Ed Davies

Again, yep: intranet of thingummies. I haven't done it yet as there's no control in my current setup [¹] but my notion is to have a router (probably running some flavour of BSD) which limits communications between various LANs: a DMZ/guest LAN, an office LAN and a control/IoT LAN. The only communication in/out of the IoT LAN allowed would be to/from the main HA hub allowing it to use NTP to get the time and for me to SSH in. Any web access would then be tunnelled over SSH for my personal use. If I decided to publish any live data for any reason then there'd also need to be a path out of the IoT LAN for the Hub to send the data elsewhere for that. [¹] apart from the fridge which is done within the attached Sonoff (not controlled over MQTT or anything)

Mine too. My only recent experience of switching mains with microprocessors is using the Sonoff TH16 which controls my fridge. What I envisage for most of the controls of my house is using a separate Wi-Fi-connected microprocessor running a relay board. Control via MQTT with messages like “relay/A49C73A4AE30/03 1” to turn relay 3 of the board with that MAC address on. Probably a few instances in different parts of the house. That's likely fine for small loads (lights, motorised valves, perhaps some pumps noting their inductivness). Where something a bit heavier needs switching then the directly microprocessor controlled relays would switch additional 230V-coil relays. I don't think I'll need anything which needs switching at high frequency (like a PV diverter) so the only likely use I'll have for SSRs is in the battery management system for last-ditch emergency protection of the battery bank if a cell is becoming over charged or discharged. The main reason for using SSRs there is the need to switch fairly brutal loads (120 amps at 50 volts DC) which could be done with a contactor but those themselves would have a not insignificant power draw 24h/day. I've also had thoughts about latching relays for this job.

I chopped a chunk out of the top of the clay drain pipe from the kitchen sink in the (I assume 1970s or 80s) extension of the house I'm renting with a hover mower. I'd noticed it just poking out of the ground and avoided it before but the grass was a bit long and I forgot.

Because the planners won't let you?

Just realised I'm unsure what you mean by “PV Direct” - I assumed direct electric heating with an immersion heater of the domestic hot water (not a thermal store) using mostly diverted PV generation. Did you mean something else? Perhaps, direct DC from the PV panels into an immersion heater without an inverter, completely separate from the mains supply?

There are some good lessons from aviation around this: redundancy is only useful if it's verified. That is, having two things, each of which can work on its own doesn't help if one can fail and you don't notice. E.g., most low-wing light aeroplanes have two fuel pumps of different types. Both types have a fairly limited life and fail once in a while. One is mechanically driven by the engine, the other is electrical. Before you start the engine you turn the electric pump on and listen to it ticking to verify that it's working. You then turn it off and leave it off except for critical phases of flight (take off and landing) so the rest of the time you're verifying that the mechanical pump is working as a side effect of normal operation of the aircraft. The Chipmunk, on the other hand, has two mechanical pumps. As such it probably actually has fewer fuel pump failures, as the mechanical pumps are more reliable than the electric ones, but without the means for pilots to verify that both are operating (they'll only be checked as part of routine maintenance every 50 or whatever hours) it greatly increases the chance of flying around for a while without any redundancy. Sort of similarly, the Challenger Space Shuttle accident can be seen as a failure to take notice of a loss of redundancy. There were two O-rings in the solid rocket booster field joints with the idea that they'd provide some level of redundancy. When it was observed that the first ring was getting burned through not enough attention was given to the fact that redundancy had been lost. They knew about it but didn't really “notice” it. This is something I'm thinking about a bit for my “Mark II” home-automation system: some system to alert me to off-nominal situations so I can investigate before they get to be real problems. E.g., in @TerryE's case the system could notice that there's more than, say, a 5°C split between the output of the two Sunamps and signal this as something to be looked into.

The Sunamp PV is pretty simple, simpler than most oil or gas boilers. It's just a question of getting support for something which was made in the hundreds, not the thousands. What I can't figure out from this thread is with @TerryE has had any problems getting said support or hasn't tried yet.

The standard practice of having a smaller power capacity inverter than the panels' nominal output makes complete sense. It's a matter of spending money where it'll give the most benefit. There will only be a few dozen hours in the year when the panels are producing within 10% or so of their nominal output. Spending money on a bigger inverter to harvest that extra doesn't make sense compared with spending it on a few more panels which will be producing extra power all year round. Bear in mind that the marginal benefit of the extra power on those days where it's produced will be small if a) you're self consuming when you're not likely to have much use for it or b) you're feeding into a variable-price grid on days when electricity prices are likely to be low. Only if you're feeding into the grid at a fixed (and significant) price (e.g., on the old FiT scheme) would the extra production actually benefit you, but that's history.

Somebody not like you? A known maliciousness is to throw breadcrumbs on somebody else's roof the night before for the birds to find as soon as it's light.

Yep. Obviously some heat losses, less obvious how much particularly if you can keep the run time down to when hot water might realistically be wanted. Perhaps even have a press button to “precharge” the pipe.

They're suggesting circulating hot water to/from the studio so that warm water is available quickly, not having to run off a lot of cold and wait for the hot to make its way through the pipe. Not all the time, just when the hot water is likely to be used there however that's timed.

