Thank you OpenEnergyMonitor: Octopus Daikin ASHP monitoring

ColinS · 2 November 2023 14:54

That is no different to my installation and I suspect many others. Perhaps in time a new breed of ‘heat pump optimisers’ will emerge who get involved before ( to specify) and after installation (to optimize).

The installers I suspect do not really budget enough (any??) set up time and so they do two things predictably 1) oversize to prevent customers complaining about the cold (few will complain about the suboptimal COP like us) and 2) use a ‘standard’ one size fits all programming approach.

It worked when they installed gas boilers that were grossly oversized and few people realised they were getting 90% efficiency when they should have achieved 98%. So why not continue doing it? Incentives would have to change…over to MCS…

matt-drummer · 2 November 2023 16:06

Thanks for all your help Colin, it has been really useful.

I think this is what I intend to do.

I think I should keep the heat pump I have even if I convince Octopus that it is too big and they offer to change it. I think I will be glad I have it on the coldest days. I can afford to run it even though the COP is not what i hoped for.

Increase my radiator sizes to exploit what I can of the heat pump output.

Add a radiator in my office. It’s a bit of a longer pipe run than my gut tells me is ideal, maybe 7 or 8 metres from another radiator but as you have essentially the same heat pump in a much bigger house the distance is probably no problem?

And then just live with it. I can find the best flow temperature that uses the least electricity even if the COP isn’t so great.

Its actually working pretty well all things considered, the house is really comfortable and it’s costing me no more than gas would have done. The house actually feels nicer with the higher flow temperatures, especially when I am sitting next to the radiator in the conservatory at my computer!

What do you think?

I am interested in any opinions or advice at this stage!

Lots of lessons learned and I hope it is of some use to somebody in the future. I found very little online about these Daikin heat pumps before I agreed to let Octopus install. If I had known then what I know now

matt-drummer · 2 November 2023 16:22

It’s actually working quite well right now, well enough to satisfy me. If I can get it to run like this for sustained periods it would be pretty good for me.

ColinS · 2 November 2023 16:30

Looking at the other Altherma 3s on the website it seems that the 9 and 10.6kw units have a common minimum compressor setting of 920 w approx. The 7kw unit at Weston Super Mare has a compressor that goes down to between 350 and 500 w. It would seem more appropriate for your needs - halving the minimum output.

Hard to say what the 7kw defrost /sub zero performance will be though but as they all seem to share a similar evaporator size they might all do the same at low temps. Worth examining the performance charts for each unit in more detail. there are certainly some anomalies in this range - I remember asking the sales rep why the 16kw had a lower output than the 14kw in certain conditions…he hadn’t a clue.

matt-drummer · 2 November 2023 16:49

My heat pump is at the front of the house as I had planning issues, a long boring story but basically it failed the MCS noise test by half a decibel and the EHO would not accept it under any circumstances at the back of the house.

Another MCS fail and a Daikin fail as the quoted maximum noise level in the brochure is what counts.

The Altherma 3 monobloc looks nicer than others, less like an air con unit plus I got approval from the local authority with this heat pump, not some other one. It’s permitted development where it is but I may have problems with a white (or yellowy creamy browny grey looking thing in time).

I am now running it at +10 on my WDC but I have left the Madoka at 22c.

It has been running quite happily for 2 hours and 15 minutes using 1kW to produce 4.5kW of heat for a while.

It’s good.

It didn’t do this on Friday when I did the same but set the Madoka at 30c, the maximum.

The last 50 minutes is at a COP of 4.10, it’s ok.

I am quite happy to run it for 16 hours a day using 1kW an hour.

I am now sitting here thinking what sort of property this heat pump would be suitable for. At it’s rated COP of 5 at it’s minimum electrical input it puts out 4.6kW of heat but it’s maximum output is only 9kW. That’s a pretty narrow window of operation and I can’t see any property needing 4.60kW of heat at 10c outside only needing 9kW when it’s -3.

matt-drummer · 2 November 2023 18:11

I changed my overshoot from 1 to 4 and this happened. Any ideas?

I assume it did a defrost here as well?

I also notice that DHW tank has gone back up to 50c, so it has performed a DHW reheat here despite reheat being off and only scheduled to heat to 50c at 14.00 each day. I’m a bit baffled by this.

matt-drummer · 3 November 2023 15:26

I think we have cracked it.

I am sure that when I change the radiators the flow temperature can come down and the heat output will remain the same. I predict I will be able to get close to the quoted COP of 5.0 achieved under similar conditions.

It was running for 4.5 hours continuously this morning from 5am and only stopped to do a defrost I think. It has now been running for 2.5 hours continuously since 13.00 and it’s looking pretty good all things considered.

Thanks to everybody for their help. I couldn’t have got here without the assistance and the OEM system.

