Thank you John for your great tutorial video's... Although here in South Africa it is not common to find ring circuits, they do exist as a lot of electricians from the UK over the years installed them at some point... I have come across it in a house that I owned a couple of years ago... needless to say I changed it to a radial circuit as it did not make any sense to me at the time... only to learn after why it was done that way...I agree with you that it should not be common practice to do it in the first place...
By far one of the greatest teacher on RU-vid. Awesome..... Keep the good work John and you shall be remembered for your good work even after you're gone
Hi John your channel is very rewarding thank you, could i ask you a question please, i have been all over the internet to try to find out how to calculate volt drop in a ring cct, i have watched your vidios on max demand and vidios on voltage drop. when you calculate volt drop for a ring main is there a different proceedure because when i do the calculations for a 32a ring ground area 106m from osg 18mv/a/m 1.2 factor and devide by 1000 the answer exeeds 5% 11.5v could you explain how to calculate voly drop correctly in a ring main please when you get the time. thank you for a great channel you have helped so many including myself. thak you.
It's not stated how it was calculated for the OSG, and there are several methods. However the worst case would be the full 32A load furthest from the origin, but the 18mV/A/m must be divided by 4 as there are 2 parallel cables and both will be half the total length of the ring. That still gives over 5% for total 106m length, however it does state 'distributed load' so they have presumably used some other method with various loads at points around the ring rather than all at a single location.
@@kimobrien. Is it illegal? In the EU ring circuits are not illegal. They are used in the UK because we have done since WW2 and the installation is cheaper. They do have their advantages.
John Burns rings were were introduced with square pin plugs which didn’t get replaced widely until 1960 ish. i remember a tv advert explaining “ring mains” as they were called then. The idea as presented was that a ring would go all around each room and then a new socket could be introduced wherever you liked in the room very easily. ( at the time sockets were surface mounted at skirting board level). However, building regs did not require the ring mains to be laid out in a ring like that and cable runs were minimised to the sockets actually installed. So the value of the ring was lost. However, shuttered sockets introduced with square pins plugs were a great safety feature. As a baby, crawling about the floor, i put my little finger in an unswitched, unguarded two pin socket. I remember the pain ( and the room) to this day.
Hi John, thanks for your videos they're most helpful but I've got a question I can't seem to find an answer to anywhere online, or even get a solid answer from other qualified sparkys with more experience.. basically, what's your take on "tree rings"? For example an old 6mm radial used for a cooker originally is now terminated into a JB or connector and then a 2.5mm ring final has been connected, both lines and neutrals respectively to the 6mm. Is this allowed so long as the connection is maintenance free? And how would you test this, and also what would you write in the test results, 2.5mm or 6mm? Of course I know it's bad practice to do this and would never do something like this when installing but for ease of getting back to the consumer unit, which isn't an option as the house has been redecorated and cables chopped into walls....therefore I'm being told to do this 6mm to 2 x 2.5mm but I'm not sure. Thanks for your time and keep up the good work!!!
Although not one of the 'standard circuits' it is permitted and nothing wrong with it. The connection does not have to be maintenance free if it is accessible, and for testing purposes it would be better if the 6mm to 2.5mm joint was accessible so it could be recorded as a 6mm circuit supplying a 2.5mm ring, each part tested and recorded separately.
John Ward hi John, I've asked you about this before but I'm still not straight with it in my own head... figure of 8 test - my bosses don't do it and say they don't need to as they calculate the r1/r2, which is fine but it doesn't show any cross connections on the ring. Would a Zs test pick it up? I would say no and that it is really important to do figure of 8 to prove the ring is in good shape. I'm finding it difficult to come up with a decent argument as to why we should be doing it - can you help me!
