Hello @bami , I’m sure others will be along with far more help than I might offer - and with far more knowledge than I but…

A couple of things occur to me, firstly, the copper piping looks very tidy but, there does not appear to be any insulation on those pipe runs to retain the heat and I suspect you have a fair heat loss due to this.

Secondly, I notice your Cop is dipping well below 3 and I wonder if though you have adjusted the temperature down (on the controller presumably) whether there is  room to lower the water law down somewhat? (in many manufacturer’s systems this ‘water law’ is called ‘Weather Compensation’.)

Then there may also be a setting on the immersion heating coil within that huge tank that is boosting the temperature? An immersion heater (usually a 3kW capacity jobbie) if running to keep your tank up to temperature rather than letting the ASHP take the strain, could easily  be consuming ~5 -10 kWh per day. You should be able to see a dial or lines on the head of the immersion heater where it protrudes from the tank and more than likely, it has an adjustment knob on it.

Sorry, more than two I realise but, with the TRV’s fully open, you may find you can reduce the flow to any particular radiator more usefully by adjusting the ‘Lockshield valve’ at the opposite end of the radiator to the TRV fitting. I have written a guide on this which I will link below, but you may find you only need to close the LS valves perhaps 1/8 or maybe 1/4 turn clockwise just to tame those offending couple of radiators. As you have read, the more ‘open’ the system is to the warm water flowing through the radiators, the more efficient it is likely to be. Using the LS valves to ‘balance’ the necessary heat in each area is a very good starting point. In conjunction with the lowering of the water law setting, you may well find improvements to the ASHP COP.

https://renewableheatinghub.co.uk/how-to-balance-radiators-the-role-of-the-lockshield-valve

Regards, Toodles.

Im sorry to hear about your challenges and agree with the points @toodles has made.

If you can give some more info (in italics) we can try to help)

This Jan was much colder than last Jan and also heat pumps consume disproportionately more when its cold, but correspondingly less when its warm.  So you should find the bills coming down quite dramatically.  However COP < 3 suggests something is wrong with the set up.   Do you know what your annual oil consumption was approximately

12kW is definitely large for 120sq m reasonably well insulated bungalow, 6kW is probably closer, but unless the installer will change it you will need to work with what you have.

In terms of weather compensation (water law) Low (15C)=37C  is too high.  This needs to be reduced to 30C or even 25C I would think.

High (2C)=50C also is high particularly as this was designed for 47.   I note all your TRVs are permanently on - well done.  Is there a thermostat, or even just the temperature sensor in the controller, that is turning the heat pump off or does the flow temp really need to be that high to heat the house.  Can you give me the make/,model or a photo.  Most likely this is the principal reason you have low COP/high bills!

Is the immersion running at all other than during the legionella cycle, as @toodles says this could be consuming a lot.

Is the DHW topping up as soon as it cools or is it on a schedule

To answer the question 'what happens in summer' - in summer it just heats the DHW unless you need space heating as well.  I cant recall if Samsung has a 'max outdoor temp for heating setting, but if it does then you can use that to switch the sapce heating off automatically when it gets warm, or Im sure you can switch space heating off altogether via the controller.

@toodles thank you!  Very quick reply for now as lunch is nearly ready. 

Would the insulated rolls be OK to insulate the copper piping to the water tank?  Having to go to B&Q this aft anyway so could pick some up.

Posted by: @bami

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Would the insulated rolls be OK to insulate the copper piping to the water tank?  Having to go to B&Q this aft anyway so could pick some up.

 

Yes as its indoors.  Do cut mitres (45 degree) at the corners so corners are insulated.  No need to insulate cold pipes only warm/hot ones.

I left some questions in my previous reply when you have an opportunity.  I think its likely, but not certain, that whatever you are using to control the nighttime/daytime temperature is harming your COP, the questions are designed to find out as well as answer things about the DHW setup.

@toodles
@jamespa 

Thank you so much for your replies 🙂

I use the Samsung G6 control panel to control the system.  That's where the water law is set.

The programmer just tells the ASHP what time to come on and at what temp in the house.

Here's one of my issues though.  Currently the temp in the north facing lounge is 19C, so if the programmer was in there the heating would be kicking in. But it's really sunny & warm outside!  I placed the programmer in the kitchen this morning and as you can see it's 25C in there (south facing).  Same in the south facing bedroom & bathroom.  So where is the best place to site the programmer? (I'll move it back into the lounge around 5pm as I currently need it hotter than 19C in there in the evening). 

I've now turned the water law low value to 30C and the high value to 47C.
However, I'll have to see how that goes.  The whole house is only just warm enough for me at the previous settings.  The lounge, as I said is already chilly and I sit under a heated throw in there.  I'd love to turn the thermostat up to 21C for the whole house (as I'm not well I'm not very active so get cold easier) but simply can't afford to increase my bill any further 🫤  The oil CH was definitely warmer.