ColinS · 3 November 2023 17:03

It looks as though the overshoot allowed it to go to 41c = 37 + 4 at 17:40 and then the pump speed must have increased a lot to drop the delta T. Have you fixed the delta T ? or left it on the HPC setting? I would suggest fixing it at 6 c for radiators. I’ve no idea what is happening with the DHW.

Hard to tell what is going on as sometimes weird things happen. For example; My unit switched off at slightly different times for a few minutes but just once per day on two or three days in a row and switched the back up heater on for 3 mins. As the evaporator had been well above zero with those external temps it cannot have frosted up but I wonder whether there is something programmed into these units. I have also seen it switch the back up on for 5 mins in the morning before the unit fires up after a night off even at 12 c outside… my back up should only come on below -6c. So phantom defrosts seem to happen.

matt-drummer · 3 November 2023 17:23

Hi Colin,

I am running my emitters as radiators so according to the manual the delta t is fixed at 8c.

It is variable if I set it to fan coils.

In the manual it mentions enabling modulation to deal with any issues, I have this set on the maximum of 10 at the moment.

All I have changed is the overshoot to 4 and gone +10 on my WD curve.

I seem to have hit a sweet spot with a flow temperature of around 43c and the return is about 6c lower.

It’s working quite well, COP is over 4 for a few hours now.

I am sure that with bigger radiators I can lower the flow temperature and get the electricity input to it’s minimum.

My new radiators have a capacity of about 180% of what I have now.

They are what I worked out as required before Octopus got involved.

The pump speed is modulating differently to what it is now.

I tried this last Friday but increased my room temperature to the maximum of 30c to see what happened. I am having much better results leaving the Madoka settings alone and have just changed the offset from the WD curve and the overshoot from 1 to 4.

It’s ok, the best I have managed so far. I think it is good that I have really extended run times, it has to be better.

The heat pump is too big and the heat loss was massively overdone but I think I can make it work ok.

The house is warmer than would be considered efficient and is a bit extravagent but I can live with that.

I am really interested to see how it performs when it is colder.

TrystanLea · 3 November 2023 17:28

Well done @matt-drummer and all involved! thanks @ColinS for all of your input! Looks like a really good result at the moment.

I’ve fixed the issue with the COP 30 min figure, I’ve switched it from calculating based on the kWh feeds which have low resolution (if coming from the heat meter directly vs power_to_kwh input processor) resulting in a figure that flipped in your case from 3.5 to 5 and back, to using the power and heat data averaged over the 30 minute period. The result is much more consistent now:

TrystanLea · 3 November 2023 17:39

Yes that should allow you to keep that same high compressor level and heat output but at a lower flow temperature, will be really interesting to hear how you get on with that and to see how the heat pump performs as it gets colder.

Is it not possible to get the Madoka to limit the room temperature but still have it come on consistently as it’s doing at the moment but say on for 1h off for 1h etc?

ColinS · 3 November 2023 19:18

Matt - working this through with you has helped me realize a few things;

The turn down ratio for most heat pumps (in equilibrium and without cycling) is only about 40% even though the compressor can be turned down by 80%. Your and my units want to operate at the minimum compressor setting of 920 w when it is 10c or above outside. They can produce a COP of 5 if the rads allow it to do so and so the output is 4.6kw. When it gets to Zero outside the compressor will ramp up to about 3.5kW but the COP will drop to say 2.5 so the output will be just below 9kw (without defrost) and about 7.5kw when defrost is considered (unless the air is very, very dry). So you can turn it down from 7.5kW to 4.6kW, 40 % turn down. Sure you could have 10 or more kW at higher temps but you do not need it and cannot use it unless you want to live in a 30c house!
In the Spring I was running with TRVs set to the room temp I wanted and a Madoka schedule for the lowest comfortable temperature and around 33 c flow temp. The established Paradigm - keep everything as low as possible. I was using about 16kWh each day at about 10c. COP was about 3.5. Now I use the same amount of energy each day but am running the house and the flow temp a lot warmer - so COP of above 4.5. So when you are at the minimum running level of the heat pump and it is stable (without cycling) you have a USE it or LOSE it situation. This will be different as the weather gets colder as a lower flow and internal temp will keep the compressor power down to its minmimum for longer.

Just one comment on your 10c modulation - that is plus or minus 10c? You might want to work out your operating sweet spot (say 37 to 45c) and place your fixed set point in the middle with enough modulation to get to each end of the sweet spot. So 41 c set point with 4c modulation.

All the best

matt-drummer · 3 November 2023 19:47

Hi Colin,

Yes, that’s about where I am at the moment. I could run the house colder but I don’t think I would save electricity, it may even use more. The best outcome seems to optimise the efficiency whatever it takes.

Once I change my radiators I will concentrate more on what works best overall, when I know what I have to play with.

