@jamespa

I presume that you have been in touch with MCS to ask them to clarify why some of their accredited installers appear to keep wanting to specify what would appear to be an oversized heat pump for your home. What did they have to say?

Posted by: @derek-m

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I presume that you have been in touch with MCS to ask them to clarify why some of their accredited installers appear to keep wanting to specify what would appear to be an oversized heat pump for your home. What did they have to say?

I haven't to be honest, but I will and thank you for the suggestion.  My fear is that they simply won't believe I know what I'm talking about ('never believe the customer') so will brush it off, but hey it's worth an email.

Posted by: @jamespa

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If the house is heated by gas or oil then its known how much energy is used in a year and from this an estimate of the design load can be calculated, given a bit of info about intermittent heating patterns

But don't forget what happened to me: seemingly not great changes necessitated by the way heat pumps work (chiefly, pivot (the word one loves to hate) from timed heating to 24 hour heating with comforts levels seeming similar) plus assumptions about efficiencies leading to all manner of confusion. I am not sure 'a bit of info' about heating patterns would have cut it. If I had just used my oil use to sanity check my heat pump sizing I would have got a very small heat pump, perhaps one third of the size I really needed, and would probably have ended up having to pivot back to oil.

Posted by: @cathoderay

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. If I had just used my oil use to sanity check my heat pump sizing I would have got a very small heat pump, perhaps one third of the size I really needed, and would probably have ended up having to pivot back to oil.

 Not necessarily, I said 'sanity check' I didn't say size.  In my view, given the vital importance of the information and the potential get it wrong, both theoretical and experimental data is required and if they differ materially it's irresponsible to proceed without understanding why.  I also said that adjustments should be made for intermittent use. 

Admittedly this is a lot easier if you have half hourly data which I would be certain could be used to build a model more reliable than any theory.  In your case it's only annual data so has to be taken with much more care.

Your plots appear to suggest that you may have an oversized hp, but of course they are confused by the PHE.   Thus I think the jury remains out on the exact contribution each of the various elements identified make and indeed your experimentally verified load.   If you fix the PHE problem it will be a lot clearer hopefully.

And finally I haven't forgotten you, in fact I am thinking about building a model to explore intermittent heating in the context of heat pumps.  However at present I'm (a) on holiday and (b) running a last ditch effort to persuade my LPA not to be complete ********* wrt my planning application to install a hp of my own.  If I fail on the latter I may lose interest, as it will have the effect of closing off my last remaining avenue to get a sane installation (anything involving MCS having completely failed).

Posted by: @jamespa

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If I fail on the latter I may lose interest, as it will have the effect of closing off my last remaining avenue to get a sane installation (anything involving MCS having completely failed).

Your persistence does you credit. I had many problems, but for different reasons, with the whole process taking over a year from deciding to go for a heat pump to having one installed and up and running. One major problem was planning/listed building consent (no permitted development because of being listed) which nearly collapsed when the council pronounced I need a bat survey (I had to persuade them it wasn't necessary, as indeed it wasn't) and then there was the terrible time with the truly dreadful LAD grant 'preferred installer'. But KBO paid off, and in the end I got there.

I'm leaning towards the idea that heat loss and so heat demand assessments are probably pseudo-science. They look impressive because there are lots of calculations, but hidden in those calculations are a wide array of assumptions, meaning many such calculations are no more than whatiffery (what if my walls are 16 inch solid stone etc). Some important variables only get a scant look in eg old leaky draughty buildings - do the air changes take that into account? I do think there is a place for empirical assessments, but there are a lot of complicating factors, eg in my case the move from timed heating to steady state heating effectively trebling the amount of heat that needs to be delivered to the house. That is not a trivial change! I am not sure how, given just the oil use and timing data, I could have predicted what my heat pump would need to deliver to achieve broadly the same comfort levels.

This fundamental weakness - not knowing what the real heat demand will be - is probably one of the key problems with heat pump installations leading to both under-sized pumps (and cold houses) and over-sized pumps (short cycling and efficiency problems). As has been said before, the fear (and potential for litigation) of the former no doubt cause many installers to err on the side of caution, and lean towards fitting over-size heat pumps.

Posted by: @robl

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I can't think of a single reason why you would want to operate a counterflow heat exchanger the wrong way around, the inefficient parallel way, in a heating or cooling application. 

The plate heat exchanger is made in Poland. Apparently they specified it that way, but maybe for other applications with higher temperatures. The installer will discuss it with the manufacturer. 

