Posted by: @iancalderbank

↑

@jamespa

Posted by: @jamespa

↑

In my own case (which I admit I quote frequently, but I think it may be not unusual), two MCS surveyors got to 16kW, my calculations (based on MCS assumptions but adjusting for fabric upgrades) get to 10.5kW, and the actual measured demand at -2 is 7.5kW.  Most of the time the demand sits just over 4kW.  So my intention is to fit an 11kW (most likely Mitsubishi) pump, but even that is marginal at 4kW.  Had the MCS brigade got their way with their 16kW+ offerings, I would be well into cycling for much of the heating season which is really quite atrocious.

if it helps, I've self installed a 16kw samsung. 15kw was the MCS number for my house. I didn't have the confidence to go smaller,  wish I had because I'm now sure I could have.  I've got 2 months minute-by-minute monitoring (installed since end march) in which we got just enough -1C to test it properly, and of course plenty of mild. Had some setup and tuning issues as you'd expected, but with a "reasonably balanced" system, cycling issues have been minor and not impacting COP. My key point for you is , it has run stably at 3.5kw output . On the even milder days when the heat demand is below that - yes it does cycle, but IMO it doesn't matter because a) the absolute value of any negative cycling impact on COP is low, because the heat demand for that day is low to start with b) with the system setup right with a good circulation volume (which I'm sure you will be doing) the relative COP impact isn't much either.

The point being, 3.5kw is below 25% of the plated value. some graphs in this post. @william1066 has the same ASHP and is getting similar numbers. So , whilst I could have saved a bit on the smaller unit, I don't believe I am overpowered to the extent that excessive cycling will ever be an issue, so I'm ok with it. If you go with 11kw plated I'd hope you'd be stable at 2.5kw if the mitsubishi behaves anything similar to the samsung.

ta

Ian

 

I agree with you that normal cycling in itself isn't a big problem.  IMO the bigger problem with an oversized ASHP (apart from them costing more) is that they tend to be less efficient than their smaller counterparts, especially when running at low outputs.  Nothing to do with cycling but a bit like running a big car compared to a small one.  

My Mitsubishi 14kW will modulate down to about 30% (of 14kW).  For me, that heats my house when it's about 9 deg C outside using weather compensation. Any warmer and it cycles about 3 times per hour.  If I use Mitsubishi's own auto adaptation, it almost never cycles; instead it uses slightly higher LWTs and lets the room temp vary within a window of 1 deg or so. AA COP is lower than with WC but I reckon consumption is the same or less as it spends a lot of time idle. 

Posted by: @sunandair

↑

You then assert that building regulations is not part of the planning process. 

These assertions of yours, apart from being inaccurate quotes are missing the point which was about my opinion about one of the roles of MCS.

Sorry for misinterpreting your post, that was not my intent. 

Nevertheless it is fact (whether or not you intended to imply otherwise) that planning consent and building regulations are totally separate in law (they derive from totally separate statutes) and take a completely different approach with completely different objectives.  If anyone doubts then please note, for example, that there are statements in the NPPF which expressly say that planning policies must not stray into the territory of building regulations!

At the helicopter level planning is about public impact. 

Building regulations are about

1 safety and

2 ensuring developers don't build stuff which functionally is complete rubbish (effectively a set of minimum standards for the construction industry)

Most of building regs, particularly the parts aimed at objective (2) apply only to new build or change of use, not retrofit, except some very specific cases 

Also, when meeting building regs, you can have an onsite discussion with a building inspector (of your choice) who has technical knowledge and, because the regs generally specify only the 'what' not the 'how' he or she can be pursuaded to accept alternative solutions.

Confusing planning consent and building regs is common (I'm not suggesting that is happening here, but it does happen quite a lot in my experience), that doesn't make it correct.

I would actually have no problem if technical aspects related to heat pumps, which have no impact on the general public, were in building regulations, that's where they should be.  Building inspectors, who are generally pretty technical anyway, could then either train up or ask consultants.  What I have a problem with is the way MCS has imported such matters into planning by the back door and the government has ignored it.

Finally I would offer an argument that nothing should be controlled by a single authority unless that authority is subject to periodic reelection.  MCS is an unaccountable private monopoly controlling, through a backdoor route, what I do _inside_ my house even though it has no public impact nor health and safety implication.  How is that right?

