Whenever my plasterer friend does any plastering in my house I always get him to overskim the edges of the box with the skim coat and then when it's dried I carefully cut it back with a stanley knife right in line with the edge of the box and it doesn't take much effort to just put a short faceplate screw into the lugs on the box to stop them filling up with skim coat then just give it a suck out with a plastic vacuum cleaner pipe with the circuit breaker switched off
I was taught as an apprentice to be polite and ask them try to not to If they overdo deliberately after that, discretely leave tiny gravel pieces in their bags of plaster. Tut tut tut.
As an amateur I am extraordinarily careful to ensure safety and have always run an earth wire between socket and back box. With your explanation I now understand better why it’s not a waste of time. I really appreciate your videos so much so that I watch some of your other videos just to learn, even if it’s not necessarily relevant to the job I’m doing (I’ve exchanged plastic light switches and power sockets with more attractive metal ones and am currently adding to the existing metal sockets in my shed). Huge thanks for giving me the confidence to do it safely. Subscribed!
@@antrobuselectrical554 depends whether the box is below or at your height! If box is situated high (I know, that's unusual!) then it might be appropriate to have the earth terminal above so that one can get a better look at it and connect to it.
Correct in the main however I had a situation where I had to use one of the biggest sized knockouts this was because I had a a few cables that had to fit through as it turned out I had to put the box with the CPC Terminal upside IT'S rare but can happen! Best wishes Warren
I guess when you mentioned about the socket being removed for decorating and the power not being off, thus rendering the front panel screws not earthed, is a strong argument for why you should earth the backbox
18:50 With my luck it's a ring with a spur so there are three sets of wires, all far too short, no slack, terminals too small to take all three wires, and a horrible battle.
EXCELLENT video John, thanks. There was way more information here than I needed but I ended up watching it all because it was so well presented and full of useful tips. I also got a Douglas Adams vibe at times because you sounded a bit like Simon Jones who played Arthur Dent in BBC's Hitchhikers Guide, and you said things like "...and the plaster has been in and cleaned it up for you, just like they don't do in real life."
The dreaded incessant 'earthing back boxes' discussion. For 30 seconds work and 6 inches of earth, just do it. The most likely person to get an electric shock from the box is anyone working on it and if the fixed lug is being relied upon, the earth is disconnected when the socket is removed.
Fixed lug - is no more rated as an electrical conductor as the loose lug ! Having installed a cooker at a friend's when he moved to a flat - and found the earth used to be via conduit, I'm not going to use anything but copper (or brass) conductors for earthing.
Hear hear to all the positive comments about this video. Great explanations, just like the best teacher in my school days. I was brought here because of an earth terminal on a back box, and wondering why, got all the answers! Peace be unto you.
Just doing my 2365 qualification, then onto the full NVQ, JIB Gold Card etc. Crossing my fingers that I can find someone as thorough and knowledgable to work for! :)
I always do a lead to the bb as my own personal preference, as I am re-assured the bb is always earthed even when the socket (at some point in its life) is hanging off the wall in peoples houses when they re-decorate / re-plaster / tiling etc.
Do you install fly leads to all metallic consumer unit covers in case someone takes the cover off while the board is live? Or what about metal conduit box lids? Both examples, in most cases relying on a screw as an Earth. Same as a socket back box. So what’s the difference? The likely hood of it being open while live I suppose? We have to draw the line somewhere.....the regs take into account finished installations when it comes to things like this. There is no requirement to consider part finished installations. I’ve never ready anything in the regs to say ‘must make provision for earthing for when the user exposes live parts during decorating’! Lol! A socket hanging off the wall isn’t a finished install! And therefore should not be live! If it isn’t live......why the need for earthing the back box with a fly lead? Let’s not talk about ‘in the real world’ either.....it’s in the real world that unqualified Wolly’s take sockets off to decorate, leave them hanging there for days and then just screw back without checking the terminal tightness! Possibly leading to fires! Tip for them.....leave the sockets in place, where the back box is earthed, and the connections are sound. Or employ an electrician to take them off safety so you can do your work. 3rd option.....fool around with it yourself! Just don’t expect me to make allowances for such stupidity while I am initially installing it! Lol! Anyway.....it’s been a long day! 😂
@Mr Brightside my thoughts exactly ...Whilst some might not live in the ' real world' the rest of us sparkies do ...no body calls a sparkie to wall paper ...although I've been called to sort out tripping MCB's in the aftermath ..several times because original installer didn't use a grommet and the Home owner pulling on the cables shorted to the earthed BB...so hmmm I think I 'll keep adding a cpc strap to the BB ;) I cant help but imagine someone tucking some wall paper under the loose socket and touching a live BB ..I know we shouldn't and dont have to take that into account at the design or install stage ..but Personally I think we should try. I'd bet even K C adds the BB cpc if he's installing in a loved ones home. plus if you get into industrial electrical work then the vast majority of removable conductive covers are supplied earthed with a seperate conductor ..not just relying on the 'screw'. not the round conduit covers though ....dont give them idea's....and i'm not having the seperate cpc argument again. I like to afford domestic customers at least the same protection where possible as the industrial ones ...preferably more ...even if it costs me a few meters of cpc per year.
@@Spark101. The brass BB terminal is included in manufacture, one would assume for a good reason - like earthing the zinc-plated BB and giving protection to the exposed fixing screws. Of which, as we see in John's demonstration, always come with one fixed and one loose female threaded lug. The loose lug would, by definition be a poor electrical connection, but often, even the fixed lug, can have issues, like zinc flashing causing a poor threaded connection, I've even come across fixed lugs being loose themselves, or poorly threaded. So as the maxim for anything potentially dangerous is - safety first, the BB lug, if fitted, should *always* be hooked up to the CPC. . // We have to draw the line somewhere... // Presumably that means cutting cost and time at the risk of safety. I would also argue, laziness... . Yes, there are plenty of *uneducated* people doing electrical work. However, the matter of qualifcation is overused, especially by electricians themselves, who with the odd exception - like John here - tend to be overly secretive about divulging their 'hard-earned' arcane electrical installation knowledgte to those - 'not in the club'. In reality, electrical installation is fairly elementary, providing one adheres to correct conductor size, voltage drops, to the circuits power requirements and understands the practical aspects (tool and equipment usage) thoroughly. It aint rocket science. Anyone who has trained in electronics can easily cope with domestic mains circuit installations. I wire sockets exactly like John here... *You'd* be hard pressed to know difference. . As for decorators, most pro decorators I know (and those not so pro, who I've advised....) don't remove the appliance socketts from the wall, but merely loosen the fixing screws enough to create a gap around the socket to paint around. This way, the rear and potentially dangerous part of the socket remains relatively guarded, with the CPC intact... Especially if the BB tail is included. And no screws get lost in the process. This can be done without necessarilly powering down that circuit, though wherever possible, I always advocate doing so as an extra precaution, depending on the installation and other domestic factors like - roaming kids, with screwdrivers... . Though I'm trained in Marine Radio and Radar Engineering, I do not have full electrical qualifications, (I do have PAT and 'mains compliance' installation, certification) but I can still perform a full professional installation, from initial electrical schedule design to final fix. I am self-educated and experienced and always refer to the latest edition of IEC/IET regs and other relevant documentation. As such, I've been trusted to undertake electrical installations, which have subsequently been examined by a 'qualified electrician' with zero faults or criticism. I even undertook (one of my first jobs...) the entire wiring schedule and installation of an 'Arts Centre' - a 17th century *public building* - that was upgraded to three phase and expanded to include a 60 seater cinema and extra gallaries. This installation also included a residence and restaurant. So that installation was pretty comprehensive. My schedule schematic of each of the four storeys of this ancient listed building was subsequently passed by the regional electrical provider and local planning body and was approved with no alterations or recommendations, other than the removal of certain parts of the orignal installation. I was 23 years old (15th/16th IEC regs). I didn't do the final testing, or hook-up, which was undertaken by council electrical contractors. The installation passed and, as far I know, is still in business. . You are a qualified wally, who choses to forgoe safety by not bothering to wire in a BB CPC tail, all for the sake of saving a few minutes or pennies... Who of the two of us, is actually the safer electrician? . Yes... I suggest you had better go and have a beer...
A socket with 2 cpc connections, I would connect one to each side of the ring as a disconnection in one will still have the other available. This is required for high cpc leakage current equipment using sockets ( 3 to 10mA, OSG sect. 7.5.3)
Well that's how you tell a good electrician because of the amount of good practice that is left out of the regs and the electrician that thinks if it's not in the regs it's not needed, they are even worse when applied to industrial wiring.
I've never understood the concept of "well its not needed so I won't do it". If there is an earth terminal, or just an empty loop terminal on a plastic appliance, and you have an earthing conductor, why not install it anyway? Its 10 seconds extra work, but it keeps them from flapping about, and has a back up in case the main protection (usually "unable to be touched") fails. I have yet to hear a convincing argument of why you'd skip that part because the regs allow it, other than saving time. So, time/productivity is more important than safety, and you'll cut whatever corners you can? Thats a great way of making a mistake when conditions change, or when regs change, and you still rely on muscle memory, and relies on a lot of assumptions which might not always hold true.
A lot of people get confused by regulations, which state only the minimum requirement, and think they instead state best practice and assume they then don't need to do anything extra. And this applies to most standards and regulations, not just BS7671.
I think it comes down to whether you feel something is necessary and if you have the relevant experience and common sense then you can make this judgement.
Hi J.W., big fan of your educational series. Rumour has it that the tradition of looping CPC though the backbox started with an awkward wording of a 14th Edition, regulation D5, where an amendment added requirement of " the earthing terminal of each socket-outlet shall be connected by a conductor complying with Reg. D.28(iii) and D.29 to an earthing terminal incorporated in the associated box or other enclosure". The reg as a whole of course related only to such situations where the earth continuity was achieved by sheath, conduit, trunking, ducting or armour, but the amendment quote was reprinted out of context so many times that sparkies just started wiring loops to all sockets with metal backboxes on the basis that as per @sseedell's comment "for 30 seconds of work and 6 inches of earth, just do it". Todays regs specifically exclude front screws as "reduced dimensions exposed-conductive-parts" from any fault protection (410.3.9 I think), so it further muddles necessity for connection to the lug in a box deep in a wall, but of course nothing wrong with it still being performed as a where-in-doubt/just-in-case/"good practice" I guess?
