JamesPa

I have one fancoil in an otherwise all radiator/ASHP system, installed because I couldn't fit a radiator large enough in the available space. Its a wall mounted Mitsubishi Ilife 2 Slim, made in Italy (as are quite a high proportion of the available fancoils with stylish enclosures). Nice (but expensive) piece of kit capable of heating or cooling. There is a view that you can dispense with condensate drains if you keep the cooling flow temp above the dew point, which some heat pumps can do automatically. Obviously you get less cooling this way. Fan auto adjusts depending on load, so better to get a bigger model if fan noise matters (because fan will then be slower). Its audible, but quieter than eg my fridge. With 20:20 hindsight I wish Id fitted a couple more so I can get a decent amount of cooling. Hope that helps

That's indeed interesting. My contacts were about 18 months ago, perhaps they have changed?

I would check this directly with Mitsubishi tech support (who are very helpful). If it is the case, which I frankly doubt, don't use ecodan, seriously. "It's mandated by the manufacturer" is an excuse some installers use to do what they want to do for their benefit, not yours, knowing you are unlikely to check.

@timhowes Whatever else you do and whether you get a grant or not please do not: Get a buffer and more than one pump (including any pump in the outdoor unit). A 2 port volumiser in the flow is OK. Don't get or any other form of system separation, eg a phe or llh, between emitters and heat pump either. Get a massively oversized heat pump, unless your loss is say 3kW or less, in which case you have no choice and anyway it doesn't matter because of the low consumption. Get external controls (exception - those specifically designed for heat pumps IE havenwise, homely or adia) If you do any of these it's highly likely you will be back on this forum complaining about poor performance. The understanding and technology of heat pumps has moved on a lot in the past 5 years, sadly some installers haven't kept up and are still following outdated practices for their own benefit not the benefit of the householder. There are of course some specific circumstances where one or more elements of the above advice doesn't apply, but they are rare in domestic situations.

Why do you want buffers and 3 pumps? Unless your house is very unusual no buffering and one pump (often included in the heat pump itself) is the way to go assuming you don't want to increase running costs by 15% or more for no benefit to anyone other than the installer. Also no fancy controls unless specifically designed for heat pumps (which currently means only homely, adia or havenwise sofaik). The bus can save money certainly, but not if you accept unnecessary components and/or a grossly oversized heat pump because any installation savings will quickly be consumed by increased running cost. My personal advice is take the bus, but not at the expense of being saddled with the wrong system. Shop around!

You won't do the second but you can avoid the oversizing (well I did anyway). In brief. I had two full three hour surveys done both getting to 16kW. Fortunately I paid only for one. My own calculations using mcs assumptions got to 10.5kW. Difference accounted for by double counting of room to room losses and the fact the surveys ignored fabric upgrades that I made a point of telling them about. Measured loss based on 2years of smart meter readings (gas boiler) is 7kW, difference accounted for by air change rate assumptions. I found 2 installers who would use my readings to infer a lower ACH than MCS default, both anyway believe ACH is often overestimated. They aren't alone, I have since heard several installers make this observation. Result was 7kW Valiant installed by mcs installer, bus grant claimed, heat pump capacity matches actual house loss. In my second round of seeking quotes I provided the evidence of measured loss up front and also told them I wouldn't accept anything bigger (and also that I wouldn't accept any system separation). That filtered out the grant harvesters and left those who genuinely want to do the right job. I ended up with a local installer on Vaullants approved list (obviously other manufacturers also have approved lists, but by the time I got to this point I had pretty much decided on Vaillant). He was already very sensible but possibly recognised he might learn a bit from the experience. My second option was someone more distant but totally switched on, he didn't get the job solely because of distance, but nevertheless I would recommend them.

Eon didn't ask me for proof of ev ownership or even the model, and doesn't require you the have a dedicated EV charger (IE the eon rules allow you to charge from a 13A socket). Can they tell the difference between your battery and a battery on wheels? will they bother?

For me (no battery, ev, ashp, pv) I can't better eon next drive and eon export. 7hrs at 6.7p, the rest very slightly more than the best fixed rate without tou. 16.5p export. So I charge the EV, do the washing and washing up, heat the dhw and bake bread at night whatever the season as the revenue from export exceeds the cost of nighttime import. This has the distinct advantage that it's simple to manage (like the one you are on). I don't even need a smart ev charger, just a 13A EV rated socket. With a battery and no EV I think I'd end up doing the same, but I can't make the business case for a battery work. I did a spreadsheet comparing the various options. The differences between the various tou tariffs weren't that large by comparison to not having a tou tariff at all, and the simplicity meant I didn't need any smarts other than the smart meter. Of course the numbers will depend on your own usage.

I went through this loop (being quoted a silly price to remove gas), albeit with a community centre (so possibly classed as commercial) not a house. In the end the gas pipe stayed in place for a couple of years until we could conveniently change 'supplier' to one who would remove it all for free (BG I think). Crazy I know but in the end it was removed and we didnt pay a penny.

