Jeremy Harris

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Jeremy Harris last won the day on November 1

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About Jeremy Harris

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  • About Me
    Retired scientist, made the decision to build our own home a few years before retirement, then had the good fortune to be able to retire early and start the self-build journey. Started our build in late 2013, took far longer than anticipated to finish, but have now moved in and we are enjoying having a house with no bills at all (except for the blasted Council Tax...). The house pays us a modest income from the excess energy we generate, over and above the energy we use for heating, cooling, cooking, hot water etc, so we now have a healthy retirement holiday fund.
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    Wiltshire/Dorset Border

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  1. The spec for our ASHP gave the dimensions for the concrete base, with two options, either two cast concrete piers or one larger, single, one. It so happened that the dimensions of each pier in the two pier option was very close to the size of a block laid on it's side, so the base for ours is made up from two piers, each consisting of two blocks laid on their side, bedded on a concrete foundation. I don't think you'd be able to secure it to paving slabs for a couple of reasons. Firstly, the ASHP really needs to be raised above ground level a bit, both to allow easy access to the condensate drain connection underneath (this is easier with the thing on two piers) and also because it may tend to be noisier if mounted on slabs (although fitting a rubber anti-vibration mount under each leg might make that work OK). I find that, at this time of the year, the ASHP tends to draw dead leaves in around it, so having a decent gap underneath it to sweep this area clear is handy. If doing it again I think I would opt to raise the ASHP up a bit more, maybe using three, or even four, blocks per side, mainly to make cleaning around it easier.
  2. I believe these are supposed to go at the top of a stand pipe, with a trap at the base. There needs to be a length of vertical pipe below this fitting, and before the trap, to allow them to work correctly, I think.
  3. We have MVHR. I can say with confidence that even with no cooker hood we get no cooking smells outside the kitchen, ever. What smells are created when cooking dissipate quickly as the air gets changed via the MVHR. If we feel there may be a smell problem we just hit the boost button to clear the smell more quickly, but most of the time we don't bother. Right now there's cauliflower and broccoli being cooked in the kitchen, and the door to the kitchen is partially open and around 6 feet from where I'm sitting. There is no smell here at all, absolutely nothing, and the MVHR isn't even on boost. I did put provision in the ceiling to fit a hood, both wiring and a bit of thick plywood behind the plasterboard as a strong point, but I never got around to installing one, as it seems it's not needed. Came as a bit of a surprise, TBH, as in our old house we were plagued with cooking smells permeating the whole house, even with an extractor hood above the hob, that was ducted directly outside.
  4. There's a lot of misreporting re: Tesla. There was never, ever, any plan to locate the European Gigafactory in the UK. Tesla never even looked at the option, or had any discussions with anyone in the UK about siting a Gigafactory here. It's been a badly kept secret that the European Gigafactory was going to be located in Germany for months now. The decision Tesla announced this week regarding the UK was about the siting of the European R&D facility, not the European Gigafactory. There was a slim chance that the UK might be chosen for the location of the R&D facility, but once it became clear that (largely for logistic reasons, plus, I suspect, some incentives) Tesla were going to locate the European Gigafactory in Germany, it made a lot of sense for them to also locate the R&D facility there too. This really should be no suprise, as the UK just isn't a volume car exporting nation. Germany exported over $260 billion worth of cars last year, the UK exported less than $60 billion. Bit of a no-brainer to locate a factory somewhere with very good transport links (no ferries, for example) if looking for a central European manufacturing hub. The fact that Germany also has some of the worlds finest automotive robot manufacturing companies, and that Tesla Gigafactories are more automated then any other car manufacturer, was probably a pretty significant factor too. I'm sure that Brexit uncertainty was (and still is) on the Tesla risk register, but I'm also pretty sure that part of the deal with Germany will have included the wording of the press statements. It's very clearly in Germany's interest to make the point that Brexit played a part in the decision, even if we all know full well that, at least as far as the big bit goes, the location of the European Gigafactory, it wasn't a significant consideration.