Used to see this kind of circuit a lot in schools etc for IT rooms and the like, usually 6mm wired to a 45 A switch on the wall which then converted to 2.5mm ring around the room. To test split the ring at a socket outlet (after safe isolation procedure of course) test and record ring continuity of conductor ends then connect for "figure 8" ring final test and be sure to include the DB connection as well as each outlet thus including the 6mm cable as if it was a conventional spur from the ring. The value at the DB will be higher than the expected ring values due to the resistance added by the 6mm cable. The highest value is recorded as R1+R2. Alternatively test ring final and R1+R2 of 6mm independently and add values together. If recording circuit in one line on test schedule then 2.5mm is the smallest conductor present in the circuit so I would record this (although if cert is handwritten you could always fit both sizes in the box). A frequent problem with this circuit was that someone would switch the switch on and have several computers start at once and the inrush current (particularly back in the days of CRT monitors) would operate a type B MCB/RCBO (poor circuit design).
@@Webbster77 why would you calculate r1+r2?? measured is the only sade and true method..Zs proves nothing ... as an example I trsted very old flats double sockets knowing they were 1950 wiring with no cpc only the metal conduit with singles inside but the conduit want connected at the consumer unit. doing a Zs test at each outlet... got good readings... so the Measured Zs is NOT a good guide to ensure a continuous earth path for fault current in absence of a cpc. r1+r2 measured is mentioned in GN3
Did you listen to Johns' explanation at all? *Before* work is carried out on the testing of a ring circuit, the main circuit breaker is switched off. Thus shutting power off to everything down circuit from the main circuit breaker. Therefore it is irrelevent whether any of the *mcbs* ( *mini circuit breakers* - I don't know what an mcg is...) are on or off. . As the two ends of the ring circuit are *disconnected* from the 32A mcb, it is obviously prudent - if you wish to avoid getting an electric shock or risk electrocution (death) - to remove the power from the circuit under test. . Finally, if you don't *know* how to use a multimeter - then you shouldn't be considering messing around with live mains circuits- or indeed anything electrical. . If you fully understood electronics or electrical theory, you'd know that this was a *resistance* test and thus it makes no difference which way around your test leads are. . The only time test lead polarity is of any importance (on a multimeter) is when testing voltages in DC ( *Direct Current* ) electrical circuits, where current flows in *one* direction only. DC circuits have *positive* [+] and *negative* [--] conductors. (Red & Black) leads of the multimeter set to read V (volts) or mV (millivolts). AC electrical circuits, by nature of being *Alternating Current,* in that current flows in two directions - back and forth (alternating) and having - *line (live/phase)* and *neutral (combined earth)* conductors (In the UK - brown & blue insulation) require any multimeter to be set to read *AC Volts* (or millivolts), the polarity (which way around) of the (Red & Black) test leads is totally irrelevant, as it is with any impedance or resistance or current (ampere) test. . You can test the conductors of domestic electrical circuits with a *good* multimeter. But generally for domestic/commercial wiring tests of this nature - a dedicated, mulit-function test instrument would be used, which have the facilty to test the resistance of insulation as well. . But my advice to you, is to go and get *fully* educated on electrical circuit theory, before going anywhere near an electrical circuit with any kind of meter.
Weve just had a new UPS installed here in the UK. Its an Italian UPS and came with Italian engineers to fit it. They dont use L1 L2 L3 they had U V W. so much for harmonization over Europe........
To be honest there was nothing stopping the wiring of red and black all that was needed was the notice at the cu. The number of times I come across mixed colors at some part of a ring they might as well had made the extension with red and black, there is plenty of it on ebay. Some of the old red and black I come across seems thicker and stronger than 6242y the grey sheathing is definitely better.
@@rickybee4537 it was more about being easy to identify which was which if it's a bit dark, everything's covered is dust, plaster, dead spiders, whatever, the red black yellow is clearly better than the dowdy EU colours. The EU thinking as I understand it was to accommodate certain types of colour blindness 🙃
Great teaching. I often use a similar method; however, you have to be 100% on top of your subject, which you certainly are! Great work from a seasoned teacher.
