I have been watching, with interest, the rebuild and replacement of a five year old Heat Pump on the Skillbuilder site.

The Results of the rebuild demonstrate How a heat pump should be installed!

The Skillbuilder channel has never given the cost of replacing the Heat Pump and the hot water tank, but the cost must have been substantial.

So , competent Heat Pump installers are available.................................but unaffordable.

My own Heat pump has finally reached a COP of 4.5 ........................but I DO NOT NEED A heat pump in these Temperatures.

As the NIC have repeatedly said of my Heat Pump ..............................NOTHING CAN BE DONE!

Abandon hope all ye who enter here!

A light-hearted, funny video that highlights the divide that exists in the world of heat pump installations as two titans clash over the industry's most contentious issue – buffer tanks.

An interesting experiment on LLHs.

As expected, after publishing the buffer tank Homeowners’ Q&A episode below, we received a lot of pushback, comments, emails and DMs from pro-buffer installers. Needless to say we invited plenty of pro-buffer installers and they all declined. 

The best-performing ASHP on heatpumpmonitor.org, installed by Damon Blakemore, doesn’t use a buffer tank, and many of the top 50 systems also skip them. Damon has always told me that buffers often aren’t sized correctly, and secondary pumps are rarely set up properly, which stems from poor design. The approach many installers take seems to be fixing problems rather than optimising performance.

Manufacturers include buffers to minimise volume and shift any flow issues to the secondary side, which avoids warranty problems. However, secondary pumps aren’t factored into SCOP figures when buffers are used, which skews performance data. 

Posted by: @editor

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As expected, after publishing the buffer tank Homeowners’ Q&A episode below, we received a lot of pushback, comments, emails and DMs from pro-buffer installers. Needless to say we invited plenty of pro-buffer installers and they all declined. 

 
Stick to your guns (which I'm sure you will).  Buffer tanks are, in most domestic cases, for the benefit of installers not homeowners.  That being the case some installers will always argue for them, just as the fossil fuel industry will continue to argue that climate change isn't a problem/doesn't exits/isn't caused by human beings/can be solved by hydrogen boilers... 
Both are wrong for provable scientific reasons and their reason for claiming what they do is apparent for all to see (not that this is any excuse at all for spreading disinformation).
Keep up the good work!

Hello All. Thought I'd throw in my experience. When we had our ASHPs installed in 2011, it came with a largish buffer tank, for all the usual reasons such as instant hot water when the heating stats called for it.

After around 6 years in, after reading up on efficiency, I decided to remove the buffer tank. I reasoned that the system was wasting lot of energy simply keeping the buffer tank up to temp. A fact confirmed by our Plumber, who is experience with ASHP systems as it happens. Our system is quite large, so surely there was enough water buffering in the pipework with out the need for buffer tank, we opined.

So, we duly removed the buffer and made some tweaks to the pipework as necessary token the system flowing.

Results were staggering. Roughly 25% drop in energy input required to give same heat output. I have measured this over several years to eliminate a mild one off winter. 

So no Buffer or LLH in our system seems to be the answer.

Hope this helps.

Cheers

Alan

Posted by: @alanb

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After around 6 years in, after reading up on efficiency, I decided to remove the buffer tank. I reasoned that the system was wasting lot of energy simply keeping the buffer tank up to temp. A fact confirmed by our Plumber, who is experience with ASHP systems as it happens. Our system is quite large, so surely there was enough water buffering in the pipework with out the need for buffer tank, we opined.

So, we duly removed the buffer and made some tweaks to the pipework as necessary token the system flowing.

Results were staggering. Roughly 25% drop in energy input required to give same heat output. I have measured this over several years to eliminate a mild one off winter. 

So no Buffer or LLH in our system seems to be the answer.

Thanks for sharing this and very pleased to hear the result.  Well done for having the courage.

