Hello from the weird year 2020. I just watched Technology Connections explaining the U.S. electrical system. He casually explained that it's not nearly as weird as the U.K. ring mains. So that's why I am here. Great explanation. Yes, I now understand why it should be removed from the current standard.
You could have have individual fuses for the two ends of the ring to discover if the ring is broken. But that would only be for the live, as the neutral is not fused anyway.
It really was prompted by CJR electrical’s videos where he keeps going on about testing ring circuits, but before that I had seen TC’s video too combined that led me here 🙂
I don't know anything about electrics and to be honest i'm not sure how i ended up here, but i find this guy strangely captivating. I'm now considering installing a new consumer unit and ring main for no reason other than John Ward showed me how.
Don't listen to the naysayers, I've seen sparks that have an IQ of no more than 50 and seem to do fine. You can lick your finger and touch the bus bar to see if it's live just do it fast, if it goes DADADADADADADADADA up your arm and you tense up it's live. Just kidding... Obviously... I did mine but I was an apprentice for two years and assisted on many a board change, and I have mild ocd the wiring is absolutely beautiful it took me absolutely ages and no one gets to appreciate it :(.
I was taught the virtues of the ring mains when I left school in the 80's and did my apprenticeship, just before moving into IT, and thought it was a great idea. Now in my 50's and having moved into various old properties (and always checking for signs of heat/loose connections in electrical outlets) this video has explained so much. Well worth 16 minutes of my life to totally change my mind as to the safety of electrical circuits.
By far and away the most lucid explanation I have ever seen. Something I've always thought should be fairly simple has always had an air of complex, don't touch, experts only etc. and John's explanation is so easy to absorb. Your a genius JW.
I am a retired electronics tech who actually did some rewiring in my father's house in the UK. The old, lead-covered cable under the floorboards was beautifully layed out and neatly dressed, but as soon as it was disturbed the old rubber insulation disintegrated. I am guilty of incorporating "a borrowed neutral" into a three-way stair lighting circuit, but I am sure that the house has been completely rewired since my father sold it in the late 1980s. I could not understand the need for a ring circuit, primarily because I understood the risk of overloading in the event of ring discontinuity. This is the first video I have encountered that explains why I was correct about ring circuits.
The Canadian Electrical code still allows ring circuits in 2015. Never used one, never seen one and didn't even know what it was until I watched this video. Great video.
Excellent teacher, excellent channel. Thanks JW. I had a 32A ring circuit in an old outbuilding, and rodents had gotten into the walls, chewed on the wires and the RCD kept tripping. I expected the worst, that the circuit had been destroyed, but the electrician isolated and removed the chewed section and I was delighted to end up with two 16A radial circuits that tested fine and with roughly the same number of sockets on each. Could have been worse.
The ring main was introduced after a long and hard war (WW2) and materials were in short supply, previously houses with electricity had few 15A sockets each wired as a spur from a fuse box. With the advent of 13a fused plugs and ring mains (as then called) with the limited and perhaps rationed cable could be used for more houses than the same amount of copper used as single socket radial circuits. Whether a ring circuit NOW represents the best practice doesn't matter because there are probably 20 million ring circuits in existance and most electricians will meet them on a daily basis.
Thanks JW you brought me back up to speed, having done house wiring back at college as part of my apprenticeship I went into electronics and only ever used household electrics when needing to do my own, I will keep this video as a reminder. Thanks again. Ray.
Old ways die hard. Ring circuits usually reliable enough.Great variety of wiring globally.Protection way better now than it used to be. A neighbour called in about faulty socket years ago. Upon investigation at the fusebox, there in place of a fuse was a 6 inch nail glowing red hot. Necessity is the mother of house fires.
Singapore, and a few other Commonwealth countries, use Ring Whatevers. Here in VietNam Singapore invested highfises are equipped wigh clunky UK Plugs although not Ring Mains. We also use US-style flat in plugs, as well as Chinese plugs. When travelling i prefer the universal connector that comprises 2 wires wiith bared ends and fit almost anything!
I'm not big fan of ring circuits, but there is the benefit that the overall resistance of the circuit is reduced considerably when you have that last leg back. I mean, it does effectively nearly double the effective CSA of the conductor, and thus capacity of the circuit, by just having that (often short) return leg. I could see there being a lot more burnt-up sockets/cables if radials with many sockets on them where more common, as connections inevitably loosen over time, resistance (impedance?) increases, and then folk go and plug electric heaters and the like into them. I know regular testing should defeat this possibility, but really, how often do people actually get their installations tested? In my experience, the answer is: much, much less than they should.
Exactly my opinion! Leaving the ring complete as is it is and reducing the breaker to 25 A would be the best option with the safety add on that a broken wire would not be able do result in an overload. Long radials always have voltage drop issues at their endings.
I will never get over how differently you Electricians in the U.K. Do things differently than us Electricians in the States. Though I know you are professional tradesmen and take great skill in your craft , and know what you are doing, something like that would never be allowed over here. Always enjoy watching the way things are done over there. Wasn't intending to be disrespectful if I was, anyways cheers from the States.
Great video. Clear explanation. Currently studying this on my Level 1 Diploma course. Makes so much more sense to install separate radial circuits throughout a domestic dwelling. Cheers!
When I first heard about these, I thought they were relics of the past. I was _shocked_ (lol) to find out that they're still in use today, and you've explained very clearly to me how they work. I wouldn't want one in my house; good thing everything here in the States is what you refer to as radial.
@@jwflame Why don't they just repeal the standard for new installations? We have plenty of old wiring over here that, if worked on by a certified electrician (on the record), must be updated to meet current standards.
I heard, and believe story that, those 2* single sockets as spurs, were often changed to double-sockets (e.g. those conversion sockets)), thereby overloading the protection requirements for unfused spurs. So, regulations changed to disallow that configuration.
@@cglees 26 =) which, is usally ok for a 2.5mm cable unless thoroughly insulated. Diversity says in pratice this double-socket-spur (or indeed, 2 single sockets as spur) is allowable. However, for some reason, 2-sockets-to-1-plug adapters are allowed un-fused, which seems kind of silly!.
I watched this when it was new. I installed a garden building on my own land for my office, it was all wired using advice from this vid without ring circuits, but higher rated cable (6mm). 5 years later, it all still works perfectly. even with a 2.7Kw heater running off it at one point, as well as a computer and LED lighting. BTW, I also have a spur direct from the consumer unit for my Ring doorbell. All common sense stuff.
The most compelling reason for ring mains/circuits as compared with separate cabling to each socket (as in the forties) is that they give the user maximum choice in where to plug in portable appliances, without increasing the amount of wiring in proportion to the number of outlets. The intention is that in a room with plentiful sockets there will not be any need for long leads on portable equipment (trip hazards) or multi way adaptors (which can be a fire hazard). Why not use a radial? The advantage of the ring over the radial is that you can test for loop resistance. This detects whether there are any poor connections at any point in the ring, which could lead to a fire risk. You can test this at any point in the ring, without visiting all the sockets. This test is the reason for most of the rules about spurs. Secondly, if a poor connection does develop, it's less likely to cause a fire unless a second poor connection arises. This is because most of the power will flow to the socket that's in use by the line of least resistance. The dodgy socket gets hot when it is used, and hopefully the consumer will notice. That socket does not get hot when other sockets are in use (unless there are TWO dodgy connections) In contrast, in a radial, if there is a poor connection at an unused socket, that socket will get hot whenever sockets are used that are further from the CU. If that socket is rarely used, or is a permanently plugged in appliance, the consumer is unlikely to notice the hot socket till it bursts into flame. So the extra cabling back to the CU is for testing and safety. There is a coherent case to support this You clearly feel the the disadvantages outweigh those advantages, but it's only fair to mention that there is some sense to the design. It's not totally daft, as you seen to imply
4mm cable is harder to pull through, more expensive to buy and the wires are more difficult to screw 2 into the back of the terminals on socket oulets. Just a few disadvantages of radial to balance things a bit.
As an American with an electrical background, I've always been interested in what a UK "ring circuit" actually is, and how it works. This is the first guy I've encountered who explained it clearly in a way I understood. Thanks for that. It does seem like a simple enough concept, but I can also see why it was probably never adopted over here, because of extra wire, expense, etc.
My employer loves a Ring circuit, they'd put one in for any socket circuit consisting of 2 or more double sockets. I personally fail to see the point most of the time. It does make sense to have a 32A circuit for a kitchen/utility and I guess the little bit of extra testing involved still beats fitting a load of sockets with two 4mm cables in them. I remember one of my college teachers saying about how he'd converted a lighting circuit wired in 1mm into a ring because it was on a 10A MCB and the cables were all buried in insulation, bet that was a head scratcher for the next guy to work on it 😂
I could have done with a ring circuit to power my twin 2400W boiler elements for my still. I actually like the concept. Cheaper than having 20 amp circuitry installed.
I shoud not say this, or even go there, but the holy grail of all audipophile nutters is their own spur and somehow the magic electricity is different and everything is better with a dedicated spur. Loved the video, learnt lots please ignore previous comment 8) .
Hello John, love the videos, crystal clear and based in reality. I'm a basic DIY'er but want to do things safely and in accordance with the standards/guidance where possible. I live in a victorian terraced house in Wales. It has a modern CU but what I'm not sure about is whether it has a ring or radial circuit. Is there an easy way to find out? I've had a look at a couple of other videos but am left confused... Many thanks, Craydon
Come to think of it, I use a similar "circuit design" on my electrical fence (that adds extra incentive for my dogs to not try to go through the yard fence). If a wire gets broken, both sections of the fence still have power. I can see a reason why the ring circuit could have an advantage from a fault tolerance standpoint, but I would still size the wire so that even if the ring was broken, it could still handle as much current as the circuit breaker for the circuit. I never rely on a house that I buy to be wired *correctly* since a previous owner might have thought he was competent to do DIY electrical work (and he wasn't) or the builder was using somewhat unskilled workers who didn't particularly care whether they did it right for the wiring installation. I've seen cases where 110VAC was on the *ground* at an outlet because some wires were touching in an outlet box. To be fair though, this was an old house which was originally built without electricity and there were still remnants of previous electrical wiring designs. There were places in the attic where some of the old asbestos and tar wiring insulation was still around (although it wasn't being used). There were also some remnants of the old "knob-and-tube" style where wires didn't have insulation on them and bare wires were run while being separated from contact with the materials of the house (or each other) by porcelain knob and tube insulations.
Hello John, I'm finding your videos to be an excellent learning resource, thank you! Could you, at some time, please do one on adding a garage consumer unit?
