JohnMo

https://acwservicesltd.co.uk/electrical-services/solar-assisted-heat-pumps/

Thermal Mass is just a common way of saying thermal capacity - The SI unit for thermal capacity (or heat capacity) is, joules per kelvin (J/K) or joules per degree Celsius (J/°C). Heavy stuff like concrete the value is high, air the value is low. But Harris and Steamy through the teddy out the cot because it "Not the Correct term" to use, but ha-ho. They exist in science they are just taken from a differing view point, an example cut and paste The centripetal acceleration is the acceleration a body experiences in centripetal motion (moving in a circle or along an arc). Centripetal acceleration always points towards the centre of the circle, hence the direction of the moving body is constantly changing (since its velocity is always tangent to the circle). On the other hand, the centrifugal force is a fictitious (imaginary) force the object experiences during circular motion. The direction of this force is opposite to the direction of the centripetal acceleration. The best example to visualise this difference is to imagine being in a car. If the car takes a sharp left turn, the passengers experience a thrust towards the right (the centrifugal force), whereas the friction between the road and the tyres results in the centripetal acceleration allowing the turn to take place. So they are equal but opposing forces.

Video -

Exactly the same a solar assist heat pump outdoor condenser, but indoors

Once compacted it's just very thin insulation, with same thermal properties as thin insulation - it has zero reflective properties without an air space to reflect into. Would use any other insulation than this. If it's first floor just 25mm EPS or XPS.

What boll0cks. I'm running pure WC. Have run WC, thermostat mode, batch charge mode and hybrids of all three. You could set target flow temp to 35, I've done that also. But ASHP just runs full load with zero modulation and will most likely never get there before the thermostat trips out. You get best CoP at a medium load position, so you want the heat pump to hit the target temp and then take control and modulate down. Any UFH with a thick screed, the floor is the dominant force, its temp dominates return temp, return temp dominates max flow temp achievable. Simple science, not because it works for me. Many on here run a thermostat based system, its just a matter of setting the lowest flow temp you can get away with not the maximum.

Because your system and house should run at that min outside temp. So run will be proportional to outside temp. Cold day run all the time, 10 degs for a couple of hours. Lowest temp to do that and get best CoP

The other acceptable running mode is pure thermostat, set a fixed flow temperature of 28, still run as a single zone. Your thick screed will demand very long times and at that temp CoP will be great.

The assumption is incorrect though. Open window you let cold air in hot out, but the thermal capacity of air is very low, building fabric the thermal capacity is very high. You close the window, the air within the building is reheated by the now warmer fabric (especially the floor) pretty quickly. You floor will not lose heat for many hours/days even with heat source off.

Some simple science Your floor even on a dull day will not be much hotter than the room, maybe 1 to 3 degs at the surface depending on outside temperature. Let's assume room is 20 degrees, floor surface 23, sun comes out room increases to 23. Now as floor is 23 and room also 23 the floor no longer transfers heat to room. Sun goes away room temp drops, floor starts giving heat to room. With a thick screed (think you have this) the floor just acts as a huge buffer for energy. Thick screed doesn't act like a radiator due to its thermal capacity, think more a swimming pool, once up to heat it isn't cooling quickly. Once you allow to cool it takes an age to heat up. Setting up WC is pretty easy for UFH, start with a gradient of 0.5. so every degree outside temperature drops you increase the flow temp 0.5 degs. Start with a flow temp of around 20 or 22 at 10 degs and 28 to 30 at -5. Ideally let it run for 24 to 48 hrs. Adjust curve up down to suit. Small changes have a big change. System doesn't need to know internal temperature. You set the curve to balance heat loss and heat input. You better starting cool rather than hot. WC is completely open loop.

That's what they have now!!!! 🙄😉 No, it's run on WC, not fixed flow temp, so fixed flow temperature would be completely different, may need a buffer if you are messing flow with TRV etc.

So you are saying to run everything at a fixed temperature, with TRV's on rads and how are you managing UFH room temps, thermostats?

