@editor I'll email that detail to you, I'm wary of seeming malicious. But if it's helpful for others I am happy to name the company in the forum, I don't think they could take issue with the facts I have given.

Posted by: @mairia

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@majordennisbloodnok The installer's reply to that query was "There is indeed a £97 difference between the two units. However, when we purchased your Heat Pump, it’s worth noting that Daikin had implemented a 4% price increase in April 2023, which coincided almost exactly with the time of your installation. We absorbed this increase on your behalf, meaning you were charged at the pre-increase rate, by us, despite the manufacturer’s new pricing coming into effect. This ensured your project costs remained consistent with our original quotation and avoided any additional charges passed on to you". This is one of my reasons for thinking a Subject Access Request is worthwhile.

Understood, @mairia. Whether you believe what the installer is telling you or not, I think @jamespa's point is the more important to focus on; get the problem sorted and get your home warm, and then use the knowledge thus gained to decide if you want to press the installer or not. That is, of course, a question only you can answer, but whatever you do decide there are a lot of people here who can provide good and helpful support so (given I didn't say so before) welcome in.

@jamespa I did pore over all the documentation I have, and was definitely not given a copy of the heat loss calculation. I do have an initial one done by the heating supplier who referred me on to the installer, but not the one following the room by room survey. The initial one does recommend 9kW but I remember then discussion that it would be 11kW and obviously have the quote and also another communication from the installer confirming that for the purposes of my Home Energy Scotland funding application. However as you say the issue for performance may not be the heat pump size at all.

Posted by: @mairia

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@editor I'll email that detail to you, I'm wary of seeming malicious. But if it's helpful for others I am happy to name the company in the forum, I don't think they could take issue with the facts I have given.

It's entirely your call whether you wish to name them or not. If you are not happy with them, it's your right to name them.

I'll let the other members guide you to try and get your system to run more efficiently.

In the time being I'd recommend you contact MCS and ask them to send you the heat loss they have on record for your property. At least that way we have a heat loss calc to work from.

@mairia A thought occured to me when I read that you still have two of the original radiators as they were new anyway. When the installer commissioned the system (before providing you with the MCS documentation etc.) do you recall whether those original radiators were checked and balanced along with all the new radiators? Though the original radiators may have previously been balanced as part your original heating system, those settings may not be those required in the new setup. What I am trying to say is unless the installer checked the radiators and included them in the balancing of the system, they may well need adjustments to their lockshield valves to allow sufficient flow at the lower flow temperatures used by a heat pump compared to a gas boiler for instance. You may find it worthwhile to note the LSV position on the coolest room fitted with the original radiators and then try opening the valve just an eighth to a quarter of a turn anticlockwise and see if this provides a warmer room. I say note the setting so that you can always return to default if no improvement is apparent.

I am suggesting this adjustment as your post rather suggests your installer may not have been the sort to carry out proper setting up in the first place! Regards, Toodles.

@jamespa that's a good point about not offsetting overnight when it's very cold. And yes that was an example of it not getting to temperature. I do have my DHW on comfort and reheat which works best for me so it's possible that the heat pump was heating the water then, I will try to monitor it more closely this winter. I don't have any monitoring other than the Daikin MMI, actually all this started when I was looking at my documentation and wondering about Homely or Havenwise and saw the photo of the ASHP information plate showing 9kW on my last service report. I've attached my spreadsheet if you want to take a look at it.

@editor for the benefit of others, the company involved is Flo Renewables in Glasgow. I should say I was very happy with the initial installation process, but changed to another service company due to less than perfect customer service and communication thereafter.

@mairia We have a Daikin Altherma 3 EDLA03 Monobloc 8 kW system and had the Homely system fitted as soon as an integration was available for this model. We have an LLH and a secondary pump  (Wilo Pico) which is switched by the Homely kit. The system works very well for us. I found the Daikin MMI somewhat clunky to use and as for the accuracy of the consumption and COP figures … well a wet finger in the air is probably as good😉. Regards, Toodles.

And I'll contact MCS, I didn't realise they would have a copy of the heat loss document. Also can I say thank you so much to all have responded so helpfully today. I was feeling quite demoralised with the dismissive responses from the installer.

@toodles that's a really useful thought, I will check them

@mairia RHH is your friend😉 Toodles.

@toodles good to know. I really dislike the MMI. I find it very awkward to use, have to go in to my garage to take readings and adjust settings, don't know why you can't do all of that on the Onecta app.