Setting the heat to a fixed 65°C is shocking, so it’s great to hear you’ve switched to weather compensation – definitely a step in the right direction. That said, achieving a COP of 2, even with this week’s cold temperatures, is still very low. There’s likely another issue impacting your system’s efficiency that needs addressing. There are plenty of users on these forums with Samsungs, so helpfully they can shed some light. A photo of the plant room might help!

As for hot water, it really depends on your household’s usage patterns. For us, working from home 99% of the time, we’ve set our hot water to 45°C with a 15°C differential. This means when the tank temperature drops to 30°C, it reheats back to 45°C. It suits our needs perfectly.

Regarding the legionella cycle, the “standard” weekly routine can be overkill for some households. If you’re regularly emptying your tank, doing the cycle fortnightly is usually sufficient, provided you’re confident about usage and water turnover.

PS - just for reference, was this an ECO4 grant?

@dinhp

I have a Samsung, so happy to answer any questions I can. It seems you have done an excellent job of altering the settings and I cant believe that the COP hasnt changed because of that. Could you be reporting the average COP over a longer period that is overly weighted by the earlier settings?

You might want to look at tariffs that will help you run more cheaply and time Hot water runs in cheap periods if you can.

Ive also mentioned the advantages of having monitoring equipment in another thread. You can soon see how this pays back when you are faced with a £700 bill.

@editor thank you I appreciate your reply. So it doesn’t sound like the DHW set up alone would be the cause of the low COP?

I’ve attached some photos if there is anything glaringly obvious that needs addressing I’d be grateful for anyone pointing it out. They are coming back to replace the external trunking which is too short and I have a list of things to go back to them with so far

- the pipe work bending out of the back of the heat pump and if that’s an issue

- the condensation pipe (I think that’s what it is?) is just drilled through existing slab isn’t draining away - we asked about if a soak away/base was needed prior to install but told it wasn’t necessary 

- to find out if there is glycol in the system, I’m not sure if there is an antifreeze valve on one of the pipes  but I thought 2 were needed

All my learning has been from Google and YouTube over the past week or so I’ve not really got much of a clue what I’m looking at. It was the home upgrade grant and they were a nice bunch but I’m a bit concerned about the level of experience with heat pumps, so I’d like an independent engineer to have a look for peace of mind. But the more I can learn the better too.

@bontwoody hi thank you for your reply! I’ve attached our consumption/generation. It’s not been in very long - the first night it used a lot before we adjusted the settings. Yesterday it did run a legionella cycle so that may skew that one but nothing today. Hopefully I’m working out the COP right! Or hopefully I’m not and it’s better than I think 🤣

@dinhp 

Ive  worked out the daily COP below and added my Outside Air Temperature, yours might be quite a bit cooler depending on where you live:

So, the relatively good news is that you achieved a COP of 3.32 on the 23rd, which isn't great but is better than the 2.19 you had initially. The better news is that Ive calculated my COP over the same days using the Samsung figures and compared that to my COP reported by my in-line certified heat meter. The Samsung figure are consistently only 80% of the actual figure.

That suggests you may be doing better than you think, particulary if its cold where you are. Looking at my figures, it seems that Samsung are over reporting the electricity used and under reporting the heat produced.

This is the sort of information you get with Open Energy Monitor, in my view worth every penny as the savings you can make by knowing what is actually happening are substantial.

With respect to your installation I would be making sure that any bare pipework outside was insulated. The ends of the flexible hoses always seem deficient in my experience.

It looks like you have one anti-frost valve, so you wont be using antifreeze. 2 valves is common, but i have seen one fitted before and some people dont even bother with that given the highly unlikely event of sub-zero temperature and no electricity for an entended period. (Unless you live in Scotland!)

@bontwoody thanks so much for taking the time to do that. Our temps are fairly similar, the day with a COP above 3 we actually set the flow temps to a Samsung manual online of -2/38 and 15/48. We moved it down to -3/40 and 15/25 after reading around online at what others were using and it has kept the house at a good temperature at the lower settings but it looks like the COP is worse rather than better, I’m sure I’m oversimplifying though. 

I will definitely have a look into the monitors and we’ve asked for a smart meter to hopefully get onto a better tariff thank you. 

Will do and good to know re the anti frost valve. 

@dinhp dont have second thoughts about your weather compensation setting. Lower is better for COP.

Im not sure what you mean by:

Samsung manual online of -2/38 and 15/48

a flow temperature of 38C at -2C outside sounds reasonable but then 48C at 15C outside is the wrong way around. I would try 33C at 15C outside as you probably wont be able to go any cooler than 33C without cycling badly and you may have to go up slightly to 34 or 35C.

If you keep an eye on if the heat pump keeps stopping and starting often that will give you a hint that it is cycling. Have a look at my blog if you want to see how I run mine with a mixture of weather compensation and a single thermostat.

@dinhp, I reached out to one of the top installers in the UK for their insights on your post and the photos you provided and they said it’s actually quite difficult to make a system run this inefficiently. According to @bontwoodyl at least the numbers are a tad better.

Here’s the installer’s feedback, which I’ve expanded upon to provide clarity and guidance, and which you can share with your new installer:

Placement of the antifreeze valve: The antifreeze valve should always be positioned at the system’s lowest point. From the pictures, it’s clear this hasn’t been done, which could lead to operational inefficiencies or future maintenance issues.

Water pooling on the floor: The water you’re seeing on the floor is likely condensation from the heat pump. This should have been directed to a drain or soakaway as part of the installation. Improperly managed condensation not only impacts efficiency but can also cause unnecessary wear on the unit and surrounding areas.

Efficiency requirements under eco schemes: Even under ECO-funded installations, there’s a minimum efficiency requirement. For MCS installations, the current minimum Seasonal Coefficient of Performance (SCOP) is 2.8. If your system is underperforming significantly, you should raise this with the installation company and escalate it to the relevant competent persons scheme if they fail to act. It’s not likely to lead to anything meaningful but worth a try. Might be worth reporting them to RECC or HIES depending on who they’re registered with.

Likely root cause: The main culprit here is almost certainly the system’s control setup. According to the installer, correcting the controls alone could provide a 50% improvement in efficiency without any mechanical changes. 

It’s frustrating to see installations like this, especially when they fail to meet even the basic standards. Let me know how you get on.

@editor thank you so much for this and please thank the installer for me - I’ll raise this with our installer and hopefully we can get somewhere. 

Hopefully I can come back and update with some improved figures!

Any advice on if I should adjust the weather compensation temperatures further yet and if so the best way to do this? Do you lower both ends or just start with one? The 23/11 looks to be our best day which makes little sense from what I’ve read about online and lowering the temperatures to improve efficiency. 

I think our Delta T is lower than it should be usually at 1 sometimes 3 - not sure how to rectify this or if I need to if anyone has any advice on that it would also be appreciated. All TRVs are set to 5. The house is holding its temp 21 in living areas and 18/19 in bedrooms - we’ve not limited any areas the radiators were designed smaller for those areas I think. There is one third party thermostat which is set up to 24 in the living room just to stop the pump turning off. 

Currently waiting on our installers to get back to me on the poor efficiency and other points  

Thanks!