The LG VRF system can be integrated with their hydro kit, allowing for the efficient utilisation of waste heat generated during cooling mode. This heat is captured and transferred to the hot water cylinder, providing a sustainable and energy-saving solution. In contrast, the Daikin system operates either in heating or cooling mode, lacking the capability for simultaneous water heating and cooling.

Lots of good information, here. Got to say, I'm happy I kept my gas combi-boiler both for the infinite hot water and an alternative for heating when it makes more sense. But more options like this are good.

You could presumably set up 2 parallel systems for larger properties with more AC units and a larger tank. Cant see why two units feeding the same cylinder would be an issue but Daikin may think differently of course. We run our ASHP hot water at 48 degrees. It’s plenty warm enough for baths, showers etc. Legionnaires is only a risk with standing warm water so if you’re regularly using all the water in the tank you don’t need an extra heating cycle - there’s a good heat geeks article on this. Of course make your own decision

Thanks for this video, I had come to a very similar conclusion myself, we are a couple of years behind you (at least), but we are planning installation of all our "Green" equipment within month or so of each other late this coming winter, but no later than the spring of 2025. My Conclusion too, is we wanted an A2A Aircon & Heating system and a Mixergy iHP Hot water cylinder (as you are now going for), technically our home might be suitable for the daikon system (it a 2 bed bungalow, we are making into a 3 bed) but I'd prefer a slightly bigger cylinder and probably at least one more unit, so while we are not settling on a particular system yet it will be A2A and a Mixergy iHP, we were first drawn to A2A because of several KZfaqrs (including yourselves) who had the Haori system installed, and it remains my current favourite but as we are not going to be ready to install until near the end of the year making the choice now seems premature. we are running about a year behind our original plans as I was going to hand my notice in at work and retire when strong rumours of redundancy and our building closing meant working for a few months longer and collecting a redundancy cheque became highly likely and is now a certainty. That's the solar system paid for I thought!

Great video, very informative. I suppose this is so early in the domestic use of A2A that choices are limited. Hope to see plenty of videos once your Mixergy is up and running. Presume it will just plug into your existing hot water pipes and then to the outside unit.

I inquired about this system when we were looking to install our A2A system. It was mainland Europe only at the time.... we could get it but without a warranty, and having to get it supplied via another country... and then no one wanted to fit it.

You are right, these systems have been available in Europe, Japan & elsewhere from some manufacturers for a while but they have never been "mass market". Most manufactures offer heat recovery hot water heating as part of their commercial VRF systems but not many do on their residential systems. The addition of a DHW cylinder to the A2A multi system does add extra complication & complexity & needs a different skill set to install it. I seem to remember that Samsung had something like this a few years ago (R410a system) but I don't think its still available in the UK. R410a systems will also struggle to get reasonable HW water temps due to their lower gas discharge temps & will therefore need to rely more on top up heat from immersion heaters which will drag down the COP's. The addition of a DHW cylinder & plumbing, to what is fundamentally a multi split refrigerant HVAC system, means that many AC companies would need to employ a plumber to do the DHW side of the system because they generally don't do plumbing &, vice versa for plumbing / heating companies. There are exceptions to this but the Heating / Plumbing & HVAC trades are still very much separate industries with different skill sets & qualifications so a system that need both skill sets are not generally popular within the Heating / plumbing & HVAC trades themselves . This is why Monoblock A2W heat pumps are far more popular within the "traditional" heating industry because no refrigerant pipework is needed between outdoor & indoor components. It is also why only AC companies will offer & be capable of installing an A2A Multi split system. I think you will be better off with a stand alone Mixergy iHP HP Cylinder which would be my preference as well.

I have been talking to Daikin and Daikin partners for over a year, but have yet to get a quote. With two outdoor units and potentially 2 x 120L tanks, it could probably handle 3/4 bedroom house with a couple of bathrooms.

a year ago I had the same idea using these kinds of systems. Daikin is not the only one: Samsung & Hitachi have similar systems combining a2s and dhw. The idea sounds great, but I really got the impression even the manufacturers don't truly believe in these setups - at least outside the "hot" regions. Maybe there are technical limitations (like the save charge that these systems are allowed to hold or limitations in refrigerant flow control) and economic reasons (not cannibalizing the "real" a2w systems). Especially a small wall mounted hot water tank (that daikin offered) doesn't look too promising... By the way - there are other and maybe more common ways of combining the systems, simply by doing all a2w with water-fancoils (similar look to wall mounted indoor units) cooling is possible too.

