My DHW flow rate change ~20 to ~24
Was that the day of your service Neil?
What was the flow rate on installation, had it deteriorated over time?
Service was on the 24th of June, there was debris (jointing putty) in the strainer basket, I was not recording flow rate in Grafana from the beginning, but no deterioration over time, just the bump
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Thanks Neil.
I’ve just myself managed to get something working using the daikin onecta cloud access. I don’t use home assistant, so I’ve just used a standalone python script. I can upload something to github if it might be of any interest.
(Unfortunately those screenshots are a bit too small to make out any details.)
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You can open the image in a new browser window and enlarge it - the resolution is there.
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Doh! I did open in new tabs, but just got the browser to scale the image, rather than clicking to let it redraw it full size
I’ve not yet found very much detail available. I’ve got LWT, external temperature, room temperature, HW temperature. Plus consumption rounded to whole kWh per 2-hour slots, same as the Onecta app.
Next project is to see if I can get anything interesting out of the Madoka using bluetooth…
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A quick way to expand almost anything viewed with a browser:
ctrl + zooms in and ctrl - zooms out.
ctrl 0 restores the zoom level to normal.
Works on Windows.
I don’t know if it works on Linux, as I use only the CLI on my linux box.
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It does - Discourse (the forum software) fits the image to the page, so zooming the page makes the image bigger, but the resolution stays the same. Opening the image (only) in a new tab or window loads the image at the original resolution. This isn’t necessarily better, though it often is, but it will never be worse.
(With the caveat that the style sheet that the page loads can change just about anything from the default values, so text and images, or panes within the window, might not zoom in the same proportion or at all. e.g, clicking the image here opens the image in a pop-up, but zooming zooms the page behind and barely affects the image on top. You must right-click and open the image in a new tab or window.)
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Yeah, that was the problem… it just scaled up the thumbnail, giving very low res, rather than loading the image at the proper size. (Firefox on linux.)
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Hi Matt, I struggle reading all the stuff on here, and no doubt this reply is in the wrong place. I wondered where you got with possibly monitoring your discharge superheat? I have slowly been learning what might be happening. One of the ‘safeguards’ for when liquid comes back to the compressor (it should be all vapour) is for the minimum speed to increase. It could be part of an algorythm. In the case of Ecodan, I think the logic is … if discharge superheat too low, and closing the Exp EEV (expansion valve) isnt doing enough, then increase the compressor speed. It would be interesting to see if Daikin have this control ‘reflex’ … or if for some odd reason, your EEV is generally open too much at cetain times
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Hi John,
Thank you for your continued interest and support.
I don’t remember when we last discussed this so here is a brief summary.
The heat pump appears to be working quite well although I have no idea whether it is working as well as it could, but generally performance seems good.
My problem is still there and it only ever noticeably manifests itself at the beginning of a heating cycle. It is not restricted to either space heating or dhw.
I can easily spot very quickly when it is going wrong and I am fortunate to be able to monitor it.
I stop the cycle as soon as I know it is `failing’ and restart it. The problem goes away.
I had a couple of visits from Octopus engineers that resulted in them sending Daikin to check the heat pump.
The Daikin engineer refused to look at the heat pump, he said it was heating water and all was fine. He said my heat meter is not 100% accurate (true) and didn’t understand what the heat created on the charts represented.
He tried to explain how to calculate heat produced and I tried to explain that was exactly what the OEM chart does using flow rates and temperatures.
It was going nowhere and he basically said that I was too fussy and he had never met anybody who went into so much detail.
He thought the heat pump was performing well when I showed him the problems, he justified this as performing well and as it should because the flow temperature was increasing.
Octopus now want to send out two higher level engineers having learned of the Daikin visit outcome.
That will happen soon, I have been unwell for a few days and couldn’t deal with it.
I don’t understand what is going wrong, something is but it is intermittent and I can’t see any particular set of circumstances that link the events together.
The heat pump was serviced in June and I have been able to identify an increase in dhw flow rate after the service. It has gone from 19lpm to 24lpm and this is when the problem first started, earlier than I realised.
