Are you absolutely categorically sure that the meters for electricity are installed correctly? That the additional heaters are not wired via the heat pump?
Hi Marko,
Yes, I am absolute certain.
When I was running the disinfection cycle, which I have now stopped, we could clearly see the data from the immersion meter. It canât be that.
The back up heater meter has never shown any use.
If the back up heater was in use surely heat would be produced and it would register on my heat meter?
The meters were installed by a qualified electrician who installs these meters every day as he works for a solar installer. I have three connections to the heat pump from the `consumerâ box on the wall next to the heat pump which houses the mcbs and meters. They are all wired correctly.
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My immersion meter has increased.
The immersion meter should have increased when doing the disinfection cycle, so should have values on it. And another indicator would be whether the 3kw is coming in after lots of hot water usage.
Just trying to rule things out.
Hi Sam,
Thanks for your help as usual.
My immersion meter does show use as I was doing the disinfection cycle at 04.00 on Fridays but I stopped it a couple of weeks ago and it has seen no use since.
The last time I did a disinfection cycle was 20 October 2023.
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It was the immersion heater.
I donât know why but it is using that to reheat the tank rather than the heat pump.
I only changed the DHW from scheduled to reheat only.
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So we both have the same problem in common. I would guess itâs one of the reheat settings we changed. Hopefully we can get more advice on the correct settings later today
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Canât reply in detail now but the issue is your settings for 8-03 and 4-03. Must go now but will reply later.
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@marko That was in the BEIS âexperimentalâ install phase, so it was part of that, rather than something they would have insisted on. I still think they would be better placed to do the âremote fine-tuningâ thing if they had that level of data, but if they can get anything like it from the Daikin MMI via the Daikin cloud, that would be significantly cheaper for them. There are limitations to that, but if it improved 90% of installationsâŠ
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Yes, sounds like a great plan! Iâve already cluttered this one up with enough facile questions and observations. Just point to it from this one!
Thanks again
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I truly donât understand what my heat pump is doing.
From 17.00 today it is running pretty well.
But nothing is any different from earlier in the day when it was pretty bad.
Outside temperature and inside temperature is similar, no changes to settings and the radiators are the same but all of a sudden it can run at a COP of 4.4 instead of 3.3
But it all goes wrong again as it has shut down.
Why now does it produce 30% more heat for the same electricity than it could earlier in the day?
From what I see it just doesnât behave consistently when conditions are the same. Itâs impossible to make judgements and changes when the goal posts keep moving.
Hi Matt, that is after defrost, the refrigerant has the extra energy it took from the water, so on the cycle immediately after(with your system that generally is less efficient) it looks like it runs more efficient.
P.S. On top of that, the flow runs 5 degrees warmer thus better heat transfer from the radiators/better efficiency.
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Hi Vinny,
I get that part but look at this. For 30 minutes excluding the boost from the defrost it runs at a COP of 4.32 consuming 1kW of electricity and producing 4.2 to 4.5 kW of heat.
If my radiators cannot take this heat at 35c flow which it was here, how has it done it between 16.58 and 17.26 but not earlier in the day when conditions were the almost the same? Room is 20.7c and outside is 10c.
Here room is 20.3c and outside is 8.6c but COP is so much worse. Electricity consumption is similar but heat produced is much less. The conditions are more or less the same but the performance is so much worse.
Right now it is using 1kW to produce 3.2kW whereas an hour ago it was using 1kW to produce 4.4kW
Why so, relatively , good between 17.00 and 17.30 compare to the rest?
All I need to do is replicate 17.00 to 17.30 and Iâll be happy!
Pity we cannot see how the flow setpoint is changing with modulation. but here is my best guess;
The COP is quite obvious on this as the electricity line is mostly sitting at the 920w minimum and the heat (output) line is initially at 4000w and then drops back to around 3500 ish. giving the COPS you mention.
I assume that you have all the TRVs set to maximum throughout the day ?
Up to 8:30 you can see that the rads are almost, succeeding in using the full heat that the heat pump is providing at 37 c flow⊠but the flow temp has still continued to rise and my estimate is that you could still get up to 4500w out without increases in the compressor electricity. That unused 500w is making the flow get hotter until, it reaches the setpoint plus overshoot - when it shuts off. You could have probably achieved a COP close to 5 with an increased flow temp of say 42c from the start. The first aim is to get a flat flow temp line (equilibrium) and not a rising one.
