Jeremy Harris

Bear in mind that smart three phase meters will almost certainly record kVA, rather than kWh. I strongly suspect that what you hope for, the offsetting of current export in lightly loaded phases against current import on a loaded phase, will be (quite reasonably) penalised by the supplier (as the local grid has to be reinforced to allow for imbalance). Single phase meters (at the moment) only measure (for billing purposes) kWh, not kVA (although some can record kVA). Three phase supplies for non-domestic use have pretty much always been billed in kVA, hence the reason that most industrial three phase users incorporate some form of PF management.

I believe that they've just had to move some Freeview multiplexes, rather than delete them, so a retune should get the channels back (assuming that the bandwidth of the aerial is wide enough). Freeview was a bit of a disaster for us, as it meant we lost all access to terrestrial TV, when the old analogue service was switched off. The flip side is that we were forced to switch to Freesat in order to continue to receive free-to-air TV. That turned out to be for the best, as the quality of signal, and resolution, we get from Freesat is very good indeed.

Best to fit the silencer as far away from the room terminals as possible. The normal place for them would be within about a metre of the MVHR unit, as that's where they are the most effective.

A three phase inverter will always export evenly on all three phases. If, say, the PV system is generating 9 kW, then the inverter will be exporting 3 kW on each phase (doesn't matter what sort of meter is fitted). Therefore, if there is a load on, say, the brown phase, then that can only be offset by the generation on the brown phase. The export on the black and grey phases will just go through the meter to the grid without being offset by self-consumption on the brown phase. Because the house will have to be wired as single phase on each floor, it's unlikely that it will be practical to arrange to load all three phases equally, in order to be able to make best use of the generated power at any instant. The only time that all the export will be able to be offset would be for a 3 phase load, as that will be drawing power equally from each phase.

Silencers may not be insulated, as the absorption layer tends to provide insulation. They are typically around twice the diameter of the duct, though, so should be noticeable.

I suspect that Grenfell has raised the profile of external fire resistance just a bit. Our build is wholly timber clad and has no fire protective coating to any of the timber. At the time, our BCO was content because all the walls were more than 1m away from the boundary, and maybe 10 to 20m away from any other building.

Are there silencers fitted to the main duct connections to the MVHR? Silencers look like this, typically: https://www.bpcventilation.com/attenuator-silencer The length of flexible duct (the silver stuff) isn't ideal, as in general it tends to impede flow a fair bit. It may be that, if your system doesn't have silencers fitted that the impeded flow from the bit of flexible duct is working as a bit of a silencer. All MVHR ducting, except for a short length coupling the MVHR to the four main ducts, should either be rigid or semi-rigid, not flexible. Short lengths of flexible duct are normally fitted to the MVHR unit in order to reduce noise and vibration transmission to the main ducts in the house.

That's OK, it's just that some seem unaware that UFH is always less efficient, and wastes more heat, than any heating system that doesn't directly heat an external surface. It's also quite limited in terms of heat output, as the heat losses to the ground rise dramatically as the floor surface temperature increases, plus there's an upper limit on heat output imposed by the maximum floor surface temperature that can be achieved. This tends to be a particular issue with older houses, that often have a high heating requirement, and has led to some finding that UFH just cannot keep their house warm. Not something you want to find out after having had it fitted. We have 300mm of high density EPS underfloor insulation (λ = 0.034 W/m.K) and yet we still waste ~8% of the heat that we put in to the heating system, because of the losses down through the insulation to the ground beneath. If we had radiators fitted to internal walls then our heating bill would be around 8% less every year. We happily pay this premium for the comfort and convenience of having UFH, accepting that it's less efficient than some other forms of heating.

I used a λ of 0.034 W/m.K for the XPS, not knowing the exact product you used, and assumed that the underlying concrete floor was 100mm thick. Using a λ of 0.033 W/m.K gives a floor U value (as far as the UFH is concerned - there will be no surface thermal resistance to account for on the top surface for this condition and the underlying ground will be in close thermal contact with the underside of the concrete floor) of about 1.19 W/m².K, pretty close to the figure I used.

The issue is the much greater heat loss as a consequence of directly heating the floor to provide heating, so raising its temperature relative to the room. This significantly increases the heat loss. For example, if the house did not have UFH, then the floor surface would be a degree or two cooler than the room temperature, due to the heat lost through the very thin layer of insulation. Assuming that the floor surface (without UFH) was 2°C cooler than the room temperature, so 19°C for the example quoted previously, then the heat loss would only be around 13 W/m² rather than about 22 W/m². Increasing the temperature of the floor temperature, by fitting UFH, always increases the heat loss to the ground, hence the need to fit a decent layer of insulation underneath it to reduce the loss and so increase the efficiency of the heating system.

