I know you are getting lots of god advice but our situation was similar and we found one other thing….(we put in ASHP on Jan 6th this year having run out of LPG 3 days earlier - into a freezing house! - it took a lot of energy to warm up the house)

but one of our issues was a sticky UFH actuator. Even though the actuator was open, water was not flowing through that circuit so that part of the house was cold.  You say your house had been largely unoccupied before you moved in? Your UFH valves could be stuck closed?

if this is happening then the Ecodan (to protect itself from damage) will not force fluid if it can’t push and the heat it generates gets diverted back to the heat pump (ie outside).

it’s worth checking your UFH flow pipes - they should be warm. If not they are likely seized. To unseize you usually just need to rotate the valve anti-clockwise ( with a radiator key under the actuator head)  a little and you should hear an inrush of water..

(No don’t overdo the rotation! You don’t want the water coming out of the manifold!)

im just a newbie myself and you may not have this problem - but it is worth a check I think?

Posted by: @editor

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here’s their take on what’s going on.

Your system includes a low-loss header and third-party thermostats, which are likely set to a fixed flow temperature of 45–55°C.

It's not, however, as if you look at the main remote controller screen you'll see the triangle indicating compensation curve is in use:

The installer noted that your flow temperature is currently set to 47°C

Worth checking what the unit thinks it's using - from the front screen:

press the bottom right button (called the 'option' button), you'll see

press the energy monitor button (the magnifying glass bottom right)

have a look at / share the Consumed and Delivered figures?

To follow on from the above post, you may wish to check all your UFH loops are open sufficiently - assuming the valve controls are in good condition, make a list of them then record how many 'half turns' it takes to close each one (so you can put it back again if necessary), then close each one in turn and open back up to 1L/m flow (or two full turns if there are no guages) and leave for 4 - 12 hours.  For rooms that get too hot, turn down half a turn per 12/24 hours until it's comfortable then tweak up/down to get perfect temp for the room (you may have to adjust other rooms' valves to compensate).  There are more advanced ways of balancing UFH but this should give you a 'quick' indication if that was the issue / get you 80% there.

@anca1808

Lots of ideas above about what could be causing your issues.  Nobody, including me, can be definitive because we don't have your system in front of us.

Can I suggest you now do a bit of 'elimination' to see which ones to pursue further and which can be rejected based on observations on the actual system?

@anca1808 a few thoughts re your high kWh usage:

1  are there any unlabelled breakers in your consumer unit that could be using power?

2  in fact, are all the breakers labelled with the circuits they protect?

3  do you have a steep driveway fitted with underground deicing cables?  I have these and they draw c4kW when activated.  I switch mine manually but some are fitted with a thermostat that switches them when icy conditions are likely and this may be faulty.

@anca1808 I'd certainly backup the suggestion from @rhh2348 to check the consumption as measured by the unit - I know it is the main culprit in your high usage figures but it is worth checking to make sure there is not another less obvious draw.

Flow temps in the low thirties are not going produce radiators that feel warm to the touch - they'll be below body temperature after all - and 19.5° suggests the rooms upstairs are being heated, adequately, even if not to your desired level.

It is good that you have a Mitsi engineer booked. I suspect that the fact you say there has been a three year gap between installation of the pump and occupation of the house could be a significant factor - it is a mechanical device filled with water, both of which will suffer/cause degradation if they sit unused. I hope that your system included anti-freeze as that has an anti-corrosion additive.

Hi all,

Just a small update between crying babies and daily struggles of moving...My partner was away until tonight so once he is back we will start troubleshooting as per above advices.

To answer some of the questions. This is an empty house. We have no electric car, no big consumers, not even a washing machine as this has not arrived. We only had time to move essentials last weekend.We did use kettle, oven and microwave. Hence why I was so panicked that with a virtually empty house, 100Kwh was enormous and unexplainable. So whatever was showing on our house smart meter, I assumed it was the heat pump.

The pipes from outside all the way to the house are now insulated.

I also changed the DHW to heat up 3 times a day for 1 h when I have a very good tarrif on Octapus Cosy.

The garage is not warm to say the hear is kept in there .

Plumber who did insulation friday said the immersion is not on all the time and that is not the culprit.  I really did not check that myself if it is on or nor

@JamesPa I will try the pump off pump on and measure things this week.

@Gary. Yes I have read the manual and settings look alright ( as far as my uneducated eyefor heat pumps) . The pump was running at 5 like you notices so I dialled down to 2 and now with the code 540 it shows 13l/min,  which i guess it s satisfactory. And yes I wull order that wifi thing off amazon once i have my interner set up end of week. I can get on melcloud then and share more data.

@JohnR. I am no expert and I know the numbers are not making anysense. Yes, I bled all radiators, but like many explained, the radiators will not get hot with the heat pump. There is an issue of hetting heating upstairs for some reason

For the last 2 days my consume went down to 47kwh per day for whole house, which I am mildly happier about ( I assume the house has now wormed up and this is the real consume, maybe insulation helped a bit) . But still the upstairs does not heat up pass 20 degrees with all Trv open and stat put high.

It is still not right in my opinion as consume is still too high and for the upstairs not to get to my wanted temperature , so the developer got in touch with mitsubishi and a specialist will come ( don t have date yet) . I will ask him to service it and check all system. I ll ask to show me as well if all ufh are open how much etc. I do not want to do it by myself as it is a bit too much if something goes wrong and i flood the house.

@rhh2348 Yes, I checked the consumed and delivered. It was turned on on 13th of february as on 14th we completed the purchase. since then until today 23rd it has consumed 791 and delivered 1700.  In january it was turned on a few days ( don t know how many) to check if it is working in preparation for our move feb/march. in those few days it consumed 728 as per the log.

@downdlfield. No cables that I know of. I will go around to see if everything is labelled.

Like I said, I am a bit out of my depth with all of this. We will start troubleshooting from tomorrow until mitsubishi comes out and hopefully reduce our consume so i do not take a second mortgage for my energy bill .. .

I will let you know how it goes and what the specilist says when he comes.

Thank you all for the help, support and advices!!

Posted by: @anca1808

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It was turned on on 13th of february as on 14th we completed the purchase. since then until today 23rd it has consumed 791 and delivered 1700.  In january it was turned on a few days ( don t know how many) to check if it is working in preparation for our move feb/march. in those few days it consumed 728 as per the log.

That consumption data is consistent with the high smart meter readings but is way too high for an efficient heat pump system. Similarly, 791kWh consumed to deliver 1,700kWh of heat indicates very poor performance and something is preventing the heat pump from runing efficiently. For comparison, since 1st January my Vaillant heat pump claims to have consumed nearly 850kWh of electricity but has delivered just over 4,500kWh of heat. By good luck or judgement I seem to have got an efficient system.

I suspect that your system hasn't enjoyed sitting idle for 3 years since commissioning.

@anca1808 Just to give you some comfort and set expectations, my Vaillant heat pump is working out 13% cheaper than gas on a like for like basis, over the period November 2024-date (which is the worst period for heat pumps!).  I haven't done anything clever, just operated it open loop on pure WC with the WC adjusted down to the lowest it will go consistent with the house being warm.  I do have a ToU electricity tarrif, without this it would be about on a par with gas.  

Please feel free to post back after Mitsubishi have visited and ask any further questions, you should not be experiencing such high consumption.

It sounds like you are getting to grips with it well.  I just want to check, are the pressure gauges in the system showing a sensible sort of pressure?  Did it drop after you bled the radiators? 

Also I just wonder if the unit itself has lost some of the the refrigerant gas it is supposed to have, but i imagine that is more the job for the engineer to check.