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Electrics

In the previous blog entry, I showed the "new" fuse box. This...

Distribution box
Distribution box.

This is for the immersion heater, the newer wiring in the bedrooms, and a socket for the living room. Literally, a socket, right there. It runs the surveillance cameras and an extension lead to this machine, the older Pi 2.

Don't ask about the older wiring. It's a rat's nest of stuff randomly tapped off of three phase, where the lights have little fuses in the switches and the sockets don't.

Now, what you can see in the fusebox photo above are some MCBs. That stands for "Miniature Circuit Breaker" and it'll trip out of too much current passes. Essentially it is there to prevent the wiring catching fire in the walls if there's too much current passing, or if there's some sort of short circuit. The MCB has two trip methods. The first is a bimetallic strip that heats according to current draw. 16A at 230V AC with a power factor of 1 (resistive loads, such as heaters) works out to be 3.68kW. The actual cut-out point is a few times more than this, say 9kW (or 48A). You're supposed to use 2.5mm wiring for 16A circuits (there's no such thing as a ring main in France), and generally speaking a single phase PVC insulated cable of 2.5mm clipped to a surface is rated about 27A. That's what it can carry in normal use. Above that it'll start to heat up, but the idea is that the MCB will heat up faster and trip out before any damage is done.
The second way an MCB can trip is an electromagnetic thing, and this kicks in if there's a short circuit on the wire, as short circuits can sink phenomenal amounts of current in split seconds.

When my MDFS server failed (2000, 2001?), it was because of something wrong with the keyswitch on the front panel that ended up with the bare unshielded live connection on the keyswitch touching the earthed metal casing (and I was holding the key - erk!). As it was an older house, it blew the fuse in the plug. It blew the fuse in the extension lead. It blew the fuse in the fuse box. And it blew the master fuse (what is that, 60A or something?). All went "pop" instantly. Smoke from the MDFS, smoke from the fusebox, and a bunch of unhappy people. Me being one of them, as the massive amount of power dumped into the casing of the thing got into the circuit board (via all the grounded sockets) and destroyed the MDFS... the line drivers in the BBC Micro... the line drivers in the A310 (luckily that was a removable board so I just tossed it) and also half of the Econet bridge had it's line drivers cooked. Oh, and the little terminator at the end of the network actually looked burnt. I'm just glad the line drivers sacrificed themselves and the losses weren't greater.
Perhaps if the place had more modern wiring and MCBs instead of the slot-in fuses that were common on all of the older properties, it might have tripped out before wrecking so much stuff.
I have tripped out the one here before. I slipped when fiddling with a Beeb PSU and a screwdriver touched the earthed case and live. A tiny spark and everything went dark followed by Mom's "Riiiick!?". To which I feigned ignorance and told her that nothing looked wrong, maybe it was a power cut? ☺ The PSU worked afterwards, but I learned my lesson to make sure I unplugged the right thing!

Now, there are two over-current protections on the wiring here, and one earth leakage protection. The first over-current protection is in the "disjoncteur", a big meaty trip switch. When we had a spinning dial meter, this box was the thing that regulated the current.

The master trip switch
The master trip switch.

Allow me to explain. In France, what you pay for electricity depends upon how much current you want. The price per unit is fixed, but the price for the provision of service varies.
The cheapest tariff is 3kW where you pay about €9,13/month. The most expensive is 15kW which is €20,85/month. They used to go up to 36kW (at ~€42/month) but that's not domestic, so people requiring those sorts of loads have been moved over to commerical or agricultural tariffs.
When we bought this place, it was rated 6kW. We discovered quickly one chilly winter that this meant difficulties in boiling water for a hot water bottle and running an electric bar heater if any other load (such as the 2kW water pump) kicked in. With the lights on, incandescent in those days, it would cross over the rated amount and the disjoncteur would trip. Since it was only about thirty francs (a couple of euros these days) to go up to 9kW, we did.
It's still rated 9kW, for which I pay €14,86/month (rather than €11,93 for 6kW). I rarely use more than six and even that's an unlikely event involving making tea and running the washing machine heating water and the water pump kicking in. In reality, the washing machine heater, the water pump, the immersion heater, the kettle (tea! tea! tea!) and the fan heater are the current draws and I rarely have more than two on at any given time. Like, in the winter, the heater and endless cups of tea maybe... In the summer? No heater, just endless cups of tea. ☺

Once the Linky was fitted, this was set to it's maximum (30 - I'm not sure if that's amps or what) as the Linky now deals with the current monitoring.

