Oh and yes, the pipes outside the heatpump are also Not insulated.....

they are comiing out tomorrow to sort out insulation ...but their plumber has no clue about the heat pump and how to optimise it . i need a mitsubishi specialist or a renewable specialist that is going to understand how the house /piping / heating is designed to work to get most of this heat pump ....

There are loads of people who will be willing to help but we will need some info first get a screenshot of the front of your controller that will be able to tell us what mode it’s running in. Is it all rads or a mix or all ufh.  Description of your house build etc.  The more detail the better.  What size heat pump is it what was your heat loss calculation.  Those pipes need insulating with primary pro don’t accept anything else, all the way from the house to the heatpump.  What size are the pipes from the heat pump they should be at least 28mm or larger depending on the heatpump model

@anca1808 - if you haven't already done so, have a look at this ABC Guide to Heat Pumps, written by yours truly. I am also a doctor, now retired, and I can assure you that if you can get your head round neurosurgery, you can get you head round heat pumps. You just need to know the anatomy and then the physiology.

Crumbs. Welcome to the forum. Are you sure you aren’t powering or heating somewhere else on the housing estate? (Other than garage and plant room).

Maybe turn everything off (at the consumer unit) for an hour and then see what you consume ?

@anca1808 I shared your situation with a top heat pump installer, and 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. At the current outdoor temperatures and with this configuration, a COP of around 2 is unfortunately expected.

The installer noted that your flow temperature is currently set to 47°C, which is far too high for underfloor heating and is contributing to the high energy consumption. Additionally, if your upstairs radiators are cold, it suggests there’s a serious lack of flow to the heating system, which needs to be addressed.

While adjusting settings might help slightly, the root of the problem appears to be the system’s physical flow configuration. To resolve this, you’ll need a professional to investigate and correct the flow issues, balance the system and optimise the settings for your underfloor heating and radiators.

If you can share your rough location, we could connect you with someone credible in your area. 

Dear all,

Thank you for being so helpful!

@cathoderay. This guide is awesome! I understand better now what is what .

@Mars . After I read 100 blogs I suspected the same and there were people with my problem and most engineers replied that there must be a flow issue. nevertheless, not my area of expertise so I am grateful for any support. I live countryside around S72.

@Carpenterstation. That is exactly what we did. we turned off everything . left stats at 19 and went to bed. this morning 30kwh extra at meter. for what? no bloody clue as house is freezing.

@jamespa. as well, 2 days ago after a bit of reading done by myself i have trv on to max all stats to max. downstairs got warm, upstairs hovered around 20 degrees with radiators lukewarm. this is after probable 12h. then because of ignorance of not knowing how to operate the system and scared about consume i started fiddling with the stats.

@gary. Thank you!! Already called mr noheatpumpsknowlegde plumer to get me that insulation!

@guthrie thank you!

Now to recap my setting so it is helpful for whoever could help

New build completed Jan 2025. Started being buld in 2021.

ASHP Mitsubishi 8.5KW commisioned in 2021 november. No clue about design instalation or heat loss as it is not on any documentation. all i have is the commisioning document. mever serviced ( fuming about that)

Cylinder and all other round stuff connected to pipes , are in an insulated garage.

Nothing is insulated in terms of pipes outside or inside garage. this gets done today.

The house is 150m2. 4 double bedrooms upstairs. opeen plan kitchen dining living downstairs. Downstairs UFH. Upstairs we have Radiators. all have trv.  Downstairs there are 4 thermostats and upstairs there is one thermostat.

We moved in the house 5 days ago. Consumed now close to 500kwh AT the meter for the whole, hence me going full on geek and reading all the blogs existent on heat pumps......

The pipes at heat pump are 28mm. in garage at all round stuff are 22mm. At radiators are 15mm.

I am attaching pictures requested, plus the current settings ( untouched by my magic fingers) on the main board that lives in the utility room. I know for sure that these can be optimised.

My issue is that i have a cold house, water that is randomly cold and hot and paying £20per day for electricity. Like I said, downstairs achieves 21 degrees , but upstairs nothing goes above 20.

Also , I hate these stats. constantly having to adjust them as some go to 12 degrees some to 19 . I do not undestand why they were put in ...Nevertheless, i have 4 of them to tell.me temperature and what i can t achieve.

trying to attach some pictures. hopefuly it works . if not let me know....they are all in something called my media...

Posted by: @anca1808

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@Carpenterstation. That is exactly what we did. we turned off everything . left stats at 19 and went to bed. this morning 30kwh extra at meter. for what? no bloody clue as house is freezing.

That needs investigation.  Its currently mild so you can do things that you cant do when its cold.  Turn the ASHP off completely for 3 hours (preferably by flicking the circuit isolator for the HP to be certain) taking meter readings before and after.  Then repeat 24 hours later with it on for 3 hours (ideally at a time when the OAT is roughly the same).  Compare and post figures together with rough OAT at the time.  This will isolate it to the HP (or not).  If the immersion is on a different circuit you could repeat with the immersion (in this case I would switch it off for 24 hrs unless the effect is immediately obvious, if you miss a legionella cycle its unlikely to cause a problem).