Hi Tim, It's interesting to compare your efforts to adapt your Air to Air system to be more like a wet system (e.g. hot water) and my efforts to adapt my wet system to have the advantages of an Air to Air system (e.g. cooling) I can easily modify my heat pump and thermostat with a switch to toggle between hearing and cooling. The limitation is that cooling the radiators has to be done with care in the settings to avoid the dew point and condensation - but a useful few degrees of house cooling can be had in a heat wave without dripping radiators. One thing I've found, and this might be useful for you too, is that because I've sealed my house up so well eliminating draughts and improving insulation, I have a CO2 and humidity build up problem. The humidity can be controlled with a dehumidifier which I use to great effect in my utility room to dry clothes efficiently. However since buying a CO2 monitor (beware fakes!) I've discovered my CO2 build up is excessive because my ACH (air change/h) is so low (which keeps the heat in at least). CO2 can exceed 1,500 ppm if I don't open a window etc. So, something I'm considering is HRV or heat recovery ventilation. This is basically a low power fan assisted four port heat exchanger ventilator where the exciting air runs past the incoming air, gives up it's heat and warms the incoming air so you don't lose heat from the property. Efficiencies can be 95%. You can also direct the exhaust to the back of your heat pump so any remaining warmth is further recovered to improve efficiency and you can even add a wet radiator/heat exchange to the incoming air so ducts coming into rooms can bring warm air - effectively increasing your wet system radiator efficiency (like a fan assisted radiator) - further improving efficiency by allowing lower flow temperature and better COP. With the heat pump operating in reverse it will improve cooling too. I'm pricing up a commercial system at the moment but it's possible to make your own which I can conveniently mount in the loft. It's all very interesting stuff!

looking to get this installed in a larger house but simply got external units at both ends of the house. Yet to get pricing as just being released but saves getting separate A2A & A2W systems. Not seen any others.

The limitations here are definitely of Daikin's own making and not a by product of mixing DHW with "AC" (not that you were suggesting they were!). The Hitachi I have - which can do up to 4 internal units and 1 DHW, have Cylinders that are 190L and 270L. And the temperature can be controlled completely rather than just 2 set temperatures. Oddly, the Daikin would have cost me about £1.5k more, for what seems like a more limited system.

Interesting and as you say not really suitable for anything other than a small 2 person household. If the water tank was bigger you could use it to do the water and 3 rooms and then get another unit that does more rooms without hot water ? At least there are options

Any ideas if there is a practical limitation to doing One hot water, one underfloor heating area of modest size, and one air unit indoors? Once you've got hot water, it seems like a nice idea to get the underfloor heating.

A question about your existing a2a system.... How often do you need it serviced? Both the indoor units and heat pump itself....

Interestingly this was the actual system we were initially recommended by Ecobubl following our heatpump air to water survey confirmed are property wasn't suitable. We waited for delivery but gave up after a year with the UK date being advised in July 2023 of April 2024 but nothing to assure us that that date would be met. I suspect that is still the case because the issue is they have to source and build a UK manufactured hot water cylinder specially for this system. The idea of moving the hot air extracted from the house in cooling process seemed logical and efficient. I suspect it is still not actually available to buy now but I can also see the advantage of having these separate too so not unhappy we ended up with AC and a separate Mixergy tank. However I'd probably go with a heatpump tank if I was doing this today as originally I expected to use excess solar to heat our hot water, an idea with Intelligent Go makes no sense at all!!

I just got off the phone with Daikin who told me they have the system but currently don't sell the system in the UK and cant provide a projected date. Kinda frustrating from them, could be perfect for the annex I'm self building.

I didn't spot what the max output of this would be? IE 5kw rated

Daikin is terrible at giving out information. Well done for putting this together. I had a few questions after reading their cryptic webpages, that question went to a local installer who phoned me but couldn’t answer the question and then didn’t respond. Ended up speaking to a Daikin representative who wasnt great at explaining anything.

I have this system installed in a two bedroomed apartment we have just bought in Italy. The aircon/heating units and the hot water tank are above the false ceiling. we just see grills in the walls. The apartment took two years to renovate and we have just moved in. We have no heating or hot water because of a legal dispute with the neighbours over the siting of the heat pump. Very funny. Very cold showers and a fan heater running full time. Once the legal dispute is resolved I will let you know how it works. Would anyone happen to know if the system can heat the domestic hot water without the heat pump running. Using a back up electric heating element?

