I’ve just come across this YouTube story about heatpump installation. I thought it was appropriate to this thread esp regarding sizing. The customer experience also clarifies the difference between disinformation in the industry and simply poor installations.

Here’s is an interesting training video from Adam (Heatgeek) targeting a discussion to the would-be plumber re- training brigade. Try viewing from 3mins onwards but esp. 3.57 onwards. For the discussion on smaller heat pumps as opposed to larger heat pumps.?.?

It is 2 years old but shows the targeting of the plumbing industry on how to future proof their businesses and careers. Any thoughts?

Posted by: @sunandair

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Much of what you say is about the specifying side and I’m sure you’re aware the installation and commissioning side also has its problems.

 MCS doesn’t appear to be giving the assurance it is set up to perform. 

For me and my installation all the problems revolved around incompatible components, hiding the fact that manufacturer and installer couldn’t get the right fully functioning parts possibly due to supply chains. Specifying third party thermostat, not communicating pumps. And on the design side, fitting a low loss header on a single circuit with good flow characteristics and simply not commissioning for optimum performance. It appeared to me that both the installer and manufacturer were silently aware of the availability problem but still pressing on with substitute parts with not a single word to the customer. How was a customer ever going to find out? Where was  MCS in preventing that sort of activity?

Sadly I haven't yet got to the installation side and as you say I am aware that this also has problems.  If I am lucky enough to find a route to get that far it will be very closely supervised and scope-minimised.  I really don't want an MCS installer anywhere near my DHW cylinder for example, I will be looking for a route whereby a regular plumber does that, or better still to retain existing (which MCS will resist but is entirely a viable thing to do).  If I have to pay VAT on this element so be it, it will likely still be cheaper to get a regular plumber to do the work and pay VAT than the MCS crew.

Posted by: @sunandair

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In the end knowledgable home owners who have the time will probably do a better job but there seems to be a-lot to learn about hydronic, design, the individual parts and commissioning. Heat Pumps must be set up properly and without certified installation  (probably better than MCS can do) the current HP rollout will get worse.

I do agree that's a risk, but at the same time local plumbers and electricians value their local reputations unlike the fly-by-night special purpose companies that have sprung up to harvest the grant.  So Im far from convinced that the standard will be any less and over time it is likely to get better through competition, which is currently sadly absent.  The optimum arrangement is probably a specialist design consultancy working with your local plumber.  HP system design isn't rocket science, its just that the whole concept of designing a central heating system has essentially been absent for decades. 

The poor installations appear to be largely due to buffer tanks, heat exchangers, poor weather compensation and oversized units.  Get the system sizing and weather compensation right or thereabouts and the need for buffer tanks and heat exchangers disappears in most cases.  Unfortunately the engineering errors, leading to poor performance and high cost, are a vicious circle, starting with system sizing based on fantasy fabric parameters and oversizing to cover rear ends.

@sunandair The videos look good.  The first pretty much confirms the main problems with design/installation discussed here and elsewhere, the second confirms how important those are.

I am more than ever convinced that one of the key causes the technical issues is system oversizing due to fabric uncertainties and high-end assumptions on both fabric and ventilation losses.  As these are real unknowns in a typical retrofit due to

• invisible fabric upgrades
• the unknown performance of double glazing 
• extensions of a different construction to the original building
• the unknown ventilation rates

it is perhaps inevitable that theoretical calculations err towards oversizing.  However the destructive effects of this are material, in terms of cost, disruption and the negative effects on performance.  Its all very fine blaming installers/surveyors (as I have done in spades), but when they cant verify key parameters of the key calculation, what else are they going to do?

I cannot see how this can continue and lead to satisfactory outcomes.  Heat pumps with a high modulation depth help, but don't fix the consequent overengineering of the system.  Range rated heat pumps would similarly help, but again don't fix the consequent overengineering of the system.  I'm being forced to the conclusion is that experimental measurements are the only way to address this problem, based on half hourly meter readings (best), annual consumption (worst and perhaps only valid as a sense check) or special observation (need to find a way to make it 'idiot customer proof ').

If anyone can suggest an alternative way to deal with the genuine uncertainties in the fabric, which can have a major (factor of 2) effect on the calculation of system size, I would be interested to hear.

Posted by: @jamespa

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I cannot see how this can continue and lead to satisfactory outcomes.  Heat pumps with a high modulation depth help, but don't fix the consequent overengineering of the system.  Range rated heat pumps would similarly help, but again don't fix the consequent overengineering of the system. 

agree with you wholeheartedly. modulation/range rating of the HP only half the problem, if the overspec also leads to an unncecessary rebuild of the the home pipework system or other components then that was work that didn't need doing.

Posted by: @jamespa

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special observation (need to find a way to make it 'idiot customer proof ').

everyone needs a heat meter installed to their existing boiler system (obviously only if its a wet CH of some sort). With remote 30 minute  datalogging to somewhere that someone suitable looks at . they aren't that expensive. especially compared to how much can be saved by knowing the info that the heat meter will provided.

So in which pocket do £5000 go?

£1000 for multiple quotes

£2-£3000 over charging for the same job because of the £5K

£1000 extra price of the unnecessary size HP

£500-£1000 a year extra in energy costs per year due to unnecessary oversizing/use of high temp/no weather compensation.

for the only benefit of not having to deal with planning permission/peace of mind neighbour wise.

In fairness I think the policy objective is quite probably to build and train the industry.  However I'm far from convinced it's doing that either (well it may be training people how to do things badly).  I have emailed MCS with some comments and await a response.  What is concerning is that nobody seems to be discussing the problem of system sizing until now, other than Peter Miller (also once a frustrated would be owner of a heat pump) referred to upthread.  It's like there is a conspiracy to avoid discussing the elephant in the room.

@jamespa any reply from Peter?

@fazel I have made contact and exchanged emails.  His coworker is supposed to call me.  However it's clear that I'm 'out of area' so I'm not sure he will take it on, but I'm still hopeful.

@jamespa PM me if you want to discuss offline.  have you considered the possibility of doing the same as Peter yourself? its something I'm pondering. For someone like Peter I suspect the "local" thing will always be important. as it would be for me if I was to do similar for local people around where I live.

Posted by: @grahamh

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@ginny i was the founder of freedom. But i dont work there any more, i haven't for 2 1/2 years, i sold it. I got fed up of people constantly asking for free advice. 

im done with the whole heat pump industry, its plagued by people who want free advice who wont stop pressing buttons, why not go back to the installer you paid to fit the unit and ask them to help, after all they have your cash. 

asking a bunch of people who have absolutely no idea what they are on about in a forum is not the best idea. Free advice is just that free and usually crap. 

Graham, you have a respectable expertise/experience in this industry, yet somehow you are happy to promote the idea that a high temp heat pump(rads at 50C, dhw way over 50C) and that weather compensation is worthless.

No wonder the results are bad if the specialist industry men are happy with a hot radiator at the expense of the customer.

Following my failed attempt to get a HP installed earlier this year I decided to have a heat pump ready unvented hot water tank installed. My showers work wonderfully now and water is being heated via an iBoost every day from the PVs. My plumber took great care to select the right tank. I thought I’d try British Gas and see if they would quote for a heat pump as they offer a guarantee of performance. They will, but only on the understanding that they would want to rip out the newly installed tank and put theirs in instead. They weren’t interested in discussing why they take this approach or what might be wrong with the tank.