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Jeremy Harris

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  1. Jeremy Harris
    All the stuff I've read about MVHR air movement suggests that the primary process is diffusion, not forced air movement as such. Diffusion will ensure that stuff like water vapour and CO2 will move naturally from areas of higher concentration to areas of lower concentration, so it probably doesn't matter too much where fresh air vents are. Extract vents are slightly different, as we usually want to ensure that water vapour is drawn out quickly, and water vapour is lighter than air, so will tend to rise to the top of rooms that have a high concentration of it (bathrooms, kitchens etc). For that reason I think that extract terminals are best placed high up.
  2. Jeremy Harris
    That looks mighty high to me during those peaks. IIRC, the peak readings I recorded in our old house were around 1600ppm or so.
  3. Jeremy Harris
    It was still a Renault 5, but the Gordini version, with the 5 speed gearbox and a bit more poke than the smaller engined R5s. As the car only weighed 450kg the power to weight ratio was a wee bit better than in the R5 donor car.
  4. Jeremy Harris
    There are a couple things to sort out, but I think it might be feasible, at least in part. First thing would be whether or not the duct runs would adversely affect the structural integrity. That really depends on the slab design, and ours at 100mm thick would be a non-starter, as the smallest ducting is 51mm deep I think. A 200mm deep slab might take it OK, but I think an SE would need to say for sure, as you don't want the slab to crack along the lines of the duct runs. Second issue concerns the heating impact on the MVHR ducts from the floor. Fresh air feed ducts running in a warmed floor would be fine, it would just add a bit of heat to the air coming in. Extract ducts would pose a problem, though, as you don't want them to be warmed up, as that would significantly reduce the MVHR efficiency. Not sure how to address that, really, as I doubt that insulating the ducts within the slab would be very effective. I've assumed that the ducts all run through the concrete, as you wouldn't really want them down inside the insulation layer.
  5. Jeremy Harris
    My first thought when I saw that was Aberfan...
  6. Jeremy Harris
    All our cables and pipes are just clipped to the side of studs or the sides of the 50 x 50 counter battens on the external wall inner faces. As an added precaution I did run aluminium foil tape on the studs/battens where the cables/pipes are clipped, in the hope that it will make them easy to detect with a cable finder (not sure whether it does or not, though). I also took loads of photos of every location where there are pipes and cables running down walls, so that I have a reference as to which side of the studs/battens they are clipped to. I've also got a load of small, powerful, neodymium magnets, plus a few fixed to the end of pencils, that are very handy for finding the buried plasterboard screws. As the plasterboard screws are pretty much in the centre of the studs/battens, I can be pretty sure that it's safe to put any fastening inline with them. I still isolate the power to the relevant circuit before screwing anything in to a stud/batten that's got cables running down the side though, as I got caught out when drilling a hole for a wall light years ago. I discovered that drilling through a cable makes a hell of a bang and totally buggers up the end of a masonry drill.
  7. Jeremy Harris
    All pipes and cables must be secured with the appropriate clips (and that means metal or fire-resistant cable clips from now on - the old plastic ones and plastic cable ties have been outlawed in the 18th Ed). Those clips need to be at the right spacing too, in the case of pipes to stop movement when taps or valves turn off and in the case of cables the spacing is supposed to be as per the regs.
  8. Jeremy Harris
    Yes, one of only two Hudson Mystics that were ever built. Hudson had produced the prototype Mystic (a metallic blue one) and then decided not to put the kit into production. I went down to Norwich and found they had a second set of (pretty rough) body panels and persuaded Roy to fabricate a space frame so I could build another car. It wasn't really a kit car, as all I got was the space frame chassis and a set of body panels, but it wasn't too hard to make the other bits needed. Hardest part was getting the gear linkage to work, as I fitted a left hand gear change lever and there wasn't much space to fit things (the prototype had a weird central gear lever between your legs).