Which brings me to the infamous Linky. The "smart meter".

The Linky smart meter
The Linky smart meter.

I have no reference to compare if the Linky is accurate or not, though I'd imagine if there was a problem then Que Choisir? (a bit like Which?) would be all over it. This, the smart meter, is extremely sensitive. And what it doesn't tolerate that older mechanical devices did was something called "startup transients". That is to say, when you are getting a motor started, you have to dump power into the capacitor to get the offset winding going, and energise the windings in general and, well, if your motor is rated something like 200W, that's the running current. It's startup current (which only lasts for a brief period, maybe a twentieth of a second) could approach a kilowatt. Washing machines are notorious for this due to the frequent activations of the motor, but anything with an AC motor (fridge, vacuum cleaner...) would do the same thing.
With a mechanical setup, these transients would pass unnoticed. With a smart meter? More than 'x' is more than 'x' and there's zero lenience. Of course, there's business to be made in not tolerating brief transients as one can then sell the hapless customer a more expensive tariff...

Anyway, the Linky will trip out at 9kVA. Not close to, not "approximately", at bang on that. Which, with some measure of irony, might be less than would be necessary to cause a thermal trip of the MCBs.

Notice, by the way, that we're measuring in volt-amps (VA) now, and not kilowatts. There's a subtle difference and it's to do with the Power Factor, and it's also measuring apparent power rather than real power. It's a more accurate way to measure, especially for times when the voltage and current aren't in phase (such as reactive loads). To put it into context, where there is a reactive component in a load, the apparent power will be greater than the real power; and if we were to have a purely reactive load (which isn't possible, but...) then it would be a situation where current would be drawn but no power would be presented to the load. It's complicated, start by Googling for "AC power factor"...
Anyway, generally kilowatts and kVA are the same thing. But they aren't exactly the same thing. Current draw is a fairly simple thing to work with. Remember I said above that the 16A was 3.68kW? Well, that's 16 amps multiplied by 230 volts to give us 3680 watts. With a power factor of one (a resistive load like a heater), this is exactly correct. With inductive or capacitive loads (reactive), it's different. So now, rather than measuring the current draw, we're measuring the power draw.
Probably means the bill went up ☺ but I can't say I really noticed much difference.

The second thing that the disjoncteur (the big black box with the four terminals underneath) does is that it acts as a "differential trip switch".

Now we're introducing a completely new sort of monitoring. You see, in an electrical circuit there should be "balance". It's often thought of as "flow" and "return" but that doesn't really make a lot of sense for AC. Suffice to say that if your live is drawing a 2.2kW load (like the washing machine when heating the water), you'd expect to see the same 2.2kW on the neutral. If what's on the live and the neutral don't match, well, then that means some current is going somewhere else. This is generally considered to be a Bad Thing.
This hardware is old, made in 1968. It predates me by a half decade and hails from the time when Bobby Kennedy and Martin Luther King were both killed, 'Nam was in full swing, the 747 was introduced, Apollo 8 was the first manned craft to orbit the Moon, and songs such as "Hey Jude" (Beatles), "(Sittin' On) The Dock Of The Bay" (Otis Redding), "Mrs. Robinson" (Simon & Garfunkel), and "BORN TO BE WI-I-I-ILD!" (Steppenwolf) were on the radio.
Because it is old, it will trip out at 650mA (which in three phase suggests a permissible loss of up to around 450W or so).
This is probably a good thing, given shonky farmer wiring, sockets outside in damp places and so on. A little bit of leakage should probably be tolerated or the thing would be tripping out endlessly.

 

RCCB

The problem is that while the disjoncteur is a type of RCCB (Residual Current Circuit Breaker, aka RCD), the 650mA rating is aimed at protecting the installation.
Currents over ~10mA will deliver a painful shock, ~50mA will be extremely painful and is the lower limit of what may prove lethal., Around 100mA is more than enough to cause severe muscle reactions which will unfortunately tend to cause you to grab on to whatever it is that's shocking you, which would lead to respiratory arrest. Remember, also, that the mains is AC so it's like being shocked over and over fifty times a second.
Therefore, I'm sure you can understand that 650mA will be absolutely useless at protecting a person. Forget respiratory arrest, that sort of current will fry your ticker.