I’m not sure what the modulation is, I don’t think it is the flow temperature. It is mentioned in the installation manual as a way of dealing with the fixed delta t of 78c when you set radiators as the emitters.

I have no idea what it does, the description is either too vague or beyond my comprehension!

What I have learnt is that this heat pump doesn’t seem happy at the lowest flow temperatures we see, there seems to be more to lose than to gain at the lower end. The best way to run it is at the lowest electrical input and make sure the house can handle it at 35c.

My gut feeling is that I will work well enough to heat this house when it is really cold and once I get radiators that can handle the minimum output of the heat pump I will have it running as efficiently as possible.

I look forward to finding out.

I will keep this updated when I make some progress, I think it’s a good lesson in how to diagnose issues and make something not entirely perfect work much better.

It has been really interesting to work through the problem in front of us and find an explanation that makes sense.

matt-drummer · 3 November 2023 19:55

Thanks Trystan.

I think Colin summed it up well with his explanation of how this heat pump works, you just seem to get more out of it by letting it produce heat, trying to reduce its output too far just makes it run inefficiently.

As I plan to change my radiators soon I am not going to spend much time now finding the best balance between COP, house temperature and electricity consumption.

There’s probably a good balance to be found in there somewhere.

Right now I am happy that we have pretty much proved that I can get a COP of 5 out of it on a heating run. Now I know it is working properly I can work to optimise it as best I can. Hopefully the radiators are my only issue now.

Thanks for sorting the problem with the 30 minute COP, I was looking for anything to explain what was going on with the heat pump. I have never been in doubt that your monitoring was working properly.

Once again thank you, I couldn’t have done this without it and if it was taken way from me I really don’t know how I would cope! Everybody with a heat pump needs this!

ColinS · 4 November 2023 11:28

No problem Matt, glad to help and I learned something in the process.

The modulation is on the Flow temperature, but it references the room temp on the Madoka.

Say you have a fixed set point of 40 c then when your room temp schedule ramps up from 16 to 20c the heat pump will monitor how quickly it is getting there. If it is too slow it ‘modulates’ the flow temp up a degree, then another, then another until it is getting there quickly enough. Once it reaches the set point it modulates down again until it reaches its equilibrium… so it could end up a few degrees below 40c if your modulation limit setting allows.

Weather dependent set point will just change where it starts this process and because my sweet spot - or efficient and realistic range is 33 to 39 (yours looks like 37 to 45 before the new rads) then I only use modulation - knowing that if it equilibrates down to 33 then that is fine by me, whatever the outside temp.

Incidentally the compressor ramps up or down to get to the flow temp set point ± modulation that the above process decides and the water pump ramps up or down to maintain the delta t (flow - return).

Hope this helps

matt-drummer · 4 November 2023 11:35

Hi Colin,

My modulation is 10, the maximum, do you think that is an issue?

I’m finding it slightly difficult to be sure what effect any changes have because I will always get to the point where the capacity of my radiators come into play and that then takes a bit of thinking about.

With my modulation at 10 then I guess it allows the heat pump to do whatever it deems necessary but that may not necessarily be efficient? Thought about it a bit and maybe if I drop the modulation it will allow the heat pump to ramp up more slowly and reduce the initial energy consumption, I’ll try reducing to 5 and see what happens.

I am now confused again, what is the overshoot, I thought that was on flow temperature? I assume that allows the heat pump to keep running even if the flow temperature set by the WD curve has been reached.

After the initial heat up the heat pump seems to settle down nicely at a COP of about 4.

The only thing holding me back now seems to be the flow temperature needed to get to this, once I sort that I should see about a 20% drop in electricity consumption whilst the heat output remains.

John · 4 November 2023 14:58

Hi all

Firstly, massive thanks to Matt, Trystan, Colin, Marko, Vinny and HydroSam for their work, analysis and instrumentation. As the owner of a EDLA09D3V3 HP, installed by Octopus along with larger radiators, I’m very interested in getting the settings optimised for electricity usage and efficiency. I’ve posted a question about P1P2 monitoring on another related thread from Matt.

I’m currently running using LWT mode only - I have to get Octopus back to move the badly placed thermostat, and I quite like not allowing family to mess with it! I am monitoring some Daikin Cloud data using a HA plugin, which only provides what the Cloud API has e.g. none of energy produced, return flow temp, flow rate and so on, but it does give me LWT, Outside temp, LWT Offset (setback) aka Target Temp. LWT Overshoot is 4deg. Family Room Temp is from a Tasmota DS18B20 in the room the thermostat should be in - you can see it’s incredibly stable.

You can see the compressor/pump cycling more/less as the Outside Temp varies up/down. I have DHW on schedule, and you can see the legionella cycle on Friday morning 2am - I should also move that to daytime, to improve COP using daytime temps, except it uses the cheap Octopus Flux power slot.

