Switches and sockets

[wobs]

When I got all the main electrical work done on our house in 2013 (almost a full re-wire), our electrician was of the opinion that the standard would eventually go back to radial circuits rather than rings. Not being an electrician, I'm not sure of his reasoning.

Interesting. I’d guess it’s because, outside of kitchens, very few devices these days are high power so a 30A circuit is overkill in most cases. It would also save cable and copper, so a bit more eco-friendly.

In practice, I’d say the modern requirement is for many more sockets rather than lots of power, which no doubt why those plug-in ‘socket strips’ are so popular these days. I have about 10 sockets in my study but I doubt I’m using more than 3A even with everything switched on!

Indeed, the average household uses about the same amount of energy than a house did in 1970, but uses many more sockets. Of course much of this is due to more efficient fridges and other kitchen appliances.

 

[malcolm]

When I got all the main electrical work done on our house in 2013 (almost a full re-wire), our electrician was of the opinion that the standard would eventually go back to radial circuits rather than rings. Not being an electrician, I'm not sure of his reasoning.

I think the reasoning is that if a ring becomes disjointed when some muppet changes a socket you are back to a radial with a little wire and that is difficult to test for. The rest of Europe seems to use radials and I imagine for them the rest of the sockets down the line might provide a clue that something isn't right. My sockets only power a computer rather than an electric heater in every socket so it should be less of a problem for me.

For the OP I'm using good quality white modern switches and sockets in my rewire together with lovely period style Chinese light fittings of surprisingly good quality. I grew up in a big 1912 house that still had the original brass switches and light fittings set into wood panelling. If I had those I would do everything to save them.

 

[overlander matt]

Interesting discussion. I have just bought a load of white plastic sockets and switches while the main 'design' decision is postponed for now. At least we have light and power with the darker evenings setting in.

On the rewire front, our electrician has gone with 30A rings for the sockets on each floor with two circuits for the ground floor and a separate one for the kitchen. What I have not previously come across is the use of RCBOs for each circuit. At a cost of approximately £40 each and a total of 20+ circuits, this new addition is proving very expensive... Our situation is slightly complicated by the house having a 3-phase supply which is only adding to the cost. Whether there are significant benefits remains to be seen - the previous owner used to run a small manufacturing business from the barn. I'll be switching to single phase there when that phase of the project eventually starts.

 

[Craig89]

The reason to use RCBOs for each circuit is if you have an earth leakage fault then you only trip the faulty circuit and not how ever much of the board that is protected by a single RCD. Its definatly the way to go if you can stomach the initial cost.

I will be getting ready to do my full rewire on my house soon and although I havent finalised all the details yet im pretty sure I will be doing all radial circuits protected by RCBOs mostly 16A circuits, 32A in kitchen and utility. As described above, terminating 2x 4mm T+E cables into the back of a socket is a bit of a pig and thats why ring mains are usually used for 32A circuits.

Matt, I personally wouldnt remove the 3 phase. I wish I had it, the cost to install it is big and already having it could be a potential future selling plus point

 

[Flyfisher]

If you have 20+ separate circuits then that's a pretty substantial installation.

Is there a reason your electrician is using RCBOs on every circuit? I ask because we have a number of separate consumer units and each of them has a RCD but with MCBs for each circuit. This means that a residual current fault on just one of the circuits will trip the RCD that feeds a number of circuits. With RCBOs on each circuit, only one circuit should trip at a time. This may or may not be important depending on your view but, as you've found, it costs more.

Our electrician mostly used 'split rail' CUs meaning that they have two RCDs feeding two 'banks' of MCBs. With lighting and power circuits equally divided across the two 'banks' it means that a fault may trip a number of circuits but not all of them, so you still have some lights and some power. Again, this may or may not be important but it's a slightly less costly solution.

But we have only a single phase supply and the rules for 3-phase supplies might be different due to the potentially much higher voltages involved.

As an aside, I've installed an 'emergency exit' LED bulkhead light near the CU in my workshop. These are basically LED lamps with an internal battery backup and can be wired so that when the mains power is on, the light is off and the battery is being trickle-charged. When the mains power is off, the light comes on, powered by the internal battery. This avoids having to fumble around in the dark looking for a torch in order to check the CU. They are only about £10 online. Just an idea.


Edit: Craig beat me to a reply and has covered some of my points.

 

[a twig]

I should confess I originally completed my education as an electrical engineer, so was just asking the question to see what people's responses were rather than out of any great desire for knowledge

Would thoroughly recommend the RCBO route if you can afford it - particularly if you are planning on staying in the place long term it will be worth it. Here we just have the two RCDs, then MCBs, as we will be selling up in a couple of years, but our next house will be a "20 year" house, and RCBOs in a new CU will be one of my first jobs.

Agree with Flyfisher's point about emergency lighting, it is available in a lot of other form factors if bulkhead fittings aren't your thing, for example you can get a natty little 2W LED downlight, the usual suspects (Aurora/Enlite, JCC etc) sell them. Again, this will be something for the next place for us!

