@editor Thanks Mars, interesting as most ASHP manufacturers a while back were stating or suggesting the reason for a hydraulic break was to ensure minimum standards of flow, therefore less cycling and therefore more efficient, as each manufacturer cannot ensure what you bolt their systems to and the fact that they know most installers will not upgrade the existing pipework within a home as its to expensive and disruptive, adding a buffer for them is a save all. Their equipment heats the hydraulic break store and engineer can do what they want feeding the rest of the system with that stored heat.

I wonder if all the manufacturers will start to drop the use of them from their literature. 

@ashp-bobba I think we’ll see a different approach to buffers in the years ahead. Volumisers are a different story.

Neil, from Grant UK, stated quite categorically in our latest video that Grant don’t mandate buffers:

@editor I am aware, open loop, less pumps, slow and steady heat generation has proven more efficient, the clever engineering in ASHP is the inverter tech and compensation partnership, anything that restricts this take away some of that.
 

@editor I think these podcasts are great. I did watch this one yesterday I think. Lets see if the MI drop buffers in their schematics as options in the future. Yes volumiser will be needed for defrost on low volume systems. Perhaps they will drop the rule with split / duel zones on buildings over 150m2. All manufacturers also still allow for duel zones in their controls at the moment. Not open loop if you shut a zone down.
 
  

@editor Can you do a podcast on standards of training, whats available, how engineers get trained, where they come from, what level they get trained to, how engineers will get trained in the future, when to use and not to use some components and so on. That would be very interesting to see what the specialist say.
 
 

@ashp-bobba we actually touched on that in yesterday’s recording that will go live on New Year’s Eve. Spoiler alert: there are very few options out there to train low temperature heating installers, but work is going on behind the scenes to improve standards.

@editor I will keep an eye out for that podcast, thank you.
Just a side note relevant to buffers, rails separators and volumisers. I may not be correct about all of them but I seem to remember that most ASHP manufacturers can provide full solutions so the ASHP and a pre-plumbed cylinder, if I remember correctly most pre-plumb cylinders come with 3 pumps, primary for the ASHP through a 3 port then connected to a rail / low loss header or the plate exchanger for DHW, heating pump on the other side of the header and a hot water pump from a plate. This in effect means most pre-plumbs come set up in one form or another as a low loss header / rail separator and a plate heat exchanger.
Not all are the same but many are. Perhaps these will not be popular in the future.

My system has one of the Telford Tempest cylinders with a 50 litre buffer tank in the bottom. It seems to work very efficiently (claimed COP of about 6 when 6C outside but a 28C heating flow temperature must be a key factor) and enables my 7kW Arotherm+ heat pump to run intermittently when it's warmer than about 7C outside and the house needs some heat but not a lot. I haven't seen any info about what's inside the buffer tank but suspect that there may some form of baffle between the heat pump circuit (pipe connections on left side) and the radiator circuit (pipe connections on right side). It's the same water in both circuits and both run as similar temperatures but the tank enables each circuit to run at its own flow rate as well as increasing the overall flow volume. The top title implies that having a buffer tank may be adversely affecting the efficiency of my system but I struggle to see how and why.

Posted by: @johnr

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The top title implies that having a buffer tank may be adversely affecting the efficiency of my system but I struggle to see how and why.

A properly installed buffer tank system can be efficient, but the challenge lies in the skills and knowledge of the installer. In the UK, many installers struggle to correctly balance flow rates before and after the buffer, leading to energy losses and reduced efficiency.

This is why many of the country’s top installers (that deliver highly-efficient systems) are moving towards open-loop, buffer-less systems. These systems deliver significantly higher efficiency, provide more uniform heat distribution, and eliminate the need for circulation pumps. Circulation pumps not only increase running costs but are also not accounted for in COP/SCOP calculations, further skewing perceived efficiency. Our buffered system has four circulation pumps because it's been so appallingly designed and fitted.

@editor  Why, oh why, are these system NOT Mathematically designed? In Electrical engineering many circuits are designed using P-SPICE Software. In electrical/Electronic engineering SPICE software calculates the behaviour and performance of an Electrical/Electronic circuit using precise mathematical models. Why are heat pumps NOT properly, mathematically designed?  

These disputes about Buffer tanks, volumisers could be settled in the flash of a PC! Does anyone know of an affordable Mathematical design software?

Posted by: @iantelescope

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These disputes about Buffer tanks, volumisers could be settled in the flash of a PC! Does anyone know of an affordable Mathematical design software?

PSPICE I think, it seems highly likely that a heat pump system, including the house, can be described in electronic terms.  Cant see the average plumber doing this though.  Its more a 'suck it and see' trade.

In all seriousness I think its becoming increasingly clear that in the vast majority of domestic situations its actually fairly easy with the exception of the first bit - determining the loss.  However once you have done that,

• Put in a heat pump of adequate size, a diverter valve and if you must a new DHW tank. 
• Roughly estimate system volume and if there is doubt put in a volumiser. 
• Dont put in a buffer, LLH, heat exchanger of any type. 
• Use pipe sizes according to heat geek cheat sheet or similar unless its a mansion or a silly route.  Prefer swept bends over elbows.  If any existing pipes are undersized assess risk and (probably) suck it and see unless its an obvious fail
• Set up WC and radiator balance as best you can and give homeowner some simple instructions how and when to tweak. 
• If homeowner doesn't want to tweak then set up WC as best you can, erring on the high side, and layer the system thermostat, not a third party one, on top to give fine control.

Obviously the above (and the associated works) has to be done properly, but I don't think it merits much simulation in the vast majority of cases.

How many plumbers actually calculate the index circuit when replacing a boiler?  Boiler manufacturers know this which is why they supply boilers with circulation pumps adequate for the majority of realistic situations.

@iantelescope They say its as a result of the combi birth and delta T changing from 11 to 20! as tech got better it required less flow so all of the existing pipework in building was instantly over sized, oversized pipework is completely fine for systems, also over sized rads (with new TRV tech at the time no longer mattered as TRV's would stop the oversized boiler from overheating the oversized rad in the room) and so on, the combi sizing chart also helped, hello Sir would you like 6lts, 7lts 11lts or even 13lts of 55 deg hot water flow? This means you will get a 20kW, 24kW, 32kW or a 36kW boiler respectively. So now you have a heating boiler oversized by 8 times the requirement just to do the hot water. From that date all new engineers generally got told the water is what matters heating will always be fine.
Now hydraulics matter, friction matters, emitters matter, pressure matters and effectively the whole design matters more than ever. I think they need to make a rule if you cannot design it or get it designed then you should not install it.
Does make you wonder if there is a whole gap in the market for ASHP designers, nice little business running around designing systems correctly.
I wonder if the big 6 (meaning power companies) design accurately and can still offer the av install £2000 less than your av smaller companies and supervise all of the sub-contractors they use to install to design when they don't have enough engineers of their own. Just a thought.