I’m trying to understand what is happening with Matt’s Daikin, and here’s my precis of my situation vs. his, to confirm my understanding:

9kW HP only reduces output by 40% i.e. from 7.5kW with defrost to 4.6kW minimum (from Colin)
My Octopus-calculated radiator output at the various room temps for 50/45 flow/return is 9.8kW (Ive checked this from Stelrad figures), but when adjusted for a flow/return of 32/27 for 12deg Outside (WD curve says 29deg + 4deg overshoot), they can only emit about 2.3kW
HP has to cycle to keep flow temp in required range for current Outside temp…
Consequent reduction in COP!
Matt has a similar problem, which he’s going to install bigger rads to fix
COP is EnergyOut/EnergyIn, so actually allowing the full 4.6kW to be continuously produced for the same energy input means the COP is better…
But my house is pretty warm with the current output; maybe I just live with the reduced COP because getting a better COP just for the sake of it, given I’m going to use that electricity either way, seems a bit pointless!

Is there something I’m missing/wrong about here, pending further instrumentation and analysis?

matt-drummer · 4 November 2023 16:20

Hi John,

What is your heat loss as calculated by Octopus?

Mine is massively overstated/overcalculate. They never listened and I knew my heat loss was around 4kW an hour at -5c outside and 21 inside.

I have analysed my data since I started heating 3 weeks ago and it confirms my heat loss at 4kW or less at -2/21. Octopus calculated 7.3kW.

They said that if it was less than 7 they would have installed a 7kW heat pump.

My radiators are big enough for the house and heat it comfortably at 30c flow and 7c outside, they are just not big enough to run the heat pump efficiently.

But I calculated a much bigger radiator requirement to satisfy my quest to run at low flow temperatures. My specification is about 180% of what I have now. I wish I had got they to change them at the time, they would have done it and it would be a lot less hassle than it is now.

My big mistake was not understanding the limitations of this heat pump, I never realised that its minimum output was so high.

But I think I can deal with it with some work, bigger radiators and increased heat loss by adding an area I didn’t intend to heat.

I am with you on COP isn’t everything but I felt the need to find out why I couldn’t get there, partly because I needed to know and partly to make sure the heat pump is working as it should be.

I think to that end we have succeeded.

Once I get a heating COP of 5 out of it I will be happy and then I can work out how much COP to give up to get the best electricity consumption in regards to comfort.

DHW is another difficult one. Mine is a bit erratic, I don’t really know why but I have taken to a daily heat to a higher temperature. My wife is happier and we use less electricity compared to a lower temperature + reheat.

I have abandoned the disinfection cycle for the time being.

I have repeated a lot of what I have said before but it is now quite a long thread and a summary is useful at times.

It will be interesting to see how you get on, when was it installed?

I know it’s money but I can’t recommend the OEM system enough, I would have been completely lost without it.

ColinS · 4 November 2023 16:22

I think 10c of modulation is too high - if the flow temp is set at 40c then this would allow it up to 50 or down to 30. Neither limit looks good for your system 30c is too low for your present rads and 50 will give you a rubbish COP. I would suggest a modulation of 4 to start with and a fixed set point of 40c - for your PRESENT system. With new rads drop the fixed set point to 34c but leave the modulation as it stands and see how it performs. Do this with NO weather dependent curve, at least to start with and then see how it goes.

The overshoot is different - all the above stuff decides where to place the set point, when the compressor is running it will try and reach this calculated set point BUT sometimes when it is warm outside the rads will shut down and the compressor will keep heating the water above the set point. So if the overshoot is low it will shut down at the set point but then cycle quickly (at high frequency). If you set a high overshoot to 4c then the comp will keep running until the flow is 4 c above the set point this will make each cycle last longer. I suspect that the Daikins are not good at fast (ie high frequency cycling), hence the suggestion to put the overshoot to maximum.

matt-drummer · 4 November 2023 16:38

Hi Colin,

My overshoot is set at 4 and I intend to leave it at that.

I let the house get cooler for a while this morning whilst we were out and set the modulation to 4. It was apparent quite quickly that it made things worse, I don’t know why but I have put it back to 10 as it is giving me the best performance I have seen.

Once I have changed the radiators I intend to run at a fixed flow, overshoot at 4 and drop the modulation to 4. I agree with you, I think a WD curve is not going to work with this heat pump in this house.

I don’t really know what the modulation is doing but i am not seeing flow temperatures drop, it’s holding up at 40c+… It seems to sit at 42c/43c quite happily with the modulation at 10.

I think the only thing holding back the COP is the flow temperature I a having to run. I really hope that increased radiator capacity is the answer that will allow electricity consumption to fall with no drop off in heat produced.

I think I will remove my WD curve tomorrow and set a fixed flow of 40c with an overshoot of 4 and modulation of 4 and see how that goes.

Tonight I just want to be warm, eat our lovely roast dinner and watch a film!