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Repiping and Reconfiguring our Heat Pump System Including Removing the Buffer Tank - Heat Pump Retrofix

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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Scalextrix

(@scalextrix)

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15/09/2025 8:39 am

@jamespa talking of being old, the house where I grew up had a multi zone heating system. Downstairs had radiators, upstairs didn't 😂

I remember scratching my name onto the frost on the inside of my bedroom window. Curiously I don't ever remember feeling cold though 😁

Now we (rightly) get upset if the room doesn't get upto temperature, how times have changed.

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JamesPa

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15/09/2025 8:50 am

Posted by: @scalextrix

↑

@jamespa talking of being old, the house where I grew up had a multi zone heating system. Downstairs had radiators, upstairs didn't 😂

I remember scratching my name onto the frost on the inside of my bedroom window. Curiously I don't ever remember feeling cold though 😁

Now we (rightly) get upset if the room doesn't get upto temperature, how times have changed.

And we (or at least some) expect to be able to do 5-4 showers in quick succession every day, and many other (largely luxury) thinks we now take for granted.

And yet people still aren't satisfied and moan about their lot. Really?

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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Toodles

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15/09/2025 8:58 am

@jamespa Your Mum used it? I still do! But, then I’m 78 in a couple of weeks😉 Toodles.

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

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Scalextrix

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15/09/2025 8:58 am

@jamespa things were shit in the "good old days", but we were happy anyway 😂

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Toodles

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15/09/2025 9:16 am

@scalextrix ‘You had a shoe box?’😉

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

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JamesPa

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15/09/2025 9:20 am

Posted by: @scalextrix

↑

things were shit in the "good old days", but we were happy anyway

Yup

Sadly consumerism, the foundation of our economy, depends on making us unhappy and thus buying ever more stuff to keep up with the neighbours or temporarily deal with our unhappiness.

This is of course totally unsustainable, but the lemmings have been 'educated' by the largely shallow self-interested media not to see that and as a result many vote for whichever self-interested individual tells them the lies they want to hear thus sealing their own, and more particularly their childrens' fate.

It's somewhat depressing.

This post was modified 2 months ago 6 times 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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Toodles

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15/09/2025 9:36 am

@jamespa The dormitories at my boarding school (in Exeter) had ice formed on the inside of the windows (single glazed of course) and that ice would sometimes be resident for several days at a time. Meanwhile, at home in Somerset, we had to keep a coal fire burning throughout the summer if we required any hot water as a back of fireplace heat exchanger mechanism was all we had. My Dad eventually installed an immersion heater in the DHW tank in about 1958/9 to alleviate the situation in our ‘shoebox’.😉 Toodles.

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

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Mars

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Topic starter 15/09/2025 5:52 pm

Day one is done.

The system’s been fully flushed and cleaned, and every lockshield has been swapped out for FRVs. They look fantastic and they’ve already exposed major flaws in our system (two in fact!).

This is shaping up to be an epic project and a huge learning experience. We’ve also filmed the first part of our video and we’re off to a flying start.

Short updates to follow this week before we unleash our content.

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GrahamF

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16/09/2025 7:06 pm

@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.

Anyway, once The Maestro has sorted it out, you will have dramatically improved performance and demonstrably reduced heating bills. Then, your position will be incontrovertible.

Of course, what you do with that information will be up to you.

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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Mars

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Topic starter 18/09/2025 9:12 am

Day 2 was a beast. All the excess zoning, on/off stats and buffer related piping, plumbing and wiring is gone. Day 3 is about putting everything back to together as an open zone and balancing all our emitters. I'll make sure @heacol gets regular coffee throughout the day to help him power through.