On paper, but many houses need circulation pipes, radiators replaced, My list was the things that (judging by what we hear here and on other forums) generally go wrong and mess up the performance, not a recipe for the whole installation. Fixing these is simple and my point is - why do we make excuses for the industry and try to shift the blame for the piss-poor performance of some to government, particularly given the farce of the condensing boiler roll out that the industry foisted on us. With a lower electric price, why wouldn't all the above stay in place, except 45 Deg. The lower unit cost allows the 45 degs to become higher, you can run a wider dT on heat pump and still have tolerable running costs. Completely agree. In fact I have long advocated engineering a modest reduction in the electricity/gas price ratio so that designing for (eg) 55C is possible from a running cost standpoint, and still offering a 45C design as a value-add cost saving upgrade. I have also long advocated reusing existing DHW tanks where there is one (again offering a new tank as a value add upgrade), NOT needlessly replacing pipework and generally simplifying rather than insisting on the gold plated (but sadly not always gold standard) approach we currently have. Finally I have long advocated allowing unvented DHW tanks heated by ASHPs and with an external (not internal) element to have external protection instead of the D1/D2 vent arrangement, a change in practice (not regulation - this can be done within existing rules) which would cut half a day or more off an installation in many cases. These changes alone could significantly reduce install time and disruption, with value added upgrades offered if the householder wants them, However I have been consistently shouted down on all of these ideas, with few practical alternative ones proposed. However to achieve 5p/kWh (suggested upthread) is unrealistic in terms of the subsidy it requires, and unnecessary. Perhaps a good compromise might be to (a) shift the policy costs from electricity to gas (its madness that electricity users pay for green policies) and (b) offer a limited subsidy for say 10 years for electricity consumed for heating by ashp (maybe instead of the grant). The risk of course is that just encourages the industry to deliver installations that perform even more poorly. That fundamental still needs fixing. not excusing, IMHO.

Ohh .. I remember having to do that - convince my time served boss that he needed to change work practices. Various occasions come to mind, but most memorably the novel idea that staff (in a technology company!) should be offered computers so that they didn't have to write long articles out by hand (and literally 'cut' and 'paste' when they wanted to revise), all for a secretary to type. It probably didn't help that he was in a relationship with the secretary!

To halve the price of electricity would, at present, require taxpayer subsidy @JohnMo - it doesn't remove the subsidy it just shifts it. And where is the evidence that our electricity prices are 'the most expensive in Europe', thats certainly not the case if you believe Eurostat. @marshian is right. Why are we even talking about tolerating unnecessarily poor installations when its SO simple, in most cases, to do it right: NO system separation, RIGHT size, design for 45C or less, NO external controls other than TRVs in the bedrooms if you insist (with, if you wish, Homely/Havenwise or the like specifically designed for heat pumps), adjust the WC properly = SCOP 4, job done! If you also tell the homeowner to get a sensible tariff, they will likely be quids in. Surely we aren't going to use the fact that we totally messed up condensing boilers as an excuse to mess up heat pumps (and then deflect the blame from industry failings to the government), or are some parts of the the industry (I say some parts because there are clearly a fair few good installers out there) really that piss-poor, that lacking in conscience and that unable to learn from its own mistakes? If the MCS closed shop cant make it happen right, scrap them and let competition sort it out. I do agree that a readjustment of gas vs electricity prices is needed, but please lets not use that as an excuse to tolerate continued industry incompetence. Time for the industry and its acolytes to cut the crap excuses and get its house in order. Early mistakes are excusable but domestic heat pumps have now been around for long enough for the 'professionals' to work out what to do, so JFDI or get out.

Im presuming this comment is intended to be funny and/or a poke at incompetent installers, in which case well said. If not then i must apologise that i dont understand it, so perhaps you could clarify?

Definite no here. Having just retrofitted an ASHP to my 1930s house there is no way I would bother with gas in a new build. Its cheaper to run by about 20%, much more comfortable (because there are fewer thermal gradients due to the way it works) and can do cooling as well as heating. Whats not to like? Incidentally, ignore the people who falsely claim that hydrogen heating is the way forward. Hydrogen does have a place but not for domestic heating, its for applications where there isnt an alternative. There is a very simple reason for this - to be green (which is the argument for swapping to it in the first place) it has to be made from electricity, and this is a factor of 3 less efficient than a heat pump, so is guaranteed to cost much more. 'Hydrogen ready' is just filibustering by vested interests in the oil industry so they can continue to sell gas boilers.

My suspicion is that the architect isn't confident about designing an ASHP based heating system so has taken the easy route out. BTW I have encountered more than one 'M&E consultant' that is similarly clueless. @johnmo is spot on the money with his comments above. Having retrofitted an ASHP to my 1930s house (solid walls, with partial fabric upgrades, good loft insulation, uninsulated floors, 200 sq m, 7kW loss) there is absolutely no way on earth I would fit a gas boiler if I were doing a new build, and I would frankly be reluctant to go back to a gas boiler if I were purchasing another 'second-hand' house. Get an ASHP design right (basically follow the principles set out above and size it correctly), and you wont regret it. Consider also if you want light cooling, an added bonus with the correct emitters.