Definitely keep the 3 phase supply, with electric vehicles on the rise, have a 3 phase supply allows the fitting of a decent external (reasonably) fast charge point rather than 13A trickle, probably talking a couple hours to 80% charge, rather than overnight.

These days there are very few situations where an electrician would put in a ring circuit rather than radial - might be worth asking his reasoning? If there are several rings per floor, then I'm struggling to envisage why you wouldn't have each as a radial, less wiring, less effort to install and more simple to fault find?

 

[88v8]

Our wiring is fairly organic. Mainly a 60s rewire in solid pvc - I mean solid as opposed to that ghastly stranded aluminium stuff - which is either on the surface or buried in the pointing.
The organic element is the apparently random circuits, where there are four lighting circuits some of which cross from upstairs to down, but only one power circuit for the whole house. Plus cooker and immersion circuits, that is.

PO had a new fuse box installed in 1993 as part of the electrical certification process. It's a complete PITA, even a bulb blowing can result in the whole house shutting down. The garage has its own fusebox and trip, but a lighting fault there used to jump over the garage trip and the circuit trip and trigger the main switch.
Fortunately this never happened while we were away as not only would we have lost the three freezers, but the cellar sump pump which also runs off the single power circuit.

We won't be doing any general rewiring, but I do intend to have RCBOs fitted, which should eliminate the problem of tripping the entire installation.

Funny you should mention radials... our ring circuit has a break somewhere. Not the LN, but the earth. I've looked behind all the sockets and there are no earths out, so I dunno. The electrician did say that technically we should have it derated into two separate 16A trips, as in effect we have two radial circuits.

Using old fittings... one has to watch for corrosion of brass components, as not only does this make for poor conductivity but corroded contacts can break. However, this can be detected with the Mk I eyeball at the time of installation. I would think that some of our switches must be approaching the magic 100yo.

Ivor

PS The exception to this modernity is the storage rads, which are still powered through a 'proper' fusebox. This is very useful as it provides a single point on which to store the fusewire. Fusewire comes in so handy when one needs something thin to poke down a hole, like yesterday when I needed to clear one of the Landy's washerjets. If it were not for the fusebox, I'd have been hunting all over the place for the fusewrire

PPS .not al electrician.

 

[overlander matt]

I should post some pictures of the new installation. There is more work to be done but we now have one large (12 way 3 phase) distribution board that has tidied up a horrendous mess. It now has the feel of a small commercial installation and the RCBOs will at least mean only one circuit goes down at a time. It won't be long before they will be mandatory in all new installations.

I had not considered the three phase as a benefit for an electric vehicle charging point. That will be useful down the line. It may also come in handy for running a heat pump in future too... For now I will suck up the costs.

Photos to follow...

 

[LeeL82]

sorry to jump on to this a bit late but id highly recommend the range from Hamilton too, ive used them myself in the past and although expensive theyre a great company to buy from, even offering bespoke services.

https://www.hamilton-litestat.com/decorative-wiring-accessories/bloomsbury/#.XarduuhKg2w

 

[overlander matt]

Time for a quick photo... I must admit I cannot find a photo of the old arrangement - you don't really appreciate the scale of the mess without it. As it stands this is what we have right now with a combination of new circuits running off the new board and old circuits off the old unit.

 

[fernicarry]

Bit late to this. Thats quite a beast you have there Matt.

One thing about RCBO's is that they are generally single pole i.e. they only disconnect the live. RCD's are 2 pole so disconnect both live and neutral. If anything the way the regs are moving is to treat neutral as if it was a live conductor. Under fault conditions you could see a significant voltage on the neutral and an RCBO will not protect you from that. In reality though that's probably not very high up the list of things that might kill you today...

I have probably 20 odd final circuits but they are spread across 3 boards. Main one in the house, and two in the outbuildings served by sub-mains. The sub-mains are protected by a time delay RCD so that you get discrimination with the RCD's/RCBO's on the sub-boards.

I do have a few RCBO's scattered around for circuits that I don't want to ever be taken out by something else tripping, the alarm and all the networking gear are on an RCBO. The garage is all RCBO's so that an 'incident' with a power tool doesn't knock off the lights too leaving you standing in the dark holding a still rapidly spinning pointy thing..... Another downside with RCBO's is that a single circuit can be out for quite some time before you notice whereas when an RCD takes out half the building you tend to notice quite quickly.

Ring circuits are a bit of a British peculiarity. Introduced post-WWII due to scarcity of copper I believe. They can end up being very silly if the area served is far away from the board, as our kitchen originally was. You have a long run in, the actual ring bit, then a long run back out again. And our kitchen ring was broken so no longer a ring and had also been extended and spurred into the bedroom above and the utility room. That's all been redone and the board moved to a more central position.

