Congrats @matt-drummer you must be really happy with the performance of the new unit! this is looking great! your running at a much lower flow temp and more consistently and a substantial improvement in COP by the looks of it!
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Thanks Trystan,
It is going quite well, really good when it is cold with minimal defrosting.
I am struggling a bit when it is warmer to find settings that work. Daikin’s initial phase of the heating cycle is quite aggressive in terms of flow rate, I can restrict it like I did with the 9kW but that causes other problems.
I just get more heat than the radiators can handle at really low flow temperatures.
But all in all, a huge improvement, it uses half the electricity and I don’t have to open doors and windows.
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Really impressive difference! really interesting to see such a night and day change, your low temp rads are really coming into their own as well, well done 
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I did say all along that I had the wrong heat pump.
There isn’t really any denying it.
I hope the people I upset at Octopus notice, at least Octopus and Daikin are starting to get some better performance and aren’t languishing at the bottom of the COP table.
It doesn’t really matter but I am happy that they can be made to work relatively well.
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It’s interesting comparing the weeks before the switch to the last few weeks:
Before COP 4.09, Outside temp 8.7C, Flow temp when running 34.7C, Room temp: 21.8C (very patchy).
After COP 4.73, Outside temp: 6.2C, Flow temp when running: 29.C, Room temp: 20.2C
Carnot efficiency appears to be generally higher with this unit, periods of ~55% of carnot vs 50%, very nice!
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Thanks Trystan.
It’s pretty good.
It has been outstanding in the colder days over the last two weeks, it was changed two weeks ago today.
I am a bit tired of heat pumps right now, it has been a traumatic five months, I just want to forget about it for the time being and see out the heating season as fuss free as possible.
I have tried a couple of times to run it on the Madoka but it hasn’t worked very well so far.
I think I am just going to leave it alone now in fixed lwt.
Maybe I will be more inclined to fiddle with it a little more come the Autumn.
I am quite happy though, not really anything to be unhappy about now.
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OK, having looked at my data and extra/interpolated from the numbers, I’ve just sent an email to Octopus aftercare asking for a review of my heat loss survey and actual data, to confirm the sizing of my 9kW (secretly 16kw!) monster. Let’s see what happens!
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Hi John,
You must be able to tell what your heat loss is at the design conditions using your data from this heating season?
How much heat did your house need to maintain the designed room temperatures at the design outside temperature?
I was able to demonstrate beyond any doubt that my heat loss was around 4kw at my design temperatures and I am sure @KnightPhoenix was able to show the same from his data.
One thing I found useful (but a bit tedious) was to calculate my heat loss over a couple of cold months.
In the Spread sheet below you input the outside temp in column B and the kW used that day into Column F.
C is auto calculated by dividing F by 24 (hours a day) so you know how many kW you need every hour.
I have split this into Heating and DHW but you can just run wit the combined figure.
This spreadsheet, with a HeatPunk survey I completed and the link to my heat pump on here provided more than enough evidence that my heat loss was actually in the 5KW region and not 7-9kW
Farnborough,Hampshire - HeatLoss Oct-Nov.xlsx (41.1 KB)
If you need anything just shout. My only goal here is to get as many of these installs above a COP of 4 as possible.
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Hi Zak,
That is really good.
One thing to remember maybe is that the heat required needs to be sufficient to maintain the designed room temperatures all of the time.
Many people talk about not needing to be so warm and night time set backs but one thing that is true with any install from Octopus is that they are not just about the current owner, it is about future owners of the property.
The heating system must be capable of meeting the design conditions even if the current owner requires a cooler home.
I think this applies to all MCS installations and many other things.
I hope you know what I mean.
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Thanks @matt-drummer @KnightPhoenix You only need to look at my EmonCMS.org entry for 18 Jan - avg ambient -1.6C, 118kWh generated for 4.9kW avg over 24 hours, room temp at 23C, to see that Octopus’ heat loss figure of 8.3kW at -2.2C is a bit unlikely. Even I’m pretty amazed by that!
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Then that is all you need.
But you don’t need to convince me or Zak, you need to convince Octopus.
John,
I am just here to tell people how I flagged my issue and the proof I provided up front.
I have worked for 15 years in customers facing software/ IT support and a year in an R&D role.
If you go to a company and say ‘i think it’s broke’ they may investigate but may also say ‘you don’t know about this we are the experts, it’s all ok’.
If you go to a company with two heat loss survey’s (or even just heatpunk calculations), evidence of your actual heating usage (over a long extended cooler period) and system data, then provide a solution showing exactly what needs to be changed they are a lot more likely to listen to you and hear you out (trust me this works in most industries).
I not only specified the heat pump change but due to the specific circumstances I also specified 5 radiator changes including a new K3 500 *2400.
Not only was I listened to but as I had done all the background work it was easy to get both the senior engineer and one of the directors on board and get the system designed to work as I wanted (40°c flow rate made possible by the smaller pump and radiator changes).
I am glad you have identified this issue and I really want anyone with one of these beasts to be able to get it swapped and have a SCOP in the high 4’s too but as Matt has said, it is Octopus you need to convince and while a one off calc works for me it may take a bit more proving to get the right people in after sales to budge.
If you don’t want to do the above you can try and call up and tell them it is running inefficiency and you believe the heat loss is wrong and ask them to check it, however unless you know what sizes the windows and doors were listed at and how much loft insulation the original surveyor specified you may not get too far.
The other point to be aware of is that octopus usually only specify a cop of 3.6 for the big unit and if you are getting this (even if it is not optiomal) they can say it is as designed.
If you then want to argue it is not operating efficiently as it should be due to being oversized contrary to part L of the building regulations (part L volume 1 section 5.8(b) " b. A sizing methodology that takes account of the properties of the dwelling, such as the
Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services
Design Guide.
Systems should not be significantly oversized.") you would need to show that it is in fact significantly oversized.
Sorry if the above is a bit long and dull in places and I am not here to bash anyone, just want to see a few more people climbing up the SCOPs and start showing everyone these things can actually work if you size end install correctly.
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To that I would add: be professional, polite but firm. State the facts, not guesses, and don’t exaggerate.
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Thanks for that. We still have the “9”.
My data shows a sub 4kW heat loss on recent cold days, hadn’t thought of that approach. Back to Octopus with that data!
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Comparing with itself, can very clearly see the improved performance (blue = before, red = after).
(Jan 1st to Feb 20th vs. Feb 21st to Mar 13th)
Here’s the same analysis for Zak’s heat pump (Nov 1st to Jan 10th vs. Jan 11th to Mar 13th)
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Thanks Tim,
It is very clear that we both had the wrong heat pump.
In some ways, Zak more than me, I was able to make the 9kW work better in my house, but I did go to extreme lengths to get the best out of it.
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