It's 410.3.9 (iii) and I've been looking for that regulation number for yonks. It's a quirky one and counter-intuitive but I see it as a good example of common sense being applied in the regulations.
Great vid as always. Newbie here, I've been taught to always earth the back box. Additional reasons include accidental penetration by drill bit etc and also could help with computer/IT earth leakage. JW do you agree with these things?
Not a bad video, John. I remember being an apprentice electrician and my boss at the time used to bash on about "terminal fill". Back in the day, socket-outlets in New Zealand had enough room for 2 x 2.5mm² wires in all of the terminals, so if you twisted the wires together, they would fit. Light switches had a maximum tunnel size of 2 x 1.0mm² solid core wire. Over the years, the Regs (and better thinking) changed with 1.5mm² being used for lighting circuits, manufacturers had to change the terminal sizes, as you couldn't get two wires into a switch feed terminal.
I use to to the exactly the same.. double up if possible.. and some of my colleague use to laugh on me.. but I do not care.. it is my choice and responsibility. Thanks for this video.
good to know i'm not the only one still using my 17th guidance notes! Except for my blue GN3 inspection and testing. GN1 is the most underated! An essential read every so often
I really like your videos where you dip into the regs a bit and discuss where things are and aren't in the regs. Re the subject matter itself, I don't see where the controversy comes from: presumably it takes an additional 60 seconds and penny worth of conductor to make the thing additionally safer for, as you say, the decorator who may or may not have a clue about why it's a bad idea to remove a faceplate without taking the power out first.
These screw terminals are quite an effort to properly connect, i wonder why the UK doesnt have these nice push-in terminals most of europe uses for decades already? Realiability doesnt seem to be much of a problem, at least around here the quick-connect sockets are perfectly fine and dont suffer from inappropriate screw torque which caused the older ones to overheat sometimes.
Excellent point re. filling the connectors, I was taught to twist the two conductors together a opposed to folding. The regs. were amended here in Ireland in Sept.17 regarding the earth conductor in T&E, all new installations must use an insulated earth conductor that is the same CSA as the phase & neutral conductors. Use of twin and earth cable with a bare conductor for same is prohibited.
Same for me on the twisting together. I was told off about doing it a few years ago (I think on the basis that it could make future fault finding difficult?) so not done it since. Twisting seemed a good idea to me.
Twisting is better in my opinion as well it would provide a more uniform filling technique for the recessed holes, no guarantee of course it works every time. It’s still worth checking.
Math Man - not keen on solid core wires being twisted together. If the screw terminal is tightened too much, it will bite into one of the copper solid core wires more than the other. Then should you need to untwist it at a latter time/date, there is a high chance of a fatigue fracture and the solid core breaking. If it happens while you are working on it, it’s a pain to strip more insulation off. If the wire is now too short, it a right pain. But worse, if the wire breaks later then when you test the circuit, you waste time chasing the open circuit fault.
Interesting - in NZ, we'd twist the phase conductors together and then put that in the terminal. Usually for socket outlets its 2.5mm^2, and so you twist the strands together and fold over for a single wire, but with 2 or more you generally twist them all together at once, cut to length, then insert without folding.
Twisting cables together makes it a pain in the arse for testing, you may have to un-twist them which usually ends up weakening the copper too much, leading to breaks in the conductor or high resistance connections if its not spotted. I cant remember the specific regulation at the moment but our regs say that each conductor should be connected separately
I was taught that as well but in the UK these days it's sometimes necessary to seperate the wiring out behind a socket for electrical inspections so it's not done at the moment. No doubt in another 10 years time they'll make it mandatory to twist the wires together, they are like that in the UK.
I’m not keen on solid core wires being twisted together. If the screw terminal is tightened too much, it will bite into one of the copper solid core wires more than the other. Then should you need to untwist it at a latter time/date, there is a high chance of a fatigue fracture and the solid core breaking. If it happens while you are working on it, it’s a pain to strip more insulation off. If the wire is now too short, it’s a right pain in the arse. But worse, if the wire breaks later and it’s not noticed, then when you test the circuit, you waste time chasing the resulting open circuit fault.
For terminating stranded wires (flex leads as UK'ers call them), crimp-on ferrules should seriously be considered. These are common in Germany and other EU countries. They're not used much in North America either, but I think they're excellent for set-screw terminations, where the strands of the wire would otherwise fray and not make 100% solid contact in the terminating fastener. I am seriously surprised crimp-ferrule sleeves are not ubiquitous worldwide.
They are used in the U.K. quite extensively, it’s required for UKCA when shipping a product with stranded wire inside for example. (some exceptions such as ultrasonically bonding the wire is deemed ok too)
@@akbarramzan7436 That's good. Here in the USA, we use crimp terminals for particular types of terminations like forks, rings, spades, etc. But what you NEVER see here are the ferrule type for some strange reason.
I never did see the point of an earth terminal in a plastic back box. You mentioned something at the end avout light switches. Do you have a viseo on this?
Plastic light switches do not have an earth terminal. When mounted to a plastic box, the terminal in the box is used as a place to secure the protective conductor.
I like the continental idea of round holes behind sockets and light switches instead of square. So much more sensible as they just use a drill to make the hole.
You'd stop liking it so much if you had to produce the tooling & specify the materials to actually make round back boxes in any material other than plastic. Rectangular boxes are much cheaper to produce. Plus the specification dates back to when electricians used a bolster (chisel) & lump hammer to recess them, & those aren't as good at producing neat round holes as they are at rectangular.
@@johnburns4017 Indeed it is, but then so is sinking rectangular ones with the correct tool, & changing would require all new design outlets & switches too. Then if adopted you'd never know in advance which of two standards you'd be working on, & have to keep tools & stock of both types. Sounds like a worse situation than the current one if you ask me.
@@beardyface8492 I think you are just being argumentative for the sake of it. It is plainly vastly more work to create a square hole in just about any material you can name. The amount of time, dust, noise and aggro involved in installing a square box in anything other than a hollow plasterboard wall completely and utterly dwarfs any consideration over the cost of producing a round box, even in metal. Have you noticed that you can buy a tin of beans in the shop for approximately 20 pence? Not only does this low price wangle you almost a pound of delectable haricot beans in a mouthwatering tomato sauce but included almost as an aside is an ingeniously manufactured cylindrical steel container.
@@nobodydoesithalfasgoodasyou The point that the standard was created back when recesses were sunk using unpowered hand tools (hammer & bolster) remains, as does the second point if you introduce a new standard.. you suddenly then never know which you're dealing with & need two sets of tools.. Plus there's the awkwardness of dual-gang sockets & switches, which you simply couldn't design with a round back-box.
Question for you, I am fitting metal face plates in my kitchen but also brushed steel surrounds or finger plates that go behind the faceplate. My question is do I need to earth them aswell as they are exposed to the outside world. They come pre cut with the two screw holes but also one in the corner, I presume for an earth.
I may have missed it but what is the recommendation for situations where the cpc has no connection point with on the accessory or in the back box I.e. Plastic boxes or lighting connectors. I normally terminate the CPC in a connector block such as a wago connector. What do you recommend John ?
I.S. 201-4 cable is not to a British Standard though. Being in Ireland, and within a mile of the border, I use plenty of both types of T&E. But I never bring either type of T&E across the border from where it is intended to be installed. Incidentally, in the south of Ireland, it is mandatory to connect a flylead to the backbox and you are prohibited from relying on the connection through the screws to the lugs.
If they specified torque settings for accessory terminal screws I really hope it would accelerate the development of accessories with spring clamp terminals!
@@millomweb well ideally 10 - 1 for the fly lead, but yes. If it was designed from scratch I'm sure it would be possible, and new socket boxes aren't typically less than 35mm anyway
Is it necessary for the “regs” to spell everything out in great detail. Surely, the metal socket fixing screws, which can be touched, render a metal back box exposed. No?
No. The regs do indeed spell this out: 410.3.9 The provision for fault protection may be omitted for the following equipment: (iii) exposed-conductive-parts which, owing to their reduced dimensions (approximate maximum of 50 mm x 50 mm) or their disposition cannot be gripped or come into significant contact with a part of the human body and provided that connection with a protective conductor could only be made with difficulty or would be unreliable. NOTE: This exemption applies, for example, to bolts, rivets, nameplates, cable clips, SCREWS and other fixings.
@@andrewcadby - Again, an industry 'advisory' - catering for cost/time effective solutions. Though I agreed with your explanation, as a matter of extra safety, I always employ a BB CPC tail on metal BB's fixed in walls.
@@Deebz270 that's fair enough, although personally I don't see the point, with the obvious exception of plastic switches etc. The odds of a backbox somehow becoming live without tripping the breaker, let alone the RCD, seem negligible IMO. Also, may I bring to your attention metal consumer unit lids. I have yet to come across one that didn't rely on its fixing screws to earth it.
What if the metal back boxdoes not have an earthing terminal? Is it ok to use one of the screws that fixes the box to the wall (that is in contact with the metal of the box), or is it better to replace the backbox entirely?
Fixing screw could be used, or you can buy brass terminals separately which fit into an M4 threaded hole. Drill a 3.3mm hole and tread to 4mm if there isn't a suitable hole already.
I find your videos incredibly helpful, informative and hilarious. You may have the driest sense of humour on the internet and I would love to have a beer with you 😂
I have seen a metal backbox secured via wood - a good insulator. A light switches securing screws made contact with a bare Line wire, making the screw _live._ It never went to earth so nothing tripped. You only knew when the screw was live when you touched the head of the screw. If the screw hole surrounds went to earth like sockets do, it would not have occurred.
Any thoughts on twisting the 2 Line/Neutral conductors together? Better connection in the socket? Continuity of the ring if the terminal happens to come loose? I have seriously considered twisting them and then soldering them so that the ring remains complete even if you have a loose socket terminal. BTW, I am not a domestic/commercial spark, my background is an Industrial spark, working on plant & machinery.
Not recommended, twisting work hardens the copper making it more likely to break, and twisting makes future testing or additions far more difficult. Solder isn't a good idea either, as solder is soft and will flow under the pressure of a screw, causing a loose connection.
I have a question, old flat all concrete , no earth wires they are all connected to the metal back back box, one of the back boxes has no earthing terminal and I can not take out the back box due to other wires coming in and out, So according to the guide notes this is acceptable but the immersion heater and power shower have no earth feels very unsafe, should I solder the earth in to the back box ?