Posted by: @kev-m

↑

  If I use Mitsubishi's own auto adaptation, it almost never cycles; instead it uses slightly higher LWTs and lets the room temp vary within a window of 1 deg or so

Thanks, useful info, adds to my confidence in aiming for the 11.2kW Mitsubishi.

Posted by: @iancalderbank

↑

. On the even milder days when the heat demand is below that - yes it does cycle, but IMO it doesn't matter because a) the absolute value of any negative cycling impact on COP is low, because the heat demand for that day is low to start with b) with the system setup right with a good circulation volume (which I'm sure you will be doing) the relative COP impact isn't much either.

Agreed.  For me, based on frequent observations of my smart meter, 4kW seems to be the key figure to hit as my system seems to sit there through much of the shoulder season when it's perhaps 7-12 outside during the day and a bit colder at night.  So that's my minimum criterion.

Posted by: @derek-m

↑

Out of interest. What is the size and type of your home? What range of heat loss calculation have been provided by your 10 prospective installers?

4bed 1930s solid wall with later extensions to a better standard, fairly high performance double glazing and partial internal wall insulation.  Two installers did full 3 hour surveys coming to 16kW.  I paid £350 for one, the other was free for reasons I don't quite understand.

The one I paid for supplied the full calculation details from which I could tell they had ignored the fabric upgrades despite the fact that I made a point in telling the surveyor about them.  I could also tell they had  counted room to room losses in the whole house total.  The other supplied only the room by room loads which were very similar and so I can only presume they did the same which is consistent with the the level of interest the surveyor took when I was telling her.

The other eight based their estimates on back of envelope figures with the usual caveats, but expected me to pay approx £300 for a final survey and quote.  Alternatively they quoted for 11kw on my instruction but made it abundantly clear that they would only install based on their own survey, which I would have to pay fir.  Obviously I'm not going to do that very often and would now (based on my experience) not even consider it without written guarantees that they would take into account fabric upgrades even if they were unable to verify them.  Many of those who gave 'estimates' also wanted to rip out lots of stuff unnecessarily.

They were all 11kW plus (but caveated as above) up to 2*16 with the exception of one who wanted to put in an 8kW hybrid system using my existing boiler.  He was early on and, had I known then what I know now, I might have accepted knowing that the boiler would likely never be used.  Sadly he went bust a few months ago.

If I were starting again I would try pre filtering by those who were prepared to do calculations including fabric upgrades that they could not see as well as actual measurements, were prepared to accept 22mm primaries to the DHW tank not insist on upgrading to 28mm consider retaining the latter and either put in a PHE and recirculating pump (like the Mixergy hp upgrade kit) or use the immersion for the final 10 degrees, were prepared to accept that 15mm at 9 bar will deliver sufficient cold water to my DHW tank and not insist on upgrading to 22mm.  Whether I'd get any takers I can't tell, I fear I'd be put in the awkward customer box, and I have tried all the local ones at the time of writing.

Alternatively I'd do it without MCS and ask the local well reputed plumber who will probably be happy to oblige (I have made enquiries)  for a similar or lower cost even though I wouldn't get the grant.

I know my case won't match others, but surely that's the point.  We have a vast array of different retrofit situations and we need innovative, intelligent and flexible not rules based, if we are to tackle them.

Hope that helps.

Posted by: @jamespa

↑

Posted by: @derek-m

↑

Out of interest. What is the size and type of your home? What range of heat loss calculation have been provided by your 10 prospective installers?

4bed 1930s solid wall with later extensions to a better standard, fairly high performance double glazing and partial internal wall insulation.  Two installers did full 3 hour surveys coming to 16kW.  I paid £350 for one, the other was free for reasons I don't quite understand.

The one I paid for supplied the full calculation details from which I could tell they had ignored the fabric upgrades despite the fact that I made a point in telling the surveyor about them.  I could also tell they had  counted room to room losses in the whole house total.  The other supplied only the room by room loads which were very similar and so I can only presume they did the same which is consistent with the the level of interest the surveyor took when I was telling her.

The other eight based their estimates on back of envelope figures with the usual caveats, but expected me to pay approx £300 for a final survey and quote.  Alternatively they quoted for 11kw on my instruction but made it abundantly clear that they would only install based on their own survey, which I would have to pay fir.  Obviously I'm not going to do that very often and would now (based on my experience) not even consider it without written guarantees that they would take into account fabric upgrades even if they were unable to verify them.  Many of those who gave 'estimates' also wanted to rip out lots of stuff unnecessarily.

