@drei in your original post, you said:

Posted by: @drei

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I'm not guessing, I’ve had an independent assessment from a Heat Geek Elite engineer at the cost of £800, thermal imaging, flow readings, everything documented.

Did the Heat Geek Elite engineer give you a design within the £800 fee, or did he just tell you everything that was wrong and how badly wrong it was? 

My impression is that there are 2-3 key problems:

1.  The buffer tank is reducing flow temperature to the radiators, so that they never get above 40C.

2.  The radiators are inadequately sized, so even at 50C they would not be big enough.

3.  The water flow rate might be insufficient to push the water around the radiators fast enough.

Is that correct?  

Quote 1 seems to be addressing only part of the problem.  If the buffer is plumbed incorrectly (in-flow from heat pump at the top, outflow to radiators at the bottom, return from radiators at the top and return to heat pump at the bottom) then correcting that would certainly help.  But removing the buffer entirely might correct it a lot more.

Quote 2 seems to be much closer to what you need.  However, I don't understand why you wouldn't upgrade all the radiators that need upgrading.  The approach I took was to install big new radiators in the rooms that needed the most heating power.  Then, I cascaded the radiators that I had freed up into rooms needing less heating power.  Cascading existing radiators down the chain would save you buying so many new radiators, but obviously, they would have to fit in the available space. 

Posted by: @jamespa

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Posted by: @drei

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I would hope so:) but this is why a Heat Geek Elite quote would really help. I had one booked in but had to cancel last minutes. Just hoping I can get them in this week. This was a free visit.

IMHO hope isnt enough in a situation like this.  My strong advice to you is, before you proceed, get the chosen quote validated against either common sense or the report you have. 

The person who produced quote number 1 doesn't mention radiator replacements at all, is doing a lot of stuff that will make no difference to your system (although its not bad practice) and appears to be retaining the buffer not converting it to a volumiser or getting rid of it altogether.  If he does what he has actually put down put down in writing you very likely wont be much better off and will have blown your 'section 75' option.

Yeah, they did call, and stated that what they intend to do is bypass the buffer, but leave it in place just in case the additional volume is needed, and again, bypass the return so that it goes Radiators ---> Heat Pump, rather than through the buffer.

I did ask him to amend the quote and clarify.

Posted by: @editor

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@drei, remind me again which county you're based in.

Hi Mars, I am in Colchester, so North Essex, all the Heat Geeks in my area are based in Ipswich.

All of the installers are happy using my radiator designs, they stated that they seem solid.

For context, please see attached the actual design, with a shortfall of about 33% per floor, however since my radiators don't get more than 40c at the moment, my shortfall is almost 60%.

These are my designs, and I am using 45 mean water temp, as it is the best of both worlds, so even if I have to go to 50c, it should be much better than my current design. I am trying to keep as many of the existing radiators as I can, in the hope that I can keep the carbon footprint low. Throwing 12 rads away, and the excess electricity used so far, I doubt my heat pump will ever become truly "green".

The only issue is that on the ground floor, I don't have the space for larger radiators, so I have to get a full 3000W electrical radiator, that matches current design.

Please have a look, and let me know your thoughts.

This is my current usage so far, which my installer keeps stating I don't understand how Heat Pump SCOP works, how to work it out and that my readings are wrong:

This is the problematic 4 pipes buffer. Since I reduced the pump speed, pumping INTO the buffer to L1, the SCOP seems to have improved slightly. I assume it is causing less distortion.

See below my reply to the Buffer Article:

I discovered that my installer’s “50 L minimum water volume” design note, wasn’t a manufacturer requirement but likely a misreading of the Samsung Installation manual (page 29 of the EHS_R-32_MONO_OUTDOOR_IM_EU_DB68-11904A-03_EN.pdf manual) .
Samsung’s own installation guide for my AE120BXYDEG (12 kW, Gen6 R32) states clearly:

Minimum total system water volume = 50 L (radiators, pipework, cylinder coil, and any buffer tank)This means that my system just needs at least 50 L total to run reliably, it does not mean you must add a 50 L buffer tank. In my setup, 19 radiators, a cylinder, and 15–18 m of copper pipe, the system likely already exceeded 50 L without any buffer.

By mistaking “minimum system volume” as “must fit a 50 L buffer,” the installer inflated the system volume unintentionally. That extra buffer tank caused hydraulic distortion, poor ΔT, and system inefficiency, precisely the kinds of failures exposing how buffer tanks are often misused as a crutch for poor design. The buffer tank created operational loss instead of solving it.

Posted by: @drei

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. The buffer tank created operational loss instead of solving it.