+John Ward Given the fun wih USB-sockest providing a loading between L-N ... I wonder if these mess up L-N crossed resistance tests?. If so, what about doing the tests as CPC-Neutral crossed, and then, separately CPC-Line crossed -- would this still provide all the appropriate test coverage so far as continuity and polarity and resistive-joints are concerned, but avoid complications of L-N loads applied? [I appreciate a full voltage L-N IR test still ould'nt be possible].
Crystal clear as usual. If all my teachers were like JW when I was at school, I'd have left with 10 A Levels (That's 10 x A levels - not 10 amp levels 😅) MANY thanks 👍
Hi John i will going to take my test soon would you able to guide " What is the design consideration in sizing a final circuit in an electrical installation? " what does it mean "in sizing" MCB rate, Cable size or DB size......?
At 23:00 surely as you go round testing, if you found inf on test 2, you would fix that before proceeding? I can't imagine starting a second test knowing I already had a problem. That means you are checking for L reversed with either N or E, or L or N not connected, or switch off. Probably I'd check the switch first as it's an easy check and easy to rectify
I'm doing a work from home course for electrical installations and the book's jargon and lack of diagrams have made things extremely hard to learn. Thanks to this video everything has come into focus. Thanks so much!
I hate the R1+R2 and such names... I wish they'd specify what they're actually measuring. John... as someone with more knowledge than many in the trade, do you find people just 'following rules of thumb' and having no idea what they're actually measuring? That worries me, and I wonder if it's why they've tightened up on the testing in the 17th ed.
(I still call R1+R2 the earth loop impedence... but part of my mind is saying no, I'm wrong, as that would include the system external to the installation, if you see what I mean)
Question: you are clear that you don't like ring circuits. So on a radial, how do you test each socket for the problems which are identified by these ring circuit tests?? It's always seemed to me that these tests are an advantage to ring circuits, rather than a problem. If I'm missing something here, please enlighten me
i always wondered how uk wiring was done.. this is rather intense. complicated and seems very unsafe.. and huge fire possible if you dont test it all the time. to how simple north America wiring,, , reminds me of the Christmas light loops, one bulb blows out and everyone one out..
Hi John. Not sure I agree with your comment about the "undesirable" additional path making a sort of figure of 8 in the centre leading to overload conditions. If the original outer ring is rated correctly, then adding any additional connections between two sockets cam only make it better (ie more current sharing) not worse.
that's all fine until "that figure of 8 part gets messed around with or added onto by Mr diy....then you technically have a hybrid radial on a ring or AKA a spur with more than one double socket on it 🤔 🤣 and then you will get a possible overload on this back to the point its in the rest of the ring... so main issue is unskilled diy persons adding or disconnection the middle part of the figure of 8 thinking its technically a "ring" opps!! overload time +🔥
Something I've come across twice now is cross-coupled rings. On an existing installation it should be very obvious - the ring is still live when disconnected - but on a new one pre-connection would any of these tests find it? Edit: Now that I'm thinking more clearly the answer's yes in all the cases I can think of.
When approximating the values for the L-E, instead of adding them together and dividing them by 4 can we not implement the formula for resistance for parallel paths as they are in parallel, so (1/r1 +1/r2) which gives us an approximation ~0.281 ohmes? Thanks
The parallel formula gives the minimum value possible(socket at the CU), whereas (a+b)/4 gives the maximum (socket half way around). However it's a weighted avg, and sockets around 70% of the ring will be closer to the maximum.
Good day John Ward, Should any regard be given, when testing socket outlet circuits, to the indicator light that on the socket? Is there a chance, that the insulation test between conductors, may damage the light? Your videos are very well presented, very informative and a pleasure to watch, thank you.
The two conductors are connected in a circle, and each measurement is across the diameter of that circle. Half of each conductor, and there are two halves in parallel, which is 1/4 of the total resistance.
Very helpful and informative thanks. But I am wondering if them plug socket testers that light up green or red to indicate a fault can do away with stage 2 & 3 tests if you have good values from test 1?