They were all 11kW plus up to 2*16 with the exception of one who wanted to put in an 8kW hybrid system using my existing boiler.  He was early on and, had I known then what I know now, I might have accepted knowing that the boiler would likely never be used.  Sadly he went bust a few months ago.

Hope that helps.

 

 

What is the floor area of your home?

What you describe is one of the major flaws in the present system, which is very much a catch 22 situation. To obtain the £5000 'bribe' one has to use an MCS accredited installer. Most installers now appear to charge £300 to £350 to carry out a heat loss survey, which may or may not be correct, and is very subjective. Consumers are advised to obtain several quotes, which could entail paying the best part of £1000, to have the same work performed several times, which I don't think would be the case if one is installing a gas or oil boiler.

As you have also stated it would appear that to be able to install a heat pump under permitted development, or particularly with planning permission, it is necessary to abide by the MCS criteria.

Unless I am missing something, there would appear to be little incentive for consumers to install heat pumps, since it would appear to be much cheaper and much easier to install a gas or oil boiler.

Did someone mention Net Zero? Were they joking? 🙄 

I have just sent the following message to my MP, I would suggest that you send something similar to your MP.

Posted by: @derek-m

↑

Unless I am missing something, there would appear to be little incentive for consumers to install heat pumps, since it would appear to be much cheaper and much easier to install a gas or oil boiler.

Unless your current heating is resistance electric (or possibly oil once electricity prices come back down) there is no financial incentive so far as I can tell, only a capital disincentive. 

Even if, like me, you are happy to do it anyway given that the running costs are likely to be similar (to gas) there are significant obstacles.  That's how I currently view it based on my personal experience and listening to what people say on this forum and buildhub.

So if you aren't a very determined, mad, bearded, tree-hugging leftie expert you will likely not bother, or if you do you will be disappointed because you had expected the running costs to be lower than your present gas boiler, having been mis-sold on the facts.

Two things need to happen imho

1. Regulation needs either to be relaxed or made sane and flexible (this is a fast moving landscape).  I assume that the government is incapable of the latter and ideologically attached to the former, which is why I advocate the former (by all means retain regulation in connection with grants, they will eventually become irrelevant)

2. The relationship between gas and electric prices, which is determined on a political basis not a market basis, needs to change.  Not a lot, perhaps 2.5 to 1 instead of 3 to 1.  Green levies currently fall on electricity prices yet in practice this is the greener fuel if used for a heat pump.

Ideally also we need a proper skills scheme (not painting by numbers) and of course proper grants/incentives would be good.  However these don't fit particularly well with current ideology so I'd personally (if slightly reluctantly) settle for the two above initially then let the market sort it out

Grant Shapps is supposed to (finally) be getting his home surveyed for a heat pump next month- maybe he’ll realise firsthand why so few are taking up the BUS grant!!

Posted by: @jamespa

↑

Posted by: @iancalderbank

↑

if it helps, I've self installed a 16kw samsung. 15kw was the MCS number for my house. I didn't have the confidence to go smaller,  wish I had because I'm now sure I could have.  I've got 2 months minute-by-minute monitoring (installed since end march) in which we got just enough -1C to test it properly, and of course plenty of mild

Thanks and noted

On another forum it has been stated, by someone who appears to know their stuff, that Samsung achieves high modulation ratio by an arguably dodgy compressor bypass trick.  Inspection of their system diagram shows that they do indeed employ the trick claimed, the net result of which is the the stable operation occurs but at roughly the energy use that would have been the case had the compressor been operating at a higher energy output.  I honestly don't know how much effect this has as I don't think Samsung publish cop at low output.  Just a warning though.

yes, I've read and had email conversation with I think the same person.  it may not be the absolute best HP in the world but its easy to understand, mass market pricing and mass market availability. I get COP of 4 at 7C ambient , LWT 37, output around 4kw. May not be good enough for the purists on openenergymonitor and there may well be more sophisticated machines that do better, but it'll do me for now and is a lot better than many "professional" installs that get discussed on this forum . anyway I'm not trying to sell you a samsung  - my point more that low turn down is do-able (lower than I was expecting) so the engineering consequences of an oversize are not as dire as seems to be being proposed . The capital cost of oversizing vs smaller unit  of same type aspect is accepted - but if comparing to a different type that can run at a significant % better COP, but if they cost 2 or 3x as much to buy... that's a lot of electricity.

