Hi Everyone,

It is strange how the same issues seem to pop up on the forum, it must be well over one year ago when CR and I were discussion the problem of having a PHE installed in his system, and my suggestion that he should consider having it removed.

@derek-m and all

We are at the getting to grips with quotes etc stage. When our extension is finished (and only then, and if we can face more disruption) in the spring we’re going for a ashp install. Neighbours have recommended their installer but looking at their web site (and our neighbours) they also install large buffer tanks (possibly piped as 4 port can’t recall, need to go round again) plus a llh for their ufh.

So how do you prevent an installer putting in all of the extra stuff, other than going with someone else.

I realise from this forum and others that an open system is best, with obvious essentials like having large enough emitters. I have used Heatpunk to size up our house and my results compare well with our gas bill, so know what is involved.

Similar question how do you stop the installer using the huge mcs defaults on leakage loss when our blower door rate are below 1ach?

Similar question to all

i understand some ashp manufacturers insist on a llh/ 4 port buffer. Who are they so that they can be ignored, together with their installers? 

Posted by: @judith

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@derek-m and all

We are at the getting to grips with quotes etc stage. When our extension is finished (and only then, and if we can face more disruption) in the spring we’re going for a ashp install. Neighbours have recommended their installer but looking at their web site (and our neighbours) they also install large buffer tanks (possibly piped as 4 port can’t recall, need to go round again) plus a llh for their ufh.

So how do you prevent an installer putting in all of the extra stuff, other than going with someone else.

I realise from this forum and others that an open system is best, with obvious essentials like having large enough emitters. I have used Heatpunk to size up our house and my results compare well with our gas bill, so know what is involved.

Similar question how do you stop the installer using the huge mcs defaults on leakage loss when our blower door rate are below 1ach?

You can try arguing with the installer.  In my experience this will work with some, but many will take no notice.  Basically its a sellers market so many don't care about anyone who argues (in fact they probably actively want to discourage them).  You will quickly find out which category any given installer fits into. 

You can ask the manufacturer the specific question via their technical support line, and you may well get an answer or even a set of approved system diagrams.  I found Vaillant, Mitsubishi, Grant, Cool Energy to be very helpful, Daikin pretty much said 'ask your installer' (even when I escalated) and Samsung haven't responded to any technical query I have posed.  One individual reported an extensive (and successful) conversation with Vaillant about some non standard requirements/simplifications that the installer had vetoed.   Obviously if you can get answers from the OEM, the installer should listen.

You can read the installation/technical guides to see what they say and use that to challenge your installer.

Other than that its find another installer.

Posted by: @judith

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Similar question to all

i understand some ashp manufacturers insist on a llh/ 4 port buffer. Who are they so that they can be ignored, together with their installers? 

From memory - Mitsubishi, Daikin, Vaillant, Cool Energy, Midea dont.  Samsung shows a buffer in an 'example system diagram' which includes just about everything under the sun (including a backup boiler - which is why the buffer is needed in that diagra,).  I'm not sure they actually insist on one, its possible that this is ambiguous, which leaves it open to interpretation.  Grant is a funny, I don't think the manual for the underlying unit from Chofu does, but Grant then set out some installation guidance/requirements (basically install it as if it were a gas/oil boiler) - you will need to check how these are implemented in practice.  I don't know about Panasonic, Hitachi, Viesmann or sundry others, my front runners quickly came down to Mitsubishi, Samsung, Daikin or Vaillant.

In your situation I would be tempted to specify when asking for quotes that a quote with an LLH, Buffer or PHE in the primary will not be considered.  That might put off those who otherwise will waste your time.  I did similar.

@toodles 

graham hendra wrote an article on why llhs used to be needed and aren’t needed any more

https://www.linkedin.com/pulse/update-ultimate-heat-pump-why-do-we-use-low-loss-header-graham-hendra/ Or at least that’s how I understood the article 
he’ obviously one of the experts! Been there, done that!

@judith Very interesting, it rather sounds as though the installers need to update their knowledge of modern products then they might take advantage of the latest designs and we could all benefit in the long run. Regards, (and thanks) Toodles.

Posted by: @judith

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@toodles 

graham hendra wrote an article on why llhs used to be needed and aren’t needed any more

https://www.linkedin.com/pulse/update-ultimate-heat-pump-why-do-we-use-low-loss-header-graham-hendra/ Or at least that’s how I understood the article 
he’ obviously one of the experts! Been there, done that!

It's both very refreshing and somewhat depressing to read this. Assuming I understand it correctly there is an admission that LLHs were added principally to stop tech support calls, with the justification that installers got the set up that would, even then, have worked without a LLH wrong.  I don't think we have reason to doubt the rationale, although some installers may consider it a bit of a slur. 

Then there follows a clear statement that things have changed in the product world, and they are no longer necessary. 

There is an element of coming clean (excellent) but also an element of we were doing a bad thing, we knew it, but it was someone else's fault (not so good).

What is unequivocally good is that its out in the open.