Do you mean FTDI? (Other USB-to-serial interfaces are available.) Could that not cause some LEDs to blink? There have been cases where very small leakages can slowly charge the capacitors in the LED electronics resulting in occasional but regular flashes of the light. E.g., the capacitive coupling between the line and switched line in traditional wiring can be enough to do this.

Interesting. Name? Where are they? Doubt I'd use them a huge amount but might be a handy place to try before carrying on to Inverness for stuff which is a bit awkward in Caithness. A PM would be handy if you feel it's not appropriate to say it publicly.

Some notes on my blog about programming recent ones: https://edavies.me.uk/2019/07/sonoff/

FFS, your very first post starts “I have the house cat cabled so no problem with hardwiring in Mac TV's etc…”.

My £0.001's worth: no experience of working on fibreglass or epoxy, etc, myself other than a little bit of rubbing down of gliders but have spent a lot of time around glider and light aircraft workshops and know that damp is one of the things most worried about for that sort of work to the extent of not doing layup or spraying indoors in a somewhat heated workshop if the air is very humid. Damp during spraying is the no 1 thing blamed for problems with the gel coat on gliders.

I'm sceptical that it's an iOS issue; if Apple had done anything silly to break Wi-Fi on iPads when used with widely used routers I think it would be quite a well-publicized matter. An alternative test would be to check your iPads with somebody else's Wi-Fi. You don't need to log on to their network, just checking the signal strength at different distances would be a good start.

Then I'd be suspecting a physical connection problem with the Wi-Fi antenna in the router. I bought a cheap end-of-line router from Maplin for some networking experiments. It worked fine as a wired router which was what I really wanted at the time but was useless as a Wi-Fi router: within one room it worked fine but as soon as you tried to use it in another room with the doors closed there was no signal. Later I opened the box up for other reasons and found that the cable from the antenna had come unplugged from (or never been plugged to) the circuit board. Plugged that it and the Wi-Fi work as well as you'd expect for a cheap router. Maybe your router's antenna or its connection have become unplugged or been damaged in some way.

Obvious question, but what signal strengths are you seeing on your iPads close to the router and at the other end of the house? Worth first working out if it's a signal strength problem or something more complicated.

For not-really-climate but relevant alternative energy reads there's also The Switch by Chris Goodall. “How solar, storage and new tech means cheap power for all”. It's often forgotten that climate is not the only reason [¹] to get off fossil fuels, just the most urgent one. [¹] maybe not even the most important reason in the long term.

Regarding “…and other Literature”, here are a few climate blogs I read: https://andthentheresphysics.wordpress.com/ http://www.climate-lab-book.ac.uk/ https://tamino.wordpress.com/ http://www.realclimate.org/ https://climatesight.org/ http://kevinanderson.info/blog/home-2/ https://michaelmann.net/blog To be honest, there's not a lot of interesting stuff on many of these any more. All the important stuff has already been said over and over and now it's just a matter of details and playing word games with deniers.

I recently read Snowball Earth by Gabrielle Walker in response to @SteamyTea's recommendation after he saw my Thin Ice blog post referenced above. It was a good recommendation. It's about climate change some 600 million years ago and only tangentially relevant to modern AGW but still a good read and helpful background on the scientific process whereby ideas get tested and slowly incorporated into scientific knowledge, how pre-historic climate is deduced and the general physics and chemistry of the carbon cycle and its effect on climate.

Very unlikely, he's quite a well read chap but not terribly sophisticated for that sort of thing. His crops all go as winter feed for his livestock or sold locally for his neighbour's similar use so he won't have sales records or anything. Also he's expanded the croft he inherited from his father quite a lot so comparison year-to-year would be difficult.

Thin Ice by Mark Bowen. My longer comments.

Indeed. Global warming means the whole globe warming on average over the long term, not all places warming all the time. There are two areas of the world which have cooled as a result of climate change: a patch of the North Atlantic south of Greenland and bits of the southern ocean around Antarctica. Since Britain's weather and climate is so influenced by conditions in the North Atlantic it's not obvious to me that the UK will warm that much, on average. Also, the actual weather we get is heavily dependent on the position of the jet stream. Arctic amplification (proportionally more warming in the polar regions than in lower latitudes) means that the contrast between low-latitude temperatures and polar regions would decrease and there are very credible theories that this results in the jet stream getting more wobbly. I think that might mean that hot spells would be hotter but not necessarily more common; there might equally be damper and cooler summers as a result. In general, I think it'd be very naive to assume that a global temperature rise of, say, 3°C would mean that Britain would have the same temperature distribution as now, just shifted right by that amount. My neighbour, who's been involved in farming the same land here in NE Scotland all his life, points out that it simply wouldn't be possible now to farm in the way he first remembers in the early 1960s. Then they relied on having a week or two of dry weather in the autumn for harvesting. Now you have to pick the right days (not weeks) to do it which is only possible with the much more powerful tractors and other farm machinery they have available. In general the contrast between winter and summer has decreased significantly. I said “now it's just meh all the time”; he agreed. It's easy to be confused by “when I were a lad” type anecdotes but when they're based on somebody's recollections of decision making of some considerable economic importance to themselves perhaps they can be taken at least a little bit seriously.