  9. Jeremy Harris
    They are internal stud walls with just a storage area behind, so the ducts run up inside the storage area to the wall-mounted terminals. It would have been easy enough to just fit the slimline oval semi-rigid duct inside the stud walls though. Someone here has used that I seem to remember, and posted photos of the ducting inside the wall. The oval semi-rigid ducting is 51mm x 138mm, so will fit in spaces where the round stuff is just too big. IIRC there are adapters to allow conversion from the oval section to the round section stuff.
  10. Jeremy Harris
    We have vaulted ceilings and I didn't bother to try and get the MVHR ducting up them at all. We have low walls either side of the upstairs rooms and I just ran the ducting up from the floor to wall mounted terminals in those low walls. This works fine, with the terminals around 4ft off the floor. In the bathrooms I fitted a small false ceiling in the highest corner and ran the MVHR extract ducting along that.
  11. Jeremy Harris
    I would think you'd wake up if the concentration gets high enough to be dangerous, as CO2 indirectly regulates respiration rate. If I remember the little bit I learned from aeromedical training years ago, a build up of CO2 causes the blood pH to decrease and this then triggers an increased respiration rate and, I think, heart rate, as the body increases its efforts to expel CO2, to try to increase blood pH back to normal levels. I know from experience in our old house that concentrations of more than 4 times the normal level don't seem to make you wake up, they just tend to make the room seem stuffy the following morning.
  12. Jeremy Harris
    No, not at all. Both can have different coil arrangements depending on the application. A thermal store holds a body of inhibited water which is heated to a fairly high temperature. It then "instantly" heats cold potable water coming in to an internal or external heat exchanger at mains pressure. The body of water inside the thermal store doesn't move or flow anywhere, it just sits there and stores heat. A UVC is a mains water pressure fed cylinder where the water in the cylinder is the hot water source.
  13. Jeremy Harris
    There's an explanation earlier, but a thermal store will drop the max output water temperature continuously whilst water is being drawn off, so needs to have a higher starting temperature in order to allow the TMV to hold the mixed DHW temperature at the right level as it discharges. An unvented cylinder will tend to deliver all of the hot water it holds at near enough the same temperature until it's empty. In general, because heat pumps both don't like running at high flow temperatures, and because they generally have a lower output than a boiler (so they have a longer recharge time) they should be used with a UVC, as they are very unlikely to be able to get a thermal store up to the 65°C to 75°C needed.
  14. Jeremy Harris
    That unit seems to be a filtration system, most probably it will use activated carbon filters that will need regular replacement (might be costly to run). An ozone odour removal unit doesn't have any filters, but works by oxidising volatile odour molecules to break them down into harmless and non-smelly molecules. My ozone generator is a home-made one that came about as an accident, when I was sorting out the design of our water treatment ozone injection system, but there are commercially available units around that do much the same job. I used to use hours in short burst to get rid of lingering smells in our old house, which wasn't that well ventilated. There are units available that continuously release a low concentration of ozone though, or that emit bursts of ozone periodically (the German made unit we have in the fridge works in bursts).
  15. Jeremy Harris
    You might be able to reduce the cost a bit by taking away risk if you can. Anyone quoting to do refurbishment work on an old building is going to add in a fair bit of contingency to cover the things that they can't see but which might end up taking a lot more time to do. Good examples would be things like the foul drainage runs, in a house that old there's a good chance that there will be a mix of different bits and the contractor may well be building in a bit of risk contingency to deal with the worst they are likely to encounter. If there's anything you can do to survey what's there, ideally gathering as much evidence you can about the exact locations of things, and their condition, then you may be able to get a better price.
  16. Jeremy Harris
    We've had two "no hot water" events so far, the first down to the unsatisfactory way the Sunamp controller tries (and fails miserably) to manage charging, the second due to me forgetting to manually reset the controller one day (after I'd discovered the failing in the controller), a procedure I have to do every day in order to make the thing work. Sunamp are fully aware of the failings in their controller, yet seem to just be putting out the message that we shouldn't read too much into the 50% discharge threshold they quote before charging will commence. Frankly the system fails to work without daily user intervention, and needs sorting out, and I'd far rather they gave some feedback about whatever they are doing to fix things, rather than just try to fob customers off. I'm reluctant to add the daily timed reset mod to the controller, on the basis that I want to see a fix from Sunamp (an acknowledgement that their present controller isn't fit for purpose would be a good start). I have doubts as to whether they are actually doing anything to address the problem we have nearly every day, personally. We are not the only customers experiencing problems, either, I'm sure.