The filters were cleaned and that might explain the increase in flow rate but I don’t think so. The flow rate was 19lpm on dhw when it was installed, that is brand new with a brand new clean filter.
The heat output on dhw is not smooth but I reacll my dhw was never that good with the 9kW Daikin I had previously which may indicate that it is just the nature of my 205l Joule slimline tank?
But, I could understand if the problem was just with dhw, it isn’t and the heating shows the same issue.
I do restrict my pump speed to 60%, as low as it can go as I found this helps with getting the heat pump to run at lower flow temperatures in milder weather.
The Daikin heating cycle always starts with around 20 minutes of full pump speed, this is quite aggressive and results in a rapid increase in return temperature which can stop the cycle.
I had a firmware update on the heat pump in May and so this is the first time I have been heating since the update.
I am inclined to remove my pump speed restriction and see if the problem persists.
Maybe it’s me and my settings but then I would expect to have consistent problems, which I don’t.
I am a bit baffled by it for now.
So that is my not so short summary of where I am at, sorry 
I have the 6kw Daikin, as we know its essentially the same heat pump to your 8kw. Mine was installed in Nov 2023 and has always done DHW runs at 24lpm.
This would be interesting. Was any change to the pump speed limitation made around the time the problem started? The manual states that when setting a pump restriction that it will be observed, unless the unit is not able to meet its minimum flow rate, in which case it will be ignored. On the CH side if I close off enough radiators then 60% pump can no longer meet the minimum flow of 7lpm. In this case the unit does not appear to just increase the pump speed a bit above 60% to achieve the desired flow, it instead jumps straight to what I presume is maximum power and flows (noisily) around the CH circuit at 21-22lpm. It will then flow at that speed under all circumstances until the heating is switched off.
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Hi Jonathan,
My pump speed has been restricted to 60% for a long time, it is a trick I learnt with my troublesome 9kW Daikin. I did this soon after installation with no issues until September.
I don’t have any trv’s or zones, all of my radiators are fully open at all times.
My flow rate at the start of a heating cycle is around 11 lpm and then it settles to a steady 6.6 lpm.
I run as radiators with a fixed dT of 10c so my flow rate in heating is always at the lowest possible and I never see it increase.
The heating problem always occurs at the beginning of the cycle when the flow rate is higher.
I need to change some settings and see what happens.
I have a slimline tank and I understand there are some settings to take account of this but haven’t looked yet.
I don’t know why it has changed, maybe something was changed at the service, but I don’t know.
I don’t get a particularly wide dT in dhw, a little over 4c at best and when the problem occurs it is down around 2c
The low dT is the symptom and it comes with increased electricity consumption, but I don’t really know whether it is an inability to deliver heat to the tank or a struggle in increasing flow temperature.
Maybe I can compare in detail what is going on when it goes wrong to when operation is more normal.
I was really expecting Daikin to know what the cause of the issue would be, I can’t imagine this is the first time a fault like this has occured.
Thanks for your summary Matt.
My hunch is that your discharge temperature is going far lower than it should at those times of low output. Not sure how this can be ‘fixed’ though. I have leaning more about my 6kW Ecodan, and the ‘tricky’ issue of controlling discharge temperure at low compressor speed.
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Thanks John.
Maybe my issue is being caused by two separate settings.
The DHW problem seems to be related to a high flow rate which gives low dT. This doesn’t always show up and is perhaps related to the starting tank temperature and how the water is distributed in the tank?
The space heating could be that I am just not working the compressor hard enough at the beginning of a heating cycle?
I have a look at @KnightPhoenix heat pump from time to time as a sort of check on my heat pump.
Our systems behave very similarly most of the time.
Today his heat pump is behaving the same as mine did when I first noticed my `problem’ during space heating.
Maybe it is not a fault at all?
It doesn’t look right or normal to me though.
https://emoncms.org/app/view?name=MyHeatpump&readkey=bfd97700dd78658dedd70ff6670b453c
I just caught my 8kW Daikin doing a similar thing. It’s running very hard today and defrosting quite often due to the cold weather. Heat output suddenly dropped from ~8kW to ~5kW. I had to stop & start it to “fix” the issue:
