Posted by: @grahamf

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I am wondering why installers have concluded that buffer tanks are necessary for heat pump systems.

1: Because, deep inside, they realise that the MCS guidance has got them installing HP's which are actually over-sized.
The buffer tank throws away heat, thereby allowing the return water to be at a low-enough temperature.

2: Because it's a profitable mistake to make.
Needlessly installing a buffer tank is pretty simple, but adds to the profits.

Posted by: @ashp-bobba

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@jamespa Oh big question ...

I just wanted to see if we could profile 1 good installation 🙂 Glass 5% full rather than 95% empty (positive approach)   

 

We could I'm sure (mine for example, nothing special at all, but it works), but it will be drowned out by the noise from the poor systems (which may well be a minority for all we know) because the latter is amplified to satisfy the interests of big oil and now two of our  political parties, and they or their friends control most of the media.

The media being what it is and controlled by those it is controlled by, it matters not a jot if 95% of installations go well.  What matters is that a fair number don't and as a result what your mates and others tell you down the pub is to avoid heat pumps at all costs (which they do)

Frankly I fear that I the battle is being lost!

The hope is that we know that the narrative can be changed, the media have become positive about electric cars and largely stopped being negative.  Of course the electric car industry delivers excellent products consistently.

Good installers and heat pump manufacturers need to get angry imho!

I am quite evangelical about my ASHP, even though the install was a nightmare, 9 months on we are pretty sorted now, although we still have leaks!

Posted by: @transparent

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Posted by: @grahamf

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I am wondering why installers have concluded that buffer tanks are necessary for heat pump systems.

1: Because, deep inside, they realise that the MCS guidance has got them installing HP's which are actually over-sized.
The buffer tank throws away heat, thereby allowing the return water to be at a low-enough temperature.

2: Because it's a profitable mistake to make.
Needlessly installing a buffer tank is pretty simple, but adds to the profits.

3: For retrofits, installers have no clue what existing pipework they are working with, what flow restrictions they may encounter and what head pressure they may require. A buffer will work in many situations where without they may encounter issues which to be fair aren't of their making. When I say a buffer will work, I mean it may prevent call outs for the installer at a cost to the owner of a less efficient system.

4: Installers are incapable of calculating pipe sizes, flow rates and head pressures, so choose the fail safe option of a buffer and extra pumps as the know that works in all situations, at the customers expense (same as #3 but this time it's definitely the installers fault).

Your #1 made me chuckle, as I have an over-sized heat pump on an open loop, and on a good day may be able to get a dT of 2-3C between flow and return (dT of 5C is a pipe dream!)

Posted by: @old_scientist

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3: For retrofits, installers have no clue what existing pipework they are working with, what flow restrictions they may encounter and what head pressure they may require. A buffer will work in many situations where without they may encounter issues which to be fair aren't of their making. When I say a buffer will work, I mean it may prevent call outs for the installer at a cost to the owner of a less efficient system.

So run it without a buffer and instead add a supplementary pump slaved to the primary if the head required is too much for the built in water pump.  Obviously if the water pump isn't built in the just get a bigger pump.  Or operate at a slightly higher DT, nothing sacred about DT5!

Plenty of ways to solve this without adding a buffer!

Posted by: @grantmethestrength

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I am quite evangelical about my ASHP

Me too, but still some people look at me as if I'm mad. 

Whilst I do accept that I probably am in fact mad, I cant see how being happy to have a greener, less expensive to run and more comfortable system than previously is any evidence of that.

@old_scientist

Posted by: @old_scientist

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3: For retrofits, installers have no clue what existing pipework they are working with, what flow restrictions they may encounter and what head pressure they may require. A buffer will work in many situations where without they may encounter issues which to be fair aren't of their making. When I say a buffer will work, I mean it may prevent call outs for the installer at a cost to the owner of a less efficient system.

4: Installers are incapable of calculating pipe sizes, flow rates and head pressures, so choose the fail safe option of a buffer and extra pumps as the know that works in all situations, at the customers expense (same as #3 but this time it's definitely the installers fault).