No, those plug in things are next to useless as they only indicate a small number of faults in certain circumstances. They can only be used on a powered circuit, and most testing should be done before power is applied.
Sir, sorry I am not a native English speaker, the afarementioned circuit is a ring circuit I guess, I am used to see radial circuits, thank you for the explanation.
So, if one phase wire is disconnected all loads lands on the other half of the ring wich will mean a potential overload situation. If this was done in the old days to save on the copper, ok. But is this still being done to this day ? It just isn't worth it in my opinion.
Rings can still be installed and some people continue to do so. However in most normal circumstances there are few if any advantages to them. The copper saving thing isn't valid now either, as that was comparing the 'new' ring system introduced in the late 1940s to the earlier wiring where every outlet had it's own individual cable back to the fusebox. However it's not clear whether any copper would have been saved even there, since lower rated outlets such as 2 amp and 5 amp would have been installed with much smaller wire sizes anyway.
Brian B - Ring vs. Radial Which you should specify depends on many factors. What are the expected loads (does the building have central heating, so will plug in electric heaters be used or not, what appliances are expected to be used, etc. etc.). How many socket outlets do you want, both NOW and in the future (when someone decides to rearrange the furniture in the rooms). Now draw up a plan on paper to work out the details. I always recommend that you specify more socket outlets than your immediate current requirements, as providing them now is far easier than making alterations later. In a rooms where there are plenty of socket outlets, the distance between the sockets will not be that far, so the difference in cable cost between two radials and a single ring circuit will be insignificant if buying drums of cable. Properly designed and installed ring circuits are just as safe as radial circuits. Ring circuits are more flexible for the end user, as they can plug any normal appliance in to any socket outlet they like. Whereas if 20A radial circuits are used, too many high powered appliances connected and switched on at the same time on one circuit will trip the MCB. Worse if the protective device is a fuse... Fuses have the disadvantage that people can put in higher rated fuses, higher rated fuse-wire, or normal wire or other conductive material. And don’t think that a MCB protected consumer unit can save the day, as I have come across radial circuits run in 2.5mm squared cable protected by 32A MCBs... Properly designed and installed radial circuit circuits have the advantage that no fixed wiring cables should overheat. But a poor conductor connection in a socket outlet could cause overheating and may result in a fire. So the argument that a fault will always show up in a radial circuit does not wash with me. With a ring circuit, a disconnection or a poor connection could result in a cable being overloaded if multiple high power appliances are in use. But as there are two current paths, it does depend on where the fault is in relation to the circuit wiring.
Tubmaster 5000 - as I said above, there are just as many potential faults in a radial circuit as a ring circuit. And there are some advantages to the ring circuit, as I outlined above. Which aspect are you referring to?
My expected r1/r2 should have been 0.92 but measured 1.20. Do you class that as high and what fault as majority of sockets all measured that!? Many thanks John 👍
Hi folks. The 230 volt ring main loop impeadance explanation is a bit misleading to begin with. John expands on it a few minutes later with a much better explanation - the protective conductor in the UK has a higher loop resistance than either the line or neutral loops as it is a bit thinner. It needs to carry enough power to blow the plug fuse or trip the ring main mcb quickly, it is not having to power a suite of 13 amp appliances. BobUK.
There are two separate ring circuits , one for the lights and one for the plug sockets , yea ? How would I find the problem that is making the fuse trip when using the light switch ?
No, lighting should be on a Radial circuit, not a ring. Any tripping would be an issue with either the light fitting or switch (whether it's wiring or the actual accessory). There is a specific video for lighting wiring, if you have not already found it.
I agree. I trained up on the 15th edition back in 1980mumble... and the changes are... enormous I recently got back into the trade and have yet to get up to date on certs, so I am working for another chap :)
this is very informative ... my only issue is sometimes i have problems understanding your words....eg you might say a word but it is as thou you eat part of the word in pronuncing it .... so i cannot make it out clearly ...can you work on that.... thanks !!