Posted by: @jamespa

↑

Also, when meeting building regs, you can have an onsite discussion with a building inspector (of your choice) who has technical knowledge and, because the regs generally specify only the 'what' not the 'how' he or she can be pursuaded to accept alternative solutions.

Confusing planning consent and building regs is common

I am sure you can now see that it would not be easy to train every building regulations officer into the Myriad complexities of heat pumps. To have their casual chats about possible alternative specification details is not the way to finalise installation details it would be far better to have that discussion with someone who knows tailored alteration inside out. Notwithstanding the thousands of installations which are needed. So, again I say another agency to handle the specifics of heat pumps seem to make sense if installation levels really did ramp up. 

Regarding your confusion between planning and building regs  it’s only confusing for a number of home owners and not for designers and architects who deal with planning applications and the associated, but separate building regulations submissions on a regular basis.

 I’m not a fan of MCS but I can see why it was set up.

Posted by: @sunandair

↑

Posted by: @jamespa

↑

Also, when meeting building regs, you can have an onsite discussion with a building inspector (of your choice) who has technical knowledge and, because the regs generally specify only the 'what' not the 'how' he or she can be pursuaded to accept alternative solutions.

Confusing planning consent and building regs is common

I am sure you can now see that it would not be easy to train every building regulations officer into the Myriad complexities of heat pumps. To have their casual chats about possible alternative specification details is not the way to finalise installation details it would be far better to have that discussion with someone who knows tailored alteration inside out. Notwithstanding the thousands of installations which are needed. So, again I say another agency to handle the specifics of heat pumps seem to make sense if installation levels really did ramp up. 

Regarding your confusion between planning and building regs  it’s only confusing for a number of home owners and not for designers and architects who deal with planning applications and the associated, but separate building regulations submissions on a regular basis.

 I’m not a fan of MCS but I can see why it was set up.

 

I cant see that there is a major problem, certainly not sufficiently major to justify setting up a parallel system.  Building inspectors are used to reviewing figures etc in which they are not specialist (eg structural engineering calculations).

There are 3 principal (domestic) use cases so far as I can see:

• retrofits where there is no government grant.  In this case the only parts of building regulations which would apply, if normal practice is followed, would be those related directly to health and safety of the occupier.  This amounts to G3 and electrical safety, which are already covered by building inspectors/competent persons schemes and with which building inspectors are very familiar
• new build (largely irrelevant at present because developers aren't bothering with heat pumps - but hopefully shortly).  In this case there are economies of scale because developers build multiple of the same houses.  So a verified design can be presented to the building controller supported by a full analysis as doubtless is the case with anything else in new build.  Or alternatively conformance is guaranteed by the builder as part of whatever they need to do to get the NHBC guarantee.
• retrofits where there is a government grant.  In this case I can see an argument for a quality control scheme associated with the government grant, the scope of which goes beyond health and safety.  I can thus, in this specific case, see a justification for MCS or similar body, which is why, I suspect, it was set up.

I suppose there is a fourth case namely self-build.  Its a minor market in this country and there are arguments either way for how it should be treated.  As its a minor market it shouldn't be a policy driver, but obviously does need to be catered for.

To my mind MCS needs to be put back in its box, and its statutory role confined to validating government grants.  If trades then choose to join it as a trade association, that's fine.  What is not fine is extending their remit to cases where the householder is spending their own money on their own house which, unless it causes a public nuisance (=planning) or a material health and safety risk to occupants, they should be free to do, as they are with any other form of heating.

I accept that this is a 'free market' approach to the retrofit business (other than in respect health and safety) where a grant is not involved.  I'm not a great fan of the free market, but have to admit that there are many cases where it works better than government.

Posted by: @jamespa

↑

To my mind MCS needs to be put back in its box, and its statutory role confined to validating government grants.  If trades then choose to join it as a trade association, that's fine.  What is not fine is extending their remit to cases where the householder is spending their own money on their own house which, unless it causes a public nuisance (=planning) or a material health and safety risk to occupants, they should be free to do, as they are with any other form of heating.

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?

So I do agree with a lot of what you say. Indeed I think many installers have tried to get involved without full commitment to a training programme but seeing it as an inconvenient route to the BUS gravy train.

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.

Good luck in your endeavours