Radian

It seems simple enough. Both battery systems would obviously like to do 'the right thing' (for normal single battery installations) and deliver any load your house imposes in preference to imports from the grid, whenever they are able to. To cooperate in the way you require, both must be able to be told not to do so in your off-peak window. If you cannot instruct them to obey this then there will always be a competition between them.

Tesla Q&A: Makes it sound very condescending! It might if there's a compelling reason to. Huff.

How long is a piece of string? Batteries can only charge from DC anyway, so an AC charger has to rectify the supply to DC anyway. Then it's just a question of the designed current limit. kWh is a measure of capacity. You already know that from the 'big print' in the brochure i.e. you bought a 10kWh battery. Do you mean how much power it takes when charging? The brochure probably tells you how long it takes to fill up from AC so divide that out. Again, for example, if they said it would take 10h to fill a 10kWh battery then it would be charging at 1kW, or 4.166A @ 240VAC. But I'm pretty sure you know all this already - so is there something else you're asking?

Well, I'm pretty cheesed-off right now. I seem to have lucked-out with my utility supplied smart meter. Unlike the vast majority of meters, mine appears to have a teensy tiny Joule buffer - something less than 450J by the looks of things. To arrive at this conclusion I added a 'live stream' of my cycle-by-cycle plot using websockets. It makes capturing elusive events much easier. Here's a long 'still' from a recent experiment... ..So here I had set things up to measure the size of the Joule bucket (what I've been assuming to be 3600J) by switching off the dump load and letting a couple of hundred PV watts leave the meter and go out into the grid for a few minutes. This is to ensure that the bucket is totally brimmed to overflowing. Then my generation is allowed to fall and power to slowly go from -ve (export) to +ve (import). A close up of the transition... The grey vertical on the left is the last meter impulse tracking my export (yes, the meter impulse LED flashes both for import and export). Then the power (green trace) climbs from -ve (export) to +ve (import). The assumed content of the Joule bucket (blue trace) then falls from the maximum clipped level (3600J assumed) as imported power is draw out from the bucket into the house. But rather than falling to zero, it only gets down 1/8th the way (around 3600/450) before the first import meter pulse arrives and I'm charged for the power. So between me and the supplier (theoretically) being billed for export and import between the two impulses, there's only a zone of around 450J where power may be pushed out and pulled in without charge. This is disappointing as it makes measurement tolerances and response times extremely tight.

Sure, I posted one photo on here a while back...

Yes, quite fascinating! A remember getting hold of some resin and activator somewhen around 1980 and filling the inside of some panels in a custom car I was building, around the time it was starting to take off as a useful product in GRP construction. I didn't see it used in buildings for a least another decade. But it appears it was first invented in the 40's by Mr. polyurethane - Otto Bayer patent for the synthesis of polyurethanes out of poly-isocyanate and polyol

At first blush yes, but you would be multiplying engineering overheads unnecessarily. Like the size of the fridge enclosure, when scaled to envelope an entire house for instance. So no, not a valid argument really.

Over 40oC there quite often. Perhaps this project is a pilot for how humans are going to have to turn to technology to remain on this planet.

Therefore the introduction could say "IT IS a refrigerator that tries to cool the outdoor world" to clarify things.

I don't think so. The bimetallic action is a mechanical movement resulting from differential expansion of two dissimilar metals bonded together. A bit like how a plank of wood will curl up when only one side gets wet. Both metals are subject to the same temperature. However, the kind of probe shown in your photo looks more like a bulb and capillary thermostat. These have a bulb in which a fluid expands in response to temperature and operates a diaphragm switch via the capillary tube.

That averages out to a constant 650W. Pretty similar to ours - which is made up from averages of 150W for the fridge and two freezers, 250W from everything on constantly like Routers, gateways, smart devices etc. and another 250W from highly intermittent but large loads like oven, kettle etc. The most dynamic loads are the fridge/freezers so I have those plugged into an energy monitoring system to log their average daily consumption to identify them separately from a whole-house energy monitor using a Current Transformer. Then the 250W base load becomes most apparent at night, and the rest (big loads) are simply what's left. Whittling down the base load is the biggest challenge.

There should have been storage instructions with the delivery. This is usual for solid wood worktops for example. If there wasn't anything outlining the conditions for storage you might raise that with them and use it as leverage.

Assuming no shading, according to PVGIS, at around 58oN with a 3.8kWp PV array on each side you could get a yearly energy production of around 4500kWh. If that was entirely self-consumed, especially after the next price cap rise, it could easily be displacing a couple of £k annually. I'm guessing it has a grid connection but off-grid might be attractive depending on how you intend to make use of the property.

Do you mean 'unfinishable'? 😉

The photo showing the foot of the stairs shows they're flush with the wall forming the outside of the under-stairs cupboard. Not so in the plan view drawings where the bottom four steps project out. Why would that be?

Sounds like you have something pulling the GPIO0, GPIO2 and/or GPIO15 pins to the wrong levels at boot time. These are the boot control bits. summary here

Around a decade ago I developed a Real Time Clock I2C module for CJE Micro’s to sell in the 'then new' Raspberry Pi market. I can't be arsed to resort to scope low-level issues with I2C these days. Not unless absolutely necessary. Have fun 😄

I know what you mean by LED but it might confuse others... now, if you called it an LRD, that would be more like it 😄

Could you not use the time library with network time protocol instead?

Constant 33.3W loss then. Our C rated Gledhill is 70W loss. Really ought to do something about it.

In my father's house the cylinder was in a built-in cupboard and he cut the full height door half way up and fixed the lower half in front of the cylinder, stable door style. He then filled the void around the cylinder with a large quantity of EPS beads. Pretty much as good as you'd think you could get - but it still made the bedroom it was in too damn hot. Conduction is the isses here. And accessing the pipework.

Logically sound I think, but in terms of intervention - rather extreme! Measuring power and flow direction using a CT is really quite simple and inexpensive by comparison. Nearly all the necessary resources are available from an inexpensive CT, ESP32 and a bunch of resistors. It also gives you the luxury of trialling code for different algorithms over-the-air and dynamically tweaking parameters over MQTT. In one of those videos Robin was re-compiling his entire code and re-flashing just to change a few values.

Oh, I think it's very useful in import-only applications like SteamyTea has. The minimal intervention has a lot going for it and it can be incredibly accurate using interrupt triggered timing to measure the period, and perfectly acceptable accuracy when polled. I'm planning to keep it as part of my energy management (diverter) for the time being as a calibration reference.

While it's true that calibration doesn't matter all that much, there is a potential issue when the excess to be diverted is small. A few tens of Watts difference between what the meter sees and what the diverter thinks it sees may mean the Joule bucket is quietly filling without the diverter being aware. If this remains the case for several minutes the meter may overflow and start exporting the few Watts represented by the measurement discrepancy. It will certainly push the equilibrium point one way or the other so the system will continue to rock back and forth, and possibly overflow (in either direction) as a result. Apart from CT non-linearity, phase error and VI calibration, one other source of discrepancy can be the anticreep parameter which Robin includes to 'tidy up' the accumulator for the Joule bucket when testing with no power passing through the CT. This can rob a few Joules when import/export is on a knife-edge.

Robin Emley put up this video showing what his meter does: Very helpful for me. I wish I'd gone through all his videos like this before I started 🙄