Where the circuit cables return to the consumer unit / panel after the last outlet, which allows the use of smaller cable as there are 2 paths for current to each outlet rather than only one.
Spurs or not on the test results we put down the highest readings correct? Either being obtained on a socket within the ring or on a spur or fused spur?
At 12:17, you say "single socket". I thought one instance of a double socket was allowed on a spur (26A being within the current capacity of a radial 2.5mm^2 T&E, C-method)? Don't have my regs to hand whilst watching this...
Hi John, when you mention that the reading will drop at the middle socket if wired incorrectly it made me wounder how do you identify what side this will happen? Or why one side increased & the other decreased. I hope you can understand how I've asked my question. Thanks for the great tutorials 👍
When you context the tails wrongly for this test, the resistance drops as you go round the circuit starting in EITHER direction from the CU, it's highest at the CU and drops towards the middle. When it starts rising again you know you passed the middle. I hope I correctly understood your q, and that I explained the answer in enough detail.
Hi John, let me ask you If connecting Line and Earth on Step 3, we double the length of the wire, why we should divide by 4? I mean, the resistance is directed proportional to the length of the cables, if we double the length we should double the resistance, isn't it?
Hello John, I am planning on a new build and wondered if I could implement radials within the house/rooms rather than having a ring system on the sockets within the 2 floor house.
great video. on the final test for polarity it would be good to mention the reading from each socket would be from outside not from the reverse terminals.
Hi John Thank you very much for your videos and the time you spent on them, and thank you for the excellent explanation in different sections. I just want a little more explanation about the values of the resistance of the Live, Neutral and Earth. Are these values of resistance always the same? How about if the conductors are longer or shorter. I have this question because you said the Spure will have some extra resistance due to the extra wire. So, the length plays a role. If the length has effect, how come you come to those values. On which length are based? Regards Mohamed
John, you mention that once you find a fault you start opening switches and sockets to rectify. Is this part of the remit? Is the procedure at this point not merely Inspection & Testing (with a report) surely any remedial work is out-with the price. Nobody wants to leave a death trap however there are many many time consuming problems once you get the covers off things. It's a fine cut off line between making a living and having a conscience that someone could get hurt. I'm probably more like you where I can't walk away from a bad installation. I always think last man frees all. Your advice would be greatly apprecaited on this matter
Depends on the context. If it's initial verification, which would be for a new installation, then all defects and faults must be located and repaired before the installation is energised. However if it's an inspection of an existing installation, it would normally be just a report on the condition, so any faults would be recorded on the report, and it would be the decision of the owner of the installation as to when those faults were repaired.
I watched another video where a company had already completed the installation and had sub contracted the testing & inspection to another contractor. He completed what he could, reported the discrepancies and let the contractor know what needed rectified before he would sign off the paperwork. I'd say this is where it could get interesting getting paid. As until the client has paid then the paperwork should be the property of the testing contractor, but if the testing contractor won't sign off (and quite rightly so) due to multiple faults with the installation standard then the installation contractor could become difficult or even use someone else not so street wise and bump the first contractor. I thought that alarm bells were ringing when he said that he was testing for another electrical firm who installed the job. Surely they would do it themselves? However getting an independent Inspector in can be good as no biased occur (or shouldn't). So many dillutees, 6 week wonder courses, electrical mates, electrical improvers, adult trainees etc these days that an Inspector really needs to be prepared for some right horror stories once they commence. And ruthless electrical contractors and clients just wanting things signed off when half the time it's non time served guys that roughed it in.
Hi, is it normal to get no resistance at the CCU while doing stage 2 of the ring final test? While doing stage one I did get resistance from all conductors, but at the CCU during stage 2 there was 0 resistance and at the socket outlets I had a reading of 0.35 ohms.
There must be some resistance, so the reading of 0 is wrong. Check that the leads are properly connected, the battery in the meter, and if it has a zero leads function that it has been used correctly and for the actual leads that are in use.
