JohnMo

Not really comparing apples with apples. OP is starting system for first time on a new build. If I'm running WC, flow temp goes to target with a couple of mins. But not so when batch heating or doing a cold start of system. Takes a few hours to get there. Cold house first time heating comes on (op case above), or first heating of the season with UFH. Even without cooling prior to heating season, floor is only around 19 to 20. In my case I have 100L plus of water, plus 56T of concrete to heat, so return temp stays low for a long time. Delta T is capped at the max allowed by flow rate and heating kW output. As return creeps up the dT stay constant and flow temp increases with return. Example from a batch charge from the other day, to show what I mean. Run started at 00:30 and was stopped to do DHW at 06:30. Window in image is 4 hrs.

You must have one powerful heat pump, that can take a new house water flow temp straight up to target temp with a big deltaT and not risk damage to compressor. My instructions clearly state EVAPORATOR WATER FLOW The nominal water flow rate refers to a 5°C temperature difference between the evaporator inlet and outlet. The maximum permitted flow rate features a 3°C temperature difference while the minimum one has an 8°C temperature difference at the nominal conditions as shown in the technical sheet. Insufficient water flow rates can cause excessively low evaporation temperatures causing the safety devices to trigger and stopping the unit and, in some extreme cases, forming ice in the evaporator and resulting in serious failures to the cooling circuit.

Either with a room thermostat Or some of these https://amzn.eu/d/e7oX9LZ, cheap on one day delivery, so you could have them tomorrow.

Emitters in your case is radiators. DeltaT is difference between two temperatures. This could be room to radiator difference or difference between flow and return temps from boiler.

So this is the first proper start/run. The way the heat works and it makes zero difference what the target temperature is initially. The heat pump starts, it monitors flow and return temperature. It tries to establish a steady return temp, and then sets flow temp to approximately the target dT (difference between flow and return temperature) above the return temp. It will not add more flow temperature until dT reduces. So if have many tonnes of house to get up temperature that has spent its whole life unheated it takes a while. This doesn't mean your settings are correct or even close, but the realities are houses when just built are very damp the water contents require loads of heat to start drying.

Go on Heat Geek they have a good write up what you are doing and why. Do you need to do it fully or just a bit of fine tune?

The OP hasn't been on since March so unlikely to answer

Simple way to think about and you have given the answer - use the most demanding airflow. So if 4P is greater than 0.3ACH, you use the 4P Double single rooms - how many people will sleep in the room - nothing to do with area. Small bedroom with bunk beds is a double room, no matter how big or small. Treat guest rooms as a single or split the difference.

Also get a heat pump cylinder with a big coil, not the mini coil Vaillant install. Had zero issues with 6kW heat pump heating a Ideal 210L - 3m² coil. Others on here have 300L and small heat pump without issues.

Just had a look at the Chofu manual (original manufacturers) only the expansion vessel shown on the heating circuit, as you say the rest is internal on the ASHP. Sound like a bit of cut and paste engineering from Grant. I would install per Chofu schematics and use the controller that Grant hide away as the controller for everything.

Has to be above £7500 to get full grant. If it cost £6k you get £6k, not the full amount.

Then why not do MCS certified scheme, then it would cost the best part of nothing.

Don't you just hate all this badge engineering? UK skill base seems to have diminished to, use heat gun or similar to remove sticker, stick on new sticker. Now UK made? Where is the innovation, product development - somewhere overseas. We under invest in training, don't have the highly skilled workforce we should have, and they have to install to the best of their ability. Government hide behind private organisations etc. Lived in Malaysia for awhile - if wasn't produced in country (with I think 80% of all material components) it carried a minimum 100% import duty.

He is running radiators - the hysterisis is different. If you need an external one Computherm Q20RF are nice, you can adjust the hysterisis down to 0.1 and do cooling. Hysterisis will affect over shoot and under shoot of room temperature. Cycling is basically based on output compared to how easily the heat generated can be moved away. A low dT between room and water makes this more difficult than a bigger dT. With UFH it's how quickly the floor can absorb the heat and at the same release to the air.

Just wish I wasn't a tax payer, and then I wouldn't feel conned, every time read one of these posts.

You want 40 in a double and 20 in a single bedroom. Dump the hall extract, not needed, unless you need to balance the numbers. Use Passivhaus numbers. Kitchen extract put both ducts to a single extract point - no value having two, keep 9. Lounge area the same one terminal, keep 4. Normal flow area, multiply 2.5, multiply 0.3. so normal flow about 83m³/h, boost multiply by 1.2.

That is just bonkers money. A heat pump connected to an existing system that isn't being modified and a cylinder.

Just looked and you look to be correct for R290. R32 look very different to midea.

20 minutes later you are finished. If your not sure what to buy or mix go to B&Q, to the bit with the sand and cement, and there will be ready mixed stuff you just add water. Mix stiff and trowel in place. Done. Procrastination gets you nowhere.

Where are your ducts going - photo?

Go outside with a cup of tea and seat, monitor what occurs over an hour. If it's cycling a lot, you will be done and dusted in 20 mins. If you have a smart meter, you should be able see increase in electric consumption and how long it lasts also, monitor flow temp on the controller etc That is just nonsense really. In that case make sure the flow rates are matched on all pumps and both pumps run together. Do you also have an UFH mixer? I assume not. You can check by measuring the flow into and out of buffer on the bottom ports, that need to be the same if both pumps are the same flow rate. Your Samsung controller will be able to control various ways. Think one way is WC and it's built in thermostat working together.

Yes - look at cycle times. I found the longer the cycle time the better the efficiency generally. Every floor and house is different. I found a min on time of 10 mins was ok, but 20 mins was better. I have recently set my WC curve to 30-35 and use a 0.1 hysteresis thermostat. The heat pump runs generally at night and runs continuoisly for many hours. It then generally remains off for the rest of the day. Also make sure you don't have any small zones calling for heat, this can drive down efficiency as you get lots of very short cyles. Heat pump running isn't that black and white, although many will make out it is - stick it on WC your in the best place - not always true as the video above demonstrates

Ideal is made in the UK, which may have advantage for parts and support? Most heat pumps are good, the install is the important bit really Generally - Volumisers are ok, buffers avoid, lots of zones avoid. If the system looks very simple that is generally good. minimal install is heat pump, 3 way diverter valve to cylinder or heating system, one thermostat. Either run weather compensation or use thermostat on fixed temp of around 35 degs. A fixed flow temperature can yield performance benifits because it allows extended runs times and avoids short cycling. If installer suggests above 45 deg flow temp, move on to next installer. Cylinder size, two things drive this. number of bedrooms (minimum size), and life style (to make it bigger). There are two of us we have 210L and wouldn't want any smaller. If you have kids coming down the line, I would suggest 300L. Discussion on OVO over the last few days on here - have a search. But no thanks from me - based on their performance when I was a customer. Octopus may be a better choice.

Filters are wonderful things, I once modified a gas turbine filter system, on an offshore generator, moved from F7 to H12, eliminated almost all the salt from the combustion air. Turbine blades were failing in under 6k hrs due hot corrosion (sulphur, salt and high temperature). Couldn't get the sulphur out of the fuel, or change the temperature, so chose to remove the salt. When I left the company, the turbines had lasted over 20k hrs, no reported issues.

Sounds like a sensor issue. Looking for a feedback it's not seeing?