Sounds like loads of PV, battery and generator is required - if you an get mains gas run the generator from that, exhaust heat exchanger, to do the heating while generator is on. And some batteries.

That's a good spot - even Cool Energy say it's a mid point valve

Then don't ask questions you don't want a truthful answer too - which isn't what you want hear!🫣

Email them back and state what you did, they will update the U values etc. Then if you get a fail, get ready to install solar PV to make up the difference.

You have a Vaillant heat pump, I would just install an ESBE electronic mixer (VRG valve and actuator) at the UFH manifold (you won't need an additional pump). Set the controller to do 2x zones, each with its own WC curve. The zone for the UFH, the Vaillant controller will control the ESBE mixer as needed to follow your defined curve. What will happen is if the radiators call for heat heat pump runs at higher temp and controls mixer to UFH. If radiators aren't calling for heat the heat pump will reduce flow temp to satisfy UFH demand only mixer will be fully opened. I wouldn't add any zone valves, leave the radiator alway open and when they don't need additional heat they run just like they are now and it keeps the water volume engaged and full circulation path for flow rate. IVOR mixers are great, but you then need to run the UFH off thermostats, as it will receive a fixed flow temp and you always need operate the heat pump at radiator temps.

Plumbing wise nothing looks obvious. UFH manifold flow meters, do you have those fully open? Fully open allows the heat pump to vary the circulation pump flow to better manage modulation. Your circulation pump doing DHW is most likely running full speed, so 20+L/min. If you have the flow meters screwed down to 1.4L/min you flow will be hitting a brick wall with a small hole in it. This could be the reason for the thump on change over also.

Had a look at mine, and pump doesn't shutdown, it may slow down but doesn't stop. As the paddle moves it doesn't cut flow off, flow basically transitions from one port to the other, with both ports open until the DHW port closed. Assuming the UFH manifold is fully open it shouldn't see an issue. Do you have the piping all clamped up as it should be? No air in the system? If it's water hammer, the pressure wave need something to hit, and bounce back. A photo of the valve and the piping to UFH may help. Assume you don't get any fault codes?

I would look how this is reflected in room layout, some rooms may only need straightening out with self levelling compound, others may need way more, it also depends on the area of the floor how much needs to be corrected. We did all the correction that was needed a short time before floor covering went on.

How are you controlling the 3 port valve and pump - is all via the heat pump controller or something else? What valve are you using?

Did you finish this after topping up system pressure?

Woke this morning, after thinking I had a stable system, with flow temps bouncing about. The bouncing occur soon after a temp drop overnight. System currently looks like 4kW heat pump at min modulation 1kW, UFH with single fan coils (60L), volumiser (50L). UFH is within 100mm slab. Previously 6kW heat pump and at min modulation 4kW, the rest the same as above. For my previous heat pump volume was king to cycle control. Current setup not sure the volume adds anything positive, it adds to system inertia and leads to slow feedback to heat pump. Think the control system is looking for a more timely feedback to changes to running parameters. The thick screed, big water volume (via the volumiser) adding too much delay to changes, such as return temp staying stable for too long after a controller input, so control throws out a further command, feedback comes back (late), so the controller keeps over compensating. We get a yo-yo as witnessed. Luckily the volumiser is easy to bypass, so this was done earlier. Within 5 mins of the change, the flow/return and power input became very stable. Looking at yesterday and todays day time temps they are almost the same, but CoP has jumped from 5.2 to 5.4 during steady running. Will see overnight as temps swing about outside, if this has calmed the down.

Then once all working again, inhibit system with heating system inhibitor and biocide (same brand and type as previously used). Or if you have glycol, add glycol to the correct ratio.

As a country we seem to do A or B, it all too binary. Heat pump or gas, best bang maybe hybrid for a lot of the existing housing stock, 90% of the time running a heat pump, almost zero plumbing changes. Oil & gas, yes or no, we close refineries, export what we produce, then buy it all back at inflated prices. We just import a pretend net zero from somewhere else. The politicians all need a good sacking and be replaced by people with common sense.