Is the immersion running at all other than during the legionella cycle, as @toodles says this could be consuming a lot.  Is the DHW topping up as soon as it cools or is it on a schedule

No clue re the immersion - how do I find this out? Yesterday (Saturday) was lovely and sunny, but the ASHP came on mid afternoon!  However, I'd left the programmer in the lounge and the lounge was only 19C, so I moved it to the kitchen (24C) and the ASHP quickly switched back off.

No schedule for the DHW, so setting one on the Samsung control panel would help a lot re the hot water I think - I'll do that now.  I really don't use much hot water.  Any guesses how long it would take the tank to heat up from cool?

Funnily enough, I got my latest elec bill today.  £222, which is more what I was expecting to pay.  However, Feb was unseasonably mild - I was expecting to pay that much when it's really cold!  I'm currently £680 in debit to EON since November 😢

Do you know what your annual oil consumption was approximately

Hard to say.  I only moved into the bungalow last March and had the ASHP installed start Nov, so only have spring, summer & autumn to go on.  It's a 500L tank and I had one delivery during 8 months and it's still about 20% full.  But DHW tank much smaller and shower was electric then (I've spent the last year renovating so everything has changed).

@bami A few thoughts, in no particular order: The thermostat obviously responds to the room it is in so is doing its’ stuff, do you have an intermediate area such as a hallway? You have extremes and this is creating problems, an intermediate temperature out of the sun but away from the north side might provide a compromise.

You possibly have an LS valve in need of opening up slightly (anticlockwise) in that coldest room - it could be it is too far closed for the room’s demand. If the lockshield valve is too far closed, no amount of increase of flow temperature from the heat pump would do much to help, so open that LSV a little, you have nothing to lose!

If you have a south facing room that is overly warm from solar gain, you might benefit from careful use of the TRV in that room - if set 1 or 2 degrees above desired warmth, it should then prevent the room from overly warm conditions but still allow heat when it is needed. Restrictive use of a TRV in this way will not affect your COP greatly - nor upset the heat pump too much! Overall, taming the warm environment during sunny times and opening the LSV in the chilly room might well improve your comfort level noticeably.

I know how you feel regarding temperature as my wife and I like to keep the whole house at 22.5 degrees C as we have a selection of medical needs and feel uncomfortable if rooms drop below about 21 C. Regards, Toodles.

@bami All good advice so far. I have a Samsung so might be able to help specifically with it. Do you know if you have a buffer tank installed?

I notice that your Samsung controller is on the tank and your are using a third party wireless controller. Many of us find that the Samsung controller is best, but it would need to be wired to where you need it so for now best stay with the arrangement you have.

I also think your heat pump is well oversized and this may be a problem in achieving good COP but it is notoriously difficult to get installers to swap in a smaller unit (Octopus excluded) so you will probably have to make the best of a bad job. The fact that your installer left the pipework uninsulated does not fill me with confidence.

The good news is that it should be possible to heat you home for less than the previous oil boiler, the bad is that it will probably require quite a bit of tweaking to get the SCOP you need.

The large winter bill is scary, but you will recoup during the shoulder season and hopefully even out. The solar panels will certainly help once we get more daylight even without a battery. I used to schedule my hot water run for about 12.30pm so as to utilise the maximum solar gain when I was using the most electricity.

The way I approached heating my house was to open my radiator valves fully in the room I wanted warmest and then tweak other rooms to suit. My thermostat is also in that room. If you can get that room to the required temperature then you know the water law settings are sufficient.

I think one of the biggest problems you might get when things warm up is rapid cycling. This is because if you heat pump is too large and the house needs less heat than the minimum output of it, then it will switch off and on and off etc. This is bad for the compressor and probably adversely effects COP. I would certainly consider investing in some kind of monitoring to have a handle on what is going on.

Alternatively you could go down the route of handing total control of you heat pump to 3rd party software like Homely. It is compatible with Samsung units.

OK

Before you go any further can I suggest you read this introduction to ASHPs, it will help you understand the technology a bit better.

In terms of optimising the set up:

Posted by: @bami

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The programmer just tells the ASHP what time to come on and at what temp in the house.

 

This is a problem.  The programmer is controlling the ASHP and, as a result, you almost certainly have the water law higher than it needs to be = more expensive.  What you need is the ASHP controlling the ASHP not any third party equipment not designed for ASHPs.

To fix this:

• Set the desired temperature on the programmer to as high as it will go (say 30C), 24x7
• Open up all TRVs if not already open
• The house will get too hot (hopefully)
• Set the high OAT end to 15C/30 (I think you have already done that)
• Set the low OAT end to 47/-2 (you said its currently at 47/2 which makes absolutely no sense unless it never drops below freezing where you are)
• Hopefully the house will still get too hot
• Slowly reduce the 47 value, changing it no more than once per day in increments of a degree until the house is just at the right temperature - if it gets too cold slowly increase it

You can use the TRV in your bedroom to reduce the temperature in that room only while you do this.

