@marzipan71

In the diagram they look and are piped like a buffer tank (an LLH is, in effect, just a small buffer tank afaik).  So far as I can tell from the schematics you posted the 'balancing bottles' appear only in the scenario where the are multiple types of emitter run at different flow temperatures

Posted by: @cathoderay

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Posted by: @jamespa

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Thats from Freedom, what does the OEM actually say

Here is the system diagram from page 4 of the Midea manual.  No buffer tank, LLH or PHE in sight.

This is a variation on efficacy vs effectiveness. That's what Midea say in their 'ideal' manual. In the real world, stuff happens, Freedom offer training courses and provide installation manuals, and that is what the installers use. Why wouldn't they? Freedom are a major supplier, surely they know what they are talking about?

You will have to ask Freedom why they varied the spec from the Midea manual.

 

I suspect the problem relates to the fact that as far as I am aware TRV's still have to be installed on heating systems, which was the norm with gas and oil boilers.

Heat pumps work much better without TRV's or on - off type controls, but many are still included, because that is how it was always done for the past umpteen years.

So to prevent their 'trained' installers getting loads of call-outs because of low flow when the TRV's started shutting down, Freedom decided it was necessary to insist on hydraulic separation, rather than produce correctly designed systems and train the installers correctly.

Maybe if they start loosing business due to all the free publicity they are getting then they may start doing their job correctly.

Thanks @jamespa - the flow in the manual is a bit confusing but in Capture 3 Daikin seem to also recommend/ mandate a 'balancing bottle' in the scenario where an old gas or oil boiler is replaced with this particular Daikin HT model irrespective of whether there are different flow temps (I think - the Daikin manuals are not the clearest) - 'When replacing an old gas or fuel oil boiler by a air to water heat pump system (EKHBRD*): please always check the specifications of the pump of the old unit [and] if the external static pressure of that pump is higher than the external static pressure of the air to water heat pump system, please install an additional pump with higher external static pressure in combination with a balancing bottle.' I had to look up external static pressure which tells you where my level of understanding is.

Posted by: @marzipan71

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Thanks @jamespa - the flow in the manual is a bit confusing but in Capture 3 Daikin seem to also recommend/ mandate a 'balancing bottle' in the scenario where an old gas or oil boiler is replaced with this particular Daikin HT model irrespective of whether there are different flow temps (I think - the Daikin manuals are not the clearest) - 'When replacing an old gas or fuel oil boiler by a air to water heat pump system (EKHBRD*): please always check the specifications of the pump of the old unit [and] if the external static pressure of that pump is higher than the external static pressure of the air to water heat pump system, please install an additional pump with higher external static pressure in combination with a balancing bottle.' I had to look up external static pressure which tells you where my level of understanding is.

 

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Basically what this is saying is that, if the water pump contained within the heat pump isn't strong enough for the job (because your heating system has too much resistance), then you will need a secondary pump.  

I'm not actually a plumber, but I would have thought/hoped that there might be a way of putting another pump inline, without a buffer, to this job. 

Posted by: @cathoderay

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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').

Based on several conversations I've had this week, there is an indication that significant information may be released in February which could call into question the accuracy of heat pump manufacturing and efficiency data. If this turns out to be the case, it could lead to serious legal ramifications for both private companies and government entities.

Interesting. Is the research which led to this sponsored by the fossil fuel industry I wonder?

Obviously we all need the facts, but there is a big war going on here between the vested interests and the human race.  I get the impression that the vested interests are beginning to get a little concerned.

Posted by: @jamespa

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I'm not actually a plumber, but I would have thought/hoped that there might be a way of putting another pump inline, without a buffer, to this job. 

 

there is, but if you read up on pump curve hydraulics as I've been doing the last few weeks, the maths is painfully non linear. you need rapidly increasing head to get the job done, and the pump cost goes up rapidly the more head you need.