Earth terminals are available separately: www.tradesparky.com/cable-and-management/conduit/steel-accessories/deta-dt40604-earth-terminal-m4-brass drill a 3.3mm hole in the backbox, thread with a M4 tap and screw the terminal in.
A very very poor path, walls don't conduct worth a damn even when damp, & that's not mentioning walls tend to be sat on an insulating PVC damp proof course even if they did. With a sufficiently sensitive instrument you *might* be able to measure the difference, it'll be swamped by the other variables & other parallel paths in a typical installation though, especially when you consider the boxes get connected to the CPC via the accessory mounting screws as well. Connected via a plated brass screw, or connected via the screw with a parallel conductor to the same very poor path, even with many instances of that one slightly corroded terminal somewhere is likely to make a bigger difference.
What about using Wago clip connectors for these things in the back boxes? Could be useful especially in 2-4 socket boxes, that are formed from separate units. In many places in Europe, we usually use 60mm (internal dia) circular plastic boxes for junctions, sockets and switches, not rectangular metal ones like in UK. The big advantage of a very popular circular ones is that they can be installed quite easily in a number of different materials by cutting a hole with a hole cutter of a proper size and a power drill, thus speeding things up considerably.
What to consider? Was the conduit _designed_ to be the CPC? If not then drawing a separate CPC isn't belt and braces but a necessity. If working on old installation you probably don't know and have no means of find out if it was a design element anyway. It may be indicated by the general absence of separate CPCs but that would be a presumption that it was okay, not proof. If it _is_ in the design, and you trust that it's properly installed doing it to spec doesn't require drawing the extra conductor and testing will show if it's acceptable. I'm quirky in that I _like_ using the conduit and usually specify it where realistic, but aware that there are reasons not to rely on it and heck, 1.5mm² green/yellow sheathed single insulated is about 15p/metre so it's got to be a very large installation before cost becomes a significant factor.
I had a case (work related) where the sparky extended wiring in new conduit without installing a CPC only to find that 'down the chain' there was some plastic conduit in place - fortunately he tested before energising.
@@calmeilles usually the person who runs the conduit wires it,in the past I have had to run cpc in even though the conduit was perfectly sound ,the designers choice not mine,for that customer I always used a cpc.
@@calmeilles I don't like using the conduit as the sole cpc..I'm and old grumpy git of many years and with too many grey hairs (the ones that are left)...experience shows me ..conduit gets damaged ...bumped with pallet trucks/forklifts/other crap..buildings move over time ..thermal expansion and contraction for 1000's of night/day cycles not to mention corrosion...joints come loose..even if designed and installed correctly...seen it in many many many factories ..99.9% of industrial customers will pay for the extra cpc if you sell it as extra 'elf and safety' and explain why....I've always thought robustness of the safety devices obviously including the CPC should be at the top of the design path. Any way stay safe ..at least I've kept working through all this covid mess.
The size has to be large enough so that it's not damaged in the event of a fault. Using the same size as the cable is OK - and in most situations that will be 1.5mm² anyway, as larger cables are rarely used for socket outlets. Smaller sizes could be used, but calculation would be required to confirm the size is adequate.
As with all John's videos, very clear and well presented and explained. Simple question, what brand of wire strippers are you using? Almost all of those available in in the UK seem to be designed/marked as for US/Canadian wire sizes. Few if any actually show the UK 6.0, 4.0, 2.5. 1.5, 1.0mm etc as the specific/clear "die"/cutter hole.
@@jwflame Thank you. Hadn't seen these on the big river UK site - until I posted the details you sent. I shall invest in a pair even though I have just bought another cheaper brand which seem OK (though only time will tell how good they are). These being US marketed means they use US wire sizes, but no grief to adapt to/determine the correct UK equivalents (especially for UK T&E and single core mains cable).
I like to use the fly lead to the back box to hold the accesory while I'm terminating the other connecions particularly when working at height so i don't drop it
I wonder what your opinion is of the current trend on some TH-cam videos to use ferrules on stranded conductors? I suppose they might reduce the chance of strands not making their way into the terminal, and maybe a bit easier to connect in awkward locations.
A good idea, and in many cases essential for fine stranded wires. Of limited value for most fixed wiring, as it's normally only 7 strands and they are of moderate size so unlikely to be missed in most terminals.
I would always use a ferrule if putting a stranded wire into the same terminal as a solid wire. Otherwise the stranded wire can sometimes be incompletely clamped or pull out entirely.
I was always told by an old electrician to earth the backboxes. His reason being people unscrew these things when decorating or wallpapering, if there is no rubber grommet and the supply cables coming through the steel back box had chaffed, then it would become live.
I always have earthed back boxes, just makes sense to me. I was taught to do it that way from college. It's a 2 minute job and safer. 😎👍 Lazy people always argue the fact.
Thanks. Doubling up should solve my problem of socket screws not getting a firm grip on wires. No sparkies I've used do that and none of the comprehensive DiY books I've had show it. I've been going round the sockets finding that the professionals left them loose or earth sleeve inside the gripping screw giving lousy to no earth connection. If cables are a bit short, I can feed through a new piece of 2CE because I used conduit between boxes - sparkies called it "electrician's dream" before they did the sloppy wiring
Three wires into that design of screw terminal makes me shudder. That would be a massive fail in the avionics industry and I'm not overly happy with it here. Two wires max. Yeah, doubling the wire over mitigates most of the problem, but that stranded wire exacerbates the problem. There are designs of screw terminal where I'm happy (ish) with three wires - the type in circular junction boxes. But not with that style of screw terminal. I'd go with looping one of the PECs into the backbox terminal. Of course, when you have a spur on a ring main, there are more wires than I'm happy with.
Firstly I am no longer an Electrician, having moved on to mains! When I started, things were ... different, the book was small and yellow for a start! Having said that .... Would anyone rely on a steel conduit with many screwed up sections (corrosion risk) as an earth? Would they not run an earth in. There would be an added bonus that your wires are copper with a lower resistance than steel! My second point is doubling over conductor ends. If you look closely at a screw connection with two single cables going into it you will see the screw end (which is slightly rounded) would force the conductors to eather side of the connection giving increased contact with the added bonus that as the screw is tightened it would deform the round copper conductor making the joint not only tighter but a better electrical contact! I think if you are putting a single conductor into a terminal you should double over the end if the connection will take it!
There's some interesting calculations you can do there, the thing is, for a given cross section, yes copper is a better conductor than steel, but once you factor in the comparatively massive cross sectional area of steel tube, you suddenly find that steel conduit has a considerably lower resistance than any earth lead you're likely to run inside it, I'm sure I even saw a video where JW did the calculations. Why add the expense of more wires & the labour of pulling them when they're not required? It'll take a hell of a lot of corrosion to raise the resistance of a big fat pipe to that of a skinny wire. Some people still do pull a CPC through, the main thing it protects against is the situation where a conduit run becomes loose or detached where it enters a box, the fastenings seem to somehow undo themselves over time, mostly from people not doing them up properly in the first place.
Back in the day I seem to remember that using steel as an earth required you to have a resistance Half that of copper. The other point I would make is that we have Many "looped services" where the mains comes in to one house and is then wired in conduit to the next house under the floor. We get them regularly as a "Bad Earth" when some luckless spark tries to do a Ze test on the looped property. Trust me, they do corrode! As I said already I am no longer a spark but are you saying you can use the armor of a SWA cable as an earth now ..... it is steel and I suspect a larger csa than the conductors!
Thank you for yet another interesting and informative TH-cam postings. I enjoyed it very much. I guess that in the majority of cases we are all doubling over the conductors to make them fit into the terminals provided. It really does make you wonder if a much improved solution could be provided by socket and switch manufacturers. I did consider whether not the end of the screw should actually operate some kind of simple clamp affair that would secure the conductors as presented (not doubled up), but the immediate concern might be that different cable conductor diameters (or solid versus stranded conductors) might not all be simultaneously served (i.e. some conductors might not be secure). I then wondered whether a different clamping arrangement could be devised - perhaps not unlike a miniature jubilee clamp that wraps around all conductors and squeezes them together. I’m not sure how that would mechanically present itself to a tightening screw, but given how many million of these fittings are being installed, you’d think it wasn’t beyond the wit of humankind to make it more simple and secure by design, rather than leaving the challenge to the installer who may or may not spot a problem. Come on manufacturers, the gauntlet has been thrown down, why not see what you can do? We can send things into space and retrieve information from them quite readily, yet we are still messing about doubling up conductors to get around the terminal shortcomings. Why is it so difficult?
Best explanation ever of the correct way to safely terminate a socket or switch. Mind you, when the screw is tightened down on two or more bent over wires, the screw itself can become exposed - sort of defeating the importance to avoid exposed conductors - nothing is ever easy :(
@@jwflame You could crimp the fly lead and one of the CPCs into a double ferrule (2 x 1.5mm2). That way you would save on the waste generated by first method you showed whilst ensuring a connection to earth is maintained if the accessory is ever removed. My preference is to put the ferruled pair into the accessory and take the fly lead to the box, but it could be done the other way around. Oh, and why not put a ferrule onto the other end of that stranded single while you're at it? I would😁👍
6:15 Ooh, I like your fancy concave screw washer things... (Sorry, I don't know their correct name) I use pan-head screws to negate the problem of countersunk "wood" screws standing proud or punching through the back box but this looks neater and less proud. (Especially if the screw has been burred a tiny bit when screwing in. - Less chance of rough metal scratching a cable...) Do you mind if i steal this please?
If you earth the metal back box and the metal faced switch or socket is screwed into it, does that Earth the socket / switch without a direct earth connection to the switch or socket itself?
Could somebody advise me, please? I have the same wiring set up in my single socket plug like the one at 25.45 in the video. That is to say 2 lives 2 neutral and 2 earths. Well there were 2 earths but one has snapped off at the base. is it ok to just use the one earth that is left and attach that to the earth on the socket? Cheers
Thanks for the interesting & useful video. I'm intrigued by your yellow cable cutter, stripper, plier as it is tailored for the uk having 1, 1.5, 2.5, 4 & 6 mm2 stripping holes. The only similar ones I've seen are designed for non uk markets having holes sizes maybe like 0.6, 0.8, 1, 1.3, 1.6, 2, 2.6. Where do you obtain ones designed for uk cable sizes.
I am an TV outside broadcast engineer by trade. When I was training in the eighties we were taught not to fold wires especialy single core as if the screw tightened down on across the loop it might not fully crush the bend and could loosen over time. Funny how things change over time.