I did the utility room as a separate radial in 4mm2. From a circuit design pov that makes sense, its just a couple of sockets on the end of a longish run, but getting 2x4mm2 into those cute little grid switches was an absolute mare of a job.

2 of our 3 rings are fused down to 16A and 20A to keep within the total 100A limit of the main board. In reality you never have any significant loads outside of kitchen/laundry other than maybe the vacuum cleaner. Not much need for 3 bar electric fires in the bedroom nowadays. The upstairs one does have a bit of a habit of tripping immediately when turned on due to the inrush from all the various small power supplies. I plan to change it to a C-curve breaker next time I'm digging around in there. European circuit design seems to favour lots of 16A radials on C-curve breakers. So much for standardisation across the EU. They made us change the wiring colours but circuit design practice is still very different.

We also have a 3-phase cable head but only one phase is connected and metered. Heating used to be by electric storage heaters so no doubt all the phases were in use at that time. Lord knows how this will play out for the majority of households when the Powers that Be force us to abandon carbon in favour of 'green' electricity. Whats going to replace my 35kW gas boiler? That'll need two phases to itself for starters... And then we have to charge the 4 EV's in the drive, another 20kW there. Oh wait, smart meters...

And now I'm off to finish rewiring the upstairs lights, so that I can then finish redoing the loft insulation, so that I can get the loft flooring back down, so that I can move all the rubbish, I mean valuable historical artifacts, that are cluttering up my office up into the loft. 3 years and counting on that task but 'nearly' done.

 

[Flyfisher]

If anything the way the regs are moving is to treat neutral as if it was a live conductor. Under fault conditions you could see a significant voltage on the neutral and an RCBO will not protect you from that.

Modern RCDs also detect residual current faults between neutral and earth, as I discovered some years ago. An MCB (and presumably an RCBO) will isolate live on a particular circuit, the main RCD will still trip if the earth and neutral are shorted by, for example, cutting the cable.

Lord knows how this will play out for the majority of households when the Powers that Be force us to abandon carbon in favour of 'green' electricity. Whats going to replace my 35kW gas boiler? That'll need two phases to itself for starters... And then we have to charge the 4 EV's in the drive, another 20kW there. Oh wait, smart meters...

That's an interesting point, when typical domestic supplies are 100A (and many only 60A), which is 'only' 24kW and broadly equivalent to a typical gas boiler these days.

With talk of banning gas boilers in new builds by 2025 that's going to be a severe challenge for the electricity grid! Personally, I doubt that proposed date will hold but it's an interesting sign of the direction in which things are headed. https://www.bbc.co.uk/news/science-environment-47559920 I wonder if domestic installations are typically fitted with 100A fuses because that's deemed to be enough and if the actual supply cables are capable of carrying higher power to the home? The mass changing of supply fuses will certainly be easier than having to re-cable the supply to all homes!

Having said that, I've also read about plans to convert the gas grid to hydrogen, so where would that leave all those electric-only houses after 2025?
https://www.thetimes.co.uk/article/net-zero-hydrogen-heating-for-every-home-climate-2tgqfjvng

As for EV charging, I recently noticed a row of Tesla 'superchargers' in a fairly local pub car park. They claim to be 150kW DC. I've no idea of the voltage they run at, but 150kW is 625 Amps at mains voltage and will be even higher at the lower voltages (presumably) used to charge the actual car batteries. This is some serious electrical engineering!!

Interesting times.

 

[LadyArowana]

You just can’t have too many sockets though can you....... https://www.thesun.co.uk/news/10266499/five-bed-million-home-bizarre-plug-sockets/

 

[Feltwell]

The Sun Lady A? I trust you found that in the servants quarters!

You do have to wonder what on earth someone was thinking of with that house!

 

[Craig89]

I have been having discussions with a couple of my mates about how many sockets is too many because I am at that stage with my house and they have both sent me that link this morning suggesting that I need that many

 

[LadyArowana]

The Sun Lady A? I trust you found that in the servants quarters!

You do have to wonder what on earth someone was thinking of with that house!

Celebrity gossip is my guilty pleasure, and the awful rags can be relied upon to deliver ‘news’ which is missed from other more salubrious papers

 

[Flyfisher]

I have been having discussions with a couple of my mates about how many sockets is too many because I am at that stage with my house and they have both sent me that link this morning suggesting that I need that many

There seem to be a lot of blanking plates as well as sockets in that house. It would have been interesting to see the contents before the rooms were cleared as a clue to why all those sockets were required.

To be fair the owners, it's not too difficult to understand why so many sockets could be required these days. A half-decent 'separates' hifi/AV system could easily require half a dozen or more sockets. I have two almost full 6-way socket strips in my study (PC, 2x Screens, printer, scanner, ethernet switch, phone charger, camera charger, desk lamp, 2x powered speakers), which I doubt is particularly unusual.

Even so, having seen that house, I'm now even more glad that I resisted the temptation to install rows of sockets in certain places. At least socket strips can usually be hidden within/under desks as required without permanently disfiguring a house in that way.