Hi. Welcome to the forum.

So from your house desciption the initial COP figures seem reasonable. I might question if the heat pump is a bit in the big side and whether you need a buffer.

Im not experienced with fan coils but if they are not in the circuit at the moment they shouldnt be affecting anything.

Your current flow temp should be giving a good COP so I think something must be occuring that you are not aware of. Can you check if the valves you think are closed actually are and any pumps that are running etc.

Welcome to the forums and I am sure you will receive much help

Posted by: @ciocoiu-alexandru

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Any advice on what could cause this drop in performance would be greatly appreciated. Thank you!

We will need more data to diagnose but here are some questions/comments

Posted by: @ciocoiu-alexandru

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. The house is built with 30 cm brick, insulated with 15 cm EPS, 20 cm mineral wool in the attic, and 5 cm EPS under the UFH. Total usable area is 160 sqm over two floors, with 20 UFH circuits

... with a 11.2kW heat pump.  Thats probably at least a factor of 2 oversized, but of course that was also true last year.

Posted by: @ciocoiu-alexandru

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I have 7 room thermostats controlling only the actuators.

This may be the major one.  Can you provide more detail what part of the heating exactly this controls and how it relates to the rest of the house

The buffer tank may be contributing but with such low FT possibly not much

Posted by: @ciocoiu-alexandru

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The heat pump runs continuously (24/7), no freezing issues.

It may be switched on 24x7 but is it cycling heavily because of eg low sysetm volume caused by circuits being switched in and out.  Some plots from MelCloud/Melpump of FT, OAT, IAT would be most helpful

Posted by: @ciocoiu-alexandru

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Current COP is 1.1 for DHW and 1.7 for space heating, with exactly the same settings as last year and no other changes.

Thats really low and the fact its low also for DHW suggests there could be a fault since there is nothing much to change here.  Has it been serviced recently?  Of course it could be a sensor problem

Posted by: @ciocoiu-alexandru

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but daily electricity consumption is very high

Have you compared this times last year at similar temps.  How are you measuring consumption?

If you could provide some plots and a bit more detail on the points mentioned it may be possible to narrow things down.  However a COP of 1.1 for DHW this year vs 2.5 last year with nothing changed (please confirm) on the DHW circuit or settings sounds like there could be a fault.

@bontwoody All the valves are closed by me, no other pumps working for fan coils

@jamespa 

Thermostats are just controlling electrovalves, nothing else. I do not have melcloud or melpump, i will install wifi module next days.

I am pretty sure that it is not cycling at all, just running continousely. 

On DHW setpoint it is the same like last year, you are right!

Daily electrical consumption i am taking from the ecodan display. I compare with electricity bill and it is prettt acurate. For octomber i had around 950 kw with outside temperatures of 12- 17 degrees.

Posted by: @ciocoiu-alexandru

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Thermostats are just controlling electrovalves, nothing else. I do not have melcloud or melpump, i will install wifi module next days.

 

Do you mean switching parts of the circuit in and out.  If so that is potentially a problem, but not the most important one to focus on just now.

Posted by: @ciocoiu-alexandru

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I am pretty sure that it is not cycling at all, just running continuously. 

There is pretty much no way it cant be cycling when the OAT is above say 10C, unless it has developed a fault   How do you conclude it isnt?

Posted by: @ciocoiu-alexandru

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On DHW setpoint it is the same like last year, you are right!

Noted and important

Posted by: @ciocoiu-alexandru

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Daily electrical consumption i am taking from the ecodan display. I compare with electricity bill and it is prettt acurate. For octomber i had around 950 kw with outside temperatures of 12- 17 degrees.

Where are you located?  I presume you mean kWh not kW?  Do you have any figures for last year?

Assuming you are in England with a design temp in the region of -2 then your house loss us likely to be ~4-8kW.  Mine is 7kW (measured) and my October consumption was 300kWh.  If these assumptions are correct then my gut feel based on 950kWh (Im assuming this is what you mean) is that a fault has developed, which needs fixing under warranty.  Comparative figures from last year, a rough location, and confirmation you mean 950kWh would help to nail this.

@jamespa 

Thermostats switching on and off some part of circuit, you have right. 

I conclude that it is not cycling by checking regular in the Menu Commisioning wizard. All time it is running.

950 kwh consumed in october. 

Location it is Constanta, Romania. I found some picture from january 2025 - on that moment outside temperatures were like now(around 5 degrees). Consumed 248 and delivered 920 kwh, this invluding the DHW.

Posted by: @ciocoiu-alexandru

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Location it is Constanta, Romania. I found some picture from january 2025 - on that moment outside temperatures were like now(around 5 degrees). Consumed 248 and delivered 920 kwh, this invluding the DHW.

Thats a sensible figure.  I dont know temps in October in Romania but you said 12-17.  950kWh consumption is way too much indicating I am guessing a fault, perhaps a compressor fault?

@jamespa compressor it is not noisy, i can hear how is modulating the pump. Tommorow will come the guy how start first time the system to see if there is all quantity of freon inside. Acording him, pump it is running continuously because some freon missing

Posted by: @ciocoiu-alexandru

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. Acording him, pump it is running continuously because some freon missing

Thats very plausible and would also account for low COP.  Repressurising the refrigerant may fix temporarily (and prove its the problem), but the question is why did it leak in the first place and has the leak been plugged!