JohnMo

My first quotes were circa £10k - which is just bonkers. Ended up installing two units (good for my layout) total cost circa £2k for self installation and professional commissioning. Compared to houses with piss poor ventilation, which is most, it's ace. More like being outside than inside. If you don't have an airtight strategy (you really should have one), I would do dMEV or MEV with humidity control and most importantly humidity activated trickle vents. This is the lowest install cost, least ongoing maintenance that gives decent ventilation with undue ventilation heat loss.

Balanced - supply and extract.

First do you need either? Optimisers, if you have definitely got shading issues from fixed objects, otherwise don't bother. Micro inverters, never seen the appeal, if you doing a battery install at same time you are likely to have a hybrid inverter anyway. Single string inverter multiple mttp's are cheap as chips and readily available, if not having a battery

Panasonic do this also

Going big isn't really playing it safe with heat pumps. You may need to add a volumiser to keep cycling in check.

Just looking at you Loopcad the dT looks to 10 degs in the most part, you are going to be nearer 4 to 6. So that will drop your flow temp a couple of degrees for the same mean temperature. The design temp flow temperature is only a very short window of the year most the time it nowhere that cold outside. Even for 600m² you heat loss of 12kW sounds very high. Especially for Hampshire.

@Benpointer, just read your profile and the spec of your house. You should be near 2.5kW heating demand in Dorset. If so the 7kW Panasonic is huge, there smallest heat pump would be better suited?

I'm at 192m2, all vaulted loads of glass, did 7 loops, all works fine, your loss must be quite a bit higher, to need an 7kW heat pump as well. Are you a new build? If so are you sure you need that big a heat pump?

Or designed for the same condition but 6 miles from the coast. Plenty of defrosting goes on, even at very low temperatures.

But vague, you need to look at the specific model, as different sizes have different pumps. Has the UFH been designed or thumb in air guess? With 16 loops the flow rate could be pretty high. So will need some thinking about. What size is your floor?

If you wet the blocks before cementing, they will stick together way better. The blocks suck all the water out of the cement and you are left with nothing to cure. Hence it being very weak bond.

Maybe a different set of rules, we have diddly to enforce manufacturer to tell us stuff, maybe other European countries demand a full range of tech data. Vaillant UK information is best part of zero. Almost trust me - we are 'Vaillant'. Even their badging is suspect, choose a 7kW ASHP and it puts 9.4kW at -2. Mitsubishi, not always easy to find, but published, have pretty robust set of data. Quite like there new 8kW with two compressors, one fixed output 2kW and one 6kW inverter driven. Should cover all bases.

Have you looked at the data book I attached above? Me thinks they just don't want to tell you. Here is snippet - all temps full range of compressor speed. All compressor sizes in data book attached above.

Not really I just installed an additional 1kWp was about £400, for everything, doing 2kWp would add £200.

Possibly the easiest solution.

Just found a trend I posted on another thread For clarity the boiler and heat pump were running, the boiler sat behind a plate exchanger and added heat to the ASHP flow. ASHP on its own takes nearly twice as long to heat cylinder.

I was doing 210L in that time frame

Can see this happening and more. Most new heat pumps are already equipped with smart grid functions - so electric company can switch on off at will, so why not PV feeding a communal battery? Octopus have tariffs that take over control of your battery, in house or in car to charge or discharge at will Wouldn't be what I would choose to do. But that's the way things are moving.

You need to go into the guidance notes (attached) page 23 on Basically 0.5 ACH based on house volume. I would also use passivhaus advise on minimum room flow rates especially for bedrooms. Then go there. If your house is large you will need to trim flow rates to closer to 0.3 once house is signed off, as 0.5ach is a bit over ventilated and humidity levels can dive in winter once house has dried out Building+standards+domestic+ventilation+guidance%2C+November+2017.pdf

A PHE need approx 1/3 to 1/2 the area of a normal cylinder coil to do the same job. Mainly due to the turbulent floe within the phe compared to almost static flow in the cylinder. When I was doing hybrid heating against a 3m² coil I was heating cylinder to 50, it would overshoot to 52. But boiler flow temp never went above 55.

Only if a seasoned professional, that isn't a politician. But have the case history to back up them old bones.

It's the only part of the house that once done, isn't easy to undo and improve, so why faff about for a few hundred pounds in savings. Do it once do it well. Unlike a ground bearing slab you are exposed to air temperature under block and beam so downwards losses are higher

It's good to have facts to allow you to make informed decisions.

No where near the same insulation value, though. I would do (did) 200mm PIR, the rest either concrete or screed.

Attached. Page 33 on At 7 degs the 10kW puts out between 7 and 15kW. The 12kW puts out 7 to 18kW At -7 the 10kW puts outs 4 to 9.5kW While the 12kW puts outs 4.5 to 13kW kl-06-e2-verze-01-18012023-2564719.pdf