I come from a industrial/commercial installation background 15yrs+ , but for the last 5yrs I have been working in Domestic. I was recently instructed by my boss to add a F.C.U. in a garage for a new Electric Door. When I arrived I found the existing Socket within the Garage that I was to spur off of, was itself a spurred off of a Socket Outlet on the adjoining Kitchen Ring. I called my Boss and expressed that I felt it would be better practice to either add a leg to the existing spurred socket to make it a part of the ring main, or to add a F.C.U. to the Ring within the Kitchen, which could then feed this existing spurred Garage Socket Outlet, and then spur off of it to feed the new F.C.U. for the Garage Door. My Boss said it was fine because it was an F.C.U. I disagreed, and expressed that it was about protecting the cable leaving the Kitchen Ring, and that the F.C.U. was only protecting anything it gave power to. I’m sure I was right, am I?
Always wired 30 or 32A with 4mm2, you are on the safe side in any scenario. For bedrooms you could use 2.5mm2 with 20A MCB which is more than enough for average house
I'd like to suggest that a ring main does have an advantage in that it halves the resistance to the furthest socket, while using easier to handle cable. Also in most situations it begins down one side of a house or room and returns along the other, enabling sockets on both sides. The alternative of two radials would double the resistance by comparison unless 5mm cable were used. Resistance can matter especially when using things like grills and halogen ovens where a small drop in voltage results in a large drop in radiant heat (I experienced this problem). It's true that electronic devices are generally neither large current devices, nor very sensitive to voltage, but if you are feeding two radials down each side of a room, why not just join the ends and complete a ring, halving the resistance. I agree that the potential to overload the ring cable with loads near the consumer unit makes a nonsense of the ring in principal when it comes to pushing 26A cable to 32A, but again, in practice, the ring will often begin some distance from the area it feeds, such that the feed to every socket has a reasonably balanced feed, the initial long feeds serving to balance the current sharing. One thing that surprises me is that you, like others, work on the assumption that the cable is required to carry only 32A worst case, when in reality MCBs will sustain around 1.5 times their rating for a long time without tripping (depending on the type of MCB), so the cable has to take 48A in fact. I think the sensible answer is to simply require that all circuits using 2.5mm cable have a 20A MCB while all circuits or spurs using 4mm cable can have a 32A MCB. With the cables thus protected at source no further rules are needed regarding spurs or number of sockets. In a bungalow my preferred method is to take spurs in 4mm cable down to each socket from junction boxes, from a 2.5mm ring in the loft that has no sockets directly on it, leaving the ring uncut where possible as it runs through the boxes. This makes life easier in many ways - no threading of two cables down inside plastic conduit (which I always use), no need to put two wires into each socket terminal, and easy access to junction boxes for adding sockets. Plus less opportunity for arcing with less joins. Of course this works well in a floored loft with easy access to the edges, but not perhaps in one piled high with glass fibre insulation. One reason that the ring worked better in the past was that it served fewer sockets, whereas today a lot of extra cable is wasted looping down the wall and back up (wiring across walls from socket to socket is not encouraged because of the increased risk of drilling into cables when fixing to walls.) My solution of using 4mm cable down from the ring shortens the cable length in the ring and is ideal in every respect.
You are missing the point, if there is a break in the cable nobody knows and nothing trips and everything keeps working. including electric oiled radiators if some lost their gas boiler for example. The wire would then burn and cause a fire!!!! Putting in a smaller fuse like you suggest would then limit people who would actually need the amperage one day for an electric heater or two because it would trip. A 4mm radial cable with a 32 amp fuse is a perfect solution, one for upstairs and one for downstairs. Obviously a separate one for an electric shower or an electric oven/cooker. 10mm or whatever they require.
@@jeremykemp3782 The days of electric resistive heaters are surely over - too expensive to run and too wasteful of valuable power. My five air to air heat pumps heat my large bungalow taking only 400W each max, all run off the ring circuits with no extra wiring. With a COP of 5.5 they deliver 5.5 kW of heating for every 1kW used (Mitsubishi, cost £800 each, £1500 istalled) Electric shower is also not a good idea - prefer 3kWimmersion heater on cheap rate. Modern fan heaters are 2kW, not 3 as used to be the case, and two fan heaters will run happily off a 20A 2.5mm circuit. There's also something to be said for a lower trip current - it avoids the need to rate the cable for 1.5 times the nominal MCB value. In practice MCBs rarely trip even on overload, and wiring rarely overheats to anything like the point of burning. And MCBs are easily reset if they do trip, alerting the user to the need to plug less in.
I agree with John ring mains can be potentially dangerous I had a situation where I did some work on a property I tested the ring a couple of weeks before when I changed the distribution board and then I went back to add a socket to find the ring now wasn't continuous luckily there was a freshly decorated wall where a socket looked as if it was tampered with as it was put back on wonky so I pulled the socket off to my surprise there was a loose connection to get to the point I filled out a cert on that property a couple of weeks before now if I never went back that ring circuit could still be a potential danger
20A radials for the win. Chances are most houses now have some sort of radial circuit from a spur...off a spur off a spur. Swap the MCB for a 20A to be on the safe side.
16:00 i Loved your hint of frustration there, rings have no place in this day and age and if the next edition or regulation want to do something sensible and worthwhile then they should ban these massively outdated ridiculous circuits.
Great explanation John , genuinely you can have the same number of spurs as you have sockets on the ring , in theory you can have as many sockets as you like as long as you don’t exceed a certain floor area of a 100 square metre. But as you rightly say it comes down to common sense. Till recently a domestic property ie a two story house had three ring mains , and two lighting circuits,one for the ground floor one for the upper floor and the kitchen had its own ring main because there would be quite a few high power appliances such as fridge freezer washing machines tumbler dryers microwave , electric toaster kettle food mixer and if you could afford it a dishwasher. Personally I think ringmains still have their place . In houses . Because if you have a fault on say the ground floor ring you still have the upstairs ring as well with the lights .
Because it's a ring it will still offer protection from the other side. If it was a radial circuit it would be a safety issue. Always try not to have punched holes in your cpc
I always used to argue with my lecturer at uni about ring circuits. He explained that if you create a ring circuit, there will be NO current within the cable. His point was that because it was acting like a massive battery terminal. So, he decided to show this with an ammeter. As you can imagine, even with a load, the ammeter displayed zero load. Now, i wasnt convinced. i argued with this lecturer for over 2 years and ended up giving up. He always took the stand that there is NO load on the ring. The point i was trying to make to him was that yes, even though the meter displayed a zero load. It was simply because the meter could NOT measure it due to it being a ring (In theory, the meter was never going to be in series as im sure you know when measuring current it has to be in series (Voltage is measured across)) as the ring was always attached at either end. Just wanted to rant a little there :)
The problem with a 4mm2 radial is that the ccc drops to only 30 amps installed in trunking reference method B if cables entering db are installed using 50x50mm trunking as an example which is quite common if in a garage etc. You can't really omit overload protection on a socket radial circuit protected by a 32amp mcb if say it was a kitchen radial. So there are disadvantages in using this method.
I guess it made sense to the committee in the '40s. It does not make sense today. At least you use an efficient voltage. 120V requires way too much copper.
I defo use ring mains for kitchen appliances with a few isolators in a cupboard so that it becomes a balanced load on cables and hidden away from worktops make a neater job, I would use it to feed for example, cooker hood, hob ignitor, dishwasher, waste disposal, hot tap, bolier. Fridge will be on its own RCBO circuit for obvious reasons such as going on holiday you don't want some thing to trip the RCD and affect the fridge if it wasn't wired in separately.
Since I came across JWs youtube videos I follow him whenever I need clarification on electrical installation. Here is one query JW !How would one supply BS7671 compliant ring circuit for sockets outlets using with 32 A RCCB when the generator supply has a lowly rated MCB say 20A or less
I only did a short course as part of a mechanical engineering day release course many years ago, so my knowledge is limited as since then I've only done DIY electrical work, appliance repairs adding the odd spur, wiring up sheds, or simple light circuits. I'm old enough to remember the days when the previous wiring circuits were still used in many older houses, before these came in; if I remember right, sockets were on the same type of circuit as lights are now (can't remember what they're called), and people would often run half a dozen things, radio, lamp, iron etc, off the light socket on the ceiling. Overload became a serious problem back then, and we had warnings about it on the tv. Now, on a circuit such as your diagram, a person could have a 12 way tower, plus half a dozen USBs on each socket, and from those towers, further extension leads. There are no warnings about overload! I know my example is at the extreme end but, even though many things draw much less power than they used to, surely we're heading towards some serious problems. Circuit breakers are so good these days, that I've almost forgotten how to change a fuse in a plug, but are they really good enough, that we can safely keep on plugging things in the way we do? Isn't it time we had warnings on the tv again? Or am I worried about nothing?
So the wire comes out the consumer unit to start the ring, but you just also return another 2.5mm wire back into the unit. Do you need to connect the wires to the same terminals in the consumer unit
The one big saftey advantage I can see with a ring circuit would be in the case of a connection going resistive or resistive break. Connections going resistive is where fires start. The connection becomes very hot due to the voltage drop across the unintentional resistance. In the case of a ring circuit though since power is still supplied from the other end the resistive connection will see no voltage drop and no power dissipation.
Electrically it's the same to attach a spur to the MCB directly as it is to attach it to a socket out on the ring, but isn't the issue that modern MCB's have two ports on either side, designed for one wire each? There is space to jam more wires in there for sure, especially if you use smaller gauge wires, but you won't necessarily get sufficient contact and grip on all your wires when you start doubling or tripling them up in the ports. Just a thought as to why people mind this sort of addition to a circuit.
below comment is not good john but i appreciate you about your work because i know that what hard work are required for sharing some knowledge for others thanks john
Very comprehensive thank you, I thought it was a great point about a wire in the ring losing connection and creating a scenario where the circuit is able to draw more than the rated 26 amp. Even worse if they are double sockets which is way more likely. Anyone is able to test this with a simple continuity check.
Im actually working in a house that has the lights wired by individual wires from the board to every room, it was built in Ireland in the late 40s and has never been updated most if the cable is vir and falls apart if you look at it
In Australia we use Daisy Chain setup for each circuit. for GPO's max per daisy chain circuit is 10A, so every GPO on that daisy chain can't exceed 10A total. In Aus you will usually find 3-4 circuits for GPO's Usually the bedrooms and lounge room will be on 1, Kitchen, depending on how many high voltage devices are to be used (Microwave, Fridge, Freezer, kettle, toaster etc you will have either 1 or 2 circuits for the Kitchen. Dining room and Bathroom will occupy 1 circuit and then you will have your outdoor appliances such as Laundry Lights will be on Separate loop with 10A max per single circuit, Hot Water heater on a 40-60A circuit, Electric stove and cooktops for kitchens will be on a a shared 40-60A circuit separate to the GPO's. This makes up your general house power. For Additional appliances (EV charging, Air Conditioning) dedicated circuits are required for each and amps per circuit will be based on the needs for the appliance +10%.