Disclaimer: What effect actually happens depends upon how the electricity passes through you. For example, dropping an amp between a bare knee and a wet shoe (or bare feet) would be off the scale painful but survivable. Dropping an amp (that's 1000mA) between your left hand and right hand with all the important torso bits in between would be like cartoon ghost-skeleton instant corpsification.
PS: Don't try this at home. ☺

Anyway, enter this little gizmo.

An RCCB
An RCCB.

The rating of the RCCB is 40A. This should be calculated as according to 1× the rating for electrical heating, immersion heaters, and electric car chargers, and 0.5× the rating of other circuits. In my box, there's 20A for the immersion heater (but it's only 2kW so probably doesn't need to be that powerful), plus three times 8A (half of 16A). That adds up to 44A. Since my current draw is not much (sure, there may well be a 2kW heater in the winter, but only one), I rounded 44A down to 40A. I mean, 44A is over 10kW, my Linky would say "nope!" before then.

Now, I had a choice. I could purchase a 40A RCCB from Amazon for €8, or I could go to my local DIY store and buy one for €65. I know the DIY place is a tad pricey, but dammit if this thing is going to trip out at 30mA and potentially save my life, then I want something made in France (I'd settle for Germany too) and not some cheap crap made in China. I mean, if I should ever end up getting a belt from the mains, trust me, I'm only going to get one shot at it. Either this thing trips and it just causes me to shout words you wouldn't find in the bible, or it doesn't and, well, let's not go there. It would be a stupid way to die.

Because my fuse box has three different brands of MCB, annoyingly the holes are not in the same place. I'm surprised there isn't some installation regulation to specify the placement of the places where the connection holes are in order that the pre-fab busbars can slot in easily.

Due to this, I had to move the immersion heater switch, and perform some mild origami on the busbar to get things to fit. You'll see they're bent at the ends like an eastern asian tile roof (for a good example, look up Meiji Jingu).

The RCCB fitted
The RCCB installed.

The way this is wired up is the mains comes in at the bottom of the RCCB (helpfully indicated by a yellow flap and big arrow). Power passes up through the RCCB to protect everything downstream. At the top of the RCCB are two busbars, one marked blue for neutral and one that's black for live. This takes the power to each of the MCBs. Power passes down through the MCBs to the screw terminals at the bottom to which the wires for the electrical circuits are connected.

Here's the setup reassembled. And, you'll be pleased to know that prodding the little "RCD Test" button (which I would imagine leaks 30mA to earth) causes the RCCB to trip out. It does not have any effect on the big disjoncteur as 30mA is negligible if you're looking out for some twenty times that.

The fusebox now
The fusebox now - I'll need to redo the labels.

Now the wiring in the bedrooms and the extension lead in the living room is protected by a 30mA leakage trip switch. The rest of the house isn't, but it's a start that something is. Little advances...

 

The vast of night

Home, illuminated by solar charged LEDs. Long exposure (~30s).

Home @ night
Home @ night - Subaru!

Looking towards the Big Dipper, for 1h45m. How many aeroplanes and satellites can you spot? In this picture, I make seven satellites and three planes.

Star trails
Star/satellite/plane trails.

 

 

Your comments:

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Anon, 13th October 2023, 01:25
Ah yes, dodgy electrics... 
 
When I first moved to where I am now, the main fuseboard ('consumer unit' in UK speak) was one of the old Wylex 6+1 units with rewirable fuse carriers, and a 45A cartridge fuse (the '+1') for the cooker circuit. A couple of the fuses had been replaced with plug-in MCBs, but the rest were the original rewireable type. 
 
A second consumer unit (now isolated) sat next to it, with a 60A and 5A fuse, both rewirable. These were for the original 'ducted air' heating system, which had been decommissioned and removed before I bought the house. 
 
All this came out and was replaced with a new consumer unit that was compliant with the then-current 16th Edition wiring regs, a 6+6 split load DIN rail with a 30mA RCD protecting the left side of the board. This stayed in place until last summer when I had solar PV installed. 
 
Because the board was a DIN-rail type, it was fairly simple to reconfigure it as a 14-way with standard double-pole switched incomer. I then replaced all the MCBs on the RCD side with RCBOs, which combine the functions of an RCD and MCB in a single-width DIN module. 
 
This also freed up two slots on the fuseboard. One was used for the feed from the solar inverter. The other one is 'reserved' for installing an EV charger 
 
The huge advantage of this arrangement of course is that an earth fault won't trip out the whole bank of circuits, just the one circuit that has the fault. 
 