  5. FWIW, the instructions for our unit indicated that fan speed 1 was only for use when the house was unoccupied, speed 2 was the normal background ventilation rate, speed 3 is the normal boost speed (humidity controlled in our case) and speed 4 is 100%, used infrequently for purge ventilation. I adjusted speed 1 right down to about 10%, enough to keep things fresh with no one at home, handy for use when we go away. I initially set speed 2 to meet building regs, then backed it off later, so that it runs at around 0.4 ACH (seems about right for us). Speed 2 is something like 30% speed, I think. Speed 3 is set to 75%, which seems fine for normal boost. I think we've only used speed 4 once, when we didn't manage to turn the MVHR off when someone nearby had a bonfire, when the extra ventilation after the bonfire smoke had died down helped to clear the air in the house quickly.
  6. I have the Salus auto balancing actuators. Best thing since sliced bread in my view. They just work perfectly, quicker to actuate than the wax ones, ensure the flow to the UFH is maximum when the system first switches on, for a fast warm-up, and then they automatically throttle back to maintain a constant temperature difference between flow and return. This temperature difference depends on the flow temperature. Below a flow temperature of (I think) 30°C they maintain a 4°C differential, above that I think they maintain a 7°C differential. We keep our flow below 30°C, as the 4°C differential seems to work very well for our system. I had ordinary wax actuators originally, but these were really slow to open, and meant that the system had to be balanced using the flow control valves, a fiddly and time consuming process to get right. We initially had problems with our kitchen getting too hot, that took ages to try and get sorted by adjustment, and when I did get the adjustment right the kitchen then took ages to warm up if the heating had been off. The Salus actuators fixed that, with no manual adjustments being needed at all. Also quick and easy to fit. The only downside is that they are a lot more expensive than conventional wax actuators.
  7. The issue here is that initially this company was promoting a product that didn't work in the way claimed at all. Caused a stir and a lot of suspicion, as they had claimed that the multifoil element could provide far greater levels of insulation than it can in practice, and consequently there was a fair bit of mistrust (well-founded, given the chequered history of the introduction of multifoil products, with their ludicrous and easily disproven claims). They changed the product completely, so that now it works almost entirely as a conventional insulation material, the foil layers do very little, other than, possibly, reducing air movement a little bit. There's no long wavelength IR to be worth being bothered about inside the fabric of the structure, so the foil is now really only there to differentiate this product from competitors. It's performs at about the same level as most other fluffy-type blanket insulation materials, and they are quoting a sensible value for λ of 0.033 W/m, pretty typical of a fibre-type insulation (rock wool is around 0.032 W/m.K, wood fibre is around 0.037 W/m.K, PIR foam is around 0.022 W/m.K) . It's no better, or worse, than most other fluffy type insulation, but that's wholly down to the honeycomb fluffy stuff, not the foil layers. It does have the advantage all fluffy blanket type insulation has of being relatively easy to fit well between frames, and an additional advantage in that it is as clean and comfortable to use as wood fibre (so much nicer than rock wool). The downside is that it has a pretty short decrement delay when compared to wood fibre, or even rock wool.
  8. Be interesting to find out how much functionality a smart charge point has with no connectivity. Hopefully there may be some ability for it to work as a basic charge point without any connectivity, but it could be a bit of a nuisance if it ends up being disabled if it cannot connect. Some of the more basic smart charge points may be a better bet than something more sophisticated, as I get the feeling that the basic models may have had the required smart functionality installed as an add-on to an existing design. If so, then it seems likely that they may well work with no connectivity without a hitch. One option is to just get a commando outlet installed, then use a portable charge point. Some can charge at 32A (the Tesla UMC allows this) and a portable charge point is a useful thing to have (although most EVs come with one, normally limited to 10 A maximum). You can buy a portable charge point that will deliver up to 32 A and plugs into a commando outlet, for about £250 or so (I've seen cheaper ones around, just can't find them right now). Wiring in a 32 A commando might not be a very costly job.