I don’t see any aspects of “doing a bad thing”, LLH are a good engineering solution to some identified problems, namely emitter sizes (and hence total system volume) too low and on-off thermostats.

i hear people regularly say, “, I’m not changing my radiators” or “I love my Hive/Tado and I’m not parting with it”. In which case hydraulic separation is essential. Until the customer learns the cost/benefits.

Or the pricing system changes so like the Netherlands gas is more than electricity per kWh (by taxation). Not efficient use of resources though.

Posted by: @judith

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I don’t see any aspects of “doing a bad thing”, LLH are a good engineering solution to some identified problems, namely emitter sizes (and hence total system volume) too low and on-off thermostats.

Sorry on my reading it does.  I quote ...

"So when you are in a low load condition you get this issue:... The flow slows down and the unit trips out on low flow alarm."

"In the really old days 2010-2013 we solved this with a bypass, if the flow dropped the bypass opened to allow a short circuit to maintain flow rate. It was OK but the installers refused to set it up correctly, quite rightly they thought the unit would cope. They were wrong."

...

"When I was a tech support engineers I got fed up with literally thousands of calls about low flow alarms so we made a solution. So in 2013 we decided to use a low loss header or plate heat exchanger to stop this problem, its a good solution but its expensive and it reduces system efficiency. But at least the unit runs without fault."

The first part says that there was a solution which didn't compromise both performance and cost a lot, but installers wouldn't use it.

The second part says that this forced them to adopt a different strategy even though they know it cost a lot and would compromise performance.  Also it falls into the category of covering over the red light with a sticking plaster!

The strange thing for me is that even my gas boiler system has a bypass in it, so I struggle to understand why installers 'wouldn't set one up correctly' with a heat pump.

Don't misunderstand me, I fully understand why it was done, and its great that its out in the open.  Its just disappointing that the reasoning has been less than transparent for so many years (so far as I can tell based on what I have read and what people say here and elsewhere), and that the practice still persists as 'mandatory' according to some.

Posted by: @judith

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i hear people regularly say, “, I’m not changing my radiators” or “I love my Hive/Tado and I’m not parting with it”. In which case hydraulic separation is essential. Until the customer learns the cost/benefits.

Thats fair enough, as long as the cost of retaining it is declared.  Customers should be able to make choices, and they should of course be informed ones.     For the same reason I should be allowed to retain my vented 140l cylinder if I wish to, but most installers will absolutely insist on ripping it out.

Hi all - following this thread with interest if a little over my head at times...I took a look at my Daikin Altherma manuals (2020 install) and the attached show the recommendations for a set up with a single type of emitter (ie rads) and the set up for multiple emitter types (eg rads and UFH). I have the latter. They talk about the necessity for a 'balancing bottle' in this multiple emitter scenario. Not able to find much about 'balancing bottles' but it looks a bit in schematic like my (assumed) LLH. I run both my emitter type zones (rads and UFH) at the same temp under a WCC so the multiple temp set points is irrelevant to me. Are these 'balancing bottles' equivalent to a LLH?

Posted by: @judith

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@derek-m and all

We are at the getting to grips with quotes etc stage. When our extension is finished (and only then, and if we can face more disruption) in the spring we’re going for a ashp install. Neighbours have recommended their installer but looking at their web site (and our neighbours) they also install large buffer tanks (possibly piped as 4 port can’t recall, need to go round again) plus a llh for their ufh.

So how do you prevent an installer putting in all of the extra stuff, other than going with someone else.

I realise from this forum and others that an open system is best, with obvious essentials like having large enough emitters. I have used Heatpunk to size up our house and my results compare well with our gas bill, so know what is involved.

Similar question how do you stop the installer using the huge mcs defaults on leakage loss when our blower door rate are below 1ach?

Hi Judith, welcome to the forum.

I suppose that you could politely ask them to explain in great detail why there is a need for a buffer tank or low loss header, or anything else that you feel may be superfluous to requirements.

Posted by: @cathoderay

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@editor - interesting. If I may also borrow a quote and refer it to @derek-m:

Posted by: @editor

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This leads us to a critical point regarding the testing practices of heat pump manufacturers in the UK. While the performance and efficiency numbers they publish are derived from standardised testing conditions for consistency and reliability in comparing various models, the specifics of whether these tests include LLHs and buffer tanks are often not detailed in the general product literature.

According to information I've received from sources well-informed about the industry, most of these test setups do not incorporate LLHs or buffer tanks. Despite this, manufacturers frequently recommend their inclusion in actual installations. This discrepancy suggests that the performance results achieved in real-world settings may not align precisely with the published data, as the test conditions under which these figures are obtained do not fully mirror the recommended installation setups.

I think this may be one of the problems encountered when modelling heat pump behaviour based on manufacturer data. The manufacturers quote efficacy (what can be achieved in ideal circs eg in a lab/RCT), whereas in the real world we get effectiveness (what can be achieved in practice, in the real world, where 'stuff happens'). In medicine, the two are often very different, and I think the same might apply to heat pumps: what the labs predict is not what you get. And that's before incorporating the PHE throttling effect (which is after all just another what you get in practice effect). 

You are indeed correct, because in the real World installers include buffer tanks, LLH's or PHE's that are not normally required.

The other point to remember is that they are testing the heat pump, not a heating system.