The downside? An MCB costs around £4. An RCBO is between £25 and £40, depending on the make. However, a 'well-known DIY chain' (hint - starts with B and ends in Q) were selling off RCBOs for £2 each. No, that isn't a typo - a couple of quid. So I basically picked up a basket full of them. 
 
Now if there's a fault in, say, the laundry room, it won't trip the entire house. 
 
I do still have 4 circuits that use a standard MCB and don't have RCD protection: 
 
* The indoor lighting circuit - all the light fittings and switches are Class 2 (double-insulated) so an earth fault could never occur, plus the potential hazard caused by the lights tripping out is far greater than any potential shock hazard (which is non-existent on a double-insulated fitting). The outdoor lighting circuit is, of course, RCD protected. 
 
* The circuit for future installation of an EV charger. Every EV charger I've seen has a built-in RCD, so having one on the supply would be superfluous. 
 
* The ring circuit for the office and servers. The combined leakage current from all those switching PSUs could easily exceed 30mA. The UK wiring regs state that appliances which can be connected or disconnected by the end-user (ie stuff with a 13A plug) must either be protected by an RCD, or 'alternate measures must be taken to provide an equivalent level of protection'. In this case I've labelled up all the sockets stating "IT / office equipment only", hard-wired as much as possible, eg there's an IEC cable coming from a fused connection unit (often mistakenly called a 'spur') which connects directly to the APC SmartUPS. All the servers and network kit then plug into the UPS. 
 
Apparently some other countries (America mostly, but some of Europe as well) think us Brits are paranoid about electrical safety, however the facts speak for themselves - the UK electrical system is one of the safest in the world.
Rick, 13th October 2023, 07:47
"is one of the safest in the world" 
Two words: ring main.
David Pilling, 13th October 2023, 13:33
Look online, France is a bit less safe than UK for electrical accidents, Spain is a lot less safe, and NL much safer. In the world, Japan is the safest, but USA is on a par with the best in Europe.
Zerosquare, 13th October 2023, 21:45
"So now, rather than measuring the current draw, we're measuring the power draw." -> I believe this sentence should be reversed, since measuring the current draw gives you a value in VA (well, A actually), while measuring actual delivered power gives you a value in watts. 
 
And you're wise not to buy circuit breakers from dodgy sources: https://www.youtube.com/watch?v=2TJEzdqtXlQ
Rick, 14th October 2023, 21:29
David: I think the current French regulations are pretty safe - perhaps better than the UK (given the whole ring main issue that people over here don't believe when one tries to describe it). For example, technically (following a 2015 revision), electrical circuits are supposed to be protected by *TWO* RCCBs. The theory being that both are unlikely to fail at the same time, so if one doesn't trip the other will. 
 
The problem France has is an awful lot of shonky wiring thrown up post-war and through the sixties where there was a big push to electrify the place. I know this place got wired up in 1968, as that's the date stamped on the main trip switch. It was probably candles and lanterns before that. 
They are tearing out the old wiring, the four bare wires, because they were a lightning, human, and wildlife hazard, plus being somewhat naff cabling, the 230V supply might be more like 210V (if you're lucky) by the time it got to the property. 
The push to get everybody onto a smart meter came with a huge plan to overhaul the network. Around here, all the three phase is now a twisted bundle of insulated conductors. 
Couple this with a lot of do it yourself electrics of varying degrees and you will have plenty of properties with electrics that would be horrifyingly substandard. This place, for instance. Where on the old part (everything that isn't the above fusebox), it's basically three phase running around with stuff tapped off of it in a haphazard manner, a rat's nest of junction boxes and wiring that probably makes sense after a few glasses of the red juice. Oh, and that main trip switch is the *only* cut-out short of blowing the master fuses. 
And the guy that did the survey said that while the wiring was "acceptable to the epoch in which it was installed but would be considered dangerous today", he also said this was one of the better ones. At least the wires run in metal conduits, especially up in the more exposed places where mice, bats, and other things-with-teeth live. 
 
Spain? Uh... I've seen Spanish wiring. It is... an adventure. 
 