The only problem with this design is that you use 26 A cables, but limit the total current to 32 A. If you used a 26 A fuse for each of the ends of the ring, there would be no way to overload a cable, even if you had a break in the circuit (Assuming you still used one double socket max for spurs with 26 A cables). You could even get to the maximum 52 A, if the current miraculously decided to actually split evenly between the two paths in the ring. The biggest advantage with ring mains using 26 A cables over radial circuits using 26 A cables is that you can draw more than 26 A from a triple socket or two neighboring double sockets. Whereas in a (properly fused) radial setup you are limited to drawing 26 A from any circuit. That means that even with the stupid single 32 A fuse, that cable closing the ring at the end gives you 6 A extra that you can draw from one socket - or up to 26 A more if you used two separate 26 A fuses.
The one point that you did not mention is that the earth connection must also go to a point on the socket back box, even the plastic back boxes will have a terminal for that.
I never knew the UK did this, its a good idea in theory but the fact that its so easy to end up putting too many amps through the conductor from a single point failure is scary.
Note that 26 amps is what the cable is intended to carry, but the standard for manufacturing that cable is probably that it can handle 32 amps without getting hot enough to start a fire in any of the materials it's likely to be in contact with. (And the materials used in houses are probably also regulated so that they cannot ignite from the temperature that your house wiring is likely to get to...) I'm pretty sure I broke the loop at one point (my baton light in the garage fell down in a storm and I snipped the wires off) and it was that way for months and nothing bad happened. I did hurry up and replace it when I read about the existence of ring circuits though! But nothing bad happened.
Ring vs. Radial Which you should specify depends on many factors. What are the expected loads (does the building have central heating, so will plug in electric heaters be used or not, what appliances are expected to be used, etc. etc.). How many socket outlets do you want, both NOW and in the future (when someone decides to rearrange the furniture in the rooms). Now draw up a plan on paper to work out the details. I always recommend that you specify more socket outlets than your immediate current requirements, as providing them now is far easier than making alterations later. In a rooms where there are plenty of socket outlets, the distance between the sockets will not be that far, so the difference in cable cost between two radials and a single ring circuit will be insignificant if buying drums of cable. Properly designed and installed ring circuits are just as safe as radial circuits. Ring circuits are more flexible for the end user, as they can plug any normal appliance in to any socket outlet they like. Whereas if 20A radial circuits are used, too many high powered appliances connected and switched on at the same time on one circuit will trip the MCB. Worse if the protective device is a fuse... Fuses have the disadvantage that people can put in higher rated fuses, higher rated fuse-wire, or normal wire or other conductive material. And don’t think that a MCB protected consumer unit can save the day, as I have come across radial circuits run in 2.5mm squared cable protected by 32A MCBs... Properly designed and installed radial circuit circuits have the advantage that no fixed wiring cables should overheat. But a poor conductor connection in a socket outlet could cause overheating and may result in a fire. So the argument that a fault will always show up in a radial circuit does not wash with me. With a ring circuit, a disconnection or a poor connection could result in a cable being overloaded if multiple high power appliances are in use. But as there are two current paths, it does depend on where the fault is in relation to the circuit wiring.
I can't speak for all sparks by I look for the easiest and least destructive options and give the customer a choice if I can. eg. Say you've got two bedrooms back to back and you want and extra socket in bedroom A. If bedroom B has an outlet on the opposite side of the wall, I can simply drill straight through from the rear of the existing one and surface mount the new outlet. Failing that easy arrangement, You can bring circuit extensions down from the ceiling or up from the floor, depending on where the existing circuit is. Typically you have to chase the wall (to be plastered and made good afterwards) or install surface trunking. If you are VERY lucky you may be able to feed a cable up/down behind the drywall if it isn't heavily insulated and there are no cross-members. This is unusual though.
I think in realty the 2.5 mm^2 can't handle the 26 Amps. it will be like a heater. In our country, it's common to use 2 X 1.5 mm^2 (10 m. wire) for 5 Amp. of current, 4 mm^2 for 13 Amp. of current, and, 6 or 8 mm^2 for 26 Amp. of current. considering the ambient temperature (50 - 70 deg. centigrade).
Thanks for explaining this peculiar arrangement. Around here you are not allowed to rely on a fuse at the end to protect a wire, ever. It has to be at the beginning. The only exception is short proof wire (with thicker insulation), for example the spur feeding a fuse or circuit breaker from a bus bar.
The fuse in the plug that plugs into the sockets isn't to protect the circuit, it's to protect the cable on the plug connected to whatever device you're plugging in. It's the distribution board/consumer unit MCB device that protects the installation circuit wiring. This makes sense as, if your installation circuit has a 32A capability, and you plug some little table lamp into a socket on that circuit, then you don't want to have to have a 32A capable flex on that lamp alongside a 32A capable lamp holder, and 32A rated switch. Rather, you design them with say, 0.5mm2 flex, 5A rated switch, 5A rated lamp holder, and install a 3A fuse into the plug to limit the maximum current the device can draw in order to protect the device from ever being able to overload the hardware it's constructed of. British socket outlets are designed to handle 13A generally (3120 watts @ 240V), and so the largest fuses available for the plugs that plug into them are 13A. This prevents there ever being the possibility of a fault on the plugged-in device/cable being able to draw current greater than the installation socket can handle, which is important when they're commonly connected to 32A @ 240V (7,680 watts) circuits.
A spur will never be loaded to more than 26 amps. And despite what they SAY, 2.5mm will take 32 amps quite happily, it just exceeds the design temperature. That's why we have margins of safety
Knew nothing of the circuits in our first house. Second had a ring circuit on each floor. Third, one for front four rooms, one for back three (a bedroom plus the kitchen and utility). All three bedrooms had one socket on the ring and one on a spur. There was, bizarrely, a 2A socket attached in one of them as well. This ring was later properly extended as more sockets were needed. My own places, single ring in first flat, two likely rings in second - one covered only the kitchen, the other all the rest. Third and fourth flats had single rings, current bungalow has two probable rings - once again one is just for the kitchen.
My whole house is only one ring circuit. I would like to separate all the kitchen sockets. Would you suggest a kitchen radial and another radial for the rest or two separate ring circuits. Would that question be dependant on total number of sockets and appliances(total load)?
For some reason my 1 bedroom flat has three socket circuits. I have three 32A breakers in my consumer unit all labelled "sockets" I have never figured out why the sparky who wired the flat decided to do that lol. I am not sure if I have radial or ring. I wanted to add a socket in the bedroom and when I removed an existing socket it only had one cable going to it.
Very often when adding many more sockets, the most convenient approach is to put them all on a new circuit, rather than disturbing existing wiring... Hence many new socket circuits. Another scenario I've come across is old electric storage-heater wiring being converted to socket circuits...
I had two in the lounge and two in the bedroom, one in the hallway and three in the kitchen. So it's like one for tyhe kitchen sockets, one for the bedroom and one for the lounge. Hallway outlet is on the lounge circuit, I know that cause I was messing around one day and tripped it out from the hallway outlet lol
Being a smaller building but having three breakers for sockets, I would guess you will have three radial circuits. They should not be on 32a breakers, Ideally 16a or 20a.
Can there be a good case for Completing a B20-breaker radial circuit, into a complete ring (while keeping the B20-breaker, not B32), as a means to reduce the Voltage Drop with little extra cable, while avoiding the 'overloading' scenario mentioned?.
This also allows for any section of the ring to be 'removed' if damaged, without having to re-run cabling / hacking out floorboards/walls/whatever. This can prove useful in many cases!. I _do_ think this is a good reason for wiring as a ring even if you use a B20 breaker...
@@sbusweb easier to "split into 2 radials' on 2x 20amp mcbs. 1 cable from 20amp mcb to sockets and another 1 cable from 20amp mcb to sockets....no join between the radial sockets...both totally separate! easier to fault find and add too
I would have added to the video, the use of FCUs being useful in some circumstances, essentially creating a 13A radial circuit wired however you like, connected into the Ring.
That end comment is a load if B.S. A long time ago we split the house into top and bottom ring mains and one for the kitchen that was when I was say 20 years old. I am 67.now there is nothing I repeat nothing wrong in a ring mains circuit at all.
Came here from Delroy. As an Aussie sparky I found ring circuits weird but probably only still in the standard because it exists in old homes. A lot like engineers still having to deal with imperial machine threads and sizes.
I have split many ring mains into two radials on 25 amp RCBOs,usually due to cumulative earth leakage,the bane of all RCD protected circuits with today’s ever increasing electronic supplies
To add extra sockets for office room, would you say a fcu to extra sockets or just add them to ring is best? Got to determine if they are a ring or radial first...
I watch technology connections, but the TH-cam algo started feeding me videos of UK electrical contractors. I found it very interesting comparing to what we have in the US. Ring circuits seem like insanity to me from US standards. Also. 32a on 14awg wire at 240v seems like an insane amount of power to have at a regular power point. Considering the average us outlet is 15A at 120v for a maximum of 1800w. 32a at 240v is 7200w. That is madness to me.
This is why all U.K. plugs contain a fuse which are typically rated at 3, 5, 10 or a maximum of 13A. The maximum loading on a U.K. socket is 3KW which is approximately 12amps.
Good explanation by drawing but I would point out in reality when you’re doing this on site you probably won’t have the layout in the drawing you done, you will have two cables twin and earth running together through the walls or on the ceiling then dropping down the wall etc , and you will pull a loop from one of the legs for the sockets , my question is do you pull the loop from both legs like I do or just from one leg like I’ve seen other people do , I’m not sure if there is a right way . It’s all still on the same ring just not sure if it evens the loads if you pull the loops from both legs ? It’s just not practical to pull one cable and then go back on yourself back to the consumer unit , so we always pull two cables , pull you’re loops at the sockets and obviously you end up with two cables at the last socket and the consumer unit to complete the ring.
This would seem to be a sensibly safe design if each leg of the ring were connected to a breaker limited to 16A per leg. Thus a single socket drawing 32A would pull both directions around the ring. This way an inadvertent break in the ring would not create a safety hazard.
I'm from the US and now live in the UK. We use radial circuits; which are much easier to deal with, add to. My wife's grandfather just had a conservatory built here, and he asked if I would add 4, 2 gang sockets. I thought no big deal. but it seems like its going to be. My plan is to break into the ring main with a 30amp junction box, and run the 4 sockets down off of that. I have calculated their amperage and voltage needs as 2.75 amps/187 volts being drawn in that room as they are only plugging in a 32" lcd, a sky box, and a couple of 60w lamps. I've been told by some sparkys, that this should be no problem. However, I'm seeing online that you can only spur off 1 socket from the ring main with the junction box. is this true. No one can seem to agree on this. I may just run a radial from the CU, straight back to the conservatory and be done with it. why are you guys still using such antiquated wiring schemes? What are your thoughts. Thank you!
With a 13A FCU you can have as many sockets as you want, and this would be the easiest and cheapest solution (also why many conservatories end up with this arrangement). With a direct connection you are only allowed one socket, more would allow the cable to be overloaded, as 2.5mm² cable is only rated to about 26A, rings have 32A circuit breakers. The overload protection is provided by the fuses in the plugs, 2x13A being approximately the maximum rating for 2.5mm² cable.
