Ed Davies

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About Ed Davies

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  • About Me
    Currently building an off-grid timber-frame A-frame house on a windy hilltop in Caithness, Scotland. Slowly.

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    Caithness, Scotland

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  1. Those with two dishwashers who follow the-use-from-one/put-away-in-the-other protocol, do you have some sort of flag to remind you which is which at any time? Should usually be obvious once you open the wrong one , I imagine, but still annoying. And there's potential for confusion when one dishwasher contains only a few apparently clean but not necessarily actually clean items.
  2. I have a similar question to @jamieled: I've used TF200 on my walls (and around my window reveals). It's stood up nicely to long exposure, about 18 months for the oldest bits. Ideally, I'd like to use it to replace the failed stuff on my that failed when it got wet and froze. I can't see the point of a membrane which can't stand freezing when it's wet - the most likely conditions for a roof failure which results in water getting on to the membrane are freezing conditions resulting in ice damming or other such problems. Apart from anything else, TF200 is shiny which will improve the insulation qualities of the roof a bit. But TF200 isn't certified for roofs. Any idea why?
  3. Does this video help? Youtube is excellent for working out most Velux stuff (compared with the Velux instructions which are not very helpful as a checklist once you know what to do and give no clue at all if you don't).
  4. I wonder how much this is all botty covering. If there's a prominent fatal fire caused by arcing the immediate question will be: why aren't AFDDs mandated the way they are for bedrooms in the US and Canada? Because they're expensive. Money before lives? Outrage. Etc. So then the question is, why are they mandated in bits of North America? And do any valid arguments there apply here with twice the voltage and half the current?
  5. Do they work (as AFDDs)? John Ward found a worrying lack of operation for another brand in this video: https://youtu.be/kVpXQa6EW3k Starts on the AFDD bit about 15 minutes in.
  6. Ed Davies


    Previous discussion of MK.
  7. Doesn't extraction stop while flushing is actually happening? Water going down the pipe (from cistern to pan) instead of air going up it. The exact opposite of:
  8. Was the panel manifold below the level of the water surface in the hot tub? Seems unlikely. If not a thermosyphon won't work.
  9. Just come across this video with some nice demonstrations of the effect of shading parts of a panel when there are two connected in series or parallel. If shading is likely to be a problem (as in @ProDave's case it definitely is) then this confirms that parallel is the right answer. https://www.youtube.com/watch?v=1qD3mN8VotQ Their results are very much in line with what I'd expect.
  10. Something with house numbers/names that people don't think about is that fire and ambulance services need to be able to read them easily, probably at night in foul weather. They may not be going to you house but knowing quickly to look elsewhere could save some valuable time for somebody else. Putting the number in paving might not be helpful if it's dark and wet or, worse, has snowed.
  11. No, that's not what a positive correlation means. There's clearly a positive correlation on a minute-by-minute basis: if it's sunny now it's more likely than not to be sunny a minute later and vice-versa. It could change dramatically in that minute but for most minutes it doesn't; even in England the weather's not that random. Still, it's equally likely to be a tiny bit more sunny or a tiny bit less sunny; just because it's equally likely to be a bit less sunny doesn't mean there isn't a positive correlation. 12 hours or 6 months out there will be a negative correlation in the sense that if all you know is that it's sunny somewhere (you don't know where or at what time of day) and somebody asked you to bet on whether it'll be more sunny or less sunny in 12 hour's time or 6 month's time you'd be better off betting it'll be less sunny. OK, if it's just past dawn on a long summer day then it'll be more likely to be sunnier in 12 hour's time but taking the solar radiation time series overall there will be a negative correlation at 12-hour intervals.
  12. That sounds about right. 1 tog = 0.1 m²K/W which is equivalent to a U-value of 10 W/m²·K which, in turn, is about the conductance from a floor to the surroundings above it. So 1 tog of carpet halves the heat flow upwards or doubles the temperature difference needed for a given heat flow. 2.5 tog would multiply the temperature difference by 3.5 which seems like about the point when a simple control strategy of keeping the slab at a constant temperature would break down.
  13. That's a pleasant surprise. But then they're probably the same Chinese modules inside anyway.
  14. But the return temperature out of the Sunamp will be something in the 50's °C which will be too high to cycle back into the ASHP usefully. Both because that's intrinsically how Sunamps work and also because of the flow rate reasons @ProDave points out. I think the only plausible scheme like this is to have a buffer tank which the ASHP heats to something like 30 to 40 °C and use that to preheat the DHW flowing into the Sunamp so that the Sunamp only has to heat the water through the last 10 or 20 °C. @JSHarris has a scheme like this but doesn't use it a lot. If you're going to have a buffer tank for your UFH anyway for flow/cycling reasons then using that to preheat the DHW might make sense. I have similar thoughts about a pre-heat buffer tank heated by solar thermal followed by a Sunamp heated by PV. That'd allow the solar thermal to operate at lowish temperature where it works more efficiently and the PV to do the just the last bit of heating of the DHW up to the use temperature where you want to use the least electricity for the purpose possible.