I was looking at my own single loop system, I get 28l/min from 8.9m of head on a 9.5m head pump (UPMM). 10kw at DT5 heats my house perfectly well, but my heat pump can take up to 42l/min and I'd like to improve performance where I can. If I was to put in a second identical 9.5m head pump, whether in parallel or in series, I'd gain as little as 1% flow rate, a pointless change of course. To get it done properly I'd need about 12m head which is one serious pump (e.g. UPMXL). £700 or so. so the answer in my case, time and money better spent on improving  the pipework for a lower head loss - which I have a couple of places to go at, come the summer.

whereas the my system setup as a buffered split would almost certainly run fine with two 6m pumps or maybe 8m at most. cheaper mass market screwfix circulating pumps, much "safer" in that there would be no need to worry about flow rate for the installer. but less efficient.

The "Balancing bottle" in the above seems just another name for a buffer/LLH (not heard that name before).

It's actually the same question I was asking the other day on the "new generation of HT heatpumps" thread. A new fangled HT heatpump is (to me) only an option for "straight boiler swap", if it can run at DT20 without having to worry about flow rate issues. (thats ignoring , for the point of this discussion only, all HT efficiency issues). If it needs DT5 same as any other heat pump we know and love/hate, then all the flow rate issues come right back, and so people start talking about adding a buffer/LLH to mitigate , and back round in a circle we go.

@jamespa, it is not the fossil fuel industry. To my understanding it's a heat pump insider whistleblower. Wonder if it'll be enough (or significant enough) to have an ITV drama next time this year.

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.

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.

System volume problems are much better solved by installing a volumiser, which is similar to a buffer tank, but without the possibility of mixing and efficiency reduction.

Posted by: @iancalderbank

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It's actually the same question I was asking the other day on the "new generation of HT heatpumps" thread. A new fangled HT heatpump is (to me) only an option for "straight boiler swap", if it can run at DT20 without having to worry about flow rate issues. (thats ignoring , for the point of this discussion only, all HT efficiency issues). If it needs DT5 same as any other heat pump we know and love/hate, then all the flow rate issues come right back, and so people start talking about adding a buffer/LLH to mitigate , and back round in a circle we go.

 

I confess I see the HT heat pump question is a bit of a side issue.  The question really is, do 'lt' heat pumps have any advantages ove HT ones.  The answer, so far as I am aware is yes, they are cheaper (for now - but I suspect its unlikely to last) and (if the HT is r290) have fewer placement constraints.  But that's about it.  Unfortunately they tend also to be noisier and uglier as well as the refrigerant having a higher gwp, not because of anything to do with the temperature they are capable of reaching, just because manufacturers combine several developments in one go and don't always retrofit improvements to earlier models.   So far as I can assess they are no more efficient at any given OAT/LWT combination than HT ones.

So whilst I agree that aggressive marketing of 'HT=straight boiler swap' is misleading, it's equally misleading to push LT pumps on the basis that running at HT is a bad idea.  You don't have to drive a car at 120mph just because it can reach that speed and nobody would rubbish a Porsche because it can (but is not forced to) be driven at well above the legal speed limit!

As it happens I am more or less certain to end up with an HT pump, running at 45C, because there isn't an 'LT' pump which fits the physical, aesthetic and noise requirements.  Is there any reason to suppose 'LT' pumps will exist at all in say 5 years?

Posted by: @editor

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@jamespa, it is not the fossil fuel industry. To my understanding it's a heat pump insider whistleblower. Wonder if it'll be enough (or significant enough) to have an ITV drama next time this year.

 Maybe not on a mainstream channel!  Perhaps 5 minutes on rip-off Britain.

At the risk of being drummed out for heretical thoughts ( ;-))) ) No, I’m sure I wouldn’t be, … would I?! Suppose this LLH is losing some efficiency - where is the loss taken place and where is the wasted energy going please? If the loss is in the form of heat that doesn’t make it across the interior of the LLH, does it radiate into the surrounding area? In my case, this will be the airing cupboard where such heat will be ‘always useful’, (harking back to the topic of uninsulated pipe runs within the home again!). If the unharnessed energy is being deflected back out into the return pipe-run to the heat pump outside, I can see that this might well be wasted heat though. Regards, Toodles.