I think you left the two ends of the earth connected to each other as well as connected to the other cable, or ditto with the live. Or some such mistake. Easy to make in practice
@@ScottMcD91 And often in cafes, etc, they don't work and it turns out the electrician disconnected them for the rest and forgot (or was too lazy) to reconnect them. Worth money to anyone willing to fix the problem on a no fix no fee basis :)
Hello. First of all nice and interesting clips. Keep it up. Have one question about checking if you have a break on wires ring circuit. Your checking the circuit by meter with resistance. Can you check the wires by continuity instead? Thank you
A good Q. Continuity detects breaks, but not dodgy connections. You need to check both, as a dodgy connection can cause a fire. A meter checks both at once, so there is no point doing a separate contiuity check.
Connect L&E from one side at the consumer unit, test at each socket until there is no continuity between L&E. Repeat for the other cable. The break is somewhere between the two sockets.
@@jwflame Assuming I'm following round the circuit from the CU in the order the cables run, I'd start as you suggest. Before repeating for the other cable, I'd take a quick look at the socket where I hit the problem. If I get lucky that will be where the problem is and it will be something obvious like a cable fallen out -- But not if I cabled it of course ;) Then check the last socket that was successful for similar obvious faults. If that's still not the problem continue as JW suggests and it will be a broken conductor between sockets. Apparently mice can bite through copper, but not more than once per mouse when they go for L. Sometimes you actually find the dead mouse: use disposable gloves to handle due to disease risk
Im confused, OG says the maximum resistance value of a ring is 0.05 ohms how come if the reading is 0.86 is accepted? (Ive seen on youtube by a qualified electrician) Thanks
The maximum value is derived from the maximum impedance for the circuit, which for a 32A Type B circuit breaker is 1.15 ohms. That is the total of the circuit resistance plus the external loop impedance, so with an external impedance of 0.35 (typical for a TN-C-S supply), the maximum circuit resistance would be 0.8 ohms. If the external impedance is less, the circuit resistance can be higher. The 0.05 is referring to when measuring the resistance of the individual conductors, they should all be identical, or at most be 0.05 ohms different from each other.
Hi Jon, Finding your videos helpful as I am working toward taking 2391-52 exams this autumn. Your explanations are in layman's terms. Just wanted to ask.... In the ring final continuity testing video did you say that the socket outlets must be switched on to carry out the testing as I cannot see why that makes a difference when each conductor is loops in to back? Thanks Duncan
socket outlets get worn over time okie you might have solid connections in the back ...but the actual receptacle part that accepts the 13amp plug might have a high resistance 🤔 so good to check or just plug and unplug your tester lead in and out a few times tends to "cure" the oxidation
Hi John, You said something like "to avoid the tests don't use ring circuits." What is the alternative? Every socket outlet wired directly back to the consumer unit with its own circuit breaker? If so that'd be a lot of wire and circuit breakers. (Thank you for the great videos.)
Radial circuit with multiple sockets, starts at the consumer unit and ends at the last socket. Cable sized appropriately for the circuit breaker. 2.5mm² and 20A is one possibility.
+John Ward that's exactly how it's done in the US. Usually a 120v 20 amp breaker and cable for each room's sockets and another for its lights. Higher current appliances have their own circuits. We even have some 230v circuits, but usually only for ovens, dryers, etc.
If it's for an EICR, then you just report on what's there - an EICR does not include repairs. For a new installation, any defects must be rectified before the certificate is issued.
I don't know, but can guess. First I will confess that I used to think r1 (arr one) was rl (arr ell) having learnt initially from books rather than a live teacher ;) Second I will comes that I thought I'd this when I first saw Star Wars and artoo success his data probe into a power socket... OK so that makes me a total nerd Now my guess is that you calculate the current on short circuit to earth as V / (r1 + r2), and in that particular equation it looks mathematical to have a one and a two. If you don't have a RCB then how fast the breaker trips on that current is important for safety. Not so relevant now RCB protection is more available than it was in the forties. Just my guess. Someone please comment if you know better