After 8:30 the sawtooth pattern gets worse - most probably the modulation is taking the set point DOWN and the compressor is tripping off at lower and lower temps as the modulated setpoint + overshoot gets lower and lower and so your rad output gets lower too. Even less of the available heat is being taken and the sawteeth get sharper and sharper as the unused heat increasing. The other possibility (which looks less likely) is that the compressor is tripping when the room temp has been achieved⊠my bet is the first explanation.
Iâd suggest the following approach (if this works then others can do the same to set up their systems);
- for the moment remove all modulation (set 8-05 = 0) 2) and remove the WD curve (1-04 =0)
- Set your fixed flow temp to 42c with all TRVs fully open. (this should apply to others who have an Octopus install with 50c design temp)
By slowly (over a few days I mean) increasing or decreasing this 42c find the temp at which you get a stable, equilibrium flow temp. (flat-lining)⊠like this.
That defines the MINIMUM temp you want your system to modulate down to. What will happen though is your system will start cycling, triggered this time by the room temp setting on the Madoka and not by the flow temp plus overshoot number. It should look a bit like this;
Once you have this MINIMUM temp you can start adding in come modulation.
Start by setting your fixed flow temp set point 2 c above the MINIMUM and then add modulation (8-05=1) at ±2 (8-06=2).
You can then fine tune these numbers after, hopefully, you have found your system equilibrium by the above process.
As we have said before - a 42c flow temp will be a lower COP than my 37c and the 32c used by the best performing ones, but not that much lower. Your only way to get the number down is to increase the rad sizes or use fan convectors in key rooms. Your highest flow temp should be your design temp of 50c perhaps.
Hope this helps
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Thanks Colin for your efforts.
Can you explain what happened between 17.00 and 17.30.
Why were my radiators able to cope here but not before or after?
What is different, can you see anything to explain it?
What we cannot see is what is happening to the flow. We can guess though. Heat output = FLOW x Delta T x Constant. So at 16:00 the flow halved when the DT doubled from 2 to 4 leaving the output the same. (same thing at 18:40). For some reason - perhaps after a system reset at 16:52 - the DT at 17:00 was 3 and the flow stayed the same throughout at a highish level. Not easy to see why the rads were able to put out more but as this is such a short period it must have been a transient effect - better mixing of water in the rads and so more even and higher rad temp perhaps? Anyones guess but an anomaly Iâd say.
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Itâs a shame I canât make an anomaly the norm!
Anyway,
I have set a fixed flow of 42c, overshoot is still 4 and modulation is off.
My heating schedule is 20c 00.00 to 05.00, 22c 05.00 to 16.00 and 23c 16.00 to 24.00
DHW is back on a schedule as I canât allow it to continue to heat at will using the immersion!
Will sort that when I work out the problem or you answer @HydroSam who has the same issue.
Obviously, being a bit dim I have another question.
If my radiators cannot take 4.6kW @ 35c flow where is this 9.1kW going at 37.6c flow?
Coming back to the earlier question on DHW and immersion heater usage. The instructions are all over the place in the Installer Ref guide. pp178 -183 and pp195-196 mainly. I can see why installers just have a standard set up given this complexityâŠbut on the other hand the Daikins are very flexible.
Iâve tried all the settings under 4-03 which defines how the immersion is allowed to operate, the results were very odd and not as described on page 196. I settled for 4-03 = 0 (restricted to disinfection and âpowerfulâ) . So the immersion does not operate at all when I am just heating the tank to 44c.
I then looked at the heat up of my system during disinfection;
and saw that it takes an hour to get to the 57c which is the HP max temp. So I set 8-03 to 60 mins (the booster/immersion heater delay). You will see in this picture that the immersion/booster cuts for just 5 mins in after 1 hour. As the HP is still producing a COP of 1.8 (with the outdoor temp at 11c) it makes sense to use the HP up to its maximum in this way. I then trimmed the disinfection target temp to 55c (setting 2-03). Disinfection is not as effective at this lower temp but I never leave the house empty for long periods with the DHW heating still running so the risk is minimal. (if you do encourage legionella by doing the opposite then stick with 60c)
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Thanks Tim!! You learn something every dayâŠ
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