Assuming this won't qualify for the Boiler Upgrade Scheme?

A2A and DHW with a single external unit sounds like such a great idea, but in reality the Daikin MultiPlus might disappoint. Low DHW efficiency: The ErP fiche ‘water heating energy efficiency’ in an average climate = 90% for the 90L and 94% for 120L variant. Compare the Dimplex Edel 200 at 146% (and modern R290 ASHPs can be >160%). The Edel’s COP(7/55) = 3.36, so the Multiplus’s COP (mysteriously lacking in Daikin’s literature!) must be about 2.0-2.2 (can’t be precise, as the efficiency algorithm considers standing losses, which Daikin also doesn’t reveal). Heat Pump maxes-out at 55 Celsius: The “Comfort” mode uses electric immersion to achieve 60 Celsius and at sub-zero ambient temperatures even the “Eco” mode will require an immersion top-up to reach 50 Celsius. Can’t run A2A cooling and DHW-production simultaneously. 2W Heat-exchanger is integrated into the cylinder and only works with the specific 4MWXM52A external unit: If either component breaks in say 5 years time, will there be a replacement unit available that is compatible with the other, or will you have to replace the whole DHW and external unit set-up? Likely no cheaper - and less versatile - than a combination of a standard multi-split and a combined heat-pump/cylinder: One might hope that an all-in-one system might offer a cost-saving. However, European online prices suggest a premium (over a conventional 3-port 3MXM52 unit) for a 4MWXM52A and EKHWET120 of about €2.5k. A Dimplex Edel 170 or 200 is about £2k. Ultimately, I really think you’ll be pleased to have your Haori and an iHP rather than a MultiPlus! There is some debate in the comments as to whether the MultiPlus could be installed with a BUS grant - which would obviously be a game-changer if it could be! Ofgem’s Boiler Upgrade Scheme: Guidance for Property Owners v2.4 is pretty clear: “1.7 ASHP systems must be hydronic (air-to-water) to be eligible under BUS. Air-to-air systems are not eligible.” (repeated in 4.7) Boiler Upgrade Scheme: Installer Guidance v2.5 is more detailed: “3.47 Heat pumps and biomass boilers must distribute heat using a liquid (normally through radiators or underfloor heating) to provide both space heating and hot water.” Some are arguing that refrigerant is a “liquid” so 2A space-heating qualifies, but the BUS Regulations 9(2)(a)(ii) and 10(2)(a)(ii) are defining a hydronic “delivery” system in which the heat pump “transfers its heat to a liquid for the purposes of space heating and hot water heating” - the key point is that the distribution liquid is extraneous to the heat pump, which transfers its heat to that liquid. I suppose a heating system that used molten sodium as the heat transfer fluid would qualify, but in practice domestic systems (sensibly!) use water or water+glycol. “2.3 being certified by the Microgeneration Certification Scheme (MCS) or an equivalent scheme.#10” Footnote 10: “The Energy Department is responsible for determining whether a scheme is equivalent to MCS. There are currently no schemes determined by the Energy Department to be equivalent to MCS.” Also “3.2 The Secretary of State is responsible for determining whether a scheme is equivalent to MCS. There are currently no schemes determined by the Secretary of State to be equivalent to MCS.” MCS only certifies hydronic systems. MCS has an “MCS HP Performance Benchmark Proposal” which includes to-air space-heating, and putatively could apply from 2025. However, the current minimum seasonal water heating energy efficiency that a heat pump needs to deliver in order to be eligible for MCS-certification is 110% (tentatively 120% from 2025, in the Benchmark Proposal), and the MultiPlus achieves only 90 or 94%. Conclusion: The Daikin MultiPlus is not currently MCS-certified and, even if at some point in the future the BUS adopts the “MCS HP Performance Benchmark Proposal” the current iteration of the MultiPlus would not qualify. The other common confusion is as to whether a 'cooling capability' disqualifies a system from the BUS. Nowhere in Ofgem's Regulations for the BUS is there such a disqualification. The earliest iterations of the RHI did prohibit cooling-capable systems. However, because all ASHPs are capable of reversing, so that they can perform a defrost, people who wanted RHI payments and cooling would hack their unit (typically just a jumper on the control board). Later versions of the RHI and the BUS sensibly didn't/don't interfere if you're intent on a cooling-capability. Of course, if you want your hydronic ASHP system to provide cooling at anything even vaguely approaching the efficacy of A2A, you'll need to fit hydronic fan-coil units, with a suitable drainage-capability.