Dreadnaught

Ah, @JohnMo, Google tells me you have a Viesman heat pump, possibly a "Vitocal 100-A" or similar? Is that so? Mine is a Vaillant Arotherm Plus 5kW. For the Arotherm, the circulation pump speed is effectively fixed (860 l/hr for the 5kW model) and there is a setting for the ΔT (albeit a setting that can only be accessed by an "expert").

Oh that's interesting, @JohnMo. Which manual is that? Its not in my manual.

Thanks @JohnMo I see the ΔT shown in your chart is about 3.5º. - Is your's set at the factory-default of 7º ΔT? - Would you be able to overlay on that chart a line for compressor modulation (%)? My theory is that, with the well-insulated houses that are common to those on this site, such heat pumps will hit their lowest-level limit of modulation for much of the time (which is 25% max compressor speed) because heat demand from the house is just so low. That includes yours during the period shown in your chart and would explain the ΔT.

I wonder how then is compressor modulation controlled by the system? A direct response to ΔT (within the operating limits of 25% to 100%)?

Thanks @IGP. Yes, I had read that post too. All very interesting. Another thing I have noticed is regarding ΔT. My understanding is that heat pumps generally target a ΔT of about 7º (or sometimes I have seen 5º referenced), which is unlike gas boilers that target something around 20º. However in @Dan F's chart above, the ΔT is just 2º after about 20 minutes of heating (24.5º supply, 26.5º return), which surprised me. Its just an observation and I am sure there is a good explanation for it. I wonder if this is just a consequence of the modulation flexibility of the compressor in the Arotherm Plus. The compressor can only modulate down to a minimum 25% of full speed, not lower. (I do note that the ΔT is user definable (setting "Compressor hyster. Heat." in the installer-level heat-pump controller settings.)

@Dan F, as an amateur non-engineer, I have been thinking deeply about the control system for the Arotherm Plus heat pumps. This thread, and your graph above in particular, has been helpful for me. I wonder do you happen to know whether "Hc2ActualFlowTempDesired" is targeting the temperature of the flow to or return from the home? I could imagine it being either.

@Post and beam, I have used that manifold on the supply side of my system (on the return-side, I use a smaller Ubbink manifold). These manifolds come with sound attenuation sponge pads that are inserted inside. Before the manifolds, on the larger diameter ducting (160mm Aerfoam) connection to the appliance, I have in-line flexible sound attenuator on both supply and extract. My system is effectively silent from the bedrooms. It is performing very well.

3.1m x 1.3m. Feels generous. One end has MVHR. The other end has cylinder and heat-pump internal bits. Will use some of the space for storage with wheeled shelving units which I will push around as needed and even remove if I need to access something big. A flexible space. (Personally I wouldn't put any type of house battery inside the house. Precautionary principle.)

In case anyone else is not familiar with "VDI 2035", as I wasn't, this is a good quick intro… https://www.heatgeek.com/heating-water-treatment-explained-vdi-2035/

Very interesting. How is the filter fitted? Do you just remove the valve and the filter wedges between the valve and the valve adapter? With my Ubbink/Brink system, the valves are quite difficult to remove once fitted. Is that a problem for you when changing the cone filter? Are these the cones… https://www.aliexpress.com/item/1005006704266648.html

Hi @Barnboy, I am afraid I don't know, sorry. This is my one… https://underfloorparts.co.uk/product/ivar-uni-mix-underfloor-heating-ufh-pump-mixing-kit-underfloor-heating-manifold-control-unimix/

Of any interest? Still available.

I wonder, are there prescribed widths or depths for a channel so as not to need to de-rate an electrical cable for being inside insulation? Nice video.

The owner of the team who poured my concrete raft was well known to be wealthy from his trade with properties owned abroad. One of his team was originally a chippie. He eventually left to join a team of small-scale house builders. Within a a few months he had convinced his new colleagues to down tools and take up concrete pouring as a means to make much more money.

(A few other disadvantages of pocket doors: (i) they tend to negate the acoustic insulation in the wall that is the pocket; (ii) they are slow and more cumbersome to operate, so better suited for occasional use.)

Welcome @G and J. I am across the border in Cambridgeshire and have a brother soon to be rebuilding anew in Suffolk near Beccles.

For peace of mind, personally I would want the intake up-wind unless the separation was say 3m or more. I would not be too concerned about duct resistance assuming you're using big fat ducts. My MVHR uses external insulated Ubbink foam ducting that is 160mm internal diameter (190mm external diameter), which is comparably huge. The resistance is such ducts, which falls by the square of the diameter, is quite low. I roughly calculated the internal flow rate within those ducts in my case to be 1.9 m/s (2.1 m/s on boost) which I considered acceptably low and should not cause problems of either pressure-drop or noise. You could do a similar calculation.

Best to put the intake upwind from the exhaust relative to the prevailing wind direction for your location (usually westerly in the UK). And ensure the intake and exhaust are both on the same building elevation to ensure even wind pressure between them. Separation: I would suggest 1.5 lateral metres minimum if you can.

@OwenF , ceiling mounted solution: no. I redesigned the kitchen and have moved the hob off the island, which makes an extractor much easier to design. I will be building it within the next 6-months. If I had kept it on the island, I would have chosen a downdraft extractor, albeit I think they are flawed in terms of effectiveness given that hot gases rise and fast.

MVHR: ensure the intake and exhaust are on the same face of the building so they are exposed to even wind pressure.

Can you find a similar door or window which is PAS24 and is similar, provide that certificate to your building control officer while explaining that your manufacturer no longer exists. I had an issue with a window being larger than the size that was PAS 24 certified by the manufacturer, and so in the strictest sense lacked PAS 24 compliance. I provided a copy of the PAS 24 certificate for the assessed size and explained the situation. My local-council's building control then said it was fine.

Timely post for me. Reinforces my idea to double-up the heating in my place under construction; am at first fix. I have wet UFH and am planning to install electric-mat UFH too on my two bathrooms, probably under LVT flooring.

I have screw piles and was advised when doing mine that this form of piling (as it does not remove any soil as such) did not trigger the Party Wall Act. My piles produced almost no vibration so it sounds like yours are not screw piles. And if yours are not then there is a good chance (as described by others above) that the type of pile that your neighbour is using may well fall under the Party Wall Act. In which case you would have plenty of powers to respond.

@HughF, that's interesting. Do you know the approximate volume of your system? Mine will be about 95 litres. It will be a similar open-loop system to the ones in this thread.

Yes, rather concerning. The "Mira Flight" tray comes in a few different forms. I was intending to buy this version below. But am now unsure. Such poor basic quality control is rather damning. Source: https://www.screwfix.com/p/mira-flight-level-safe-rectangular-shower-tray-white-1200mm-x-900mm-x-25mm/250hr