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Big Changes Coming to Our Heat Pump System

Mars · 2025-09-14T09:39:26Z

After years of living with an underperforming system and much deliberation on our part, we’ve finally decided to take up Brendon’s (@heacol) long-standing offer to come and help improve it. He’s been incredibly generous with his time and advice over the years, and now he’ll be spending a few days with us to properly diagnose what’s wrong and make the necessary changes. Our goal is to significantly improve our system’s efficiency, and we’ll be documenting the entire process here on the forums and in a series of YouTube videos. The idea is to show, warts and all, why our system has been underperforming, and what Brendon does to put it right. I think it’ll be a fascinating case study, and hopefully useful for other homeowners who find themselves in similar situations. Here’s what we already know is on the cards: The buffer tank will almost certainly be bypassed (though it may get repurposed as a volumiser... we’ll see what Brendon decides). The army of circulation pumps we currently have will be cut down to something far more sensible. FRVs will be fitted to all radiators to allow proper balancing across the system. The whole system will get a much-needed flush too. The other big area of focus is zoning. Our system has multiple zones controlled by on/off thermostats dotted around the house. I’m very curious to see how Brendon approaches this, what he suggests and how it all works in practice once the changes are made. As a point of reference and context, our lifetime SCOP is 2.7, and we're hoping that the work carried will hopefully improve running costs, but more importantly, that we can deliver uniform heat around the property, where we currently have a lot of rooms that struggle to get to temperature. For us the acid test will be our TV room, the most challenging room in the house. If Brendon can get that rad up to temperature with consistent flow, I’ll consider it a huge win. Brendon will be with us for several days, so if you have any questions you’d like me to put to him while he’s here, please post them below. I’ll do my best to address them in follow-up posts or in the YouTube videos we publish.

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Air Source Heat Pumps (ASHPs)

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Toodles

(@toodles)

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Joined: 3 years ago

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18/09/2025 11:27 am

@grahamf “Things can only get better” (Sorry) Toodles.

Toodles, he heats his home with cold draughts and cooks his food with magnets.

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Mars

(@editor)

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Topic starter 18/09/2025 1:23 pm

Posted by: @grahamf

↑

@editor your engineer's attitude is truly horrifying. I suspect he realises that he messed up, but can't bear to face up to it.

I don’t think he does, because he's a very arrogant individual. We still have the occasional run-in on email or social media. The difference is that six years on, I actually know a lot more and can clearly see the “errors” that were brushed off at the time. Yet they still insist everything is fine.

He also has a habit of bad-mouthing me to other installers whenever our system comes up, which is fine. Hopefully, the remedial work we’re doing now will shine a very bright light on his bad practices, the lack of design and the frankly shocking commissioning.

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JamesPa

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18/09/2025 1:49 pm

I'm intrigued by this exercise, so far you haven't reported that it was necessary to do anything other than the obvious. If thats the case then its yet another example of how the industry is messing up.

There is a thread on buildhub (repeated on openenergymonitor) at present, where an electrical engineer is asking for advice. In summary he has received 3 quotes for the same 7kW Vaillant based system, but 2 out of 3 want to fit a buffer tank and one wants to microzone it. So thats 2 out of 3 'advising' the wrong thing! Its scary

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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GrahamF

(@grahamf)

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18/09/2025 2:38 pm

@jamespa I find this rather strange. We have had three gas boiler systems installed. I also know about my parents' and children's gas boiler systems. None of them has a buffer tank.

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

This post was modified 19 minutes ago by GrahamF

Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation

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GrahamF

(@grahamf)

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18/09/2025 2:45 pm

@editor I found this Wikipedia article on Noel Burch's Four Stages of Competence model.

EN.WIKIPEDIA.ORG "https://en.wikipedia.org/wiki/Four_stages_of_competence"

Four stages of competence - Wikipedia

It appears that your installer may be stuck at the "Unconscious Incompetence" stage.

"The individual does not understand or know how to do something and does not necessarily recognize the deficit. They may deny the usefulness of the skill. The individual must recognize their own incompetence, and the value of the new skill, before moving on to the next stage. The length of time an individual spends in this stage depends on the strength of the stimulus to learn."

This post was modified 12 minutes ago by GrahamF

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JamesPa

(@jamespa)

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18/09/2025 2:52 pm

Posted by: @grahamf

↑

@jamespa I find this rather strange. We have had three gas boiler systems installed. I also know about my parents' and children's gas boiler systems. None of them has a buffer tank.

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

Not a clue quite frankly, other that to disguise problems which otherwise might lead to call outs. It seems still to be endemic sadly.

@editor has done 2 podcasts on buffer tanks, on each one only installers who advocate against were prepared to appear, those who advocate for declining. That says all we need to know in my book.

This scandal risks destroying the uk heat pump industry by underpinning what the oil industry wants us to believe, namely that heat pumps don't work/are inefficient. It is imho a disaster.

Of course the heating industry has form with installing for its own convenience not for the customer. Most condensing boilers sold since they became available in 2005 are set up so they don't condense, negating the whole point and increasing running cost by 10%, impairing comfort, but reducing call outs. The last person to service my gas boiler before it was removed, even had the cheek to reset my boiler flow temp to max even though I had turned it down!

This post was modified 3 minutes ago by JamesPa

This post was modified 2 minutes ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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