Hi John, thanks for the useful video. I have recently bought a static caravan in which the ring main for the sockets is protected by a 20A breaker. The wiring is 2.5mm T&E. Is there any reason why I may not be able to increase the breaker to 32A? Would the incoming supply from the park affect this - although there are much bigger vans on the park than mine which must have higher loads?
Hi John, excellent videos. I wonder if you could offer some thoughts on choice of radial over ring in a kitchen, I have estimated the max diversified load at 23.7A, whilst a 2.5mm can just about support that, i'd presumably have to put a 32A MCB, as 20A MCB is too low. I don't want to put two radials in the kitchen because eventually somebody will do some maintenance turn off one kitchen MCB without realising there are 2 and kill themselves, not my problem but not ideal. So that leaves me thinking of a 4mm radial circuit with a 32A MCB, is that a more sensible approach in your opinion and will standard sockets easily take 4mm connections?
Yes, a 32A radial in 4mm is ok and most sockets will easily accept 2x 4mm conductors. Some sockets will actually take 2x 6mm. Another option is a 25A radial in 2.5mm cable, provided the cable is not installed in insulation or other ways which reduce it's capacity.
Connecting a socket direct to the consumer unit. Does this have to be a miniature ring? or can it be a single strand of twin and earth connected to the 32a breaker that the main house ring is connected to?
John, thank you for this video (and all the others) I do like and enjoy your style of delivery. I have a design question for you. I am designing for a small shed workshop (15 ft x 8ft) with a maximum load of 6Kw and had originally specified a ring final circuit using 4mm2 Twin and Earth protected by a 32A MCB (Type C because the workshop machinery has a couple of 2000 watt induction motors and wanted to avoid nuisance tripping on start up current surge). Having watched your video on the Satan's child I am now having second thoughts. I will be fitting a small consumer unit anyway and have space for three MCBs, one of which will support the lighting circuit and with a ring one MCB way would have been unused. So - would I be better off specifying two radial circuits, assume equal load on each, using 4mm2 T&E protected by their own 20A MCB (Type C)? The loads are Table saw 1500W, Dust extractor 1500W, Bandsaw (600W), Chop Saw 1500W - plus other more portable power tools - unlikely that 2 to be in any use at any one time. The power to the shed is all being done properly (Part P) and an SWA cable being run from the house consumer unit protected by a 32A TypeC MCB on the RCD protected side of the board to the workshop consumer unit.
A 32A ring would be done with 2.5mm cable, 4mm is oversized unless the cable is installed in insulation or other unfavourable conditions. 20A radials would also use 2.5mm. A 32A radial would be 4mm. You can have multiple circuits if you want, but as the whole lot is connected to a single 32A supply, there isn't really any point - a single 32A radial would be fine, and would also be far less likely to trip when larger loads are switched on.
John Ward Thanks for that John. Does it make any difference that the SWA (3 core 4mm2) is a 27 metre run between the supplying consumer unit and the workshop consumer unit? I was upgunning the workshop ring or radials because I was concerned to meet earth loop impedance requirements of being protected by a Type C breaker. I do not want to be under sizing then having to rip out and redo with larger. Grateful your view.👍
I think one 32A circuit is better as it can cope with startup surge currents better without tripping. There is no problem with cable protection, as your likely load is less than the 6kW of even a single 2.5mm cable (26A continuous rating). Lights must be off a 6A MCB circuit, or a fused spur from your ring.
That formula doesn't apply to a ring circuit. Rings are a special case, and it's assumed that the loads on a ring circuit will be evenly distributed, so that the current is fairly evenly shared between the two cables connected to each socket outlet, so that the current in the cables won't exceed 20A.
Hi, thanks for your videos. Could you please make a tutorial about how to connect/wire a 3 gang switch so it controls 3 devices for example? In my kitchen, I have a ventilator, ceiling light and led light under the cabinets and I have 4 set of cables (each having a Ground, L, N) coming out from the wall ready to be connected to a switch.
I want to add about 5 unswitched socket (in a ring final circuit) behind my entertainment unit this is because once everything is put in place I would not have access to the socket to switch individual items on and off a bit like when you install a washing machine or a dishwasher. I would like to add 5 switches to these unswitched socket so I can individually switch them on and off, seen a lot of videos but none showed the above example would be grateful if you could do a video on it, many Thanks
Hi John, thanks for the great instructional videos. You say there aren't really any legitimate reasons to put in a Ring circuit these days, what what about where cable length is a factor? I have a large house, with 2000sqft downstairs. I currently have a 32a ring circuit for the sockets with, at a guess, 100 metres of 2.5mm² T&E. If I were to convert this to a 20a radial, wouldn't I suffer from severe voltage drops at the end of the circuit? I read that a 20a radial should have no more than 30 metres of cabling. Is this right? Thanks a lot for any insight you provide.
30m of cable for 20A is correct but only if the entire 20A load is at the end of the cable. In reality it will be distributed along the cable and the maximum length can be much longer. The 106m limit for a 32A ring also requires a distributed load
Thanks John. Would you still use a 20a Radial with 2.5mm T&E in my situation where the length of the circuit is quite considerable? The circuit would simply cover the downstairs sockets (albeit 20+ double sockets) with no high wattage appliances. You may have guessed from my questions that someone is trying to convince me that the rewire should be a ring. Thanks again!
John, if you are able to reply it would be much appreciated! My electrician wants to install a ring circuit for my largish kitchen. I would prefer radials for all the reasons you mention. I have asked for one "above counter" radial for kettle, microwave, toaster and myriad other small appliances, and one "below counter" radial for dishwasher, dryer, washer, fridge freezer and wall sockets for lamps, the hoover etc. He is adamant that one radial will suffice, citing diversity which I understand, but from experience I know that on weekends for example I will be using literally every appliance at once and would prefer two radials. Am I being unreasonable? Is there any reason why he is so reluctant? I am happy to pay for an extra RCBO and minimal additional cable costs and there are several unused ways in the CU recently installed the intention being to add the new kitchen circuits once it was extended. Should I be looking for a new electrician?
One radial might do, but no reason to not have two, it would be slightly more work but that's hardly a problem. It's your house, so you should have what you want. Some people are stuck in doing things the same old way, and may not like doing other methods.
John Ward Thanks! I couldn't see why it seemed to be such a problem but wasn't sure if there was a reason why he wasn't so keen. it's all chargeable work after all and to me at least makes sense from a capacity / overloading point of view, even if there are only a handful of days a year when everything is running flat out.
Spencer Wilton - the advantage of the ring circuit, is that you can choose long after the wiring has been installed what appliances you want connected and switched on without having to worry about socket is connected to what radial circuit (assuming we are comparing one 32A ring to two 20A radials). If properly installed, a ring is no less safe and no less reliable than a radial. At 230V, each 20A radial can supply just 4600W. A single 32A ring can supply 7360W. True, two 20A radials can supply more power, but if you connect too many high power appliances into one 20A radial, you risk the MCB tripping and spoiling your day (especially if it trips when you are not paying attention).
Richard Ashworth - Yes, If a ring circuit has a break, there is a risk of a conductor overheating. However the risk of a fire is not as great as some people imagine. Firstly, when installed, the circuit should be properly tested to confirm that the ring is complete with no breaks. Second, for a fire to occur, enough current has to flow to actually overheat the conductor. Whether this occurs very much depends on the type of loads connected to the ring circuit (that has the fault). And where the loads are and where the break in the ring is. In reality, not many ring circuits actually have a total continuous current flowing that will overheat 2.5 square mm cable. Even if appliances with a total power rating of say 6.9kW are connected to the ring (30A at 230V), unless all of these appliances are all one side of the break, the current will be split between two different circuits to the consumer unit, and the resulting separate currents in the separate cables is likely to be below the value that will cause overheating. Even if you are very unlucky and do end up in a situation where the current flowing through one of the 2.5 square mm ring cables is exceeding the recommended value and the temperature of the cable exceeds it’s recommend maximum value, this does NOT mean that it will automatically catch fire. As has been shown, you have to grossly overload a cable for it to get hot enough for the insulation to catch fire. I once came across a house where an entire kitchen was wired as a spur off a ring circuit. All wired in 2.5 square mm cable. The cable ran from a terminal/junction box in the void between the ground floor and the first floor and ran to the kitchen (which was in an extension). This cable ran daisy chain style to all the double sockets in the kitchen (of which there were a considerable number). The kitchen had all the normal high power appliances (washing machine, microwave oven, kettle, fridge, freezer etc.). Despite this not being in compliance with any U.K. regulations, the cables showed no signs of overheating or damage. Of course I strongly recommended that the installation should be rewired. If peace of mind is required, it is recommended that any and all electrical installations should be inspected and tested every ten years.
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Hello from the weird year 2020. I just watched Technology Connections explaining the U.S. electrical system. He casually explained that it's not nearly as weird as the U.K. ring mains. So that's why I am here. Great explanation. Yes, I now understand why it should be removed from the current standard.
ME TOO! - hello from the USA :)
lodno
I also looked this up after watching the Technology Connections video about our electrical system!
It was suggested to me after his video! Lol
Apparently TH-cam is recommending the same videos to all of us. Greetings fellow curious cats!
Technology Connections brought me here!
I watched the same video from TC, but never took the initiative to follow through on my homework until the algorithm brought me here
So he doesn't have a Video on that topic? *Sadface*
You could have have individual fuses for the two ends of the ring to discover if the ring is broken. But that would only be for the live, as the neutral is not fused anyway.
Yup! I almost fell asleep though listening to this guy. The lip smacking at the end woke me up though.
It really was prompted by CJR electrical’s videos where he keeps going on about testing ring circuits, but before that I had seen TC’s video too combined that led me here 🙂
I don't know anything about electrics and to be honest i'm not sure how i ended up here, but i find this guy strangely captivating. I'm now considering installing a new consumer unit and ring main for no reason other than John Ward showed me how.
I know nothing about Rockets but I saw a video on TH-cam and I am now considering going into outer space. Lets hope Peter Wilson was not serious.
Don't listen to the naysayers, I've seen sparks that have an IQ of no more than 50 and seem to do fine.
You can lick your finger and touch the bus bar to see if it's live just do it fast, if it goes DADADADADADADADADA up your arm and you tense up it's live.
Just kidding... Obviously...
I did mine but I was an apprentice for two years and assisted on many a board change, and I have mild ocd the wiring is absolutely beautiful it took me absolutely ages and no one gets to appreciate it :(.
I was taught the virtues of the ring mains when I left school in the 80's and did my apprenticeship, just before moving into IT, and thought it was a great idea. Now in my 50's and having moved into various old properties (and always checking for signs of heat/loose connections in electrical outlets) this video has explained so much. Well worth 16 minutes of my life to totally change my mind as to the safety of electrical circuits.
By far and away the most lucid explanation I have ever seen. Something I've always thought should be fairly simple has always had an air of complex, don't touch, experts only etc. and John's explanation is so easy to absorb. Your a genius JW.