I don't believe that the USA is on par with the best in Europe. Did you read that on an American site, by any chance? The power grid is known to be woefully antiquated. A lot of homes, especially the older ones, are equally out of date and not really designed for the loads being put on them by modern things. Like in France, when the wiring regulations are updated the older stuff is "grandfathered", meaning that it gets referred to as "installed in common with the practice of the time" rather than a flat out failure. Which is why I'm sure there's a good amount of cloth covered rubber wiring... just like here... which explains my strict "look don't touch" policy (as the stuff crumbles). 
In the US, there's also a big problem of houses wired in the 60s and 70s using aluminium wiring (was cheaper). Turns out that aluminium in contact with copper corrodes, which can loosen connections causing arcing and potentially start fires. This isn't a code violation as it's prevalence mean it was grandfathered in, but any place with the two together can be considered a risk. 
Then there's the oddity that is known as "backstabbed" wiring, where for some switches and sockets the wires are simply pushed into clamps rather than being wound around a screw or, as in the UK and France, that special terminal that's a little copper tube with the screw that clamps the cable in place firmly. The backstabbed wires could work loose. This practice is permitted, even in new constructions. 
 
Even worse, for older buildings, behind the walls there may be a cloth covered live wire running along the battens on ceramic knobs, with the (bare!) neutral wire about a foot apart running in parallel. 
 
Plus, I'm sure you've seen transformer explosions on YouTube. From the little pole-mounted things going bang to big substations blowing up. One thing most of these have in common is that you'll invariably hear somebody saying "aw my gad!". Because, it seems, exploding transformers is something that happens in America. 
While I'm sure it could happen anywhere, it seems much more prevalent a problem leftpondian ways, and possibly a result of underrated transformers being run beyond spec by the demands of modern life. It's probably a good thing electric cars aren't making that much impact in the US, or they'd all go pop. 
 
Europe also has a win in using 230V rather than 110V. This means lower current in the cables, plugs, connections, etc. A 2kW bar heater at 230V draws 8.7A but at 110V it's about 18.2A!  
 
When it comes to reliability, France ranks first (survey by World Bank/CEER/EIA). Then South Korea, followed by Switzerland, then the UK. America is ninth, between China and UAE. 
 
I will give you a win for the three-pin plug. The UK plug is a very nice design, plus one of the few in the world with a built in fuse. Shrouded terminals and an earth pin to open protective flaps. 
 
Here in France (and also applicable to Germany and similar countries), most sockets usually have flaps preventing access to the conductors, but these flaps are activated by ramming the plug into the socket. It takes mechanical force to push the thing out of the way, and over time this can wear and either fail open, or refuse to open (and in this latter case if the person tries to fix it by applying more force, then stuff might break inside). The three phase sockets have no such protection, a child can easily stick a nail inside. There is no need for shrouding as the sockets are recessed so in a properly designed socket, the body of the plug slides within the walls of the socket prior to contact being made. 
However, like with the American sockets, the outlet wire tends to protrude from the rear of the plug, not the bottom like in British plugs. Which does rather give people the habit of lazily unplugging things by yanking on the cable and pulling the plug right out of the socket. Dead easy to do even with the chunky 16A plugs. Try that with a British plug and you might find it'd be simpler to pull the socket off the wall than the plug out of the socket. 
 
Zerosquare: Had a feeling that would be Big Clive, but bloody hell. There ought to be a way to hold the tat bazaars liable for supplying such blatantly dangerous goods. 
Well done that guy's intuition that felt that the things "didn't feel right". 
And, Big Clive, dripping sarcasm all the way through that video. 
 
Note that when I'm talking about VA vs watts, I mentioned that there's a difference between real power and apparent power, and the latter is why we use VA. Instead of simply measuring the current passing through the system we're measuring the power that is being supplied. But it's not the real power (as would correlate to amps, watts, etc) but the apparent power delivered. It's a complicated topic, and AC can behave in odd ways. 
 
I think another part of the change is that in the old days most loads were resistive. You had incandescent lights, you had water heaters, you had cookers and bar heaters. Sure, you will have had some capacitive loads like motors, but the average house didn't have that many. A fan, a washing machine, a fridge... 
 
...these days, the reactive loads probably outnumber the resistive ones by orders of magnitude. Switch mode power supplies and low current lighting. 
While that might only be two items, the first one counts for pretty much ALL modern tech. Monitors, televisions, internet boxes, DECT handsets, mobile chargers, etc etc etc etc. 
 
I'm quite sure there are subtle differences that the modern meter (in VA) would pick up that might be missed by an older meter (in units, or kW/h). 
jgh, 15th October 2023, 06:25
I think it was around the late 1990s that the UK Discovery Channel stopped showing US home maintainance programs due to thousands of letters from horrified UK electricians at the televised implication that things like joining wires with toothpaste caps was an "ok" thing for a UK audience to do.
Rick, 15th October 2023, 06:39
Oh, yes. Quite. 
 