I like that ! The less wire in the terminal the greater the compression and bite ! If 2 single core, there's a risk that only one is trapped under the screw - mechanical testing of each wire after fitting is always a good move. I liked the stacked folds shown in this video - gets everything clamped - just be sure to tighten the screw properly.
@@millomweb technical here: why dont all sockets have the terminals with the flat bit that actually contacts the wires not the screw, they contact across the whole gap
The way I look at it is that any exposed metal must be earthed (except in the case of double insulated systems); the screws are exposed in most cases, and even where they are not, generally no tools are required to remove the parts hiding the screws; therefore, the screws must be earthed. If the accessory has no earth strap, as in the light switch, then the box must be directly earthed; if the accessory does have an earth strap, it's sufficient to rely on that to ground the box that the screws fix into. For the case of insulated plasterboard boxes and non-grounded accessories, it can be considered as double insulated and no ground is therefore required.
I remember back in the early 90s my NICEIC inspector queried as to why I used a 1.5mm earth wire to the back of the steel box. I thought he was accusing me of overkill but his point was it should really be a 4mm in the case of a 32A ring main circuit as a 1.5mm technically won't be able to handle the maximum direct fault current if the box became live. He was one of those sorts that thought the IEE should have run everything past him before they came up with any regulations. Yes he has a point but he can go boil his head, always done it that way, so does everyone else and now I see you also do it then it MUST be OK 👍😊
I run the T&E earth conductor to the box connection then an earth link to the socket. This means less chance of the protective earth loop being disturbed by decorators.
I can think of many things that we could do to cater for the ‘what if’s’ Truth is.....the regs already cater for a safety standard that is considered acceptable. And the regs say we don’t need them on socket back boxes most of the time! I haven’t put fly leads on socket back boxes for around 10 years now. Not gonna start either. Only time I would, if the sockets were not RCD protected, which is unlikely! Nice video though John. I just don’t agree that the fly lead is needed. If some plonker takes the socket off while live.....he can’t complain if he gets a belt! Just like if I, someone who knows nothing about gas, deserves everything I get if I take my boiler apart while the gas is still on! We can’t always work, having to take into account the very very stupid! And at our own cost, against the current standard!
I’ve never done it either (25 years) on a socket. You shouldn’t be taking a socket off if it’s live and you defiantly shouldn’t if your not a electrician.
I always put flylead to back box but found it a bit strange when earthing plastic box! Trouble is you can get pulled up for not doing it,bit of a nightmare if you've finished.
@@tommochelsea72 People do it because there is no good alternative :(, houses in the UK normally have a whole floor (with the exception of the kitchen) on one circuit so keeping the power off while the wallpaper/paint dries is rather impractical :(
Wire wrapping clockwise 2/3 of the screw terminal helps when you tighten clockwise it pulls the wrap to the remaining 1/3 gap around terminal and if you pull on the terminal it will ensure the loop on the Earth wire does not come away from under the screw. Screw based tightening using this kind of technique and torquing (yes NEC 2020 code in USA provides some guidance on torque settings for socket screws if no manufacturer guidance - I disagree with you respectively it does makes a difference though annoying, at the very least it creates an additional safety step and helps to concentrate the mind that it’s been done correctly) research has shown at least in the USA wire wrap around screw terminals to be the most effective in ensuring the best connection even better than the clamping and recess hole conductor terminations like in the U.K. sockets. However, the proviso is if the wire wrap method is done correctly only in those circumstances would it work the best and reduces fire risk. Here learning good technique and checking is critical. John not convinced you can always guarantee the fold over method guarantees double the conductor available for the bottom of the screw to bite on. It could be that the loop you form the screw actually bites down on the inner side of the loop, so you assume that it’s secure but the bite down is covering a smaller inner surface area which could come loose overtime no torquing could also mean greater risk of loosening over time. That fact it’s in a recessed hole with no clear line of sight is a problem. Maybe a type of ferrule suitable for solid conductors ( is there a such a thing?) would help you to fill the recessed hole much more uniformly helping with the security of connection? Maybe worthwhile mentioning some of the physics of this process in future videos, use of specific fastener methods and or thread locking? Pre-loaded bolts (or nuts) rotate loose (or fasteners in them) as soon as relative motion between the male and female threads takes place. This motion cancels the friction grip and originates an off torque which is proportional to the thread pitch and to the preload. The off torque rotates the screw loose, if the friction under the nut or bolt head bearing surface is overcome, by this torque. There are usually three common causes of the relative motion occurring in the threads: 1. Bending of parts which results in forces being induced at the friction surface. If slip occurs, the head and threads will slip which can lead to loosening. 2. Differential thermal effects caused as a result of either differences in temperature or differences in clamped materials. 3. Applied forces on the joint can lead to shifting of the joint surfaces leading to bolt loosening. Take a look at www.vdi2230.de/engineering%20fundamentals.pdf www.researchgate.net/publication/222178347_Experimental_study_of_loosening_of_threaded_fasteners_due_to_dynamic_shear_loads Maybe you could look much more closely at the international standards around socket design and use. These things are so ubiquitous a part of all our lives it’s worthwhile understanding the science behind the safety standards around their design. For a more USA (UL, NEMA, NEC) focus ( I am sure there are other more detailed U.K., IEEE standards for your case). You have opened up a can of worms but it’s an important one to have opened. iaeimagazine.org/magazine/features/a-journey-back-to-basics-with-receptacles/
I always use a seperate lead from the backbox to the accessory. It would also be nice if the accessory terminals were gates like on consumer unit MCBs/RCBOs, would make a more reliable connection and less likely for loose connections.
Techincally, if the screws are in direct contact with the metal body behind the wall, then YES, it should be earthed as if that metal casing becomes LIVE under fault, those screws on the front panel will also be live. Therefore exposing a live 230v connection externally.
I don't really get why the method isn't: Take the CPC from the ring (assuming ring due to 2 cables) to the earth terminal on the box, then a wire from the terminal to the socket/switch. This way the back box is earthed even if the socket/switch is disconnected and wires capped off. Or in the case of a spur (naughty but it is everywhere) the downstream cable is still bonded. Earthing conductors are massively oversized these days where the facility is protected by and RCD, but most of the UK electrical stuff is oversized as it is the better way to be, but the requirements for the quality of bonding are much less than they need be - still where safety is the game this is the correct approach.
I dont think torque settings could be introduced until wire manufacturers can be exact and precise with the copper density... I would imagine it varies very slightly which would render torque setting useless. I think the future might be all push fit or clip fit connections. Beautifully explained as always John... thank you. Always enjoy your vids. P.s. Hands up all you Ham Fisted sparks and DIYers that have tightened them screws so hard that you crushed the copper through... surely I'm not alone. 😄 🙂👍
Australia here - we don't use back boxes. Not unless it's a concrete wall. Then a bonding conductor must be made-off as our outlets are double insulated.
Another crackin upload...got me thinking about how interesting it would be to see a wee showcase seeing how quick and efficient allso the different different ways other sparkies could make off and screw up a double skt..... working on new builds doing it 40 times a day it becomes effortless but its interesting to how others do it do you strip multiple cores at once with some nice New bahco snips or old school pliers !!!?
The most practical, down to earth and very specific electrical videos on TH-cam.
And like you has a brilliant, pithy sense of humour!
I am convinced most plasterers feel it is their duty to fill those holes with splodge.
Sure that's a module on their training course
Like painters fill door hinges.
Whenever my plasterer friend does any plastering in my house I always get him to overskim the edges of the box with the skim coat and then when it's dried I carefully cut it back with a stanley knife right in line with the edge of the box and it doesn't take much effort to just put a short faceplate screw into the lugs on the box to stop them filling up with skim coat then just give it a suck out with a plastic vacuum cleaner pipe with the circuit breaker switched off
At least yours bother to leave a cut out.
I was taught as an apprentice to be polite and ask them try to not to If they overdo deliberately after that, discretely leave tiny gravel pieces in their bags of plaster. Tut tut tut.
As an amateur I am extraordinarily careful to ensure safety and have always run an earth wire between socket and back box. With your explanation I now understand better why it’s not a waste of time. I really appreciate your videos so much so that I watch some of your other videos just to learn, even if it’s not necessarily relevant to the job I’m doing (I’ve exchanged plastic light switches and power sockets with more attractive metal ones and am currently adding to the existing metal sockets in my shed). Huge thanks for giving me the confidence to do it safely. Subscribed!
Tip: position the earth terminal on the metal back box so that it's at the bottom, much easier to connect to
I always do this even though I dont bother fitting an earth to the back of sockets
@@antrobuselectrical554 depends whether the box is below or at your height! If box is situated high (I know, that's unusual!) then it might be appropriate to have the earth terminal above so that one can get a better look at it and connect to it.
Correct in the main however I had a situation where I had to use one of the biggest sized knockouts this was because I had a a few cables that had to fit through as it turned out I had to put the box with the CPC Terminal upside
IT'S rare but can happen!
Best wishes Warren
I guess when you mentioned about the socket being removed for decorating and the power not being off, thus rendering the front panel screws not earthed, is a strong argument for why you should earth the backbox
18:50 With my luck it's a ring with a spur so there are three sets of wires, all far too short, no slack, terminals too small to take all three wires, and a horrible battle.
You forgot to mention, it's also a single socket just to increase the "pain in the arse" factor
And set back under a kitchen cupboard for maximum contortions.
"Let's not give the manufacturers too many ideas" 😂
EXCELLENT video John, thanks. There was way more information here than I needed but I ended up watching it all because it was so well presented and full of useful tips. I also got a Douglas Adams vibe at times because you sounded a bit like Simon Jones who played Arthur Dent in BBC's Hitchhikers Guide, and you said things like "...and the plaster has been in and cleaned it up for you, just like they don't do in real life."
The dreaded incessant 'earthing back boxes' discussion. For 30 seconds work and 6 inches of earth, just do it. The most likely person to get an electric shock from the box is anyone working on it and if the fixed lug is being relied upon, the earth is disconnected when the socket is removed.
Fixed lug - is no more rated as an electrical conductor as the loose lug !
Having installed a cooker at a friend's when he moved to a flat - and found the earth used to be via conduit, I'm not going to use anything but copper (or brass) conductors for earthing.