From my point of view the Wilo-Younis Pico pump has made a big difference. The ASHP is producing more heat than before presumably as a response to flow-return temperatures. As mentioned before the heat transfer rate and temperature of the fluid leaving are different parameters. The former is driven by the temperature difference at each point on the plate whereas the later is about thermal equilibrium as the fluid leaves. I see the temperatures differences reducing with this pump and it is dependent on flow rate of the secondary. 

I need to be patient as it not be until late September that I need the heating. It is important to keep the installer on side.

Phil

Posted by: @cathoderay

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Posted by: @jamespa

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If the house is heated by gas or oil then its known how much energy is used in a year and from this an estimate of the design load can be calculated, given a bit of info about intermittent heating patterns

But don't forget what happened to me: seemingly not great changes necessitated by the way heat pumps work (chiefly, pivot (the word one loves to hate) from timed heating to 24 hour heating with comforts levels seeming similar) plus assumptions about efficiencies leading to all manner of confusion. I am not sure 'a bit of info' about heating patterns would have cut it. If I had just used my oil use to sanity check my heat pump sizing I would have got a very small heat pump, perhaps one third of the size I really needed, and would probably have ended up having to pivot back to oil.

I think what one really needs to get this empirical "heat pump size" is for the house to be run with the fossil based heating reconfigured  as close to "heat pump steady state mode, MCS design conditions "  that can be achieved (lowest flow temp that can get away with, all rooms heated, long run times ) for 2-3 days in cold weather (needs a decent duration to reach fabric steady state), and measure the heat throughput on a frequency of no less than hourly. That , IMO, gives a reasonable number for the upper limit for heat pump  size.

the yearly burn number has too many variables for it to be accurate.

Posted by: @jamespa

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[It frankly beggars belief that some experimental data is not taken into account, there is plenty of evidence to show that the current methods get it disastrously wrong in a significant proportion of cases.

<snip>

(taken from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606834/Report_on_compliance_with_MCS_installation_standards_v32.pdf)

that graph is awful. even ignoring the ones where the installer estimate is zero, it's awful. could you please check that link reference? I wanted to have a read, it doesn't work for me.

ref your planning thing - I appreciate you appear to have had a lot of exchange with your LPA which is of course private to you. But have they actually said, they will tell you to remove it, if you self-install or install with a non MCS installer, in such a way that would have been compliant(0.6m3, noise, 1m etc?) if you'd used an MCS installer? Given that exactly this is what pretty much every other self-installer in the country has done (including me) , and I haven't read on the forums of there being lots of self-installers / non-MCS installs being told to de-install by over-zealous planners? better not to ask permission? 

so also, from the gov.uk page:

G.1  Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards or equivalent standards.

(my bold on the last two words). If you can show that you are designing to best practice as per all your heat loss calculations that you have clearly done, then would the 2nd point be the one that counts for you?

@iancalderbank pesky parenthesis ) at the end "v32.pdf)"

@jamespa Have a look at this chap, I've seen the video a while a go, but couldn't find it lately.

Peter Miller, he is an unhappy HP customer turned MCS accredited designer that uses professionals to put in practice his ideas. His mantra is the lowest cost to the customer and without oversizing.

It looks like he is based in Suffolk, check his twitter feed, he is involved in conversations with John Cantor and probably on the community.openenergymonitor.org/latest as well.

Maybe this is the person you are looking for.

twitter.com/PeterEastern

https://conga.uk/

https://www.youtube.com/watch?v=SGiT_f_KKZM&t=593s

Posted by: @filipe

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From my point of view the Wilo-Younis Pico pump has made a big difference. The ASHP is producing more heat than before presumably as a response to flow-return temperatures.

This is good to hear your installer is working well and  trials are being rewarded with new insights. The slower pump speed in the secondary (closed loop) is probably doing several things.

1. The slower speed probably better matches the primary pump speed so heat transfer into the secondary circuit will be higher. 
2. slower speed through the emitters will allow more heat to be given up to the room space thereby creating the best opportunity of cooling the returning water temperature.
3. the returning water is therefore more ‘empty’ of heat energy so it can absorbe more heat energy from the plate heat exchanger. (Thinking back to the coal waggon analogy) if the waggon is empty when it arrives at the stationPHE it can be loaded with more coal.

this improvement IN HEAT TRANSFER, should exist for contra flow or parallel flow. But maximum heat transfer, as stated previously, will be achieved by Contra flow.

If the zones close as you said, that’s an issue of zone setup rather than heat transfer… you might want to avoid creating shutting down zones at first until you’ve got the heat delivery optimised. 

Great energy saving on the pump also. 👍🏼