I forgot about the propensity for joining two wires by twisting them together and shoving a threaded cap on the end (which would explain the toothpaste cap). It's as if they've never heard of screws, or terminal blocks... 
Anon, 15th October 2023, 17:35
I have to admit that even now I still have a bit of a grudge against the Discovery Channel. Not because of anything they show, but because back in the early 90s the Discovery Channel shared a transponder (Sky channel 41) with what was by far my favourite channel, CMT Europe. Just before 4pm, CMT would just cut out, to be replaced by a black screen with the Discovery logo top-left for a minute or so. 
 
Not sure what the aversion to a ring main is. It does have one huge advantage, which is that the CPC (Circuit Protective Conductor - aka the 'earth wire') has redundancy. If there's a break then there's still an earth, so breakers can trip and RCDs can operate if there's an earthing fault. 
 
I'm not sure why the French are so down on ring circuits, if done properly they're actually a really good idea. Particulary with regard to earthing continuity. 
 
The American way of doing things might fly over there as they use a split-phase supply, with only 120V between phase and ground. With a lower voltage you can get away with lower safety standards. 
 
Incidentally the phase to ground voltage is why all hand-held power tools on a building site use a 110V supply. The step-down transformer is configured as 55-0-55V, with the centre tap referenced to neutral on the supply. So there's 110V between the outer taps, giving enough voltage for power tools to operate correctly, but with a maximum phase-earth voltage of 55V. Which is going to tingle a bit but is unlikely to be fatal. In any event, the mandatory RCD will disconnect the supply should such a situation occur.
Rick, 15th October 2023, 18:27
Damn, that was a long time ago. I remember CMTE. 
 
The problem with the ring main is that people use lower capacity wiring because the current flows in both directions, so if it's a 20A circuit (say) then one can use 10A rated wire. 
Problem is, because if it's circular nature it's near impossible to tell if there's a break in the wire, at which point you're risking running a single wire out of spec. 
 
In France, it's strictly spur circuits. And yes, earth can break just like live/neutral, but a simple plug-in widget will tell you if there's any problem, including a missing earth. 
Just tested it on the power strip that runs the ADSL router. It correctly reports "Missing Earth" as it's plugged into an old (non-earthed) socket. This isn't a problem for me as there's nothing there that actually needs to be earthed, it's either the amplifier (two pin plug) or power bricks. 
 
Yes, humans are non-linear resistors, and 55V is often below the breakdown threshold so it shouldn't dump the amps across the delicate parts. Especially important given that building sites tend to be harsh environments to work in. 
Anon, 15th October 2023, 19:30
Yup, I miss CMT Europe. Mind you, modern 'country' is just complete crap, so probably not missing much. And the American CMT channel no longer even plays music videos, just wall-to-wall re-runs of the Dukes Of Hazzard... 
 
UK wiring regulations require the use of 2.5mm2 twin and earth cable for wiring ring circuits. Which has a current capacity of 27A if surface mounted, 23A if in trunking with other cables, or worst-case (mounted in a wall surrounded by thermal insulation) 18.5A, with a diversity rating of 24A (source - IEEE wiring regulations). The breaker for the ring circuit must be rated at 32A. By applying diversity to the loading, it's clear that one 'leg' of the ring main (if the two sides become separated) would never be overloaded to the extent where it presents a hazard. 
 
Now if some cowboy were to wire up a ring main circuit using 1.5mm cable (diversity rating 17.5A, combined rating 34A, 'well the breaker trips at 32A so that'll be fine, right?') then the point about ring circuits may well be valid. 
 
As for breaks in the cable, when testing the installation one has to do a continuity test between the two legs of the ring, both individually and in series, an earth continuity test, and an insulation test between live-neutral, live-earth and neutral-earth. The modern 'megger' is quite brilliant as it gives you an actual cable resistance, rather than the old type where you had to crank the handle and get a reading of 'up' or 'down'. 
 
All four ring circuits here are on 32A breakers, 3 of those are RCBOs (so RCD and MCB combined). As I mentioned in the earlier comment, the IT ring is on a normal MCB with all sockets clearly labelled as "no RCD present". The other three ring circuits (upstairs, downstairs, laundry room) are RCD protected (via the RCBO). 
 