Have to add another ~22 W/m² to that figure for the heat wasted in warming the ground under the house, too, so the true heat input (what's actually being paid for) will be around 74 W/m².

25mm of XPS underneath UFH will give a floor U value of around 1.2 W/m².K, so with the floor surface at, say, 26°C, a room temperature of 21°C and an underfloor ground temperature of 8°C then the heat loss into the ground will be about 42%. 26°C is not a particularly high floor temperature for UFH, either. It equates to a power output, for the conditions above, of about 52 W/m².

I agree with @PeterW both from the sound and from the image it looks like that mushroom terminal is almost completely closed, hence the noise. If all the fresh air supply vents are opened a bit then the noise should reduce and it should be possible to turn the fan speed down and still get loads of ventilation. Having the vents closed probably explains the CO2 readings as well. Looks like the system was never properly set up or commissioned to me.

As others have said, glass is not a liquid and doesn't flow once cooled at all. Old window glass was never flat and uniform, we didn't get truly flat glass for use in normal windows until about 60 years ago, when float glass was invented. Before that date glass was often imperfect and of uneven thickness, and this uneven glass was usually, but not always, installed with the thickest edge facing down, as @Ferdinand mentions. Our first house had windows that had been installed in 1903 (after a fire) and the glass in those was uneven and slightly distorted, a consequence of the cylinder method that was used to make window glass. If further proof was needed that the "glass is a liquid" story is a fallacy, then a look at very old glass artefacts will quickly make the point. There are surviving glass bottles from the Roman period and none show any effect from gravity distorting the glass after they were made.

I've always had the feeling that the only reason that internet-type connectivity and protocols are being used to connect home controls and sensors is because there are a lot of people around who are used to coding for apps etc, so to them every problem looks like it can be solved with an app. There are other ways to do this, though, that are inherently pretty secure. I'm running a hardware focussed mesh network here, that uses a pretty robust wireless communication system. It's cheap and reliable, and for me, as a hardware person, it's easy to code. In around 4 years or so of having been working it's yet to crash or glitch, and comes back after a power outage within about 1 or 2 seconds. It can't talk to the internet, but only because I've chosen not to provide that capability. It could pretty easily serve data to some sort of web-connected device if needed.

I spent a week flying from a field near to @AnonymousBosch a few years ago. The field was full of sheep and they much preferred grazing on the shorter grass on the strip. They'd learned over time to wander off to the side of the strip whenever anyone was landing or taking off. The only exception I can recall is the strip's famous "jumping sheep", that allegedly leapt up and hit the wing strut of a friend's aeroplane...

I didn't get a mobile until 1990, but it did become a much-used bit of kit. I never went anywhere without it. That's gradually changed, though. First I started getting the feeling that the thing was dominating my life. My employer seemed to think that having me "on call" almost 24/7, without paying me for the privilege, was OK, and I started to resent it. By about 2006 I was getting into the habit of turning the phone off when I left work, helped by not being able to get a signal at home. Now I rarely ever turn the mobile phone on. We can't get a signal here and I really don't see any need for the thing. Since January this year I've made two calls on it and received one...

We have a couple that belong to this forum under the tool loan scheme: https://forum.buildhub.org.uk/forum/167-tool-loan/ From those figures it does seem as if the MVHR just hasn't been set up properly, something I suspect isn't uncommon, as it takes time to do it properly and it's a bit of an iterative process, as making big adjustments to one terminal can have a knock on effect to the others. There's guides as to how to set up an MVHR system here: domestic_ventilation_compliance_guide_2010_edition.pdf NHBC MVHR Commissioning.pdf

A CO2 concentration as high as over 1500ppm suggests that the unit may not be set up properly. As mentioned earlier, setting up and balancing an MVHR system can be a bit of a tedious process, and I strongly suspect that many systems are installed and never properly balanced. If this is the case, then there's a fair chance that both the ventilation may not work as intended and that the power consumption may be a lot higher. Blocked filters won't help, either. The normal outdoor CO2 concentration will be a bit over 400ppm usually, and the house should be sitting just a bit higher (ours is currently sitting at 439ppm, but the MVHR is on boost from cooking lunch). A CO2 level, with the MVHR running at the background ventilation rate and the house occupied, should normally be around 600 to maybe 800ppm (ours tends to sit around 550 to 600ppm with both of us in, but the house is relatively large for just two people).

As I previously mentioned, the pure economics don't yet stack up. We currently export more than 50% of the power we generate, and I can recover some of that (although not much in summer) for later use. The plan is to try to get the house to be off-grid, in effect, during the summer and for it to be as close to 100% running on off-peak E7 in the winter. The payback time is pretty much the useful life of the battery packs, but the advantage of having a reliable back up power supply if there are power cuts swings it for us. I've been looking at getting a reliable generator that could deliver around 2.5 kW or so, but can offset the cost of a decent generator against the cost of the batter system, in effect.