Hear hear to all the positive comments about this video. Great explanations, just like the best teacher in my school days. I was brought here because of an earth terminal on a back box, and wondering why, got all the answers! Peace be unto you.
Just doing my 2365 qualification, then onto the full NVQ, JIB Gold Card etc. Crossing my fingers that I can find someone as thorough and knowledgable to work for! :)
I always do a lead to the bb as my own personal preference, as I am re-assured the bb is always earthed even when the socket (at some point in its life) is hanging off the wall in peoples houses when they re-decorate / re-plaster / tiling etc.
I also run the CPC loop to the backbox with a link to the socket for the same reason
Or as can happen the m3.5 mounting tabs detach.
Do you install fly leads to all metallic consumer unit covers in case someone takes the cover off while the board is live? Or what about metal conduit box lids? Both examples, in most cases relying on a screw as an Earth. Same as a socket back box. So what’s the difference? The likely hood of it being open while live I suppose?
We have to draw the line somewhere.....the regs take into account finished installations when it comes to things like this. There is no requirement to consider part finished installations. I’ve never ready anything in the regs to say ‘must make provision for earthing for when the user exposes live parts during decorating’! Lol!
A socket hanging off the wall isn’t a finished install! And therefore should not be live! If it isn’t live......why the need for earthing the back box with a fly lead?
Let’s not talk about ‘in the real world’ either.....it’s in the real world that unqualified Wolly’s take sockets off to decorate, leave them hanging there for days and then just screw back without checking the terminal tightness! Possibly leading to fires!
Tip for them.....leave the sockets in place, where the back box is earthed, and the connections are sound. Or employ an electrician to take them off safety so you can do your work. 3rd option.....fool around with it yourself! Just don’t expect me to make allowances for such stupidity while I am initially installing it! Lol!
Anyway.....it’s been a long day! 😂
@Mr Brightside my thoughts exactly ...Whilst some might not live in the ' real world' the rest of us sparkies do ...no body calls a sparkie to wall paper ...although I've been called to sort out tripping MCB's in the aftermath ..several times because original installer didn't use a grommet and the Home owner pulling on the cables shorted to the earthed BB...so hmmm I think I 'll keep adding a cpc strap to the BB ;)
I cant help but imagine someone tucking some wall paper under the loose socket and touching a live BB ..I know we shouldn't and dont have to take that into account at the design or install stage ..but Personally I think we should try.
I'd bet even K C adds the BB cpc if he's installing in a loved ones home.
plus if you get into industrial electrical work then the vast majority of removable conductive covers are supplied earthed with a seperate conductor ..not just relying on the 'screw'. not the round conduit covers though ....dont give them idea's....and i'm not having the seperate cpc argument again.
I like to afford domestic customers at least the same protection where possible as the industrial ones ...preferably more ...even if it costs me a few meters of cpc per year.
@@Spark101. The brass BB terminal is included in manufacture, one would assume for a good reason - like earthing the zinc-plated BB and giving protection to the exposed fixing screws. Of which, as we see in John's demonstration, always come with one fixed and one loose female threaded lug. The loose lug would, by definition be a poor electrical connection, but often, even the fixed lug, can have issues, like zinc flashing causing a poor threaded connection, I've even come across fixed lugs being loose themselves, or poorly threaded. So as the maxim for anything potentially dangerous is - safety first, the BB lug, if fitted, should *always* be hooked up to the CPC.
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// We have to draw the line somewhere... // Presumably that means cutting cost and time at the risk of safety. I would also argue, laziness...
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Yes, there are plenty of *uneducated* people doing electrical work. However, the matter of qualifcation is overused, especially by electricians themselves, who with the odd exception - like John here - tend to be overly secretive about divulging their 'hard-earned' arcane electrical installation knowledgte to those - 'not in the club'. In reality, electrical installation is fairly elementary, providing one adheres to correct conductor size, voltage drops, to the circuits power requirements and understands the practical aspects (tool and equipment usage) thoroughly. It aint rocket science. Anyone who has trained in electronics can easily cope with domestic mains circuit installations. I wire sockets exactly like John here... *You'd* be hard pressed to know difference.
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As for decorators, most pro decorators I know (and those not so pro, who I've advised....) don't remove the appliance socketts from the wall, but merely loosen the fixing screws enough to create a gap around the socket to paint around. This way, the rear and potentially dangerous part of the socket remains relatively guarded, with the CPC intact... Especially if the BB tail is included. And no screws get lost in the process. This can be done without necessarilly powering down that circuit, though wherever possible, I always advocate doing so as an extra precaution, depending on the installation and other domestic factors like - roaming kids, with screwdrivers...
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Though I'm trained in Marine Radio and Radar Engineering, I do not have full electrical qualifications, (I do have PAT and 'mains compliance' installation, certification) but I can still perform a full professional installation, from initial electrical schedule design to final fix. I am self-educated and experienced and always refer to the latest edition of IEC/IET regs and other relevant documentation. As such, I've been trusted to undertake electrical installations, which have subsequently been examined by a 'qualified electrician' with zero faults or criticism. I even undertook (one of my first jobs...) the entire wiring schedule and installation of an 'Arts Centre' - a 17th century *public building* - that was upgraded to three phase and expanded to include a 60 seater cinema and extra gallaries. This installation also included a residence and restaurant. So that installation was pretty comprehensive. My schedule schematic of each of the four storeys of this ancient listed building was subsequently passed by the regional electrical provider and local planning body and was approved with no alterations or recommendations, other than the removal of certain parts of the orignal installation. I was 23 years old (15th/16th IEC regs). I didn't do the final testing, or hook-up, which was undertaken by council electrical contractors. The installation passed and, as far I know, is still in business.
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You are a qualified wally, who choses to forgoe safety by not bothering to wire in a BB CPC tail, all for the sake of saving a few minutes or pennies... Who of the two of us, is actually the safer electrician?
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Yes... I suggest you had better go and have a beer...
Selecting and Erecting sounds like a handbook for Hen nights.
A socket with 2 cpc connections, I would connect one to each side of the ring as a disconnection in one will still have the other available. This is required for high cpc leakage current equipment using sockets ( 3 to 10mA, OSG sect. 7.5.3)
Niceic even say you should
Well that's how you tell a good electrician because of the amount of good practice that is left out of the regs and the electrician that thinks if it's not in the regs it's not needed, they are even worse when applied to industrial wiring.
I've never understood the concept of "well its not needed so I won't do it". If there is an earth terminal, or just an empty loop terminal on a plastic appliance, and you have an earthing conductor, why not install it anyway? Its 10 seconds extra work, but it keeps them from flapping about, and has a back up in case the main protection (usually "unable to be touched") fails. I have yet to hear a convincing argument of why you'd skip that part because the regs allow it, other than saving time. So, time/productivity is more important than safety, and you'll cut whatever corners you can? Thats a great way of making a mistake when conditions change, or when regs change, and you still rely on muscle memory, and relies on a lot of assumptions which might not always hold true.
A lot of people get confused by regulations, which state only the minimum requirement, and think they instead state best practice and assume they then don't need to do anything extra. And this applies to most standards and regulations, not just BS7671.
I think it comes down to whether you feel something is necessary and if you have the relevant experience and common sense then you can make this judgement.
“Good practice” - generally used as an excuse by electricians not to keep up to date.
Hi J.W., big fan of your educational series. Rumour has it that the tradition of looping CPC though the backbox started with an awkward wording of a 14th Edition, regulation D5, where an amendment added requirement of " the earthing terminal of each socket-outlet shall be connected by a conductor complying with Reg. D.28(iii) and D.29 to an earthing terminal incorporated in the associated box or other enclosure". The reg as a whole of course related only to such situations where the earth continuity was achieved by sheath, conduit, trunking, ducting or armour, but the amendment quote was reprinted out of context so many times that sparkies just started wiring loops to all sockets with metal backboxes on the basis that as per @sseedell's comment "for 30 seconds of work and 6 inches of earth, just do it". Todays regs specifically exclude front screws as "reduced dimensions exposed-conductive-parts" from any fault protection (410.3.9 I think), so it further muddles necessity for connection to the lug in a box deep in a wall, but of course nothing wrong with it still being performed as a where-in-doubt/just-in-case/"good practice" I guess?
It's 410.3.9 (iii) and I've been looking for that regulation number for yonks. It's a quirky one and counter-intuitive but I see it as a good example of common sense being applied in the regulations.
I love this guy. this is something that was on my mind 2 days ago and now Mr Ward has made a video.
Great vid as always. Newbie here, I've been taught to always earth the back box. Additional reasons include accidental penetration by drill bit etc and also could help with computer/IT earth leakage.
JW do you agree with these things?
Not a bad video, John.
I remember being an apprentice electrician and my boss at the time used to bash on about "terminal fill".
Back in the day, socket-outlets in New Zealand had enough room for 2 x 2.5mm² wires in all of the terminals, so if you twisted the wires together, they would fit.
Light switches had a maximum tunnel size of 2 x 1.0mm² solid core wire.
Over the years, the Regs (and better thinking) changed with 1.5mm² being used for lighting circuits, manufacturers had to change the terminal sizes, as you couldn't get two wires into a switch feed terminal.
I use to to the exactly the same.. double up if possible.. and some of my colleague use to laugh on me.. but I do not care.. it is my choice and responsibility. Thanks for this video.
good to know i'm not the only one still using my 17th guidance notes! Except for my blue GN3 inspection and testing. GN1 is the most underated! An essential read every so often
I really like your videos where you dip into the regs a bit and discuss where things are and aren't in the regs. Re the subject matter itself, I don't see where the controversy comes from: presumably it takes an additional 60 seconds and penny worth of conductor to make the thing additionally safer for, as you say, the decorator who may or may not have a clue about why it's a bad idea to remove a faceplate without taking the power out first.
These screw terminals are quite an effort to properly connect, i wonder why the UK doesnt have these nice push-in terminals most of europe uses for decades already?
Realiability doesnt seem to be much of a problem, at least around here the quick-connect sockets are perfectly fine and dont suffer from inappropriate screw torque which caused the older ones to overheat sometimes.
Oh no, that would be far too easy. Plus it would spoil the fun of going round tightening all the loose terminals during an EICR
Flauschlab well I can’t say about domestic but the industrial ones do fail quite often, just my experience.
@@dogwalker666 might be due to the push-in terminals for industy are made out of chinesium.
@@nightshadelenar that would not supprise me klippon and entrelec are not as good as they used to be.
