps are designed for different climates and perform better with more sustained lower outside temperatures. They cannot have designed it to work like this when data from the competition is so readily available?

matt-drummer · 30 October 2023 20:47

Low flow temperature

High flow temperature

Really high flow temperature

Really not much in it, room temperatures the same in each case except the really high flow where I let it get as high as it could. It made barely any difference to the COP, it should have destroyed it compared to the other examples.

Heating is barely any better than DHW heated to 50c.

And this is a Daikin 10.6kW Altherma 3 in Basingstoke.

Why would it be producing so much more heat than mine for less electricity, it’s essentially the same heat pump? Flow rate is the same, outside here is 3c warmer, my room temperature is 1c higher and my flow temperature is about 2c higher.

matt-drummer · 30 October 2023 23:02

Is there any clue to monitoring issue here?

COP for 30 minutes is 4.73 which is more like where it should be but COP in window is only 3.68 for 27 minutes.
I see discrepencies between these two figures all the time now. I don’t recall seeing this for the first week of heating but for the last week I have been noticing this.

It may be something or maybe not?

matt-drummer · 31 October 2023 17:30

DHW today

DHW yesterday

I don’t see how it can be so different, starting temperature was the same and everything else is similar. Just the amount of electricity used today is significantly more

ColinS · 1 November 2023 19:32

Matt,

I’ve been monitoring the energy use for DHW in my daikinhants11kw installation and thought it might be useful for you to compare with. IF your COP readings are wrong due to metering issues this will get round this to get to the absolute heat pump performance. I have a 250Litre tank and, although the probe only measures tank temp at one point the delta T vs electricity usage on the tank for yours should be proportional.

How big is your tank and how do i identify you on openenergymonitor.org? I might then be able to do the comparison for you.

You can see there is a wide scatter of results- the points at the top right are for the legionella cycle.

Colin

ColinS · 1 November 2023 20:10

Just realised I can only do it for you with the tank temp … are you measuring that?

HydroSam · 1 November 2023 20:55

Matt
It might be nothing but the response of your flow and return temperature data doesn’t look quite right to me. It’s more ‘steppy’ than others, and seems to often have a lower resolution jumping around a degree. If you compare to my hot water trace from today, temp data is much smoother. I wonder if the temperature probes aren’t seated correctly?

FYI - Also an 11kw Daikin but the older generation, and they seem to have changed the heating characteristics. Mine goes full bore from the start, whilst yours and the DaikinHants 11kw of @ColinS
are more gradual in temperature rise.

matt-drummer · 1 November 2023 21:12

Hi Colin,

I changed to a scheduled DHW heat @ 14.00 every day to 50c on Thursday 28 October.

I have disabled the disinfection cycle for the time being as well as the reheat. Scheduled + reheat at 45c used more electricity than heating to 50c once a day. It would also reheat and then heat again a couple of hours later on the schedule at a COP of less than 1. That’s just stupid!

The starting point probably varies but I know today was 35c as I checked and I am pretty sur every day has been 35c except for Saturday which was 37c.

My tank is 205 litres and I am an Octopus customer in Ipswich. The only one so far on there.