Still in the pre-delivery stage for the battery system, but it will be AC coupled and limited by the equivalent of a G100 relay to prevent export, so it doesn't (as I understand it) need any specific additional DNO approval. Three phase would be useful for a high power EV charge point, if you really believe that you will have a genuine need to regularly charge at home at around 88mph or so. I can charge at 7 kW, but never do so, as I've not yet had a need to charge that fast, and charging at a lower power (typically around 2.5 kW to 4 kW) during the day means that charging is mostly free. In the 8 months of so that I've owned an EV I've never had a need to fast charge either at home or at a destination, as the car invariably ends up sat at a destination charge point for several hours, often overnight, so 7 kW is more than enough. An EV capable of a 250 mile journey would need a charge time of around 9 hours or so at 7 kW, which is generally fine for an overnight charge. Also worth bearing in mind that not many EVs are capable of accepting a 22 kW AC charge. Mine can only charge at 11 kW from a three phase 22 kW charge point, although it will charge at around 50 kW or so from a DC charge point. The emphasis on car fast charging has shifted to DC, as the weight and volume of an onboard 22 kW AC three phase charger is a penalty that many manufacturers think is unacceptable, especially given that there are few 22 kW AC charge points around anyway. Be extremely wary of running domestic loads on different phases, as there is a high peak voltage between phases (415 VAC). For this reason, you would need to split out the house supply by physical area, rather than load, when arranging the single phase supplies from a three phase incomer. Typically this would be done by floor, so the ground floor would be on one phase, the first floor on another, etc. The snag is that this most probably won't come close to balancing the loads, as most of the high load stuff will probably be on the ground floor. I'm personally far from convinced that three phase makes much sense, unless you have a very specific high power requirement that needs it. The loss of offset from PV generation is a big negative - having a three phase connected PV system means you need to synchronise loads across all three phases in order to take advantage of the power being generated. This is easy enough to do on a single phase supply, but not at all easy on three phase. I would guess that you would end up "wasting" at least half, maybe more, of your generated power, and importing from the grid a great deal more to make up for this.

Probably the Pylontech battery packs and the Luxpower inverter, as it's an expandable system.

For a 175m2 house, the background ventilation rate, at building regs rate, should be 52.5l/s. If you count all the supply terminals in the house, and divide 52.5 by that number, that will give the average supply flow rate. So it you have, say, 8 supply terminals, then the average flow rate for the background ventilation rate from each of them should be about 6.56l/s. It's quite important that the fresh air supply rate for the whole house matches the extract air flow rate for the whole house. It can be a bit of a faff to set this up during commissioning, and I suspect that some systems are never properly set up.

The flow rates look pretty high to me. Do you know the volume of the house/rooms? Building regs require the background ventilation rate to be at least 0.3 l/s/m² of floor area, so the flow rate sum of all the extracts (or the sum of all the fresh air supplies - should be the same as the extracts) should be the total house floor area multiplied by 0.3. For example, our house has a total floor area of 130m², so requires a whole house ventilation rate of 0.3 x 130 = 39l/s. We have a total of 6 fresh air supply terminals, so each only needs to provide about 6.5l/s. If your are supplying 8 to 13l/s then that suggests that the house may be being over-ventilated, and that may be a possible reason for the noise. 13l/s is the highest extract rate needed under building regs, for the kitchen terminal. Building regs also require that bathrooms and utility rooms have an extract rate of 8l/s and WCs 6l/s, but those rates can be provided by the boost function, I believe.

Possibly, it depends on how large they are, how much wind there is and how much power the water pump needs. I've been looking at using a small solar panel to power a pump for a small water feature. I want to be able to pump around 10 litres per minute (about the flow rate of a shower) to a head of about 0.2 to 0.3m to create a small artificial stream. The power needed to move that much water is between about 0.32 W and 0.5 W, and allowing for the efficiency of the water pump it looks as if I'd need between about 1 W to 1.5 W of electrical power from a solar panel. This is surprisingly little, I had to double check the sums to make sure I'd got them right. I can now see how the small solar pond fountains work as well as they do; they just don't need very much power at all. If your wind sculptures had a swept area (the area exposed to the wind) of, say, 1m², then with a wind speed of just under 5mph the theoretical power available would be around 4.92 W, but allowing for the efficiency of the generator the electrical power output would probably only be around 2 W, but even so it seems quite possible to use a fairly large wind sculpture to drive a water feature. Doing as @PeterW suggests, and making the drive purely mechanical, would probably improve things slightly.