I am a retired electronics tech who actually did some rewiring in my father's house in the UK. The old, lead-covered cable under the floorboards was beautifully layed out and neatly dressed, but as soon as it was disturbed the old rubber insulation disintegrated. I am guilty of incorporating "a borrowed neutral" into a three-way stair lighting circuit, but I am sure that the house has been completely rewired since my father sold it in the late 1980s. I could not understand the need for a ring circuit, primarily because I understood the risk of overloading in the event of ring discontinuity. This is the first video I have encountered that explains why I was correct about ring circuits.
Fantastic Explanation, 6 years later your video was recommended to me. All praise the algorithm.
The Canadian Electrical code still allows ring circuits in 2015. Never used one, never seen one and didn't even know what it was until I watched this video. Great video.
Excellent teacher, excellent channel. Thanks JW. I had a 32A ring circuit in an old outbuilding, and rodents had gotten into the walls, chewed on the wires and the RCD kept tripping. I expected the worst, that the circuit had been destroyed, but the electrician isolated and removed the chewed section and I was delighted to end up with two 16A radial circuits that tested fine and with roughly the same number of sockets on each. Could have been worse.
The ring main was introduced after a long and hard war (WW2) and materials were in short supply, previously houses with electricity had few 15A sockets each wired as a spur from a fuse box. With the advent of 13a fused plugs and ring mains (as then called) with the limited and perhaps rationed cable could be used for more houses than the same amount of copper used as single socket radial circuits.
Whether a ring circuit NOW represents the best practice doesn't matter because there are probably 20 million ring circuits in existance and most electricians will meet them on a daily basis.
Who else came here after Technology Connections (06/20) drove you to a search?
Yep, me also!
I've seen this two years ago.
yes i did
So then it's a no for you, @@usingthecharlim.
Here as well from Technology Connections
Thanks JW you brought me back up to speed, having done house wiring back at college as part of my apprenticeship I went into electronics and only ever used household electrics when needing to do my own, I will keep this video as a reminder. Thanks again. Ray.
You described how to wire a ring main up perfectly clear,I understood it perfect! Thank you !
Old ways die hard. Ring circuits usually reliable enough.Great variety of wiring globally.Protection way better now than it used to be. A neighbour called in about faulty socket years ago. Upon investigation at the fusebox, there in place of a fuse was a 6 inch nail glowing red hot. Necessity is the mother of house fires.
Singapore, and a few other Commonwealth countries, use Ring Whatevers.
Here in VietNam Singapore invested highfises are equipped wigh clunky UK Plugs although not Ring Mains.
We also use US-style flat in plugs, as well as Chinese plugs.
When travelling i prefer the universal connector that comprises 2 wires wiith bared ends and fit almost anything!
I'm not big fan of ring circuits, but there is the benefit that the overall resistance of the circuit is reduced considerably when you have that last leg back. I mean, it does effectively nearly double the effective CSA of the conductor, and thus capacity of the circuit, by just having that (often short) return leg. I could see there being a lot more burnt-up sockets/cables if radials with many sockets on them where more common, as connections inevitably loosen over time, resistance (impedance?) increases, and then folk go and plug electric heaters and the like into them. I know regular testing should defeat this possibility, but really, how often do people actually get their installations tested? In my experience, the answer is: much, much less than they should.
Exactly my opinion! Leaving the ring complete as is it is and reducing the breaker to 25 A would be the best option with the safety add on that a broken wire would not be able do result in an overload. Long radials always have voltage drop issues at their endings.
I will never get over how differently you Electricians in the U.K. Do things differently than us Electricians in the States.
Though I know you are professional tradesmen and take great skill in your craft , and know what you are doing, something like that would never be allowed over here.
Always enjoy watching the way things are done over there.
Wasn't intending to be disrespectful if I was, anyways cheers from the States.
Great video. Clear explanation. Currently studying this on my Level 1 Diploma course. Makes so much more sense to install separate radial circuits throughout a domestic dwelling. Cheers!
When I first heard about these, I thought they were relics of the past. I was _shocked_ (lol) to find out that they're still in use today, and you've explained very clearly to me how they work. I wouldn't want one in my house; good thing everything here in the States is what you refer to as radial.
They should be relics of the past, unfortunately plenty of people still insist on installing them.
@@jwflame Why don't they just repeal the standard for new installations? We have plenty of old wiring over here that, if worked on by a certified electrician (on the record), must be updated to meet current standards.
Crystal clear and comprehensive as always. Thanks.
I heard, and believe story that, those 2* single sockets as spurs, were often changed to double-sockets (e.g. those conversion sockets)), thereby overloading the protection requirements for unfused spurs. So, regulations changed to disallow that configuration.
13x2=......?
@@cglees 26 =) which, is usally ok for a 2.5mm cable unless thoroughly insulated.
Diversity says in pratice this double-socket-spur (or indeed, 2 single sockets as spur) is allowable.
However, for some reason, 2-sockets-to-1-plug adapters are allowed un-fused, which seems kind of silly!.
I watched this when it was new. I installed a garden building on my own land for my office, it was all wired using advice from this vid without ring circuits, but higher rated cable (6mm). 5 years later, it all still works perfectly. even with a 2.7Kw heater running off it at one point, as well as a computer and LED lighting. BTW, I also have a spur direct from the consumer unit for my Ring doorbell. All common sense stuff.
A spur off the CU for a door bell? That's got to be a first! 🤣🤣🤣🤣
Now that i moved to london i found your videos very helpfull understanting uk domestic instalations. Thank you very very much.
Where have you come from to the UK? Are you working as an electrician here, and if so what country did you learn your trade? Thanks
Crystal clear and very much appreciated , why can’t all d I Y videos be made like this . Great job
Came for the education, stayed for the shade this man had to throw on ring mains 😂 seriously though, very clear and useful video!
The most compelling reason for ring mains/circuits as compared with separate cabling to each socket (as in the forties) is that they give the user maximum choice in where to plug in portable appliances, without increasing the amount of wiring in proportion to the number of outlets.
The intention is that in a room with plentiful sockets there will not be any need for long leads on portable equipment (trip hazards) or multi way adaptors (which can be a fire hazard).
Why not use a radial?
The advantage of the ring over the radial is that you can test for loop resistance. This detects whether there are any poor connections at any point in the ring, which could lead to a fire risk. You can test this at any point in the ring, without visiting all the sockets. This test is the reason for most of the rules about spurs.
Secondly, if a poor connection does develop, it's less likely to cause a fire unless a second poor connection arises. This is because most of the power will flow to the socket that's in use by the line of least resistance. The dodgy socket gets hot when it is used, and hopefully the consumer will notice. That socket does not get hot when other sockets are in use (unless there are TWO dodgy connections)
In contrast, in a radial, if there is a poor connection at an unused socket, that socket will get hot whenever sockets are used that are further from the CU. If that socket is rarely used, or is a permanently plugged in appliance, the consumer is unlikely to notice the hot socket till it bursts into flame.
So the extra cabling back to the CU is for testing and safety. There is a coherent case to support this
You clearly feel the the disadvantages outweigh those advantages, but it's only fair to mention that there is some sense to the design. It's not totally daft, as you seen to imply
Fairly strong opinions being expressed at the beginning. You certainly aren't shy !
4mm cable is harder to pull through, more expensive to buy and the wires are more difficult to screw 2 into the back of the terminals on socket oulets. Just a few disadvantages of radial to balance things a bit.
Radial circuits don't have to be 32A, or use 4mm² wire.
Cheap, easy and dirty. Typical UK.
As an American with an electrical background, I've always been interested in what a UK "ring circuit" actually is, and how it works. This is the first guy I've encountered who explained it clearly in a way I understood. Thanks for that.
It does seem like a simple enough concept, but I can also see why it was probably never adopted over here, because of extra wire, expense, etc.
I guess now I need to understand more about what a Consumer Unit is/does.
@@UncaBeeTV UK consumer unit == US circuit breaker panel. The physical engineering is slightly different but the function is exactly the same.
My employer loves a Ring circuit, they'd put one in for any socket circuit consisting of 2 or more double sockets. I personally fail to see the point most of the time. It does make sense to have a 32A circuit for a kitchen/utility and I guess the little bit of extra testing involved still beats fitting a load of sockets with two 4mm cables in them.
I remember one of my college teachers saying about how he'd converted a lighting circuit wired in 1mm into a ring because it was on a 10A MCB and the cables were all buried in insulation, bet that was a head scratcher for the next guy to work on it 😂
It's not Ring, like the new video doorbell button; just "ring," the generic object.
I could have done with a ring circuit to power my twin 2400W boiler elements for my still. I actually like the concept. Cheaper than having 20 amp circuitry installed.
I shoud not say this, or even go there, but the holy grail of all audipophile nutters is their own spur and somehow the magic electricity is different and everything is better with a dedicated spur. Loved the video, learnt lots please ignore previous comment 8) .
Hello John, love the videos, crystal clear and based in reality. I'm a basic DIY'er but want to do things safely and in accordance with the standards/guidance where possible. I live in a victorian terraced house in Wales. It has a modern CU but what I'm not sure about is whether it has a ring or radial circuit. Is there an easy way to find out? I've had a look at a couple of other videos but am left confused...
Many thanks, Craydon
Come to think of it, I use a similar "circuit design" on my electrical fence (that adds extra incentive for my dogs to not try to go through the yard fence). If a wire gets broken, both sections of the fence still have power.
I can see a reason why the ring circuit could have an advantage from a fault tolerance standpoint, but I would still size the wire so that even if the ring was broken, it could still handle as much current as the circuit breaker for the circuit.
I never rely on a house that I buy to be wired *correctly* since a previous owner might have thought he was competent to do DIY electrical work (and he wasn't) or the builder was using somewhat unskilled workers who didn't particularly care whether they did it right for the wiring installation. I've seen cases where 110VAC was on the *ground* at an outlet because some wires were touching in an outlet box. To be fair though, this was an old house which was originally built without electricity and there were still remnants of previous electrical wiring designs. There were places in the attic where some of the old asbestos and tar wiring insulation was still around (although it wasn't being used). There were also some remnants of the old "knob-and-tube" style where wires didn't have insulation on them and bare wires were run while being separated from contact with the materials of the house (or each other) by porcelain knob and tube insulations.
Hello John, I'm finding your videos to be an excellent learning resource, thank you! Could you, at some time, please do one on adding a garage consumer unit?
Very clear concise explanation of ring circuit.
I come from a industrial/commercial installation background 15yrs+ , but for the last 5yrs I have been working in Domestic.
I was recently instructed by my boss to add a F.C.U. in a garage for a new Electric Door. When I arrived I found the existing Socket within the Garage that I was to spur off of, was itself a spurred off of a Socket Outlet on the adjoining Kitchen Ring.
I called my Boss and expressed that I felt it would be better practice to either add a leg to the existing spurred socket to make it a part of the ring main, or to add a F.C.U. to the Ring within the Kitchen, which could then feed this existing spurred Garage Socket Outlet, and then spur off of it to feed the new F.C.U. for the Garage Door.