And ruin the fun of hunting lose neutrals? Pft
I'm afraid I'm old enough to remember when lighting circuits didn't have earths at all.
That’s because it’s not a big deal
@@w415hyz Unless you fit metal switchplates on a wooden back box!
Any mileage in putting a crimp end thing on multiple wires going to a connection ?
I love these videos - 100% authoritative and practical.
Amazing video, very clear with the right level of detail
Excellent point re. filling the connectors, I was taught to twist the two conductors together a opposed to folding. The regs. were amended here in Ireland in Sept.17 regarding the earth conductor in T&E, all new installations must use an insulated earth conductor that is the same CSA as the phase & neutral conductors. Use of twin and earth cable with a bare conductor for same is prohibited.
Same for me on the twisting together. I was told off about doing it a few years ago (I think on the basis that it could make future fault finding difficult?) so not done it since. Twisting seemed a good idea to me.
Twisting solid core conductors is not a good idea in my opinion as they break off so easily.
Twisting is better in my opinion as well it would provide a more uniform filling technique for the recessed holes, no guarantee of course it works every time. It’s still worth checking.
Math Man - not keen on solid core wires being twisted together. If the screw terminal is tightened too much, it will bite into one of the copper solid core wires more than the other. Then should you need to untwist it at a latter time/date, there is a high chance of a fatigue fracture and the solid core breaking. If it happens while you are working on it, it’s a pain to strip more insulation off. If the wire is now too short, it a right pain. But worse, if the wire breaks later then when you test the circuit, you waste time chasing the open circuit fault.
Interesting - in NZ, we'd twist the phase conductors together and then put that in the terminal. Usually for socket outlets its 2.5mm^2, and so you twist the strands together and fold over for a single wire, but with 2 or more you generally twist them all together at once, cut to length, then insert without folding.
Twisting cables together makes it a pain in the arse for testing, you may have to un-twist them which usually ends up weakening the copper too much, leading to breaks in the conductor or high resistance connections if its not spotted. I cant remember the specific regulation at the moment but our regs say that each conductor should be connected separately
I only twist if I’m trying to get 3 wires in a difficult spot, otherwise I don’t bother
I was taught that as well but in the UK these days it's sometimes necessary to seperate the wiring out behind a socket for electrical inspections so it's not done at the moment. No doubt in another 10 years time they'll make it mandatory to twist the wires together, they are like that in the UK.
I’m not keen on solid core wires being twisted together. If the screw terminal is tightened too much, it will bite into one of the copper solid core wires more than the other. Then should you need to untwist it at a latter time/date, there is a high chance of a fatigue fracture and the solid core breaking. If it happens while you are working on it, it’s a pain to strip more insulation off. If the wire is now too short, it’s a right pain in the arse. But worse, if the wire breaks later and it’s not noticed, then when you test the circuit, you waste time chasing the resulting open circuit fault.
For terminating stranded wires (flex leads as UK'ers call them), crimp-on ferrules should seriously be considered. These are common in Germany and other EU countries. They're not used much in North America either, but I think they're excellent for set-screw terminations, where the strands of the wire would otherwise fray and not make 100% solid contact in the terminating fastener. I am seriously surprised crimp-ferrule sleeves are not ubiquitous worldwide.
They are used in the U.K. quite extensively, it’s required for UKCA when shipping a product with stranded wire inside for example. (some exceptions such as ultrasonically bonding the wire is deemed ok too)
@@akbarramzan7436 That's good. Here in the USA, we use crimp terminals for particular types of terminations like forks, rings, spades, etc. But what you NEVER see here are the ferrule type for some strange reason.
Absolutely love your videos; as much for the dry humour as for the excellent advice and tutorials 😃
It's dry humour as water and electricity doesn't mix.
I never did see the point of an earth terminal in a plastic back box. You mentioned something at the end avout light switches. Do you have a viseo on this?
Plastic light switches do not have an earth terminal. When mounted to a plastic box, the terminal in the box is used as a place to secure the protective conductor.
I like the continental idea of round holes behind sockets and light switches instead of square. So much more sensible as they just use a drill to make the hole.
You'd stop liking it so much if you had to produce the tooling & specify the materials to actually make round back boxes in any material other than plastic. Rectangular boxes are much cheaper to produce.
Plus the specification dates back to when electricians used a bolster (chisel) & lump hammer to recess them, & those aren't as good at producing neat round holes as they are at rectangular.
@@beardyface8492
Drilling a round hole with modern drills is *easy.*
@@johnburns4017 Indeed it is, but then so is sinking rectangular ones with the correct tool, & changing would require all new design outlets & switches too. Then if adopted you'd never know in advance which of two standards you'd be working on, & have to keep tools & stock of both types.
Sounds like a worse situation than the current one if you ask me.
@@beardyface8492 I think you are just being argumentative for the sake of it. It is plainly vastly more work to create a square hole in just about any material you can name.
The amount of time, dust, noise and aggro involved in installing a square box in anything other than a hollow plasterboard wall completely and utterly dwarfs any consideration over the cost of producing a round box, even in metal. Have you noticed that you can buy a tin of beans in the shop for approximately 20 pence? Not only does this low price wangle you almost a pound of delectable haricot beans in a mouthwatering tomato sauce but included almost as an aside is an ingeniously manufactured cylindrical steel container.
@@nobodydoesithalfasgoodasyou The point that the standard was created back when recesses were sunk using unpowered hand tools (hammer & bolster) remains, as does the second point if you introduce a new standard.. you suddenly then never know which you're dealing with & need two sets of tools..
Plus there's the awkwardness of dual-gang sockets & switches, which you simply couldn't design with a round back-box.
Question for you, I am fitting metal face plates in my kitchen but also brushed steel surrounds or finger plates that go behind the faceplate. My question is do I need to earth them aswell as they are exposed to the outside world. They come pre cut with the two screw holes but also one in the corner, I presume for an earth.
I may have missed it but what is the recommendation for situations where the cpc has no connection point with on the accessory or in the back box I.e. Plastic boxes or lighting connectors. I normally terminate the CPC in a connector block such as a wago connector.
What do you recommend John ?
I sleeve it long and bend it over so nothings exposed and the sleeve holds on, call me tight but I wouldn't waste a wago on that!
Just cover it with insulation ?
Thanks JW, really instructive - learnt a lot.
@6:09 I wonder what the basis is for CE marking the backbox? And is that a real CE mark or the dreaded 'China Export' mark?!
You could use Ireland's I.S. 201-4 cable that has insulated (and fatter) CPC
I.S. 201-4 cable is not to a British Standard though. Being in Ireland, and within a mile of the border, I use plenty of both types of T&E. But I never bring either type of T&E across the border from where it is intended to be installed. Incidentally, in the south of Ireland, it is mandatory to connect a flylead to the backbox and you are prohibited from relying on the connection through the screws to the lugs.
Thanks for this and your other videos. Very interesting & helpful for me as a DIYer
If they specified torque settings for accessory terminal screws I really hope it would accelerate the development of accessories with spring clamp terminals!
I don't know how they're better. With so little contact surface, I don't know how they manage to handle the current.
@@millomweb I don't know exactly how they work but terminating each wire separately gives a much more reliable connection
JW did a video on Wago connectors.. Take a look, shows you how they works and are constructed.
@@dg2908 From that, you're suggesting a socket should have 9 terminals on the back of it instead of 3 !
@@millomweb well ideally 10 - 1 for the fly lead, but yes. If it was designed from scratch I'm sure it would be possible, and new socket boxes aren't typically less than 35mm anyway
Is it necessary for the “regs” to spell everything out in great detail. Surely, the metal socket fixing screws, which can be touched, render a metal back box exposed. No?
No. The regs do indeed spell this out:
410.3.9 The provision for fault protection may be omitted for the following equipment:
(iii) exposed-conductive-parts which, owing to their reduced dimensions (approximate maximum of 50 mm x 50 mm) or their disposition cannot be gripped or come into significant contact with a part of the human body and provided that connection with a protective conductor could only be made with difficulty or would be unreliable.
NOTE: This exemption applies, for example, to bolts, rivets, nameplates, cable clips, SCREWS and other fixings.
@@andrewcadby - Again, an industry 'advisory' - catering for cost/time effective solutions. Though I agreed with your explanation, as a matter of extra safety, I always employ a BB CPC tail on metal BB's fixed in walls.
@@Deebz270 that's fair enough, although personally I don't see the point, with the obvious exception of plastic switches etc.
The odds of a backbox somehow becoming live without tripping the breaker, let alone the RCD, seem negligible IMO.
Also, may I bring to your attention metal consumer unit lids. I have yet to come across one that didn't rely on its fixing screws to earth it.
What if the metal back boxdoes not have an earthing terminal? Is it ok to use one of the screws that fixes the box to the wall (that is in contact with the metal of the box), or is it better to replace the backbox entirely?
Fixing screw could be used, or you can buy brass terminals separately which fit into an M4 threaded hole. Drill a 3.3mm hole and tread to 4mm if there isn't a suitable hole already.
I find your videos incredibly helpful, informative and hilarious. You may have the driest sense of humour on the internet and I would love to have a beer with you 😂
I have seen a metal backbox secured via wood - a good insulator. A light switches securing screws made contact with a bare Line wire, making the screw _live._ It never went to earth so nothing tripped. You only knew when the screw was live when you touched the head of the screw. If the screw hole surrounds went to earth like sockets do, it would not have occurred.
What wire did you use to earth the BB that is separate?
Any thoughts on twisting the 2 Line/Neutral conductors together? Better connection in the socket? Continuity of the ring if the terminal happens to come loose? I have seriously considered twisting them and then soldering them so that the ring remains complete even if you have a loose socket terminal. BTW, I am not a domestic/commercial spark, my background is an Industrial spark, working on plant & machinery.
Not recommended, twisting work hardens the copper making it more likely to break, and twisting makes future testing or additions far more difficult.
Solder isn't a good idea either, as solder is soft and will flow under the pressure of a screw, causing a loose connection.
I have a question, old flat all concrete , no earth wires they are all connected to the metal back back box, one of the back boxes has no earthing terminal and I can not take out the back box due to other wires coming in and out,
So according to the guide notes this is acceptable but the immersion heater and power shower have no earth feels very unsafe, should I solder the earth in to the back box ?
Earth terminals are available separately: www.tradesparky.com/cable-and-management/conduit/steel-accessories/deta-dt40604-earth-terminal-m4-brass
drill a 3.3mm hole in the backbox, thread with a M4 tap and screw the terminal in.
