JohnMo

So reverting back to option 1 and 2. Option 2 just looks too complex, so in all probability will be to install and control. Option 1 is basically a hybrid ASHP gas boiler installation. Almost any ASHP is pre equipped to run hybrid mode out the box, some are more difficult than others. The Daikin ASHP especially for hybrid installs is designed to work with other manufacturers gas boilers and you set up to manage which heat source is online based on cost or emmisions. You could also get away with a smaller ASHP as you would design to say +3 degs instead of -3 degs. So ASHP is utilised 95% of the time, gas boiler for other few percent.

Could you just heat the pool and use it as a thermal store. So heat pump just continually manages pool temp. Then take water direct from the pool and circulate through the UFH? Or take via a plate exchanger to keep them seperate. Could do all with an all seasons pool ASHP. Use a plate heat exchanger as DHW preheat before cold water is entering an unvented cylinder, and let the ASHP heat that via a 3 way valve a couple of times or even once per day? Or just heat with an immersion as very little work would need to be done.

Range is 2 to 23 l/s. I have one set about 4 - you have to take the cover of to check it running as it is completely silent. CV2-GIP.pdf

Hi welcome - have visited your site many time, very informative.

Or Shelly H&T, currently 40% off, at Shelly store, similar output. Not sure how you get data to excel though.

Make from a higher density EPS or XPS, mine are just XPS in a metal casing. MDF laminated with EPS, to give some mechanical strength. Other issue is filters unless you have the external to the unit.

Looks good, but the heat exchanger looks very small. How about using individual extract fans say Greenwood dMEV, let them feed to the heat exchanger. The fans come with built in humidity sensors, are fully user adjustable. Then just run the supply at fixed speed. For the short period of boost in a single room, unbalancing isn't really much of an issue.

@BeelbeebubOr just use one of these off the shelf items to control from a buffer https://www.ebay.co.uk/itm/126168847679?hash=item1d603fd53f:g:dzwAAOSw93JlRK6R&amdata=enc%3AAQAIAAAAwJE0AgmF7NYnmL%2Bb3NHl2nvvJs%2BbcZvTFN%2BOBVKGewKstjeKAYl2eR3SSF2IJmsxwJYj09wDR9tEYcC1gFA%2Blp2Q5jIZ4TqaTTGhDjMjQuo6yjexVnRtNY0jqE%2BLMSSMxYRgwEFD5E3kVXPIa%2BDEcgcwiYhvsOH8C6%2BCc4Gb6M1KyeGASY4cuRXY2VK6cr0%2FBZSNOPYEQ7HEs1LuEpFlzPFOgQfLpBBaxK8a9yearpCZWrEPzaT5vybPfl8mZhHgaw%3D%3D|tkp%3ABk9SR4r5ub_9Yg Clima500.pdf

Simple thermostat is all you need (thick screed 0.1 hysterisis, thin screed any thermostat will do), if single zoned with a heat pump on weather compensation, you can actual run without a thermostat. Mine has done nothing for weeks, outside temperature has ranged from -3 to +14 Basically if the house becomes hotter due to solar gain etc, the heat input into house reduces due to floor to room dT reducing. The return flow to heat pump stays slightly warmer, heat pump reduces input to maintain dT across flow and return. Your WC curve needs to be setup well for this to work in practice.

My thoughts also, no wonder this thread is 40 pages long

In another statement you made earlier you stated it was for heat only, but obviously it heat and cool like you expect from an A2A. So are you applying for full planning permission? I have attached the noise data for my A2W and it can be seen distance is your friend. A2A piping isn't that much of an issue for long distances.

So is this MVHR unit you made yourself? What are the temperature sensors you used?

You don't need vents under a ground bearing slab. You would need the telescopic vents under block and beam to ventilate the space.

Are words that could mean to get royally fu..ed over. We had a rental, the agent was phoned by tenant to get a basic repair, asked what was involved and where the tradesmen were travelling from. Turns out they were travelling circa 100 miles each way to do a 10 minute job. I got my own trades from then on.

That may be true for a gas boiler, which has an almost direct relationship between consumption and power output, but not a heat pump. For my ASHP (similar would be true of a GSHP) - for the same weather conditions electric consumption increases by 25%, not 6% if you increase flow temp from 30 to 45.