My Boss said it was fine because it was an F.C.U. I disagreed, and expressed that it was about protecting the cable leaving the Kitchen Ring, and that the F.C.U. was only protecting anything it gave power to.
I’m sure I was right, am I?
Always wired 30 or 32A with 4mm2, you are on the safe side in any scenario. For bedrooms you could use 2.5mm2 with 20A MCB which is more than enough for average house
Cost you a fortune in cable would have to take half a brick depth out to cap that up 🤣
I'd like to suggest that a ring main does have an advantage in that it halves the resistance to the furthest socket, while using easier to handle cable. Also in most situations it begins down one side of a house or room and returns along the other, enabling sockets on both sides. The alternative of two radials would double the resistance by comparison unless 5mm cable were used. Resistance can matter especially when using things like grills and halogen ovens where a small drop in voltage results in a large drop in radiant heat (I experienced this problem). It's true that electronic devices are generally neither large current devices, nor very sensitive to voltage, but if you are feeding two radials down each side of a room, why not just join the ends and complete a ring, halving the resistance.
I agree that the potential to overload the ring cable with loads near the consumer unit makes a nonsense of the ring in principal when it comes to pushing 26A cable to 32A, but again, in practice, the ring will often begin some distance from the area it feeds, such that the feed to every socket has a reasonably balanced feed, the initial long feeds serving to balance the current sharing.
One thing that surprises me is that you, like others, work on the assumption that the cable is required to carry only 32A worst case, when in reality MCBs will sustain around 1.5 times their rating for a long time without tripping (depending on the type of MCB), so the cable has to take 48A in fact.
I think the sensible answer is to simply require that all circuits using 2.5mm cable have a 20A MCB while all circuits or spurs using 4mm cable can have a 32A MCB. With the cables thus protected at source no further rules are needed regarding spurs or number of sockets.
In a bungalow my preferred method is to take spurs in 4mm cable down to each socket from junction boxes, from a 2.5mm ring in the loft that has no sockets directly on it, leaving the ring uncut where possible as it runs through the boxes. This makes life easier in many ways - no threading of two cables down inside plastic conduit (which I always use), no need to put two wires into each socket terminal, and easy access to junction boxes for adding sockets. Plus less opportunity for arcing with less joins. Of course this works well in a floored loft with easy access to the edges, but not perhaps in one piled high with glass fibre insulation.
One reason that the ring worked better in the past was that it served fewer sockets, whereas today a lot of extra cable is wasted looping down the wall and back up (wiring across walls from socket to socket is not encouraged because of the increased risk of drilling into cables when fixing to walls.) My solution of using 4mm cable down from the ring shortens the cable length in the ring and is ideal in every respect.
You are missing the point, if there is a break in the cable nobody knows and nothing trips and everything keeps working. including electric oiled radiators if some lost their gas boiler for example. The wire would then burn and cause a fire!!!! Putting in a smaller fuse like you suggest would then limit people who would actually need the amperage one day for an electric heater or two because it would trip. A 4mm radial cable with a 32 amp fuse is a perfect solution, one for upstairs and one for downstairs. Obviously a separate one for an electric shower or an electric oven/cooker. 10mm or whatever they require.
@@jeremykemp3782 The days of electric resistive heaters are surely over - too expensive to run and too wasteful of valuable power. My five air to air heat pumps heat my large bungalow taking only 400W each max, all run off the ring circuits with no extra wiring. With a COP of 5.5 they deliver 5.5 kW of heating for every 1kW used (Mitsubishi, cost £800 each, £1500 istalled) Electric shower is also not a good idea - prefer 3kWimmersion heater on cheap rate. Modern fan heaters are 2kW, not 3 as used to be the case, and two fan heaters will run happily off a 20A 2.5mm circuit. There's also something to be said for a lower trip current - it avoids the need to rate the cable for 1.5 times the nominal MCB value. In practice MCBs rarely trip even on overload, and wiring rarely overheats to anything like the point of burning. And MCBs are easily reset if they do trip, alerting the user to the need to plug less in.
I agree with John ring mains can be potentially dangerous I had a situation where I did some work on a property I tested the ring a couple of weeks before when I changed the distribution board and then I went back to add a socket to find the ring now wasn't continuous luckily there was a freshly decorated wall where a socket looked as if it was tampered with as it was put back on wonky so I pulled the socket off to my surprise there was a loose connection to get to the point I filled out a cert on that property a couple of weeks before now if I never went back that ring circuit could still be a potential danger
20A radials for the win. Chances are most houses now have some sort of radial circuit from a spur...off a spur off a spur. Swap the MCB for a 20A to be on the safe side.
* Spur FROM a spur FROM a spur.
16:00 i Loved your hint of frustration there, rings have no place in this day and age and if the next edition or regulation want to do something sensible and worthwhile then they should ban these massively outdated ridiculous circuits.
I’ve put a few new sockets on existing 32amp 4mm wire radial no problems love it.
Great explanation John , genuinely you can have the same number of spurs as you have sockets on the ring , in theory you can have as many sockets as you like as long as you don’t exceed a certain floor area of a 100 square metre. But as you rightly say it comes down to common sense. Till recently a domestic property ie a two story house had three ring mains , and two lighting circuits,one for the ground floor one for the upper floor and the kitchen had its own ring main because there would be quite a few high power appliances such as fridge freezer washing machines tumbler dryers microwave , electric toaster kettle food mixer and if you could afford it a dishwasher. Personally I think ringmains still have their place . In houses . Because if you have a fault on say the ground floor ring you still have the upstairs ring as well with the lights .
How’d you get the current to pass through the hole 7:06?
albert sparks hopefully not it’s the cpc
Because it's a ring it will still offer protection from the other side. If it was a radial circuit it would be a safety issue. Always try not to have punched holes in your cpc
Remember, the paper is insulating. So the hole is actually a break in the insulation. Logically, it must conduct.
Magnetic induction.
Lawrence D’Oliveiro 😂🤣😂🤣😂🤣
I always used to argue with my lecturer at uni about ring circuits. He explained that if you create a ring circuit, there will be NO current within the cable. His point was that because it was acting like a massive battery terminal. So, he decided to show this with an ammeter. As you can imagine, even with a load, the ammeter displayed zero load.
Now, i wasnt convinced. i argued with this lecturer for over 2 years and ended up giving up. He always took the stand that there is NO load on the ring.
The point i was trying to make to him was that yes, even though the meter displayed a zero load. It was simply because the meter could NOT measure it due to it being a ring (In theory, the meter was never going to be in series as im sure you know when measuring current it has to be in series (Voltage is measured across)) as the ring was always attached at either end.
Just wanted to rant a little there :)
The problem with a 4mm2 radial is that the ccc drops to only 30 amps installed in trunking reference method B if cables entering db are installed using 50x50mm trunking as an example which is quite common if in a garage etc. You can't really omit overload protection on a socket radial circuit protected by a 32amp mcb if say it was a kitchen radial. So there are disadvantages in using this method.
I guess it made sense to the committee in the '40s. It does not make sense today.
At least you use an efficient voltage. 120V requires way too much copper.
Very interesting as always but twice as amusing 👍😃 love your commentary on this video!
I defo use ring mains for kitchen appliances with a few isolators in a cupboard so that it becomes a balanced load on cables and hidden away from worktops make a neater job, I would use it to feed for example, cooker hood, hob ignitor, dishwasher, waste disposal, hot tap, bolier. Fridge will be on its own RCBO circuit for obvious reasons such as going on holiday you don't want some thing to trip the RCD and affect the fridge if it wasn't wired in separately.
Since I came across JWs youtube videos I follow him whenever I need clarification on electrical installation. Here is one query JW !How would one supply BS7671 compliant ring circuit for sockets outlets using with 32 A RCCB when the generator supply has a lowly rated MCB say 20A or less
I only did a short course as part of a mechanical engineering day release course many years ago, so my knowledge is limited as since then I've only done DIY electrical work, appliance repairs adding the odd spur, wiring up sheds, or simple light circuits.
I'm old enough to remember the days when the previous wiring circuits were still used in many older houses, before these came in; if I remember right, sockets were on the same type of circuit as lights are now (can't remember what they're called), and people would often run half a dozen things, radio, lamp, iron etc, off the light socket on the ceiling.
Overload became a serious problem back then, and we had warnings about it on the tv.
Now, on a circuit such as your diagram, a person could have a 12 way tower, plus half a dozen USBs on each socket, and from those towers, further extension leads. There are no warnings about overload!
I know my example is at the extreme end but, even though many things draw much less power than they used to, surely we're heading towards some serious problems.
Circuit breakers are so good these days, that I've almost forgotten how to change a fuse in a plug, but are they really good enough, that we can safely keep on plugging things in the way we do?
Isn't it time we had warnings on the tv again? Or am I worried about nothing?
So the wire comes out the consumer unit to start the ring, but you just also return another 2.5mm wire back into the unit. Do you need to connect the wires to the same terminals in the consumer unit
yes
The one big saftey advantage I can see with a ring circuit would be in the case of a connection going resistive or resistive break. Connections going resistive is where fires start. The connection becomes very hot due to the voltage drop across the unintentional resistance. In the case of a ring circuit though since power is still supplied from the other end the resistive connection will see no voltage drop and no power dissipation.
Hello John. Thanks for all the videos. Have you though about a short intro on the organ at the start Monty Pythonesque styleeeeee. Good Luck lad
What this actually demonstrates is that a new cable size needs to be adopted. Instead of 2.5mm2 or 4mm2, 3mm2 is what is required.
Electrically it's the same to attach a spur to the MCB directly as it is to attach it to a socket out on the ring, but isn't the issue that modern MCB's have two ports on either side, designed for one wire each? There is space to jam more wires in there for sure, especially if you use smaller gauge wires, but you won't necessarily get sufficient contact and grip on all your wires when you start doubling or tripling them up in the ports.
Just a thought as to why people mind this sort of addition to a circuit.
below comment is not good john but i appreciate you about your work because i know that what hard work are required for sharing some knowledge for others thanks john
Very comprehensive thank you, I thought it was a great point about a wire in the ring losing connection and creating a scenario where the circuit is able to draw more than the rated 26 amp. Even worse if they are double sockets which is way more likely. Anyone is able to test this with a simple continuity check.
Im actually working in a house that has the lights wired by individual wires from the board to every room, it was built in Ireland in the late 40s and has never been updated most if the cable is vir and falls apart if you look at it
In Australia we use Daisy Chain setup for each circuit. for GPO's max per daisy chain circuit is 10A, so every GPO on that daisy chain can't exceed 10A total. In Aus you will usually find 3-4 circuits for GPO's Usually the bedrooms and lounge room will be on 1, Kitchen, depending on how many high voltage devices are to be used (Microwave, Fridge, Freezer, kettle, toaster etc you will have either 1 or 2 circuits for the Kitchen. Dining room and Bathroom will occupy 1 circuit and then you will have your outdoor appliances such as Laundry
Lights will be on Separate loop with 10A max per single circuit, Hot Water heater on a 40-60A circuit, Electric stove and cooktops for kitchens will be on a a shared 40-60A circuit separate to the GPO's. This makes up your general house power. For Additional appliances (EV charging, Air Conditioning) dedicated circuits are required for each and amps per circuit will be based on the needs for the appliance +10%.