 

Its worth being aware that there are (at least) two reasons why removing a buffer tank saves energy, and its not necessarily heat loss from the tank that is the major contribution:

1. You aren't having to replace the heat lost from the buffer tank - however if the buffer tank is inside the heated envelope the energy isn't really 'lost', and anyway with a well insulated buffer tank it should be no more than 1-2kWh/day

2. A buffer tank, unless very well set up, results in a temperature drop between the flow from the heat pump and the flow to the emitters because flow and return mix in the tank.  This means that the heat pump must operate at a higher flow temperature to get the same flow temperature at the radiators, and that means it is less efficient (lower COP) by very roughly 3% for each degree drop.

The latter is a function of the thermodynamics of heat pumps so doesn't apply to fossil systems, which may be why some heating 'engineers' don't understand it!

It is possible to set up a sufficiently tall buffer tank to avoid the flow and return mixing, and thus circumvent (2), but there are far too many reports where this has not been done (or is not even possible given the equipment/wiring used) 

 

 

Posted by: @alanb

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Hello All. Thought I'd throw in my experience. When we had our ASHPs installed in 2011, it came with a largish buffer tank, for all the usual reasons such as instant hot water when the heating stats called for it.
After around 6 years in, after reading up on efficiency, I decided to remove the buffer tank. I reasoned that the system was wasting lot of energy simply keeping the buffer tank up to temp. A fact confirmed by our Plumber, who is experience with ASHP systems as it happens. Our system is quite large, so surely there was enough water buffering in the pipework with out the need for buffer tank, we opined.
So, we duly removed the buffer and made some tweaks to the pipework as necessary token the system flowing.
Results were staggering. Roughly 25% drop in energy input required to give same heat output. I have measured this over several years to eliminate a mild one off winter. 
So no Buffer or LLH in our system seems to be the answer.
Hope this helps.
Cheers
Alan

Thats great to read!
Have you any detailed figures? Is the benefit more in shoulder season or in the coldest periods for example?
 

Hi all,
Trying to jump on an existing thread before creating a new one.
We're looking at getting an ASHP installed and im having the buffer/no buffer deliberation. 
Currently looking at a 5kW Vaillant and our system volume is ~200L.
Installers are speccing buffers and one even said because of the new R290s you MUST have a buffer - I can't see this anywhere in research. Is this a thing, and if not any tips on how to push back?
(Bonus: this 'experienced' installer said that the unit doesn't have to be >1m from the boundry is the fan isn't pointing at it. It'd help... but I dont think they're right)
 

You need to use Heat Geek, BG or Octopus to be certain of no buffer. You may get a volumiser (smaller tank in series) depending on your system. Don’t give in to LLH brigade!

One company who normally install buffers were willing to do a lower temperature system without one once the ‘estimating engineer’/salesman spoke to the boss. But we reasoned why go with a company with little experience of the design.

@samiebon1, there’s a lot here that raises red flags with this installer’s advice, and I’d strongly recommend considering other options. This setup sounds like it could lead to complications down the road. Is this installer a one-man operation or a small company?

@judith is spot-on about low-loss headers. After nearly two months of behind-the-scenes conversations with installers we’ve interviewed for the podcast, I can confidently say buffer tanks are rarely needed. In retrofit setups, volumisers can sometimes be appropriate, but that’s typically where it ends. So, no need to second-guess your decision. I don’t think this installer is right for you.

Where are you based?

Posted by: @samiebon1

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Hi all,
Trying to jump on an existing thread before creating a new one.
We're looking at getting an ASHP installed and im having the buffer/no buffer deliberation. 
Currently looking at a 5kW Vaillant and our system volume is ~200L.
Installers are speccing buffers and one even said because of the new R290s you MUST have a buffer - I can't see this anywhere in research. Is this a thing, and if not any tips on how to push back?
(Bonus: this 'experienced' installer said that the unit doesn't have to be >1m from the boundry is the fan isn't pointing at it. It'd help... but I dont think they're right)
 

Check whether by 'buffer' they mean 2port volumiser (the key feature being 2 port).  That's ok.  It's typically 20-50l..  Vaillant do put a volumiser on most if not all of their  system diagrams and sofaik it does no harm.  It can go in flow or return (there are arguments both ways)but not between the two.  Anything else - avoid.

Assuming you are in England then the 1m from boundary rule applies.  I think it does elsewhere but would have to check to be certain.