  9. A smart charge point usually connects via wifi, although I believe some can (rather dodgy in my view) accept an Ethernet cable. If there's no connection, then there may be be no way to turn the charge point on and off, schedule off-peak charging, etc, as I believe it's managed via an app. I have concerns as to whether security has been adequately addressed with smart charge points, TBH. At least one system is so deeply flawed that it created a bit of a stir when this was exposed (although I believe it's being addressed now, although this isn't much consolation to the few thousand who already have the Raspberry Pi version):
  10. No it doesn't, but a condition of the OLEV grant is that you have to have a charge point installed that does have external data gathering and charge control capability, much like a smart meter. You can't get a grant-funded installation without this feature. My charge point has a (manually switchable) option to charge when there is excess PV available, but the rather limited J1772 signalling protocol used for both a safety interlock and signalling maximum available charge current is a restriction. The minimum charge current is 6 A (and most cars are very inefficient when charging at 6 A), so any PV system needs to be generating in excess of this before car charging can start. My implementation takes a pragmatic view that partial charging from excess PV is always beneficial if the cost of charging is lower than the off-peak rate. I used to adjust the charge current on the fly to allow for this, but that was flawed, because the car onboard charger was both slow to respond and had a fairly long latency (it didn't respond quickly to the control pilot increasing duty cycle to signal that more current was available). I've ended up with a fixed solar charge current setting of 12 A, together with a bit of code that keeps the car charging for as long as the cost is less than 8p/kWh. If the charge cost stays above 8p/kWh for 20 minutes, then the car stops charging until either the PV starts to generate more, or until the next off-peak time period.
  11. I've DIY'd three charge point installations now, including building the charge points themselves. The OLEV grant only applies to "smart" charge point installations, and like all subsidies it seems that the installers are absorbing the grant money as a bit of additional profit. The grant is 75% of the installed cost up to a maximum grant of £500, and guess what? No installers claim less than the full £500... There are a few charge points around for ~£200 to £250 or so that work just fine. On top of that there will be the cost of a run of 6mm² cable (maybe 10mm² if it's a long distance), plus an enclosure with a Type A RCBO, a couple of henlys and lengths of tails cable. Not wise to connect a charge point to a spare way in an CU, IMHO, as it will draw 32 A for several hours on end, and things may get a bit warm in there. Another thing to consider is whether you want to install a tethered charge point or a non-tethered one. Tethered ones are easier to use, just unhook the cable and plug in, but they look a bit uglier, as there will be a few metres of hefty cable coiled up around the thing. A socketed unit means getting the lead out of the car every time you want to charge, and plugging it in both ends, but does tend to look a bit neater. Personally I'm not a fan of smart charge points, for a few reasons. Firstly, on a point of principle I object to data being collected about my car charging habits, for several reasons, not least of which being that a failure to charge for a few days would be a reliable indicator that I'm not at home. Secondly, users of various makes of smart chargers are reporting that, like pretty much all app controlled kit, reliability can be a bit flaky. Tales about of cars not charging as expected, charge rates being randomly reduced, user interfaces falling over and some charge points refusing to play nicely with some devices. The bottom line is that a charge point is just a switched power outlet, and doesn't need anything other than a means to turn it on and off. I prefer being able to do this easily and reliably with a switch, as it then needs no 'phone, internet connectivity, sanction by whatever authority controls the smart features, etc in order to work. I want to be sure that my car charges when I want it to, not when someone else decides I'm allowed to.
  12. The only caution I'd raise with using bales would be rodents. Rats and mice really love straw; within hours of stacking a barn the little buggers would start moving in en masse.
  13. May be, I've seen a few odd things happen, but nothing quite as clear cut as this. Hopefully you can just file the corners off the pegs to get them to fit.
  14. The files I got were like this, with the little pegs square: The printer could have printed them as round pegs, just a matter of angling the piece up off the build plate and adding some supports. This stuff gets done in the slicer (Cura is one such product, I use the slicer that came bundled with the Photon). Most slicer programmes seem able to rotate parts, add supports, add a printing base, etc, either automatically or manually. The only slight downside of using supports is that they leave little marks on the print, rather like the sprue marks on an Airfix kit.
  15. With a bit of luck you may be able to see the result tomorrow - managed to catch the post OK. Looks to me as if directly exporting the .stl file from AutoCAD works just fine.