And whats a "GPO" in Australian?
@@icarossavvides2641GPO means general power outlet. In other words where you plug your appliances into.
The only problem with this design is that you use 26 A cables, but limit the total current to 32 A. If you used a 26 A fuse for each of the ends of the ring, there would be no way to overload a cable, even if you had a break in the circuit (Assuming you still used one double socket max for spurs with 26 A cables). You could even get to the maximum 52 A, if the current miraculously decided to actually split evenly between the two paths in the ring.
The biggest advantage with ring mains using 26 A cables over radial circuits using 26 A cables is that you can draw more than 26 A from a triple socket or two neighboring double sockets. Whereas in a (properly fused) radial setup you are limited to drawing 26 A from any circuit. That means that even with the stupid single 32 A fuse, that cable closing the ring at the end gives you 6 A extra that you can draw from one socket - or up to 26 A more if you used two separate 26 A fuses.
Thanks for an excellent factual presentation 👍
The one point that you did not mention is that the earth connection must also go to a point on the socket back box, even the plastic back boxes will have a terminal for that.
I never knew the UK did this, its a good idea in theory but the fact that its so easy to end up putting too many amps through the conductor from a single point failure is scary.
Note that 26 amps is what the cable is intended to carry, but the standard for manufacturing that cable is probably that it can handle 32 amps without getting hot enough to start a fire in any of the materials it's likely to be in contact with. (And the materials used in houses are probably also regulated so that they cannot ignite from the temperature that your house wiring is likely to get to...)
I'm pretty sure I broke the loop at one point (my baton light in the garage fell down in a storm and I snipped the wires off) and it was that way for months and nothing bad happened. I did hurry up and replace it when I read about the existence of ring circuits though! But nothing bad happened.
Ring vs. Radial
Which you should specify depends on many factors. What are the expected loads (does the building have central heating, so will plug in electric heaters be used or not, what appliances are expected to be used, etc. etc.). How many socket outlets do you want, both NOW and in the future (when someone decides to rearrange the furniture in the rooms).
Now draw up a plan on paper to work out the details. I always recommend that you specify more socket outlets than your immediate current requirements, as providing them now is far easier than making alterations later.
In a rooms where there are plenty of socket outlets, the distance between the sockets will not be that far, so the difference in cable cost between two radials and a single ring circuit will be insignificant if buying drums of cable.
Properly designed and installed ring circuits are just as safe as radial circuits.
Ring circuits are more flexible for the end user, as they can plug any normal appliance in to any socket outlet they like. Whereas if 20A radial circuits are used, too many high powered appliances connected and switched on at the same time on one circuit will trip the MCB. Worse if the protective device is a fuse... Fuses have the disadvantage that people can put in higher rated fuses, higher rated fuse-wire, or normal wire or other conductive material. And don’t think that a MCB protected consumer unit can save the day, as I have come across radial circuits run in 2.5mm squared cable protected by 32A MCBs...
Properly designed and installed radial circuit circuits have the advantage that no fixed wiring cables should overheat. But a poor conductor connection in a socket outlet could cause overheating and may result in a fire. So the argument that a fault will always show up in a radial circuit does not wash with me.
With a ring circuit, a disconnection or a poor connection could result in a cable being overloaded if multiple high power appliances are in use. But as there are two current paths, it does depend on where the fault is in relation to the circuit wiring.
So how do electricians add an extra socket when the cable is behind a plaster or brick wall?
I can't speak for all sparks by I look for the easiest and least destructive options and give the customer a choice if I can. eg. Say you've got two bedrooms back to back and you want and extra socket in bedroom A. If bedroom B has an outlet on the opposite side of the wall, I can simply drill straight through from the rear of the existing one and surface mount the new outlet. Failing that easy arrangement, You can bring circuit extensions down from the ceiling or up from the floor, depending on where the existing circuit is. Typically you have to chase the wall (to be plastered and made good afterwards) or install surface trunking. If you are VERY lucky you may be able to feed a cable up/down behind the drywall if it isn't heavily insulated and there are no cross-members. This is unusual though.
I think in realty the 2.5 mm^2 can't handle the 26 Amps. it will be like a heater. In our country, it's common to use 2 X 1.5 mm^2 (10 m. wire) for 5 Amp. of current, 4 mm^2 for 13 Amp. of current, and, 6 or 8 mm^2 for 26 Amp. of current. considering the ambient temperature (50 - 70 deg. centigrade).
Thanks for explaining this peculiar arrangement.
Around here you are not allowed to rely on a fuse at the end to protect a wire, ever. It has to be at the beginning. The only exception is short proof wire (with thicker insulation), for example the spur feeding a fuse or circuit breaker from a bus bar.
The fuse in the plug that plugs into the sockets isn't to protect the circuit, it's to protect the cable on the plug connected to whatever device you're plugging in. It's the distribution board/consumer unit MCB device that protects the installation circuit wiring. This makes sense as, if your installation circuit has a 32A capability, and you plug some little table lamp into a socket on that circuit, then you don't want to have to have a 32A capable flex on that lamp alongside a 32A capable lamp holder, and 32A rated switch. Rather, you design them with say, 0.5mm2 flex, 5A rated switch, 5A rated lamp holder, and install a 3A fuse into the plug to limit the maximum current the device can draw in order to protect the device from ever being able to overload the hardware it's constructed of.
British socket outlets are designed to handle 13A generally (3120 watts @ 240V), and so the largest fuses available for the plugs that plug into them are 13A. This prevents there ever being the possibility of a fault on the plugged-in device/cable being able to draw current greater than the installation socket can handle, which is important when they're commonly connected to 32A @ 240V (7,680 watts) circuits.
The point is that spurs will have a 32A breaker on a 2.5mm^2 wire, John makes that point at 11:00.
A spur will never be loaded to more than 26 amps. And despite what they SAY, 2.5mm will take 32 amps quite happily, it just exceeds the design temperature. That's why we have margins of safety
Knew nothing of the circuits in our first house. Second had a ring circuit on each floor. Third, one for front four rooms, one for back three (a bedroom plus the kitchen and utility). All three bedrooms had one socket on the ring and one on a spur. There was, bizarrely, a 2A socket attached in one of them as well. This ring was later properly extended as more sockets were needed. My own places, single ring in first flat, two likely rings in second - one covered only the kitchen, the other all the rest. Third and fourth flats had single rings, current bungalow has two probable rings - once again one is just for the kitchen.
My whole house is only one ring circuit. I would like to separate all the kitchen sockets. Would you suggest a kitchen radial and another radial for the rest or two separate ring circuits. Would that question be dependant on total number of sockets and appliances(total load)?
For some reason my 1 bedroom flat has three socket circuits. I have three 32A breakers in my consumer unit all labelled "sockets" I have never figured out why the sparky who wired the flat decided to do that lol.
I am not sure if I have radial or ring. I wanted to add a socket in the bedroom and when I removed an existing socket it only had one cable going to it.
Very often when adding many more sockets, the most convenient approach is to put them all on a new circuit, rather than disturbing existing wiring... Hence many new socket circuits.
Another scenario I've come across is old electric storage-heater wiring being converted to socket circuits...
I had two in the lounge and two in the bedroom, one in the hallway and three in the kitchen. So it's like one for tyhe kitchen sockets, one for the bedroom and one for the lounge. Hallway outlet is on the lounge circuit, I know that cause I was messing around one day and tripped it out from the hallway outlet lol
Being a smaller building but having three breakers for sockets, I would guess you will have three radial circuits. They should not be on 32a breakers, Ideally 16a or 20a.
Can there be a good case for Completing a B20-breaker radial circuit, into a complete ring (while keeping the B20-breaker, not B32), as a means to reduce the Voltage Drop with little extra cable, while avoiding the 'overloading' scenario mentioned?.
This also allows for any section of the ring to be 'removed' if damaged, without having to re-run cabling / hacking out floorboards/walls/whatever. This can prove useful in many cases!. I _do_ think this is a good reason for wiring as a ring even if you use a B20 breaker...
@@sbusweb easier to "split into 2 radials' on 2x 20amp mcbs.
1 cable from 20amp mcb to sockets
and
another 1 cable from 20amp mcb to sockets....no join between the radial sockets...both totally separate!
easier to fault find and add too
I would have added to the video, the use of FCUs being useful in some circumstances, essentially creating a 13A radial circuit wired however you like, connected into the Ring.
That end comment is a load if B.S.
A long time ago we split the house into top and bottom ring mains and one for the kitchen that was when I was say 20 years old. I am 67.now there is nothing I repeat nothing wrong in a ring mains circuit at all.
@Mark Sesum you can have a fault on any radial circuit, making it potentially lethal.
You did not get the content of the video.
@Mark Sesum -When the ring is completed you double the load carrying capacity of the circuit +reduce to a minimum the voltage drop.
Came here from Delroy. As an Aussie sparky I found ring circuits weird but probably only still in the standard because it exists in old homes. A lot like engineers still having to deal with imperial machine threads and sizes.
Very interesting thanks John. I often wondered why the ring circuit concept was introduced.
what happens if you got powerful equipment in your bedroom?
Happy wife?
I have split many ring mains into two radials on 25 amp RCBOs,usually due to cumulative earth leakage,the bane of all RCD protected circuits with today’s ever increasing electronic supplies
To add extra sockets for office room, would you say a fcu to extra sockets or just add them to ring is best?
Got to determine if they are a ring or radial first...
Major newsreader vibes but I learnt a lot, thanks!
I watch technology connections, but the TH-cam algo started feeding me videos of UK electrical contractors. I found it very interesting comparing to what we have in the US. Ring circuits seem like insanity to me from US standards. Also. 32a on 14awg wire at 240v seems like an insane amount of power to have at a regular power point. Considering the average us outlet is 15A at 120v for a maximum of 1800w. 32a at 240v is 7200w. That is madness to me.
This is why all U.K. plugs contain a fuse which are typically rated at 3, 5, 10 or a maximum of 13A. The maximum loading on a U.K. socket is 3KW which is approximately 12amps.
Excellent explanation thanks, needed a refresher.
Good explanation by drawing but I would point out in reality when you’re doing this on site you probably won’t have the layout in the drawing you done, you will have two cables twin and earth running together through the walls or on the ceiling then dropping down the wall etc , and you will pull a loop from one of the legs for the sockets , my question is do you pull the loop from both legs like I do or just from one leg like I’ve seen other people do , I’m not sure if there is a right way . It’s all still on the same ring just not sure if it evens the loads if you pull the loops from both legs ?
It’s just not practical to pull one cable and then go back on yourself back to the consumer unit , so we always pull two cables , pull you’re loops at the sockets and obviously you end up with two cables at the last socket and the consumer unit to complete the ring.