As they almost always do so far as can be judged from this forum (and basic physics)..  Based on what I have seen over two years on this forum (and what I have personally experienced) buffers should, IMHO, be banned other than in a truly exceptional case where there there is a proper engineering justification which has been independently verified by someone who understands the issues (much like there were, and possibly still are, things that you cannot do with your pension without first taking independent professional advice).

Posted by: @drei

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Please have a look [at the design/rad spec pdfs], and let me know your thoughts.

I get the general idea with the spread sheets, I did something similar, but it is a little difficult just looking at pdfs, as so many things have changed. If you can post the actual spreadsheets (just the relevant worksheets), it will be easier to comment. If not, just add your own sense check check sums.

One general comment for now (I also had limited wall space) - can you use more K3s, and get rid of that 3000W electric radiator monster? K3s are large - almost all of mine are K3s - but if placed between furniture the protrusion is less obvious, and over time you sort of get used to them. 

Posted by: @cathoderay

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Posted by: @drei

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Please have a look [at the design/rad spec pdfs], and let me know your thoughts.

I get the general idea with the spread sheets, I did something similar, but it is a little difficult just looking at pdfs, as so many things have changed. If you can post the actual spreadsheets (just the relevant worksheets), it will be easier to comment. If not, just add your own sense check check sums.

One general comment for now (I also had limited wall space) - can you use more K3s, and get rid of that 3000W electric radiator monster? K3s are large - almost all of mine are K3s - but if placed between furniture the protrusion is less obvious, and over time you sort of get used to them. 

 

I tried to add the workings on the PDF, as I realised there is no formula. I can duplicate my spreadsheet as everything I have is on Google Sheets. Kept it that way for easy access across devices.

I think in principle my design is OK.

In regards to changing the rads, if I replace 19 rads with Panel K2 and K3, it will definitely work, but that means £6000+ just in radiators, and I would have to throw away at least 15 rads, less than 2 years old, maybe I can sell them, but for the headache, it would probably be easier to load them in a truck and take them to the scrap iron or the recycling centre, which will be a huge carbon footprint (yep I am still thinking of that, as that was the whole point of the heat pump).

I was hoping to still keep the designer look, as they are nice, and my wife really hates the panel rads, and only upgrade to K2 and K3 where necessary without having a choice.

As a last minute resort, I may just have to go via the full panel upgrades, and only use the double column vertical rads, to replace the existing towel rads.

Posted by: @drei

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£6000+ just in radiators

That is a lot for just rads, I think if you got trade prices on standard K3s you could cut that down a lot, plus scrapping metal these days is actually recycling it, not going into landfill.Only you and your wife can decide whether the extra dosh is worth the designer look. 

@drei I think someone else mentioned that you could just replace the biggest radiator and cascade the others down to different rooms. I did it saves a packet

Posted by: @drei

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See below my reply to the Buffer Article:

I discovered that my installer’s “50 L minimum water volume” design note, wasn’t a manufacturer requirement but likely a misreading of the Samsung Installation manual (page 29 of the EHS_R-32_MONO_OUTDOOR_IM_EU_DB68-11904A-03_EN.pdf manual) .
Samsung’s own installation guide for my AE120BXYDEG (12 kW, Gen6 R32) states clearly:

Minimum total system water volume = 50 L (radiators, pipework, cylinder coil, and any buffer tank)This means that my system just needs at least 50 L total to run reliably, it does not mean you must add a 50 L buffer tank. In my setup, 19 radiators, a cylinder, and 15–18 m of copper pipe, the system likely already exceeded 50 L without any buffer.

By mistaking “minimum system volume” as “must fit a 50 L buffer,” the installer inflated the system volume unintentionally. That extra buffer tank caused hydraulic distortion, poor ΔT, and system inefficiency, precisely the kinds of failures exposing how buffer tanks are often misused as a crutch for poor design. The buffer tank created operational loss instead of solving it.

You are correct that the Samsung docs recommend a minimum system volume of 50L, but note the key word there is minimum. In reality, the system volume should be significantly larger.

I have the 12kW Samsung gen6 ASHP, and our system volume is ~190L, comprising ~45L in the system pipework, ~95L in the radiators and a 50L volumiser (not buffer). So even with 140L native system volume, we still have a 50L volumiser. The additional volume gives higher thermal mass which should in theory help with short cycling, but most importantly in my opinion it ensures there is sufficient heat energy in the system to adequately perform system defrosts in winter. If you do not have sufficient heat in the system, it is possible to descend into a defrost spiral sucking all the heat from the system, with the heat pump then working flat out replacing it only to entering another defrost cycle...

See this thread and the YouTube video in the first post.