Great video for those learning the trade. Thank you
Wouldn’t fly leads on metal boxes alter earthing? Reasoning is, if the box is cemented I go the wall, it provides an earth path through the wall.
A very very poor path, walls don't conduct worth a damn even when damp, & that's not mentioning walls tend to be sat on an insulating PVC damp proof course even if they did. With a sufficiently sensitive instrument you *might* be able to measure the difference, it'll be swamped by the other variables & other parallel paths in a typical installation though, especially when you consider the boxes get connected to the CPC via the accessory mounting screws as well. Connected via a plated brass screw, or connected via the screw with a parallel conductor to the same very poor path, even with many instances of that one slightly corroded terminal somewhere is likely to make a bigger difference.
Love the videos John keep up the good work 😁👍
What about using Wago clip connectors for these things in the back boxes? Could be useful especially in 2-4 socket boxes, that are formed from separate units. In many places in Europe, we usually use 60mm (internal dia) circular plastic boxes for junctions, sockets and switches, not rectangular metal ones like in UK. The big advantage of a very popular circular ones is that they can be installed quite easily in a number of different materials by cutting a hole with a hole cutter of a proper size and a power drill, thus speeding things up considerably.
I came across one of those double sockets with no earthed screw holes earlier this year.Made by CED.
I still always use a seperate lead from the backbox to the accessory,had this drummed into me 40 years ago when I trained as a spark.
QQ: what if this is installed in a kitchen with stainless steel Splashbacks?? Does that change anything?
When wired conduit always pulled cpc ( belt and braces?).
What to consider? Was the conduit _designed_ to be the CPC? If not then drawing a separate CPC isn't belt and braces but a necessity. If working on old installation you probably don't know and have no means of find out if it was a design element anyway. It may be indicated by the general absence of separate CPCs but that would be a presumption that it was okay, not proof.
If it _is_ in the design, and you trust that it's properly installed doing it to spec doesn't require drawing the extra conductor and testing will show if it's acceptable.
I'm quirky in that I _like_ using the conduit and usually specify it where realistic, but aware that there are reasons not to rely on it and heck, 1.5mm² green/yellow sheathed single insulated is about 15p/metre so it's got to be a very large installation before cost becomes a significant factor.
I had a case (work related) where the sparky extended wiring in new conduit without installing a CPC only to find that 'down the chain' there was some plastic conduit in place - fortunately he tested before energising.
@@calmeilles usually the person who runs the conduit wires it,in the past I have had to run cpc in even though the conduit was perfectly sound ,the designers choice not mine,for that customer I always used a cpc.
@@calmeilles I don't like using the conduit as the sole cpc..I'm and old grumpy git of many years and with too many grey hairs (the ones that are left)...experience shows me ..conduit gets damaged ...bumped with pallet trucks/forklifts/other crap..buildings move over time ..thermal expansion and contraction for 1000's of night/day cycles not to mention corrosion...joints come loose..even if designed and installed correctly...seen it in many many many factories ..99.9% of industrial customers will pay for the extra cpc if you sell it as extra 'elf and safety' and explain why....I've always thought robustness of the safety devices obviously including the CPC should be at the top of the design path.
Any way stay safe ..at least I've kept working through all this covid mess.
can you use 1.5mm for all type of cable or dose the earth fly lead have to mach the cable you are using
The size has to be large enough so that it's not damaged in the event of a fault. Using the same size as the cable is OK - and in most situations that will be 1.5mm² anyway, as larger cables are rarely used for socket outlets.
Smaller sizes could be used, but calculation would be required to confirm the size is adequate.
As with all John's videos, very clear and well presented and explained. Simple question, what brand of wire strippers are you using? Almost all of those available in in the UK seem to be designed/marked as for US/Canadian wire sizes. Few if any actually show the UK 6.0, 4.0, 2.5. 1.5, 1.0mm etc as the specific/clear "die"/cutter hole.
Ideal T-Stripper, part number 45-120-341
@@jwflame Thank you. Hadn't seen these on the big river UK site - until I posted the details you sent. I shall invest in a pair even though I have just bought another cheaper brand which seem OK (though only time will tell how good they are). These being US marketed means they use US wire sizes, but no grief to adapt to/determine the correct UK equivalents (especially for UK T&E and single core mains cable).
I like to use the fly lead to the back box to hold the accesory while I'm terminating the other connecions particularly when working at height so i don't drop it
thanks for your many great videos. good way to learn the British regulations.
I wondered: are ferrules on stranded wires not required in the UK?
I wonder what your opinion is of the current trend on some TH-cam videos to use ferrules on stranded conductors? I suppose they might reduce the chance of strands not making their way into the terminal, and maybe a bit easier to connect in awkward locations.
If installing the bb put the earth lug at the bottom, it's far easier to see when kneeling!
A good idea, and in many cases essential for fine stranded wires. Of limited value for most fixed wiring, as it's normally only 7 strands and they are of moderate size so unlikely to be missed in most terminals.
I would always use a ferrule if putting a stranded wire into the same terminal as a solid wire. Otherwise the stranded wire can sometimes be incompletely clamped or pull out entirely.
Highlight of lockdown another JW video😊
10:30secs bend radius breached?
I was always told by an old electrician to earth the backboxes. His reason being people unscrew these things when decorating or wallpapering, if there is no rubber grommet and the supply cables coming through the steel back box had chaffed, then it would become live.
I always have earthed back boxes, just makes sense to me. I was taught to do it that way from college. It's a 2 minute job and safer. 😎👍 Lazy people always argue the fact.
Thanks. Doubling up should solve my problem of socket screws not getting a firm grip on wires. No sparkies I've used do that and none of the comprehensive DiY books I've had show it. I've been going round the sockets finding that the professionals left them loose or earth sleeve inside the gripping screw giving lousy to no earth connection. If cables are a bit short, I can feed through a new piece of 2CE because I used conduit between boxes - sparkies called it "electrician's dream" before they did the sloppy wiring
Three wires into that design of screw terminal makes me shudder. That would be a massive fail in the avionics industry and I'm not overly happy with it here. Two wires max. Yeah, doubling the wire over mitigates most of the problem, but that stranded wire exacerbates the problem.
There are designs of screw terminal where I'm happy (ish) with three wires - the type in circular junction boxes. But not with that style of screw terminal. I'd go with looping one of the PECs into the backbox terminal.
Of course, when you have a spur on a ring main, there are more wires than I'm happy with.
Firstly I am no longer an Electrician, having moved on to mains! When I started, things were ... different, the book was small and yellow for a start!
Having said that .... Would anyone rely on a steel conduit with many screwed up sections (corrosion risk) as an earth? Would they not run an earth in. There would be an added bonus that your wires are copper with a lower resistance than steel!
My second point is doubling over conductor ends. If you look closely at a screw connection with two single cables going into it you will see the screw end (which is slightly rounded) would force the conductors to eather side of the connection giving increased contact with the added bonus that as the screw is tightened it would deform the round copper conductor making the joint not only tighter but a better electrical contact! I think if you are putting a single conductor into a terminal you should double over the end if the connection will take it!
There's some interesting calculations you can do there, the thing is, for a given cross section, yes copper is a better conductor than steel, but once you factor in the comparatively massive cross sectional area of steel tube, you suddenly find that steel conduit has a considerably lower resistance than any earth lead you're likely to run inside it, I'm sure I even saw a video where JW did the calculations. Why add the expense of more wires & the labour of pulling them when they're not required? It'll take a hell of a lot of corrosion to raise the resistance of a big fat pipe to that of a skinny wire.
Some people still do pull a CPC through, the main thing it protects against is the situation where a conduit run becomes loose or detached where it enters a box, the fastenings seem to somehow undo themselves over time, mostly from people not doing them up properly in the first place.
Back in the day I seem to remember that using steel as an earth required you to have a resistance Half that of copper. The other point I would make is that we have Many "looped services" where the mains comes in to one house and is then wired in conduit to the next house under the floor. We get them regularly as a "Bad Earth" when some luckless spark tries to do a Ze test on the looped property. Trust me, they do corrode!
As I said already I am no longer a spark but are you saying you can use the armor of a SWA cable as an earth now ..... it is steel and I suspect a larger csa than the conductors!
Are those cup washers on the back box fixing screws, if so a appreciative nob your way John for attention to detail
I hope you meant nod
@@jocramkrispy305 obviously subconsciously john's attention to detail left more of an impression than originally thought, lol
Thank you for yet another interesting and informative TH-cam postings. I enjoyed it very much.
I guess that in the majority of cases we are all doubling over the conductors to make them fit into the terminals provided. It really does make you wonder if a much improved solution could be provided by socket and switch manufacturers. I did consider whether not the end of the screw should actually operate some kind of simple clamp affair that would secure the conductors as presented (not doubled up), but the immediate concern might be that different cable conductor diameters (or solid versus stranded conductors) might not all be simultaneously served (i.e. some conductors might not be secure).
I then wondered whether a different clamping arrangement could be devised - perhaps not unlike a miniature jubilee clamp that wraps around all conductors and squeezes them together. I’m not sure how that would mechanically present itself to a tightening screw, but given how many million of these fittings are being installed, you’d think it wasn’t beyond the wit of humankind to make it more simple and secure by design, rather than leaving the challenge to the installer who may or may not spot a problem.
Come on manufacturers, the gauntlet has been thrown down, why not see what you can do? We can send things into space and retrieve information from them quite readily, yet we are still messing about doubling up conductors to get around the terminal shortcomings. Why is it so difficult?
Best explanation ever of the correct way to safely terminate a socket or switch. Mind you, when the screw is tightened down on two or more bent over wires, the screw itself can become exposed - sort of defeating the importance to avoid exposed conductors - nothing is ever easy :(
Thanks for sharing. Too many people wanting to do the minimum 👍
have you got a link to the screw fixings you’ve used for the metal back box looks neat?
www.screwfix.com/p/screw-cups-8ga-carbon-steel-200-pack/78689
is it just countersunk screw you’ve used then or a pan-head?
is it just countersunk screw you’ve used then or a pan-head?
Standard countersuck woodscrew.
No bootlace ferrules as per your ferrules video??
Not necessary for solid core wires.
For the stranded wire.