This would seem to be a sensibly safe design if each leg of the ring were connected to a breaker limited to 16A per leg. Thus a single socket drawing 32A would pull both directions around the ring. This way an inadvertent break in the ring would not create a safety hazard.
I'm from the US and now live in the UK. We use radial circuits; which are much easier to deal with, add to. My wife's grandfather just had a conservatory built here, and he asked if I would add 4, 2 gang sockets. I thought no big deal. but it seems like its going to be. My plan is to break into the ring main with a 30amp junction box, and run the 4 sockets down off of that. I have calculated their amperage and voltage needs as 2.75 amps/187 volts being drawn in that room as they are only plugging in a 32" lcd, a sky box, and a couple of 60w lamps. I've been told by some sparkys, that this should be no problem. However, I'm seeing online that you can only spur off 1 socket from the ring main with the junction box. is this true. No one can seem to agree on this. I may just run a radial from the CU, straight back to the conservatory and be done with it. why are you guys still using such antiquated wiring schemes? What are your thoughts. Thank you!
or just put in a 13a fcu after the junction box, then I can put in the 4 dual gang outlets?
With a 13A FCU you can have as many sockets as you want, and this would be the easiest and cheapest solution (also why many conservatories end up with this arrangement).
With a direct connection you are only allowed one socket, more would allow the cable to be overloaded, as 2.5mm² cable is only rated to about 26A, rings have 32A circuit breakers. The overload protection is provided by the fuses in the plugs, 2x13A being approximately the maximum rating for 2.5mm² cable.
John Ward thank you for the advice!
Hi John, thanks for the useful video. I have recently bought a static caravan in which the ring main for the sockets is protected by a 20A breaker. The wiring is 2.5mm T&E. Is there any reason why I may not be able to increase the breaker to 32A? Would the incoming supply from the park affect this - although there are much bigger vans on the park than mine which must have higher loads?
Hi John, excellent videos. I wonder if you could offer some thoughts on choice of radial over ring in a kitchen, I have estimated the max diversified load at 23.7A, whilst a 2.5mm can just about support that, i'd presumably have to put a 32A MCB, as 20A MCB is too low. I don't want to put two radials in the kitchen because eventually somebody will do some maintenance turn off one kitchen MCB without realising there are 2 and kill themselves, not my problem but not ideal. So that leaves me thinking of a 4mm radial circuit with a 32A MCB, is that a more sensible approach in your opinion and will standard sockets easily take 4mm connections?
Yes, a 32A radial in 4mm is ok and most sockets will easily accept 2x 4mm conductors. Some sockets will actually take 2x 6mm.
Another option is a 25A radial in 2.5mm cable, provided the cable is not installed in insulation or other ways which reduce it's capacity.
So was the UK solution to the ring circuit deficiency the addition of the 30ma ground fault circuit breaker in the consumer unit?
any chance you could do a video on discrimination and how its approached at the design stage?
Connecting a socket direct to the consumer unit. Does this have to be a miniature ring? or can it be a single strand of twin and earth connected to the 32a breaker that the main house ring is connected to?
John, thank you for this video (and all the others) I do like and enjoy your style of delivery. I have a design question for you. I am designing for a small shed workshop (15 ft x 8ft) with a maximum load of 6Kw and had originally specified a ring final circuit using 4mm2 Twin and Earth protected by a 32A MCB (Type C because the workshop machinery has a couple of 2000 watt induction motors and wanted to avoid nuisance tripping on start up current surge). Having watched your video on the Satan's child I am now having second thoughts. I will be fitting a small consumer unit anyway and have space for three MCBs, one of which will support the lighting circuit and with a ring one MCB way would have been unused. So - would I be better off specifying two radial circuits, assume equal load on each, using 4mm2 T&E protected by their own 20A MCB (Type C)? The loads are Table saw 1500W, Dust extractor 1500W, Bandsaw (600W), Chop Saw 1500W - plus other more portable power tools - unlikely that 2 to be in any use at any one time. The power to the shed is all being done properly (Part P) and an SWA cable being run from the house consumer unit protected by a 32A TypeC MCB on the RCD protected side of the board to the workshop consumer unit.
A 32A ring would be done with 2.5mm cable, 4mm is oversized unless the cable is installed in insulation or other unfavourable conditions.
20A radials would also use 2.5mm. A 32A radial would be 4mm.
You can have multiple circuits if you want, but as the whole lot is connected to a single 32A supply, there isn't really any point - a single 32A radial would be fine, and would also be far less likely to trip when larger loads are switched on.
John Ward Thanks for that John. Does it make any difference that the SWA (3 core 4mm2) is a 27 metre run between the supplying consumer unit and the workshop consumer unit? I was upgunning the workshop ring or radials because I was concerned to meet earth loop impedance requirements of being protected by a Type C breaker. I do not want to be under sizing then having to rip out and redo with larger. Grateful your view.👍
I think one 32A circuit is better as it can cope with startup surge currents better without tripping. There is no problem with cable protection, as your likely load is less than the 6kW of even a single 2.5mm cable (26A continuous rating). Lights must be off a 6A MCB circuit, or a fused spur from your ring.
I just want 2 sockets in my loft,,,any idea how I can do it,,I’m not an electrician but I’m a good fisherman
I can't read,i can't write but i can drive a tractor😃
E K 🤣🤣🤣🤣🤣
Great video, I would like help to understand how I can satisfy the the formula Ib
That formula doesn't apply to a ring circuit.
Rings are a special case, and it's assumed that the loads on a ring circuit will be evenly distributed, so that the current is fairly evenly shared between the two cables connected to each socket outlet, so that the current in the cables won't exceed 20A.
Hi, thanks for your videos. Could you please make a tutorial about how to connect/wire a 3 gang switch so it controls 3 devices for example? In my kitchen, I have a ventilator, ceiling light and led light under the cabinets and I have 4 set of cables (each having a Ground, L, N) coming out from the wall ready to be connected to a switch.
I want to add about 5 unswitched socket (in a ring final circuit) behind my entertainment unit this is because once everything is put in place I would not have access to the socket to switch individual items on and off a bit like when you install a washing machine or a dishwasher. I would like to add 5 switches to these unswitched socket so I can individually switch them on and off, seen a lot of videos but none showed the above example would be grateful if you could do a video on it, many Thanks
Great video. Answers most DIY questions!
Hi John, thanks for the great instructional videos. You say there aren't really any legitimate reasons to put in a Ring circuit these days, what what about where cable length is a factor? I have a large house, with 2000sqft downstairs. I currently have a 32a ring circuit for the sockets with, at a guess, 100 metres of 2.5mm² T&E. If I were to convert this to a 20a radial, wouldn't I suffer from severe voltage drops at the end of the circuit? I read that a 20a radial should have no more than 30 metres of cabling. Is this right? Thanks a lot for any insight you provide.
30m of cable for 20A is correct but only if the entire 20A load is at the end of the cable. In reality it will be distributed along the cable and the maximum length can be much longer. The 106m limit for a 32A ring also requires a distributed load
Thanks John. Would you still use a 20a Radial with 2.5mm T&E in my situation where the length of the circuit is quite considerable? The circuit would simply cover the downstairs sockets (albeit 20+ double sockets) with no high wattage appliances. You may have guessed from my questions that someone is trying to convince me that the rewire should be a ring. Thanks again!
John, if you are able to reply it would be much appreciated!
My electrician wants to install a ring circuit for my largish kitchen. I would prefer radials for all the reasons you mention. I have asked for one "above counter" radial for kettle, microwave, toaster and myriad other small appliances, and one "below counter" radial for dishwasher, dryer, washer, fridge freezer and wall sockets for lamps, the hoover etc. He is adamant that one radial will suffice, citing diversity which I understand, but from experience I know that on weekends for example I will be using literally every appliance at once and would prefer two radials. Am I being unreasonable? Is there any reason why he is so reluctant? I am happy to pay for an extra RCBO and minimal additional cable costs and there are several unused ways in the CU recently installed the intention being to add the new kitchen circuits once it was extended. Should I be looking for a new electrician?
One radial might do, but no reason to not have two, it would be slightly more work but that's hardly a problem.
It's your house, so you should have what you want.
Some people are stuck in doing things the same old way, and may not like doing other methods.
John Ward Thanks! I couldn't see why it seemed to be such a problem but wasn't sure if there was a reason why he wasn't so keen. it's all chargeable work after all and to me at least makes sense from a capacity / overloading point of view, even if there are only a handful of days a year when everything is running flat out.
Spencer Wilton - the advantage of the ring circuit, is that you can choose long after the wiring has been installed what appliances you want connected and switched on without having to worry about socket is connected to what radial circuit (assuming we are comparing one 32A ring to two 20A radials). If properly installed, a ring is no less safe and no less reliable than a radial. At 230V, each 20A radial can supply just 4600W. A single 32A ring can supply 7360W. True, two 20A radials can supply more power, but if you connect too many high power appliances into one 20A radial, you risk the MCB tripping and spoiling your day (especially if it trips when you are not paying attention).
@@Mark1024MAK and if your ring is broken for whatever reason, you risk over current. I'd rather have 2 20A radials than a house fire.
Richard Ashworth - Yes, If a ring circuit has a break, there is a risk of a conductor overheating. However the risk of a fire is not as great as some people imagine. Firstly, when installed, the circuit should be properly tested to confirm that the ring is complete with no breaks. Second, for a fire to occur, enough current has to flow to actually overheat the conductor. Whether this occurs very much depends on the type of loads connected to the ring circuit (that has the fault). And where the loads are and where the break in the ring is. In reality, not many ring circuits actually have a total continuous current flowing that will overheat 2.5 square mm cable. Even if appliances with a total power rating of say 6.9kW are connected to the ring (30A at 230V), unless all of these appliances are all one side of the break, the current will be split between two different circuits to the consumer unit, and the resulting separate currents in the separate cables is likely to be below the value that will cause overheating. Even if you are very unlucky and do end up in a situation where the current flowing through one of the 2.5 square mm ring cables is exceeding the recommended value and the temperature of the cable exceeds it’s recommend maximum value, this does NOT mean that it will automatically catch fire. As has been shown, you have to grossly overload a cable for it to get hot enough for the insulation to catch fire. I once came across a house where an entire kitchen was wired as a spur off a ring circuit. All wired in 2.5 square mm cable. The cable ran from a terminal/junction box in the void between the ground floor and the first floor and ran to the kitchen (which was in an extension). This cable ran daisy chain style to all the double sockets in the kitchen (of which there were a considerable number). The kitchen had all the normal high power appliances (washing machine, microwave oven, kettle, fridge, freezer etc.). Despite this not being in compliance with any U.K. regulations, the cables showed no signs of overheating or damage. Of course I strongly recommended that the installation should be rewired.
If peace of mind is required, it is recommended that any and all electrical installations should be inspected and tested every ten years.
Any reason why you didn't talk about fused spurs (eg for spurs off spurs)?