In addition as suggested by @toodles, in the coldest room, open up the lockshield valve (the valve opposite the TRV

Posted by: @bami

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No schedule for the DHW, so setting one on the Samsung control panel would help a lot re the hot water I think - I'll do that now.  I really don't use much hot water.  Any guesses how long it would take the tank to heat up from cool?

Definitely do this as it could be costing a lot if its continually reheating.  Try 90 mins once per day as a starting point, suggest noon when its warmest.

If you start on this and report back as you go along we can tweak things as necessary, but fundamentally you want to get to the point where the controller is doing nothing and the water law is as low as it can be whilst keeping your house warm.  From there it might be worth a bot of further tweaking, but until you get to this point we dont know that you are operating at most efficient

Finally lets do some very rough and ready calcs on your oil.  You used 400l March-October.  However in reality thats March, April, September, October, 4 months (not a lot of heating in summer).  So likely you would use about 1000-1500l in a full year.  I think heating oil is about 70p/l, so you would be looking at an oil bill of 700-1000 per year.  You can expect your ASHP if we can get it working properly to cost about the same, but of course you will only see this in the heating season say September-April, and most of it will be in December-February.  

I hope that helps.  If you perform the optimisation above you should see your COP rise with a bit of luck.

I've just noticed that @bontwoody has posted.  I agree with all of what he has said.  In particular he is right that your heat pump is well oversized and homely would be a good investment.  However you have said you cant spend any more on changing things so Im working in my advice above with what you have.

@bontwoody Thank you so much!

No clue if I have a buffer tank.  There is nothing extra to the pics I originally posted, so if there is a buffer it's inside the water tank.  No idea how I would know/check this?

I also think the pump is oversized, though I do have 12 rads.  Be interesting to see if Rothwells will give me the design spec etc. There was definitely confusion when the installers were here as they were expecting to see a much smaller pump!

I know I need some kind of decent monitoring equipment, but as I'm not working due to the brain tumour money is tight so it will have to wait sadly.

@jamespa This is great, thank you 🙏🏻

Set the low OAT end to 47/-2 (you said its currently at 47/2 which makes absolutely no sense unless it never drops below freezing where you are)

I re-read the manual today (hard as aimed at the installer not the end user and is full of stuff I don't understand!) but I did see from that the low end should be -2C so I've already changed that this aft.  No clue why it was set to 2C!

Thanks for advice re how long to have DHW on for - I've done a schedule now which surely must be cheaper than heating it constantly.

I shall do as advised and report back in a week or so.

Posted by: @bami

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No clue if I have a buffer tank.  There is nothing extra to the pics I originally posted, so if there is a buffer it's inside the water tank.  No idea how I would know/check this?

 

I dont think there is a buffer tank because I cant see enough connections, I think you have just a pre-plumbed unvented cylinder kit for which I think this may be the manual, but @bontwoody may be able to confirm or correct.

Posted by: @bami

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I also think the pump is oversized, though I do have 12 rads.  Be interesting to see if Rothwells will give me the design spec etc. There was definitely confusion when the installers were here as they were expecting to see a much smaller pump!

I reckon your house is ~6kW (and certainly max 8kW) not 12kW based on your oil consumption, size and insulation.  The problem with oversizing is it leads to cycling on/off which reduces COP (by an amount that is unfortunately unknown, although one can make a very crude attempt at modelling it).  The unit is also about twice as tall as it needs to be (I don't know whether that matters!).  It might' be worth contacting the installer, it sounds like they know its oversized and its only a day's job to swap!

Posted by: @bami

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Thanks for advice re how long to have DHW on for - I've done a schedule now which surely must be cheaper than heating it constantly.

Yes.  There are some parameters related to DHW that you can tweak in the installer menu, they are the 'FSVs' (field setting values) starting 30. 

TBH I dont completely understand Samsung speak (I have a Vaillant, but of course the principles are identical) so it may take a bit of discovery as to what they mean.  However if you try it timed (which is definitely what you want) and see what doesn't work, you can focus in on the tweaks that matter (hopefully with the help of @bontwoody  who actually has a Samsung, unlike me.)

Posted by: @bami

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I re-read the manual today (hard as aimed at the installer not the end user and is full of stuff I don't understand!) but I did see from that the low end should be -2C so I've already changed that this aft.  No clue why it was set to 2C!

Well done!.  From your initial description of your system it is clear that you are fully capable of understanding this as well, if not better, than quite a few of the so called 'professionals'.  Unfortunately Samsung isn't the easiest language to understand and the controller is a bit basic, but persevere and Im sure you will get there.