I also have a radial power circuit supplying the hi-fi / home cinema system in the front room. Slight overkill but as I was rewiring the house anyway it wasn't really any extra effort. This runs off a 16A RCBO (as it uses 2.5mm cable) and feeds two double sockets, one of which is surge and RFI filtered. 
 
Also I checked the board, there's actually 5 circuits that don't have RCD protection. There's a radial circuit going to a dedicated outlet to power the fridge-freezer in the kitchen. In case of an earth fault... it'll just trip the relevant ring circuit, and won't destroy a few hundred quid's worth of food in the freezer. 
 
The 'el-cheapo' way of doing things now in the UK is to fit a high-integrity consumer unit, which has twin RCDs (each feeding a bank of MCBs), with 2-3 slots for RCBOs for circuits like a fridge-freezer, emergency lighting, air-con (as the leakage from an air-con unit can cause nuisance tripping). Mainly because an MCB costs about £4, whereas an RCBO is about £25. On the other hand, if you can run to the extra expense (or you happen to hit lucky and pick up a job lot of RCBOs like I did) then you dump the separate RCDs and just use RCBOs for everything. 
 
You made an interesting reference to "grandfather rights" - the situation in the UK is similar. If you're upgrading part of an installation, it has to be wired in accordance with the regulations that were current (no pun intended) at the time the installation was first commissioned. However if you're re-wiring, the new installation has to comply with the regulations in force at that time. 
 
This caused an interesting situation here as my house was built in 1974, so the original installation would have been made according to the 14th edition. However, I re-wired the house in 2006, by which time 16th edition was in force. 
 
So with the 'grandfather rights', any new circuits or alterations have to comply with the 16th edition, not 18th. Which is why I can get away without RCDs on the lighting circuits (the current 18th edition regs are that all circuits 'must be RCD protected, unless alternative provisions are made to prevent faults of the nature that an RCD is intended to protect against'). 
 
Technically my lighting circuits don't need RCD protection as I've employed 'alternative provisions', namely that all light fittings are Class 2 (double-insulated) and thus contact with live parts is impossible, even under a fault condition. 
 
(Yes, I do hold a current IET / IEEE qualification, why do you ask? :) )
Rick, 15th October 2023, 20:44
CMT plays old TV programmes? Sounds like they went the way of MTV (that being said, MTV:DE played a lot of Daria with on-screen subs that I could ignore) when I was watching it way back when. 
 
It looks like for "up to 8 sockets" you can use 1.5mm cable with a 16A breaker (maximum), or up to 12 sockets with 2.5mm cable and a 20A breaker (maximum). The kitchen has to be on a separate circuit with 2.5mm cable, a 20A (max) breaker, and up to 6 sockets. 
Lighting can be up to eight lights on 1.5mm cable and a 16A (max) breaker, but the regulations advise the use of 10A. 
Ovens, freezers, and washing machines must be on individual circuits with a dedicated 2.5mm cable and 20A breaker. 
Electric hobs must be on a single 6mm cable with a 32A breaker (or 2.5mm with a 20A breaker if it's a three phase model). 
A 16A car charger has to be on a dedicated 2.5mm cable with a 20A breaker. A 32A charger has to be on a dedicated 10mm cable (damn!) with a 40A breaker. 
Fitted heaters / heat pumps / etc - 3500W (1.5mm, 16A), 4000W (2.5mm/20A), and so on. 
 
Sockets are counted per plug hole. So a dual socket unit counts as two. 
 
There's other interesting stuff, like if you're running three phase and you plan to draw 4kW, that's 8A so you can run 1.5mm cable 120 metres, 2.5mm cable 200M, and 4mm cable for 320M. 
 
For single phase, 4kW is 18A so it's not permitted on 1.5mm wiring. For 2.5mm, up to 21M, and for 4mm up to 34M. 
That means my orange extension lead, that I think is 2.5mm, is only rated for 1.5kW over it's 50M length. Remind me of that when I plug the 2kW chainsaw into it. ;) 
 
I don't have any certification. I'm the sort of sad git that reads this sort of thing for fun (and then forgets most of it). 
Anon, 15th October 2023, 22:08
The USA version of CMT apparently hasn't played music videos for a long time. CMT Canada apparently still does. Oh well. 
 
10A breaker for lights? The UK regulations state that you have to use a 6A breaker for lighting circuits. 
 
Ovens and hobs can share a 40A circuit. (An electric hob takes far more juice than an oven.) Prior to 18th Edition, the cooker circuit (whether for a free-standing cooker or separate oven and hob) wasn't required to have an RCD unless the cooker control unit had an integral socket. (Mine doesn't.) 
 
