JohnMo

You quote people to ask other questions or clarification, so it does help

One of the reasons I went for 300mm centres so I could run without mixers. My floor needs approx 32 degs at -9. Go for closer centres, you get to the point where @Nickfromwales comes from. You need a buffer and mixer. So you charge the buffer at minimum acceptable flow temp and then let down the temp to cluster to 20. The other way in milder weather, run heat pump at the lowest temperature that gives you acceptable heat pump behaviour - so about 25 degs and shut the heat pump off once house gets to a defined temperature. You use the thermostat as a energy manager not a comfort thermostat. So set point is just above your normal WC room temperature.

@jimseng not sure how you are doing your quotes but no one gets notified without the user name being included.

Yep Yep

We asked all the contractors at site, how good there signals were, most rubbish, except Vodafone, which was great.

Mean flow temp give an output approximately, if well insulated it's close enough to get you started. But surface temp and mean flue temperature are very different animals. You can have a mean flow temperature of 30 degs and wide pipe spacing and deep screed and floor temp may only be 25 or less. Another attachment is a simple to read graph for screed floor, if you have carpet the tog value will downgrade the W/m² output, tiles little or no effect. No why would you flow at that temp for an output of 370W, your mean water flow is going to be sub 25 degs. Just read off the attached graph for you pipe spacings and output - use a streamline between pipe spacing and go through W/m² to get mean flow temp. Carpets without major care can kill the floor output, especially at low output. If you want carpets get radiators. Or be prepared for poor outputs.

Interesting fact, datasheet says at 30 degs and 2 degs outside the max output is 4.3kW. However if you enable smart grid and use SG1 settings the ASHP pumps out 6kW, while giving a CoP of around 4.5. Reason I did this was to heat the summer house to a usable temperature.

They need line of sight to work well. I would just do 4G/5G if you can. I am on unlimited data for £15 per month.

I would actually step back and ask why? Does your room have adequate ventilation? Above 60% Humidity: In a typical room (20°C), the dew point is approximately 12°C. Since your water is much colder (6°C), heavy condensation is guaranteed. At 50% Humidity: In the same 20°C room, the dew point drops to roughly 9°C. While lower, it is still above 6°C, meaning condensation will likely still form, but at a slower rate. Below 40% Humidity: To completely stop condensation on a 6°C pipe in a 20°C room, you would typically need to lower the humidity to below 40% (where the dew point is roughly 6°C or less) So I would be looking to fix your ventilation, not faffing about with hot water - then your issue will disappear. And you will have a healthy indoor environment as well.

That's easy - but when there are more than two in the house, almost never happens.

We my break it - lets hope not

I would expect seals within the system to complain and not last long with hot water. But @ProDave say 6 lt isn't much draw off from your cylinder - if it's a combi no hope, you'll just use gas and still fill with cold water.

Not sure how useful that is in the real world. I currently have my compressor restart hysterisis set at 4 degs, any lower than that you don't get a successful restart because floor slab has then equalised in temperature and the heat pump has no where to dump the heat. So at a flow temp of 20, in real world you need what ever you are heating to to drop temperature down to 16 - that just will not happen. My WC curve calculation says I need to flow 22 degs at 10 OAT, but I think realistically I may need to set a higher temperature. It's programmed like that for now, if we get a mild day any time soon I can test it. I always find ensuites difficult to heat. We have the bedrooms cool, so heat from the ensuite just bleeds onto the bedroom. But even at around 20 they are comfortable as floor is radiating heat at you anyway

Didn't say it couldn't control well with silence - it can, but you still have flow temperature distortion. That's ok in a mixed system with a reasonable flow temp difference but not in one with only a couple of degrees. Electronic offer zero distortion if you want it, so radiator demand goes, electric mixer become an open piece of pipe.

I posted the information you need, last night so you missed it. I used one, it's same in many respects to most mechanical UFH mixers it requires a minimum (always on) mixing, so there is always temperature distortion through the mixer. You try to regulate this with various internal adjustments but it's always there. You're sounding like me.

Low flow temperature makes little or no difference, what layout you do, as dT for loops is so low. It's currently 2 degs outside and on 300mm centres our flow dT is closed to 2.5 degs. Our pipes are 100mm down, so by the time the heat has migrated to the surface, there is very even surface temperature. I have just up and down pipes, nothing fancy.

We all want that - in our dreams, you can 1 or 2 of your choices - never all 3. Unless you move to another country (not inside the UK)

UFH design get a a free trial version of loopcad, do your own design. Design by room heat loss and balance system out of the box by loop design. Keep everything simple. If you only want heating downstairs you need to design heat output to meet whole house heat loss. Some are ok with that, some hate it. If you have a big hall upstairs stick a big radiator or two and run at UFH temps, if room are a little cool you just open the doors and let some heat in. If you like warm bedrooms you may need heat in every room. But everything needs to sized correctly. Smart homes crap and heat pump is a utter waste of money and effort. Not needed will not help anything. Sorry to be blunt and to the point. Either run WC or a simple centrally located thermostat to drive heat pump on and off (if you do this you also need to run a hotter flow temp so get slightly worse CoP/running costs). Pre plumbed cylinder is an utter waste of money - as 90% of the equipment on a pre plumbed cylinder isn't really needed.

I have two Titon units, without preheat, they just slow the incoming air fan, if it detected a freeze condition is likely and then once cleared back to normal speed. We have seen -9, we are only 6 miles from the coast and have a lake in front of the house, so the worst conditions for freeze up. No issues after 5 years. Would recommend looking at Titon HRV, British made with direct phone support, should you need it, spares are readily available if you need them. Can be as simple or complex as you want.

Just use immersion, I wasn't for it a couple of years ago, but tried it a few months ago (after plenty of here say they heat water that way) and overall my electric consumption hasn't jumped up much. Heavy water use day I use more electricity, low use days, I use less. Latest crop of R290 ASHPs, more or less all seem to do it.

Something like an ESBE VRG valve and ARA600 actuator. Not an on off actuator. Your flow temp difference between GF and FF is only going to b e a few degrees. Lets say 5 degs. GF wanting say 25 and FF 30 degs. ASHP pushes out 30 degs, the electronic mixer just mixes down to 25 degs for GF. This flow temp changes based on outdoor temperature. No robot needed, no 1-10V signal needed.

Almost all currently available heat pumps do this out the box - you only need one mixer for the lowest flow temp zone. Shouldn't need a volumiser either, unless you over sized the heat pump. Basically work on the basis of 20L per kW minimum output, system volume, if you achieve this no volumiser is needed. Complexity - a temp probe down stream of mixer, connected to heat pump control/wiring centre. 3 wires to mixer from same control/wiring centre. Set controller to two zones, set the two WC curves, job done.

Or let the ASHP controller do the work, two zones, so two WC curves, controller can use an electronic mixer, such a an ESBE, the ASHP controls flow temp to coolest flow temp, no buffer needed, no temperature distortion, no additional pumps. Just run as fully open system with two flow temps, one unmixed and one mixed.

Here are couple of documents to get you started UFH-System-Design.pdf UFH output calculation.pdf

Simple answer you ASHP company should do this for you. They need to do a room by heat loss calculation anyway. They will know the UFH design, because you will pass it over to them. They will then be able to state at design temp the flow temp. Flow temp required will also vary with a screed depth and floor make up insulation etc and floor covering. So a little fine tuning may be needed.