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RobLe

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  1. We have PV, heatpump, battery, elec car. It’s actually cheaper, faster, and simpler to charge the car overnight with 7.5p IOG electricity than use ‘spare’ PV electricity (for which we get 15p) - better for us and the national grid to export it. Of course we have measured export, not deemed, which seems more ‘honest’ than deemed and a diverter.
  2. I’ve been converting our flat roof garage into a workshop. It’s adjoined to the house, and has an up-and-over metal door. Ages ago I put 50mm of celotex on the inside of the metal door, giving it a calculated U value of around 0.5W/m2k - of course this ignores draughts around it. Calc: celotex lambda=0.025W/mk, so U=0.025W/mk / 0.05m=0.5W/m2k The outside wall has 100mm celotex, floor 50mm, roof 150mm equivalent. The insulation is mostly internal - likely I’ll only heat it locally when needed with IR panels rather than with a thermostat. For comparison with the U values you gave; an old single glazed window U value is 6W/m2k, modern double glaze is 1.2W/m2k. I think you’ll be disappointed with a 5W/m2k ‘insulated’ door.
  3. I'm pretty sure that to get the grant, you must swap out a fossil fuel heater entirely with an ASHP, and the ASHP must be heating only. Many of them can be retrospectively altered to include cooling, as almost all ASHP have built in reversing valves in order to defrost more effectively (than using a heater internally) - so it's a firmware change, or a dongle added on to "authorise" cooling. I can understand the mcs intention behind disallowing cooling - but I think cooling is a significant personal benefit of a heatpump over a conventional gas boiler, so it would encourage ASHP uptake for a little extra electricity use in summer.
  4. Prob just say a power factor of 1 (ie. only ‘real’ power flows). As you say, the ‘charger’ just instructs the car what power to take and when - all the power electronics needed between the AC mains and the battery is in the car, and this is what’s actually determining the power factor (but it will still be 1).
  5. Flow rate is super hard - I was lucky enough to have access to a pro blower door, so I compared results between that fan and the pro kit, and made the graph I attached based on it. The pro kit itself is calibrated, and has two differential pressure measurements - one to give room-external pressure, and the other measures across an orifice at the fan inlet; the data goes into a PC which uses the calibration data to give the flow. If you use the same fan type, you can follow the lines graph I made to give flow at a given voltage and pressure.
  6. You can block up an mvhr by wrapping up the filters with clingfilm - I found that a lot easier than blocking off the outdoor vents, as in our case that involves using a ladder on our garage roof!
  7. I’ve done this before, and have a set of recommended parts - links below to a suitable fan, power supply, and differential pressure sensor, total under £200. You can halve that cost by using a car battery charger and no measurement. https://www.ebay.co.uk/itm/171452099291?itmmeta=01HPJ04NFJ122390GS5BHYCSTA&hash=item27eb576adb:g:AlsAAOSwFLBabz6P&itmprp=enc%3AAQAIAAAA0MHDPIuVE6xMauIT%2B2m3GgQGT8tYsJluxspKLHSwqw2b%2F%2BOcaIly6fBGJylxh3zb5Jt%2BiqjJU5XVvqa3u%2FGMfqCwPjrLEMb5lBzMdLjDfJaGcBD9prP5gR7rYGam3WEHjv5VII7atBOJ1Unhve0fvtuur%2Bo265pYJwGbp2rnHX06VlE%2FewjhoSs4bRG1t%2BVUnBzbF13HZ%2FF3YP7vcD3wY6utJXhe6t2NLy10Vn%2Fn1EUdVjVhKb41RcAUTjvMW8GNMdSgeSgJzKTo1gIgBqDsLTo%3D|tkp%3ABk9SR-jXksC0Yw https://www.aliexpress.com/item/1005003681719599.html?gatewayAdapt=glo2esp select 15V 20A variant https://www.aliexpress.com/item/1005005320909441.html?spm=a2g0o.order_list.order_list_main.15.44d11802qTJLEi Using those parts, I got the flow versus voltage and pressure relationship below. Of course, it won’t be super accurate - but what do you expect for £200 of bits?
  8. R290, propane. Cheap, efficient, no f-gas restrictions on disposal as not a GWB problem. First used in ac systems 100 years ago, so not exactly new! Flammability is it’s only downside - not a big issue these days, as most heatpumps are mono blocks outside - just don’t site immediately by a drain or openable window. Lots to pick from - I’d get a Vaillant Arotherm plus if I were buying a unit (I diy-ed my own propane gshp, there’s a thread on build hub somewhere). Keep the installation simple for efficiency - only one zone, no TRVs. Get weather compensation fitted and working!
  9. We have a 4 bed all elec house, induction hob, tiny gshp, kettle, toaster, all usual mod cons. We make no attempt to desynchronise things when cooking etc - often turning on stuff together, and so I guess our 3.6kW 15kWh hybrid inverter must max out and a bit of peak mains sneaks in sometimes. Even so, in the last 30 days the app ‘Octo-Aid’ says our IOG low rate use is 99.7%, peak rate 0.3% - somehow it can’t end up that significant. What did make a noticeable difference was tweaking the offset power, to ensure we weren’t trickling in 10W all the time.
  10. The argument I heard was that a large natural convection pattern sets up with a window opposite a radiator, leading to an annoying cold draft from the window along the floor to the rad. Of course, decent windows and so low heat loss will mean this airflow speed will be low so don’t worry about it.
  11. We had a solic 200 pv diverter to our immersion for a few years. Similarly it lived near the fusebox, with a short CT cable, and then a long (7m) cable to the immersion. Never had any trouble with it, didn’t notice any interference generated by it. As has been mentioned, you’ll only get a full mains waveform out when it’s really sunny, most of the time it will be ‘phase controlled’ and lower rms voltage, which is it working correctly with the available spare solar power.
  12. I’ve had a pp3 type of these usb lithium cells in a smoke detector. Thought it was great at first, then found it has high self discharge (not normally an issue with lithium), and lower energy store. Upshot was it only lasted a couple of months in a smoke detector, while a non usb rechargeable lithium lasts years before it squarks. Don’t flatten them tho, no bms inside cheapie pp3 lithium.
  13. Embodied CO2 of the new concrete poured into foundations if you dig out what’s there. Will the new building be heavier or lighter than the old, would influence my thoughts.
  14. We have a hybrid battery system, smart meter, octopus go. Import 7.5p (from 00:30 to 04:30), export 8p. Lots and lots of effort, octopus took forever to gets things right(it’s still not), it’s now almost as good as the spinny meter would’ve been. 👿. There are better rates, octopus io notably, we would need another meter upgrade and no doubt lots of time talking to octopus, gah. We must’ve lost our spinny meter 15+ years ago - if you have one it’s like a magic 100% efficient, infinitely big battery😈. I guess if you import a lot more than export (all elec house + car) then there is an incentive to go smart and get a tou tariff.
  15. A ‘gold dust’ spinny wheel meter! Technically theft when it spins back, so using the grid as storage. Morally fine imho to do so, you’re probably on average exporting when the country needs electric. Or get a hybrid battery, smart meter, Octopus tariff, jump through loads of MCS hoops, and be back more or less where you were with the spinny wheel meter. So long as the dno is aware, afaik it’s not your ‘fault’. Don’t send meter readings lower than the previous, that’s asking for it! Elec car charge point, give elec away in summer ? 😈
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