There is a difference between heating being on continuously and the heat pump giving a heat rate at a constant rate. As detailed in point 2. above. But still no detail on your system specifics or how you operate it? I will await details before responding again.

Again no, the same material that is thicker has an increased thermal resistance. A material has thermal conductivity defined by W/mK, The thermal resistance or R-value is calculated by using the formula R-Value = l/λ Where: l is the thickness of the material in metres and λ is the thermal conductivity in W/mK. takes into account the actual material thickness, the 'U' value is just the inverse of the 'R' value So thickness has a big impact. Double the thickness half the heat transfer. Otherwise you just insulate your house with 1mm insulation and all would be good.

A 1/4" BSP or NPT has an outside diameter of about 1/2" (close to M12), so likely to that. Two minute job to remove that section, take to plumbing merchant, b&q, Screwfix etc, and find the plug that fits.

Bottom of trench supposed to undisturbed as dug. You sort are answering your own question If you can't, is it being used? If not use flood it with concrete. Move on to next difficulty. If it's being used that's a whole heap of work - if you can't leave it.

It likely to a standard plumbing thread size, so 1/2" looks about right. Not something you get on a car.

No it won't, it doesn't work like that. I thought did until I tried it, with my summer house - the heat pump works against you, not for you. The only way it works like that is by turning up the flow temperature or running a way lower dT (moving the mean flow temperature up)

My carpet isn't the issue, it was just an example. No doesn't happen in practice. The real answer to the transfer process is not a simple one. So will work through what happens. Water flows through a pipe at temperature X. The temperature transfers to the screed or concrete in a uniform manner, up, down and sideways until it meets a thermal resistance. The resistance could be heat flow from other parts of the pipe, insulation or the floor surface. The further the heat has travelled away from the source (the pipe wall) the lower it's temperature as the heat energy spreads outwards from a small pipe. A water pipe section will interact with the other parts of the UFH array. So for well insulated modern house. 1. For a given flow temperature, say 30 degrees, with dT of 6, mean flow temp is 27 degrees. This is around 20W/m2 output to the floor. Floor will have a surface temperature between and 3 and 4 degrees warmer than the target room temperature. If you have insulation above the floor surface the heat transfer to the room is restricted. Move to point 2. 2. A heat pump will modulate it's output to keep return temperature stable, but also to manage a fixed dT and maximum preset flow temp. Once at maximum flow temperature the heat pump will modulate output to its lowest point for a given flow rate, then dT reduces between flow and return, over a period of time (minutes or hours) below its minimum preset point, the heat pump stops adding heat (it's compressor shutdown). Move to point 3. 3. For a given heat flow into the floor (product of flow rate and dT). The more restrictive the surface finish is, the more difficult the heat transfer mechanism. So instead of transferring the heat from the pipe, to the floor, to the room (heat flow is restricted by floor covering), the return flow temperature stays slightly warmer, decreasing dT quicker than normal and shutting down the heat compressor sooner. Less heat is actually transferred to room. To compensate you either increase flow temperature or you accept a cooler room, as in the case for our bedrooms. Add a 4 port buffer, you could easily be flowing 5 or more degrees hotter than you thought you needed. Also if you are running zones and on/off timings, these all add to a rubbish CoP.

People think that MVHR is the best and only solution, but you need something fit for purpose above all. You already have trickle vents, but they are rubbish on their own, they rely on a fan somewhere else. To give room/house cross ventilation. dMVHR units are only any good in a single room, unless to get the forward reverse ones in pairs. The prices start to stack up really quickly. My view is this Replace trickle vents on all windows with humidity sensing units, these are closed or open in response to humidity being sensed in the room. Then either dMEV in the wet rooms or MEV. MEV again you get or specify you want humidity sensing extract terminals. The above will give you ventilation only when and where needed. Look in the ventilation section on here, loads of stuff there on design.

We have a mix of oak floor, tiles and carpet. The carpet is very insulating, so much so, that very little heat escapes to the room. To make it work you need to run higher temperatures. But they are bedrooms so we don't bother. Anyway back to your question, to get past the insulating effect are you running a higher temperature than you expected? If so you will be getting lower CoP and have higher running costs. Having a 4 port buffer with a good amount of mixing going on, will make make matter worse. So need more info really on the full system your running temp etc

Insulated plasterboard inside the walls? No undoing or redoing work.