You may also be able to trace it by observing the flashing light on the meter (if you have an electronic meter).

One of the pictures suggesting DHW is programmed to heat from 7.30-12 in the evening - really?  An hour and a half twice per day (not at prime heating time) might be better.

Posted by: @anca1808

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@jamespa. as well, 2 days ago after a bit of reading done by myself i have trv on to max all stats to max. downstairs got warm, upstairs hovered around 20 degrees with radiators lukewarm. this is after probable 12h. then because of ignorance of not knowing how to operate the system and scared about consume i started fiddling with the stats.

OK.

A couple of things - I think you might have moved in when it was very cold.  All heating systems, but particularly ASHPs, consume much more energy when its cold.  Also in the first few days after you turn heating on you do spend a vast amount getting the fabric of the house up to temperature, but that occurs once only!  We dont notice it with gas, but because we do with electricity.  it does even out over the season.  Hopefully you are now consuming MUCH less, but thats not saying there isnt work to do.

You definitely need to leave the thermostats turned up at least 2C above the desired temperature (to act as limiters, not controllers) and most of the TRVs open.  You shouldnt need to fiddle once things are set up.  Dont worry if radiators are lukewarm or even if they dont feel warm at all, that is how they are supposed to be - only just warm enough to heat your house which, when its mild outside, can feel like they are almost cold (I did say you had to forget everything you knew about gas boilers).   

You definitely want to adjust your WC settings so you dont have to fiddle with the thermostats (and save money).  The current temperatures, being neither warm nor cold, arent ideal for adjusting WC so I might wait until it gets a bit cooler (next week).  Then I would go ahead leave your thermostats turned up to full, your TRVs fully open, and adjust your WC settings which you do in the screen three up from the bottom picture.  Leave at least 24 hrs before you start, then one step at a time, adjusting only once every 24hrs, turn down the target temperature at the high end until the house temperature is where you want it to be.  You may need to balance the emitters if you find that variations between rooms arent what you want, if you need some information on how to do that please post back.  

Once you have done this, had the insulation fixed, checked that the immersion isn't on much of the time (as suggested above), take some more electricity readings (recording the OAT and date as well) and lets see where to go next.

Some with specific Mitsubishi experience may be able to comment on the Mitsubishi specific settings a bit more, but its probably something generic not model specific.

I have the same heat pump and all of those setting look spot on, you are running pure weather compensation with a reasonable curve, the house shouldn't be cold, so the issue is in the emitter side of things rather than the heat pump.

If the heat pump was running flat out 24 hours a day and it was freezing outside it may use 100KWh in a day.  How much did you use yesterday its much milder, if its a similar amount I would suspect you need to find the immersion that's the logical culprit.

In the running information menu when the heat pump is heating put in code 540 and report the value that is the flow rate of the heat pump needs to be 15L/min with your pump set at 5 I suspect its much higher so can be dialed back but if its very low that won't help heating.

The hot water settings look fine as well other than what James said move the schedule to overnight when you don't need to heat as much.

Unless you are having very high hot water usage i.e. multiple baths a day you should only need to heat it once.  We heat 12-2am to 47C that's enough for 2 showers, washing up and a full bath without reheating at any time during the day.

If you don't have the MAC-567IF Advanced Interface to give you access to Melcloud I would purchase it £60 on ebay.

I know there's a lot of people offering help and advice, that's the great thing about the internet! 🙂

If you're using 100kWh per day, that's 360,000 kJ of energy in 24hrs, or 4.2 kJ per second.  That means you have an average power usage of 4.2 kW.  Or, you have something that's consuming 17amps and it's running all the time.

What do you have in the house that uses lot's of electricity?

There's the immersion heater in the hot water tank, an electric cooker, fan heaters in garden buildings.  Do you have an electric car that you're charging?

I believe EcoDan units can be configured with an auxiliary immersion heater to supplement the heat pump.  Maybe others can help identify if you have one.

Regards

Bob

The numbers don't make sense. 100kWh/day of electricity into the house, if directly converted to heat (eg four x 1kW electric fires), should make a modern 4 bed house feel tropical and if the heat is being lost in the garage then tht should be an oven. The heat pump is rated at 9A for 7C outside and 35C flow temperature. If it's operating continuously under that condition then it would use about 50kWh/day. What is using the rest of the power and where is the 150 - 200kWh of heat generated by the heat pump going? My maximum daily heat pump power consumption was 28kWh in January with an average outside temperature of -3.7C and that's for a 1970's 4 bed house with cavity wall insulation but will be thermally worse than any recent house built to current regulations (and I would hope that a builder would ensure that there would be no build deficiciences in their own house).

Has anyone checked that there is no air in the system? Have the upstairs radiators been vented? Any air in the pipes tends to move to the highest places once the water is circulating.

Does the heat pump blow out cold air when it is operating?

What temperature are the various pipes around the cylinder? Subjective hot/warm/cold is sufficient at this stage and should reveal if warm water is going to the heating system.