 

3.  Some pipe work is always hidden, but some is always visible too.  The pipes connected to the old boiler, water pump, water tank (if present), zone valves and radiators will all be visible.  Only if pipe size changes in an invisible place, will the installer lack information. 

4.  If installers lack the skills to do basic sizing calculations, then that certainly is a serious problem, which needs to be addressed with training.  Unfortunately, some installers may not feel too comfortable with the maths involved.  They have not needed this so much for gas systems, so this is quite a culture shock for them.

I disagree that a buffer and extra water pumps work in all situations.  My definition of working includes meeting customer requirements and expectations in terms of comfort (consistent and high enough temperature in all rooms) and running costs.  

Renewable Heating Hub would not even exist, if Mars’s system with a buffer and many zones had met his requirements.  This forum and many others are littered with people who are dissatisfied with their systems and many include buffer tanks.

We know that installers have suffered from this poor engineering, as measured by repeated call-outs, complaints and reputational damage.

Agreed, and I'm in no way trying to defend poor system design or the use of buffers, just trying to rationalise why some installers choose to use buffers by default in every install.

Posted by: @old_scientist

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Agreed, and I'm in no way trying to defend poor system design or the use of buffers, just trying to rationalise why some installers choose to use buffers by default in every install

In other words, “Know thine enemy”

Posted by: @majordennisbloodnok

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I 

In other words, “Know thine enemy”

General Ignorance, the universal enemy in so many ways!

@ashp-bobba, I’ve never said or implied that the entire heat pump industry is shit. The reality is more nuanced, and I’ve spent a lot of looking at professionals in the industry and it’s not that the sector lacks talent, it’s that it hasn’t been set up to succeed.

The framework around it is fundamentally weak. MCS, which is meant to safeguard quality, provides little meaningful consumer protection and has failed to set tangible benchmarks for what “good” looks like. Training across the board is patchy… even programmes like Heat Geek, while useful, don’t prepare people to consistently design and install top-performing systems. 

And then there’s the installer landscape: plenty of very good and even great engineers out there, but also many who believe they’re good when, in practice, their installs are poor (classic Dunning–Kruger effect). The problem is the system doesn’t filter those out, and homeowners are left to pick up the pieces. We’re a classic case. Our installer doesn’t know why we’re unhappy with our system that he thinks has been installed very well. We have a SCOP of 2.7 and patchy heat distribution, but he thinks it’s mission accomplished and it’s a very good installation. There’s nothing you can do to upscale installers like this. 

The video I’m preparing isn’t about slagging anyone off for the sake of it. Our first installer got it wrong; badly wrong. Period. Brendon has made changes that will hopefully deliver what was missing: consistent comfort across the house, lower running cost and improved efficiency. That’s the positive side, and of course I’ll highlight that too. I want our case to a blueprint for how to rectify a bodged install. But the reality is that this work is intensive, time consuming and can be expensive on top of an already expensive first install. 

But if we’re serious about heat pumps scaling to 600,000 installs a year, we need to stop pretending the framework is working. There are excellent projects and excellent people in this space, but until the industry is structured to consistently deliver that level, homeowners will keep facing unnecessary pain. I’d rather see the UK fit 100,000 heat pumps annually properly, than slap in 600,000 a year with 500,000 of those needing rectification work because they’re were rubbish.  

It’s been a seriously intensive week and Brendon’s grafted through a mountain of work.

• Buffer tank is gone: now repurposed as a volumiser.
• All zoning stripped out: we’re now running fully open loop.
• Every circulation pump removed and replaced with a prototype delta-T modulating pump (18m head and an absolute beast).
• FRVs fitted: just need a final tweak this week to fine-tune volumes once Brendon has done his calculations.
• UFH has been balanced

We do have one niggle left: the heat pump controller is dropping into standby after finishing its hot water cycle instead of moving smoothly into central heating. I’ll be speaking with the manufacturer to get that sorted… not sure what’s causing this.

It’s been a heavy, full-on week and Brendon must be shattered! Videos will follow in the coming weeks, along with plenty of posts to help others tackle bodged installs or set up systems properly where zoning, microbore and buffers have been holding them back.