JohnMo

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.

What goes up, must come down. Was involved in an offshore wind farm and it had an onshore sub station, the noise at the sub station had been attenuated really well, but the village about 3 miles away had a nice focussed beam of noise coming down on them, apparently way noisier than you would have expected, anyway £1 million pounds later they had it fixed.

A crankcase heater is generally in the 50W so 50W/h or so. But if it's about 5 degs or below then and water temp has cooled within the heat pump, it may be doing antifreeze cycle of the heat pump, it starts the circulation pump and could also start the heat pump to input heat into the system?

The amount of frosting is directly related to the flow temp of the water and outside temperature. The more work you ask the heat pump to do (i.e. hotter flow temperature) for a given outside temperature the more likelihood of frosting up. So as @ReedRichards says perhaps the WC is just set wrong.

Starting to come to the conclusion, I either leave as it is; a wireless on/off switch, or I need to run a external cable.

Outside observation Sounds like a pretty big ASHP you are looking to install, could your efforts be better spent making fabric improvements to the house so you could install a way smaller heat pump and get down to single fan unit? Also without very careful design your proposal could end making the noise worse, rather than better, and end up focussing the noise in a single direction. Choose make or model of heat pump also makes a real difference in noise production and how annoying it is to othes.

Different sheet of paper, with different tick boxes. Can't get away from those tick boxes.

Never really understood why anyone goes block and beam for anything. Cold breeze under the house when ever it's cold outside. Maybe a good reason, but I wouldn't.

1. At any high point where air can accumulate. 2. As long as it becomes a new high point, pipe always slopes upwards to vent point.

Have ASHP and cylinder, currently operating on an on/off signal from thermostat, with a signal being sent wirelessly. Want use the digital input terminals on the heat pump for a different purpose, so need to connect a PT100 probe. Does anyone know how I can transfer a PT100 probe output wirelessly to the heat pump - is it possible. I have home assistant if that's any help

I have two very different spaces to heat, the house and have UFH in the summer house (it is used most days by the wife) the UFH manages the min temp set point (10 deg), a direct electric heater does the rest. If I batch heat the house overnight I end up spending using the electric heater to keep the summer house above 10 deg. My heat pump has minimal inputs similar to @jack. But I do have a double set point input - unfortunately it's a multi purpose input and I use that for cylinder heating thermostat call for heat. Last night, on cheap rate, I used the immersion to heat the cylinder as a trial, cylinder was at 48 degs this morning and heated in 45 mins. So that works ok. I have another option to connect the cylinder via a PT100 probe, but is just about impossible to route the cable, so would need a wireless option (new thread I think). That would leave the dual set point connection open to use. So dual set point - have one set point set high to batch charge the floor, once up to temp use the thermostat to switch to the lower setting and ASHP circulation pump would continue, but as the flow temp would be pretty high the ASHP would be unlikely to start up, summer house borrows heat from the house.

We have a slab below the insulation for structural reasons, so cold pipes are within that, zip tied to the rebar. Used flexible conduit over those pipes. We only have one electric cable in the floor to our island, this is in our top slab with the UFH pipes, that was in solid 21.5mm plastic drain pipe.

The simple answer is, there is no simple answer. Every house is different Nd every owner has different expectations of house temp. Generally good rules are 1. Always flow from the heat pump at the lowest acceptable temperature. Acceptable meaning gives the house internal temp consistent with your expectations. 2. Run heat pump for long periods, this goes with 1. allowing low flow temps. 3.Try to have house at a consistent temperature, don't allow to cool down to much, if you want it cooler at night only set back the temp a couple of degrees, otherwise the heat pump can't catch up with heat demand. Weather comp allows point 1. (Lowest flow temp). Fixed temp maybe not, depends on the house time temperature constant. Normal house with rads or UFH weather comp.

Flick a switch changes ASHP from heating to cooling. Just set to run at 11.5 degs, (no condensation seems to form at that temp) run at times likely to have a decent amount of solar. Need to automate it for next year. Have home assistant and solar forecast already built in. So thinking, June to Aug, if solar forecasts X kWh forecast the smart relay switches on heat pump from say 10am to 5pm. It's not fantastically effective, but does knock the excess heat off - solar gain only reason we get hot inside. It's all run on excess PV, so cost is basically zero. But get your point on a fan coil. Our outside temp rarely goes above 25 degs, so EER is circa 6 while cooling.

He is wanting the heat pump to output a higher temperature that it's currently programmed to do. So instead of flow say 30 degs, increasing to 32 during cheap rate. Lexone will manage house temp, not flow temperature.

So have just adjusted stuff, upped WC curve up a couple of degrees and set thermostat to 20.5, so it controls the temperature, have set it at 20.5 from 0:40 to 20:00hrs. Our PV diverter has a built in boost timer, so have set immersion on timer overnight during E7 hours for four hours. Tonight's temps very similar to last 24hrs, i.e. sub zero, so can compare usage day on day tomorrow evening.

Heat pumps even quite basic ones, normally have a dual set point option, that is selected via an open/closed zero volt switch. Dual, or double set point have seen in lots of manuals. Normally need an external switch or relay to operate. If you have a simple time switch or smart relay - done. Like this one also.

I have a thermostat, but could just as easily be a time switch as it does little or no temperature control. That's it a 3 way diverter to the cylinder or UFH, no buffer. Any cooling is done via UFH circuits. All done via WC. ASHP modulates it's output based on return temperature without any interference from me. Are you sure you need 9kW with a 155m2 house?

I got them from a local blind supplier, since I wrote the above, I have charged once. They are used almost every day and go up and down on demand no issues.