@@PebblesChanThese ones are good for 1.5mm 6491X cable:
cpc.farnell.com/pro-power/sten-1508/ferrules-uninsulated-bootlace/dp/CN11651
@@jwflame You could crimp the fly lead and one of the CPCs into a double ferrule (2 x 1.5mm2).
That way you would save on the waste generated by first method you showed whilst ensuring a connection to earth is maintained if the accessory is ever removed.
My preference is to put the ferruled pair into the accessory and take the fly lead to the box, but it could be done the other way around.
Oh, and why not put a ferrule onto the other end of that stranded single while you're at it? I would😁👍
Of course, it goes without saying (so much so that I feel the need to say it) that any method needs to conform when tested.👍
This video is a cure for insomnia
what snips are these?
cpc.farnell.com/ideal/45-120-341/metric-wire-stripper-0-75-6-0/dp/TL00610
@@jwflame thanks John!
Thanks john, its good to see the legislation on why we do these things, wouldnt have been able to find that info on my own, cheers.
6:15 Ooh, I like your fancy concave screw washer things... (Sorry, I don't know their correct name) I use pan-head screws to negate the problem of countersunk "wood" screws standing proud or punching through the back box but this looks neater and less proud. (Especially if the screw has been burred a tiny bit when screwing in. - Less chance of rough metal scratching a cable...) Do you mind if i steal this please?
If you earth the metal back box and the metal faced switch or socket is screwed into it, does that Earth the socket / switch without a direct earth connection to the switch or socket itself?
It would but that arrangement is not permitted. Covered later in the video.
It's regulation 543.2.7
www.flameport.com/electric/steel_conduit/using_conduit_as_cpc.cs4
Very good - thanks for sharing 👍
Learnt so much. Thank you.
Could somebody advise me, please? I have the same wiring set up in my single socket plug like the one at 25.45 in the video. That is to say 2 lives 2 neutral and 2 earths. Well there were 2 earths but one has snapped off at the base. is it ok to just use the one earth that is left and attach that to the earth on the socket?
Cheers
Both earth wires must be connected, otherwise sockets elsewhere on that circuit will not have an earth connection.
@@jwflame OK - thanks so much for the reply.
Thanks for the interesting & useful video. I'm intrigued by your yellow cable cutter, stripper, plier as it is tailored for the uk having 1, 1.5, 2.5, 4 & 6 mm2 stripping holes. The only similar ones I've seen are designed for non uk markets having holes sizes maybe like 0.6, 0.8, 1, 1.3, 1.6, 2, 2.6. Where do you obtain ones designed for uk cable sizes.
It's an Ideal 45-120-341, can be obtained here: cpc.farnell.com/ideal/45-120-341/metric-wire-stripper-0-75-6-0/dp/TL00610 and many other places.
@@jwflame Thanks
I am an TV outside broadcast engineer by trade. When I was training in the eighties we were taught not to fold wires especialy single core as if the screw tightened down on across the loop it might not fully crush the bend and could loosen over time.
Funny how things change over time.
I like that ! The less wire in the terminal the greater the compression and bite ! If 2 single core, there's a risk that only one is trapped under the screw - mechanical testing of each wire after fitting is always a good move. I liked the stacked folds shown in this video - gets everything clamped - just be sure to tighten the screw properly.
@@millomweb technical here: why dont all sockets have the terminals with the flat bit that actually contacts the wires not the screw, they contact across the whole gap
Great video, really informative
The way I look at it is that any exposed metal must be earthed (except in the case of double insulated systems); the screws are exposed in most cases, and even where they are not, generally no tools are required to remove the parts hiding the screws; therefore, the screws must be earthed. If the accessory has no earth strap, as in the light switch, then the box must be directly earthed; if the accessory does have an earth strap, it's sufficient to rely on that to ground the box that the screws fix into.
For the case of insulated plasterboard boxes and non-grounded accessories, it can be considered as double insulated and no ground is therefore required.
I remember back in the early 90s my NICEIC inspector queried as to why I used a 1.5mm earth wire to the back of the steel box. I thought he was accusing me of overkill but his point was it should really be a 4mm in the case of a 32A ring main circuit as a 1.5mm technically won't be able to handle the maximum direct fault current if the box became live. He was one of those sorts that thought the IEE should have run everything past him before they came up with any regulations. Yes he has a point but he can go boil his head, always done it that way, so does everyone else and now I see you also do it then it MUST be OK 👍😊
I run the T&E earth conductor to the box connection then an earth link to the socket.
This means less chance of the protective earth loop being disturbed by decorators.
At least that way round, if the socket earth is good, it's also proving the backbox earthing !
I can think of many things that we could do to cater for the ‘what if’s’
Truth is.....the regs already cater for a safety standard that is considered acceptable. And the regs say we don’t need them on socket back boxes most of the time! I haven’t put fly leads on socket back boxes for around 10 years now. Not gonna start either. Only time I would, if the sockets were not RCD protected, which is unlikely!
Nice video though John. I just don’t agree that the fly lead is needed. If some plonker takes the socket off while live.....he can’t complain if he gets a belt! Just like if I, someone who knows nothing about gas, deserves everything I get if I take my boiler apart while the gas is still on!
We can’t always work, having to take into account the very very stupid! And at our own cost, against the current standard!
I’ve never done it either (25 years) on a socket. You shouldn’t be taking a socket off if it’s live and you defiantly shouldn’t if your not a electrician.
I always put flylead to back box but found it a bit strange when earthing plastic box! Trouble is you can get pulled up for not doing it,bit of a nightmare if you've finished.
@@tommochelsea72 You shouldn't. But you _know_ at some point someone will. :)
@@tommochelsea72 People do it because there is no good alternative :(, houses in the UK normally have a whole floor (with the exception of the kitchen) on one circuit so keeping the power off while the wallpaper/paint dries is rather impractical :(
Brilliant demo. Thanks
Wire wrapping clockwise 2/3 of the screw terminal helps when you tighten clockwise it pulls the wrap to the remaining 1/3 gap around terminal and if you pull on the terminal it will ensure the loop on the Earth wire does not come away from under the screw. Screw based tightening using this kind of technique and torquing (yes NEC 2020 code in USA provides some guidance on torque settings for socket screws if no manufacturer guidance - I disagree with you respectively it does makes a difference though annoying, at the very least it creates an additional safety step and helps to concentrate the mind that it’s been done correctly) research has shown at least in the USA wire wrap around screw terminals to be the most effective in ensuring the best connection even better than the clamping and recess hole conductor terminations like in the U.K. sockets. However, the proviso is if the wire wrap method is done correctly only in those circumstances would it work the best and reduces fire risk. Here learning good technique and checking is critical.
John not convinced you can always guarantee the fold over method guarantees double the conductor available for the bottom of the screw to bite on. It could be that the loop you form the screw actually bites down on the inner side of the loop, so you assume that it’s secure but the bite down is covering a smaller inner surface area which could come loose overtime no torquing could also mean greater risk of loosening over time. That fact it’s in a recessed hole with no clear line of sight is a problem. Maybe a type of ferrule suitable for solid conductors ( is there a such a thing?) would help you to fill the recessed hole much more uniformly helping with the security of connection?
Maybe worthwhile mentioning some of the physics of this process in future videos, use of specific fastener methods and or thread locking?
Pre-loaded bolts (or nuts) rotate loose (or fasteners in them) as soon as relative motion between the male and female threads takes place. This motion cancels the friction grip and originates an off torque which is proportional to the thread pitch and to the preload. The off torque rotates the screw loose, if the friction under the nut or bolt head bearing surface is overcome, by this torque.
There are usually three common causes of the relative motion occurring in the threads:
1. Bending of parts which results in forces being induced at the friction surface. If slip occurs, the head and threads will slip which can lead to loosening.
2. Differential thermal effects caused as a result of either differences in temperature or differences in clamped materials.
3. Applied forces on the joint can lead to shifting of the joint surfaces leading to bolt loosening.
Take a look at www.vdi2230.de/engineering%20fundamentals.pdf
www.researchgate.net/publication/222178347_Experimental_study_of_loosening_of_threaded_fasteners_due_to_dynamic_shear_loads
Maybe you could look much more closely at the international standards around socket design and use. These things are so ubiquitous a part of all our lives it’s worthwhile understanding the science behind the safety standards around their design.
For a more USA (UL, NEMA, NEC) focus ( I am sure there are other more detailed U.K., IEEE standards for your case). You have opened up a can of worms but it’s an important one to have opened.
iaeimagazine.org/magazine/features/a-journey-back-to-basics-with-receptacles/
Oh the arguments I've had about this! I don't do it anymore though
I always use a seperate lead from the backbox to the accessory. It would also be nice if the accessory terminals were gates like on consumer unit MCBs/RCBOs, would make a more reliable connection and less likely for loose connections.
By gates, do you mean rising clamp terminals?
Techincally, if the screws are in direct contact with the metal body behind the wall, then YES, it should be earthed as if that metal casing becomes LIVE under fault, those screws on the front panel will also be live.
Therefore exposing a live 230v connection externally.
I don't really get why the method isn't: Take the CPC from the ring (assuming ring due to 2 cables) to the earth terminal on the box, then a wire from the terminal to the socket/switch. This way the back box is earthed even if the socket/switch is disconnected and wires capped off. Or in the case of a spur (naughty but it is everywhere) the downstream cable is still bonded. Earthing conductors are massively oversized these days where the facility is protected by and RCD, but most of the UK electrical stuff is oversized as it is the better way to be, but the requirements for the quality of bonding are much less than they need be - still where safety is the game this is the correct approach.
I dont think torque settings could be introduced until wire manufacturers can be exact and precise with the copper density... I would imagine it varies very slightly which would render torque setting useless. I think the future might be all push fit or clip fit connections.
Beautifully explained as always John... thank you. Always enjoy your vids.
P.s. Hands up all you Ham Fisted sparks and DIYers that have tightened them screws so hard that you crushed the copper through... surely I'm not alone. 😄
🙂👍
Australia here - we don't use back boxes. Not unless it's a concrete wall. Then a bonding conductor must be made-off as our outlets are double insulated.
was so useful. Thanks a lot
great video..pure info!
Thanks for the informative video :)
Another crackin upload...got me thinking about how interesting it would be to see a wee showcase seeing how quick and efficient allso the different different ways other sparkies could make off and screw up a double skt..... working on new builds doing it 40 times a day it becomes effortless but its interesting to how others do it do you strip multiple cores at once with some nice New bahco snips or old school pliers !!!?