JohnMo

Postcrete?

The way they are made there is alway flow mixing you cannot stop it. I tried two different makes before I realised. I have no mixer and no pump, just use circulation via the ASHP circulation pump.

No, it doesn't care, mine was run through insulation space by the gas engineer.

Certainly looking at the annotated photo, you have hot water going through the flow meters and return water at the bottom. How the mixing occurs doesn't matter as @ProDave says. It looks to be doing what it should be. With all UFH mixers there will be a higher temp going into the mixer than out to the UFH loops, 10 to 15 degs is pretty normal and that's what you have. The mixer takes some hot water from the boiler, adds some return water. So if you have 10l/min around the loops, you may take 6 to 8l/min from the boiler supply, the rest is reused return water. If you want to remove the pump and mixer and direct couple, you would put the flow in at the top and flow out at the bottom. Switching the pump of will give you zero flow, as the pump pulls the water through the mixer, the mixer acts as hydraulic sepereration.

Hot normally goes to the flow meters. DeltaT looks large for a heat pump, normally around 5 to 6. Are you running rads and UFH at the same temperature?

In our last house (1820 build) it had a cellar room, stone floor, 3" thick stone shelves, and even though that part of the house was very well insulated, that room was always the same, cool temperature. SWMBO wish of stone shelves, may be a wise one, they take lots of energy to heat up.

Question do you need the 50mm concrete below the insulation, could that be insulation? EPS or PIR. Your French doors U value is quite poor, we have double glazed French Doors and had Krypton fill double glazed unit and good frames and an overall U value (frame and glazing) of 1.1. So some improvement could be made there. The old one if double glazed will be circa 2 to 2.5 U value, if single glazed 5 at best guess.

? No idea what you you talking about

Do you need 32mm mdpe, 25mm should be fine. You really need an accumulator between pump and house, otherwise your supply will feel rubbish. 100L should be fine, but bigger the better. Aren't you having filters? Min required would be a UV filter to kill bugs etc. I have fed my whole house via a hot and cold manifold, all with 16mm. Once the pipe is in wet room, branched from there. For the 18m use a secondary returns circuit, with thermostat and timer or wait for about a minute h your choice.

Would cost a small fortune, I doubt its even available at that thickness.. No one would buy it that thick 10mm thick 1.2m2 is £230! Old buildings you need to be careful with condensation also.

Possibly places like China - they like to lend

You can easily join two manifolds,so that would not be an issue. One thing to concider for phase one is boiler short cycling, the heating times for the radiators and UFH are very different, so you could end up with only the UFH on. The boiler is likely to shirt cycle. Have a read through this thread, may answer some questions you didn't have.

Yep - That is the real scam. It should be part of the unit cost, you use more kWh you pay a bigger proportion.

Biggest dream ever, never happen, as nuclear is possibly the most expensive energy we have.

In Scotland we have been on a a zero CO2 grid for the last week (of me monitoring), using mostly offshore wind. Today our grid mix is 89.2% wind and rest from hydro. So not exactly wasted. Where I live has zero wind today, but offshore there is, hence being able to produce most of Scotland's energy needs. Trouble with nuclear it takes about decades in planning, decades to build, costs mega money, and you are left with 1000s of years worth of lethal waste materials. And that's because if it goes wrong, it can go very wrong. A wind farm on the other hand can take a couple of years from start to finish and full production. Wind will have outages due to no wind, the turbines can be taken off line for maintenance one at a time, nuclear, is likely to offline annually for mainland inspection, so nothing is on-line all the time.

The restrictions are normally in place due to visibility of traffic. We had a corner plot quite a few years ago, and we're explicitly banned from installing any fence of any kind by a road junction. You say you are on a corner plot, is there a road junction nearby or do you drive your car out of the plot on to the road?

That may be true, but the heat pump to get best efficiency starts flowing at as low temperature possible. Only increasing temp to maintain a circa 5 deg dT. This where a small coil is rubbish, as it is unable to transfer any meaningful heat to the cylinder, until it gets to a high temperature, then you are unlikely to get time required to heat the contents before tripping out on high temperature due to dT margin not being maintained.

Biggest trouble you will have is convincing anyone that the 90L capacity is acceptable for a heat pump. Typical industry recommendations attached for heat pump cylinder sizing.

Trouble I found is being able to manage the dT required to keep the heat pump happy with a small coil. The heat pump will ramp up to max temp very quickly and is unlikely to get the cylinder hot (48 deg) in one hit. 90L isn't much usable water at a low temperature, either. Why not just do 90L with an immersion, or heat pump via the indirect coil, see what the max temperature is in one heat cycle, set thermostat 1-2 deg below this, then time the immersion heater to come on and finish heat to 60 deg? At least you will have a decent amount of usable hot water.

Do you have a buffer? If so a suggestion to what may be going on. Assume the heatmiser is controlling the pump the central heating side of the buffer. The heat pump circulation pump is controlled by the heat pump controller, if this is set to weather compensation mode the the heat will be managing the heat in the small loop to the buffer?

I would be tempted to install a small MVHR unit upstairs and not go dMVHR. You need an external supply and extract terminal also, that's the only issue. Have an air supply in the master bedroom and extract in the bathroom. Have the supply in the corner of the bedroom as from the door as possible, same in bathroom have to extract as far from door as possible. Your flow would be, comes in to bedroom, would then pass through bedroom, out the corridor and into bathroom, refreshing the whole hall also. Your existing extract in the bathroom could be dumped and the holes blocked up. Mitsubishi make a small MVHR unit, which come up on eBay quite often for cheap prices. The other option would be to set up a cascade ventilation scheme. You could use a couple of dMEV fans, which are almost silent, to get the air from one place to the other. First extract air out of the bedroom into playroom above, then extract air down into the bathroom. No ducts are required. Remove the extract fan in the bathroom and install a dMVHR unit. This way set up a big circulation of air and heat is recovered in a space where noise isn't an issue. Make sure your bedroom door has a space at the bottom for air movement.

So an ASHP and electric heating both use electric. Any electric heating except heat pumps produce heat at 100% efficiency. So one kWh in, one kWh out. The difference is a heat pump, takes one kWh of electricity and converts to 3 to 5 kWh. You never mentioned if you are doing a conversation, renovation or new build?

Not really - they are living in a past reality. I deleted the rest because that was rude.

My view is if you can here noise in the water system you have air in it. Are you sure something isn't calling for heat. The circulation pump should only be on if you have a call for heating or DHW. So I would guess the installer has a setting or two wrong (there will be a few ways to call for heat and various ways to operate circulation pump)

Had a few conversations about airtightness during our build, only the electrician appreciated it's importance. Everyone else, basically said it was shite and utter nonsense, that will lead to a mouldy smelly house. Lucky I ignored the neanderthals. We have a pretty uneducated population about building science, so much so that the EPC may was well be written in Chinese, as very few will read or even if they do, actually understand it. Last house we sold had zero downloads of the EPC.