Basically on 17th edition and earlier, an RCD was only mandatory for a circuit that could have removable appliances connected to it (eg a ring main) or a circuit that fed equipment in a 'hazardous location' (eg a bathroom - so the shower circuit had to have an RCD). Fixed appliances and lighting circuits were not required to have an RCD prior to the 18th edition of the wiring regs. 
 
You are allowed to 'spur' up to two sockets off a ring circuit - a double socket outlet counts as two. HOWEVER... if you connect a fused connection unit (whether switched or unswitched) as the spur, you can wire any number of sockets into this. The thinking being that the separate fuse will protect against overload. 
 
It's actually commonly used in outbuildings. For example I'm having a summerhouse put in. I've run a length of 3-core 4mm armoured cable to the end of the garden. This is connected to its own 20A non-RCD circuit. The cable then terminates onto a fused connection unit with an integral RCD, with all the power outlets in the summerhouse being supplied from this. In addition there will be a FCU fitted with a 3A fuse in place of one of the power outlets which will supply the lighting in the summerhouse. 
 
ObGeek: I've also run (alongside the 4mm SWA cable) a length of armoured Cat5 to provide a gigabit Ethernet connection in the summerhouse when it's installed. I'll also be installing a second access point up there as a repeater, using the Ethernet connection as the backhaul. Which means I should get full N300 coverage across the garden as well as indoors. (All infrastructure is hard-wired using gigabit Cat5, of course.) 
 
Once the summerhouse is erected (fnar fnar!) I'm intending to build a Raspberry Pi with a touch screen into the wall, run PiCore Player on it, build some decent car speakers into the front walls of the summerhouse so I can sit in there in the evening and chill out with my favourite tunes. Like this playlist that I've constructed after finding a whole bunch of VHS recordings made from CMT Europe back in the early 90s...
Rick, 15th October 2023, 22:47
As I mentioned somewhere else here (in an entry or a comment elsewhere), I've come across Epic Rock Radio. So, prog rock, power metal, side order of soft goth, and songs where six minutes is considered brief, many are at least eight minutes, some push the quarter hour marker. We're getting into material that is broken into interrelated sections (like Octavarium by Dream Theater, or anything by Nightwish that's over ten minutes but Ghost Love Score is the one most people would point to - there's even in orchestral intermission in the middle!). 
 
Bliss... ;) 
Rick, 15th October 2023, 22:55
About the only "country song" I remember (*) is one of the first ones I heard - "Christmas Carol" by Skip Ewing which ticks just about every box in the country cliché list, and is off the scale soppy as well. 
 
* - I'm not counting Glen Campbell. Blame mom for that. 😂
Anon, 15th October 2023, 23:11
Now I've actually heard of Dream Theater. I even have a couple of their albums (picked up in the 5 for £1 on CDs offer at one of the charity shops). 
 
Falling Into Infinity I kinda liked. The track "Hollow Years" reminded me a little of some of Sting's solo stuff, eg "It's Probably Me" (off the opening credits to Lethal Weapon 3). 
 
Train Of Thought... listened through it... sorry, it's a no from me. It just sounds like noise, and (to my ears) not pleasant. 
 
I just checked in Winamp (yeah yeah, I still use it, not found anything better to use on the PC as a music player). The longest single track I have is 46:53 - track 4 (the title track) of "Waiting For Cousteau" by Jean-Michel Jarre. 
 
The next one (not including "ABBA Undeleted" at 23:28, a medley of outtakes and otherwise unreleased material) is 'Autobahn' by Kraftwerk, coming in at 22:47. My guess is when that was released (1974) it took up the whole of side 1 of the LP. (Tracks 2 to 5 on the CD were obviously side 2.) 
 
At the 'shortest songs' end, not including outtakes, interludes or album intros, there's things like "Monkey Let The Hogs Out" by Jerry Douglas (1:02), "Goodbye Cruel World" by Pink Floyd (1:14), "What Do You Want" by Adam Faith (1:34), and of course The Beatles "Why Don't We Do It In The Road" (1:41). 
 
I'm so glad I've got copious amounts of disk space.
Anon, 15th October 2023, 23:18
One of the greatest 'traditional' country songs: 
 
https://www.youtube.com/watch?v=-j3hkiatoac 
 
I think I already posted a link to 'Maybe You Were The One' in a comment on another blog post, so I won't repeat that one here.

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