  17. Jeremy Harris
    As @Ed Davies has already mentioned, you're mixing up units. The Watt is a unit of power. The Watt hour is a unit of energy.
  18. Jeremy Harris
    No. The heat input when it's -10 deg C is about 1.6 kW The 38 kWh figure is the heat energy required.
  19. Jeremy Harris
    Not sure if that reply was to me or not, but here goes anyway. Not sure whether you mean power or energy, but I'll answer for both. In very cold weather (-10°C outside), with no incidental heat gain, the house needs a heat input power of about 1.6 kW to maintain 21°C room temperature. That equates to about 38.4 kWh of heat energy over 24 hours. However, our heating does not use PV generation, as in winter it's both low and unreliable (same goes for solar thermal), so we use off-peak E7 to run an ASHP at a COP of around 3.5, so the energy usage for heating in very cold weather is about 11 kWh per day. We've never had temperatures that low here though, the lowest we've seen is about -5°C, and then only for around half a day at most, so in reality that 11 kWh/day figure is more than double our normal cold weather usage. We don't ever need to heat the floor as high as 24°C, as that would give us a heat output of about 2.4 kW, far more than we ever need in the coldest weather. The highest temperature we ever need to heat the floor to is about 23°C.
  20. Jeremy Harris
    For a new build there's no real reason to ever consider fitting a solar thermal system, though, as they just don't make economic sense. The only reason to consider fitting one would be if the roof layout was such that there was only a small area available to fit any system, perhaps because of shading.
  21. Jeremy Harris
    At the moment it's still at the consultation stage, and I've not seen anything that's definitive, other than that there will be an export payment system to replace the export payment element of the FiT. My guess is that there will be an insistence on smart metering in order to get the export payment, but there is a potential snag in that, although smart meters can measure and record export they aren't yet approved to do so.
  22. Jeremy Harris
    Pretty much the only place to put the kit, really, as there was no easy way to get the pipework down to any other space in the house. It was a 3 bedroom bungalow built around 30 years ago at a guess, with an oil fired central heating system, with the boiler in the kitchen and the tank completely filling what had been an airing cupboard. The original hot water cylinder had been removed and replaced with a bigger one when the evacuated panels were fitted. It would have made more sense, in terms of maintainability, if the installer had fitted a smaller cylinder and left space in the cupboard for the pump and controller, but it may be that the bigger tank was needed to best utilise the solar thermal.
  23. Jeremy Harris
    I'm afraid I'm not going to volunteer to look at another solar thermal system ever again. I agreed to look at the one I managed to get going last week without realising just what a PITA the thing was to access. The pump and controller were right at the back of the loft space, in a shallow roof pitch bungalow that had masses of fibreglass loft insulation.
  24. Jeremy Harris
    Because PV is cheaper through life per kWp than solar thermal. The price of PV has reduced a great deal over the past few years, whereas the price of solar thermal has pretty much stayed the same. Add in that PV produces energy that can be used for many purposes, not just to heat hot water, and that even when the FiT ends there will still be an export payment, and it is really a bit of a no-brainer. I'll just add that I spent the best part of a day last week trying to fix someone's evacuated tube solar thermal system. It had been installed about 5 years ago and the installer had since gone bust, leaving the owner with no easy way to get the system fixed. It was not a lot of fun crawling around in a loft replacing the faulty controller and then faffing around refilling and venting the system. Made me thankful that I don't have to deal with all that complexity with our PV system.
  25. Jeremy Harris
    Protect and Survive, for some reason it's ingrained in my memory, perhaps because for a few years I kept an emergency grab bag to hand, and had a plan to nick a big yacht and sail south of the Equator if I had enough early warning of incoming missiles (which at the time I was reasonably sure was likely, as where I worked was a second wave target zone).
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