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

 
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Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 6 months ago
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4506
Topic starter 14/09/2025 10:39 am   [#2457]

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.


This topic was modified 7 months ago 2 times by Mars

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 Old_Scientist
(@old_scientist)
Honorable Member Member
Joined: 2 years ago
Posts: 397
14/09/2025 12:26 pm  

Posted by: @editor
↑

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.

If the goal is to deliver uniform heat around the property, I'm wondering why there are multiple zones, so like you I am interested to see Brendon's approach here. I guess your property is significantly larger than ours (and may therefore require more complex solutions), but I'm very much a fan of the KISS approach and just having one simple wide open zone with properly sized radiators for each room and balanced flow.

Good luck and I'm looking forward to following your journey.

 

 


This post was modified 7 months ago by Old_Scientist

Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.


   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4506
Topic starter 14/09/2025 1:07 pm  

@old_scientist, our system was royally bodged six years ago. No design, no thought, they simply dropped the heat pump in and set it up to run like a boiler. All the zoning we had was carried over from the old oil boiler, and there was never any conversation about whether this should be reconfigured.

Back then, we knew nothing about heat pumps, and that naïve trust is what ultimately led to our experience, the very experience that pushed us to create Renewable Heating Hub. It was, in every sense, an average, cookie-cutter installation.

In later conversations with the engineer assigned to our job (who very much rates himself and hates when I call this out, so I’ll refrain from naming him), his response was staggering. He basically laughed it off, saying he didn’t understand the fuss because we run a bivalent system, and if we’re cold or rooms aren’t reaching temperature, we should just fire up the oil boiler.

It’s exactly this kind of dismissive attitude that’s behind so many sub-par installs in the UK. And what makes it even more concerning is that this same engineer is regularly invited to speak at renewable and heat pump events. Frankly, that’s scary.


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 Brendon Uys
(@heacol)
Prominent Member Contributor
Joined: 5 years ago
Posts: 415
14/09/2025 5:49 pm  

@editor No pressure then 🤣 🤣



   
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 Grantmethestrength
(@grantmethestrength)
Reputable Member Member
Joined: 1 year ago
Posts: 184
14/09/2025 8:21 pm  

Really looking forward to this! Maybe volunteer as a guinea pig for the latest greatest heatpump with the latest greatest controller! Did you ever think you would become a heat pump influencer! You may need to set up an “Only Fans Heat Pumps” account!!!!!!!!


Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w + 13x 480w Solar Panels
Sigenergy 10kW Inverter
25kWh Sigenstor battery


   
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 ASHP-BOBBA
(@ashp-bobba)
Honorable Member Member Professional Installer
Joined: 1 year ago
Posts: 439
14/09/2025 9:00 pm  

@editor looking forward to the case study 🙂

 

 


AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.
Professional installer. Book a one-to-one consultation for pre- and post-installation advice, troubleshooting and system optimisation.


   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4506
Topic starter 14/09/2025 9:13 pm  

Posted by: @heacol
↑

@editor No pressure then 🤣 🤣

No pressure at all - the UK heating world is watching! 🤣 

 


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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4506
Topic starter 14/09/2025 9:18 pm  

Posted by: @grantmethestrength
↑

Really looking forward to this! Maybe volunteer as a guinea pig for the latest greatest heatpump with the latest greatest controller! Did you ever think you would become a heat pump influencer! You may need to set up an “Only Fans Heat Pumps” account!!!!!!!!

I think it's going to be a very interesting project and one that I think could be used as a blueprint for other retrofits. 

As for “Only Heat Pumps”, I’m not sure the world is quite ready for seductive shots of flow temperature graphs and half-stripped circulation pumps. Mind you, if Brendon pulls this system into shape, I might just consider it… subscription tiers based on kW output. 😉 

 


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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4506
Topic starter 14/09/2025 9:18 pm  

@ashp-bobba thanks Simon!


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 Lucia
(@lucia)
Honorable Member Member
Joined: 2 years ago
Posts: 354
14/09/2025 10:01 pm  

Posted by: @heacol
↑

@editor No pressure then 🤣 🤣

Busman's holiday. 🫢😂

 



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4506
Topic starter 14/09/2025 10:19 pm  

Posted by: @lucia
↑

Posted by: @heacol
↑

@editor No pressure then 🤣 🤣

Busman's holiday. 🫢😂

I had to Google that… 😞

 


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Subscribe and follow our YouTube channel!


   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 4677
15/09/2025 9:01 am  

Posted by: @lucia
↑

Busman's holiday.

You are too young, 50s-60s expression (or earlier?) which my mum used frequently.


This post was modified 7 months 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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