JohnMo

Heat pumps stop and start heating just like boilers do, but the circulation pump continues to run. Controlled stop starts of the heating cycle are fine so a run time of circa 10 mins or more is fine. Anything shorter is short cycling and wastes energy. The working volume of water is the prime reason for ok cycling or short cycling. Various formula are available to calculate the min working volume and cycle times. So if you are heating rate is fixed, the more water you have to heat the longer it takes. So can either install a buffer or keep system volume engaged by have a single or a couple of large zones.

Yep no issue. We did our finished floor before the walls got built. A few low spots were sorted with a few bags of self leveling screed.

Or simpler, cheaper is to keep radiators or UFH loops engaged to match the ASHP suppliers min water volume. So a 5kW ASHP even without modulation, with about 50L engaged will be quite happy and not short cycle at about 0.5kW heat demand.

Heat pumps are rated and sold to suit the supplier. They always produce loads of heat when it's warm, which diminishes as the OAT drops. This is why they (MCS and others) say size for 99.6% of the year. So you are not oversizing. Oversizing is never an issue when it's cold, but is an issue when it's normal winter temps sort of around 5 to 10 degs. You need way less heat, but your heat pump is producing way to much power even at min turn down.

Your pipe surface temp is say 25. This heat dissipates outwards (up, down and sideways). At 200mm centres, this heat transfers out sideways 100mm, it will never get to 23 as a 16mm pipe is the source of heat. The further from the heat source the lower the temp. The concrete in the floor is pulling heat and spreading it out over a much bigger area. The heat continues to be consumed to make up for the house heat loss. It's a bit like standing in front of a radiator its hot, take a step or back you don't feel the heat - it's still there just spread out.

I suppose going back to my previous post about cool energy, at least the advertising is clear about modulation. @JamesPa have you asked them (Cool Energy) about a heat pump, as with another thread they do MCS installs and seem amiable to a different approach?

So in practice does that mean they really just change the running speed to get different capacity ratings. So although they could be the same unit, the 5kW would near silent, the big one not so? Or is it the small one has next to no modulation, while the big one can modulate down to about 4 to 4.5kW?

Mine starts to expand out as the temperature increases - only a degree or so, as it goes from 35 to 60. Plus DHW flow ramps up to manage dT, it isn't a set temperature, as dT decreases, the heat pump controller increases flow temp to a managed dT and provides variable flow temp (slowly increasing as it moves through the heat cycle). Once flow hits max temperature the heating cycle is stopped, it doesn't stay there it stops, because it's ran out of control of dT.

That's all to do with energy flow through the floor. Nothing to do with solar gain. You are heating lots of tonnes of concrete, which in turn gives heat to the room. If you let the floor have to much heat, it takes for ever, for the heat to be given up and the room continues being heated. Same when the room is cooling, by the time you have lost 0.5 deg in room temp the floor is way to cold to react quickly, so the room continues to loose heat until the UFH has caught up. Solar gain - If your room temp is targeted at say 20 deg, the floor surface temp will be in range of 21-23 deg. If you get solar gain and the room starts to exceed 20 degs, the floor to room deltaT reduces, so the floor gives off less kW of heat. If the room goes above the floor temp, the floor stops giving of heat and could start to absorb it. A thermostat does nothing to help control solar gain.

Maybe I'm reading it incorrectly. Makes sense that it's min max modulating range

Cool energy already have that built in to their range of heat pump, with plenty of overlaps.

Room may not need UFH in it if lots of UFH pipes already pass through that area. For example our utility has the manifold in it so has no dedicated UFH loops, same with the hallway. If you have a DHW cylinder in the utility, again no need for UFH. Have seen plans with UFH in a plant room, plenty of heat there already without adding more. Hysterisis is the off set between the set point and reaction point. A 0.5 deg hysterisis with a set point of 20. Will switch off the heating at 20.5 and back on again at 19.5. Now concider your floor will take circa 12 hours to change room temp 1 deg. So a normal hysterisis thermostat is just too slow. Room temps will vary by 3 to 4 degs which is less than ideal. We started with a 0.4 hysterisis thermostat and that just didn't cope, so upgraded to 0.1. Have you thought about cooling, you may not think you need it, but can be a zero cost adder with the right ASHP. Ruining cool water through the floor loops certainly helps in summer, if you have PV running costs can be close to zero. We added 1kWh to a our daily electric bill having cooling on from 8am to 5pm.

Looks a big heat pump, your floor is a similar insulation value to mine, I am in 100mm concrete. I just have 7 loops in 194m2. Pert-al-pert, I have found a little easier to install than pex-al-pex. I would suggest you look at the thermostat hysterisis, you need one with a very small hysterisis, with a thick floor, otherwise you will get wild swings in operation if the thermostat ever works. I'm using 0.1 deg hysterisis. You will need to take a look at how the rooms are mapped for UFH - do all rooms need it etc.

The thermostat calls for heat, this should send a signal for the boiler to start and also tell the pump to start. When there is no call for heat the boiler and pump should be switched off. Within the wiring centre there should be dedicated connection for the pump. If remember correctly pump has a slight delay in starting after a call for heat.

That's a lot of pipe in the floor. It may be worth putting up you favoured plan for some feedback. Would be worth adding floor area, floor buildup and heat source. If you know the building loss that is also benificial.

They all use standard programs and it's rubbish in rubbish out generally. Fill the whole floor space with pipes, the variation will possibly be pipe spacing, or how they have laid the pipes out and run lengths. I assume you have UFH on ground and 1st floor with all those loops?

This is the manufacturer drawing of the install - below The pump to the panel is flooded, so has to suck from the bottom and out the top, it cannot pull down as it would immediately get full of air. At shutdown all panel water drains back to drain back unit. At startup the water is pushed up through the panel from to top. Doing the other way round may have issues with the drain back system and would fall through the panel too quickly. There is little no flow through a CCT as it provides hydraulic separation. I didn't want flow through the circuit when ASHP is in cooling mode. With the pump I can control the flow rate through that part of the system also, pump at the moment is set to min speed, so when it's running only draws something like 5w. If it's adding an average of a kW when running, that's not bad. The main pump to the panel is set at speed 2, so draws about 30w as it's bigger pump.

If there any chance of rodents it stops them chewing through the insulation. Easy way to pull the joints tight. Doesn't look so scruffy when complete as no gaps or different colours. Can't see it reducing or increasing heat loss. Any heat at the surface is at one with the air around the lagging anyway.

Please see attached

Pipework all installed, couple of minor leaks sorted, system levels checked then piping insulated. Operating - Will coincide a legionella cycle within the ST controller with a timed heating cycle of DHW by the ASHP, and see how it goes. This will take return water from DHW heating, and add heat via the close coupled tee. For UFH I will run the ST as follows Panel temp 10 degrees above return flow temp back to heat pump, this allows for a temp transition cross the PHE within the drain back unit. With a Hysterisis of 6 set. This is simulating bottom of cylinder temp. Will heat the return flow via a CCT to a max of 35 degrees. This is simulating the top of cylinder temp. Wet and very cloudy here today, rubbish solar day.

Love to see anyone win that case in court, man tries to save planet, court instructs him to remove your heating, and install oil or gas boiler which by then are banned.

Exactly - my thoughts also.

Just over 3.4 and 3.1kW, one south eastern and the other south western directions. What's the o/p?

I saw a video of someone in the states doing the same. He just removed the fan blades and the coil temp sensors, moving the sensors on to the new coil. The remains of the unit mounted in the wall next to the cylinder.

Agreed, but the coil dia looks too big and too short. I thought they small dia and a quite a few meters of pipe?