DanDee

another example to study https://emoncms.org/app/view?name=MyHeatpump2&readkey=0c28f25dea9e38f983d9c83a6dd455c0

I don't have experience with this in order to give you a proper answer. From what I've seen around, the wrong number(ACH) can drive up(double) the required capacity. The general number(if rule of thumb) of ACH is quite high vs the reality. Just to give you my understanding of 5ACH=1air change per 12 minutes, I doubt your house goes from 20 to whatever temp is outside in 12 minutes, with all windows closed and no active heating. https://trystanlea.org.uk/roombyroomheatloss2 https://openenergymonitor.org/heatlossjs/ I've changed the ACH to 5 in this table and it doubled the requirement An example from twitter of a discussion on the topic of the right ACH. From my understanding 1.5-2ACH and 3(bathroom only) should be your max rule of thumb without actual testing.

Keep in mind, the A/W albeit limited in modulation, it runs in a range where the COP is at its best. It might even be designed as such. The A/A is free to use the whole range, but the portion toward the maximum is at a lower COP that rated(10kW). Always look at the output data of the unit for the -5..-7..-10C it is lower than rated a 7C. This is an example from the Vaillant A/W of two sizes using the same unit, with the extra compressor speed modulation at the top, putting out the extra power. Yes with A/A is always like that, the rated label matches the cooling rated capacity

https://www.ncm-pcdb.org.uk/sap/pcdbsearchresults.jsp?heatPumpType=3&emitterType=0&type=362&serviceProvision=1&brand=Mitsubishi+Electric&model=Ecodan+8.5+kW&modelQualifier=PUZ-WM85VAA&pid=31&btnSubmit=Search https://www.ncm-pcdb.org.uk/sap/pcdbdetails.jsp?pid=31&id=104645&type=362&mid=020047 https://www.ncm-pcdb.org.uk/sap/pcdbdetails.jsp?pid=31&id=104641&type=362&mid=020047 One link says WC-no for mitsu as well, another link says yes, no other details as to what is that and why, so ignore. Also reversible-no, a lie.

They are selling Riello as their monoblock option. https://www.toshiba-aircon.co.uk/products/air-to-water-heat-pumps/

is WC=weather compensation you are referring to?

It looks like it does have WC. It would be impossible to be a rebranded device yet not carry the most important feature of a modulating heat pump. I don't believe we can find any HP without WC or other similar function. Those 3 links are manuals for the Riello HP's

https://www.toshiba-aircon.co.uk/wp-content/uploads/2023/02/Technical-Specifications-Manual-04-16.pdf https://www.toshiba-aircon.co.uk/wp-content/uploads/2023/02/20230221_IM_NXHM004-016_EN.pdf https://www.toshiba-aircon.co.uk/wp-content/uploads/2023/02/20230221_OM_NXHM004-016_EN.pdf

should've said: There are millions of heat pumps to be installed outside the ones like your case That doesn't mean you are not right, but then those that make those hp's in order to provide the listed result, aka SCOP, have to request certain device size to be paired with their systems to achieve both the SCOP and longevity of the system. So where is the middle ground? Keep your cylinder but tweak the coil or use an external HEX to match the HP.

There are millions of heat pumps to be installed outside your particular case, from electric only, oil boilers, gas boilers without DHW cylinder, gas boilers with DHW cylinder that needs to be changed and new builds. There are not enough installers to meet the demand without you particular case anyway. The most important hurdles being overpricing and lack of control over the end result.

correct, as the installer will use these schematics as guidance(even thought they are what needs to be done), presents to Vaillant what they want to do and Vaillant gives them the OK. It's just that they had to put some disclaimers on some of these documents, because ultimately it's what is being done on site that matters, warranty wise.

That's just telling everyone that those schematics are just an example, and that ultimately the person planning and installing a system is the one responsible to make sure everything is technically safe and sound. It has nothing to do with any product represented in the schematics, or the actual warranty contract one is involved when buying Vaillant products.

https://www.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/arotherm-plus-1/quick-guides/all-schematics-wiring-notes-1799366-2626556.pdf

in the meantime https://www.shopclima.it/en/mitsubishi-electric-pxz-4f75vg-2x-msz-ap25vgk-msz-ap35vgk-erst20d-vm2d-ecodan-multi-3-1-pxz-r32-system-with-msz-ap-wall-units-and-200-l-hydrotank-7-5-kw.html

Check the data book https://www.hrponline.co.uk/media/pdf/a5/7f/f2/20_PAC_DB_350_Data_book.pdf Keep in mind the 2:1 modulation you read about is from the air/water hp topics, the A/A has to deal only with 20C air in which the refrigerant has to condense, whilst the A/W refrigerant has to condense in range of temperatures from 20 to 50 ish. Thus make it impossible for the A/W to use the whole range modulation of the compressor/refrigerant pressure. The 10-12-14 kW A/A discussed here have the same compressor, basically being the same double fan unit. The data sheet says it's minimum can be 3kW. Before anything else you should focus only on a proper professional heat loss calculation, only then look for quotes. Without that it's like trying to put a V8 in a Mercedes A class. So what do you have A, C, E, S class?

Whilst in the UK you can buy Mitsu only as monoblock , in the Netherlands they sell only split systems.

No cycling in DHW, just poor performance. If it's not the low COP that would drive you crazy, the reheat time will do for sure with a minuscule coil. https://emoncms.org/app/view?name=HighbanksASHP&readkey=a6242a5576f8fa23493b70dad6c7d9fe https://emoncms.org/app/view?name=MyHeatpump&readkey=23437bdf4c5212a780f9bcf6f03cc688

I'm waiting for the moment when you are going to take the decision to just insulate your home such that it would be futile to want to install any heating system.

The issue with the hp cycling uncontrolled is to many unnecessary start stops(wear). Depending on the HP it can have an effect on efficiency or not. I cannot tell you exactly what and how, but some HP's are running efficiently only after the initial 5-10 minutes, other from the start. Some are unable to modulate efficiently such that every start soon triggers a stop and then a restart (forever). Such my conclusion that is better to control this with a fixed low temp and a thermostat. to keep it simple, let it run at 35 flow unless bellow 0C outside(random numbers) good COP but too many starts on panasonic Mitsu 6kW good COP on UFH without DHW, but is never able to modulate down to 3kW just goes berserk triggering start stops but very good output when needed Mitsu 14kW left on it's own, it's either cycling it's brain out or not, random.

not mine, but an example of one left to do it's thing

Some do like your case some not. I said 5 minutes, but 10 or 15-20 minutes cycles are still too often for a whole year.

"First heat cycle will be good as a ready source to a sorb heat, but once heated, it just a radiator what goes in comes out" Because of the extra volume of water+iron that you would have in each room, if the requirement is low you gain a few hundreds of watts buffer on the whole system, as that water+iron looses the heat into the room. But as you mention running with 25C maybe the benefit is minimal/pointless.

Did anyone looked into the fact that once the heat requirement is under the minimum output of the HP, it shouldn't be allowed to try and weather compensate, but just be controlled as a boiler, on a fixed low flow temp? This part of the automation seems to work great only when the output/requirement can match, for the rest of the time it just starts and stops every 5(random number) minutes.

It would actually be the perfect in room buffer, for the spring/autumn seasons.