EXTENDING SOCKET CIRCUITS - ADDING TO RING and RADIAL CIRCUITS
There are many frequently asked questions to do with extending socket circuits…
Can we extend a ring circuit, can we add to a radial circuit?
What size fuse must it be and what size cables are permitted?
How many sockets can I add?
And just what is the difference between ring and radial circuits?
The answer is that we can extend or add to both radial circuits and ring circuits and in this video we will show you some of the more popular methods of doing this. We will also describe the difference between ring and radial and why fuse size and cable size matters for safety and reliability.
The important thing is that we carry out any extension of a circuit safely and correctly. As well as wanting to supply the customer with the circuits that they want and need, we must also consider the extra circuit length and how this affects the maximum permitted Zs values for different circuits. An overextended or incorrectly arranged circuit may have a detrimental impact on the health and safety of the users of the new sockets and in this video we look at how this equates to cable lengths and layout.
You may also want to view the following LearnElectrics videos which are related to this topic …
RING and RADIAL CIRCUIT DIFFERENCES …
• RING and RADIAL CIRCUI...
SPURS ON SPURS …
• SPURS ON SPURS Extendi...
This video is No.99 on our KZhead channel where we have videos on a wide range of electrical topics.
To see a full list of all our LearnElectrics videos, click on the link below.
/ @learnelectrics4402
You can also view all our videos by typing LearnElectrics all one word into the KZhead search bar.
Always work safely, electricity can be dangerous. If you are unsure, stop and seek advice.
This video is provided for guidance only. Every electrical situation is different, please check and ensure that you are applying this learning information to your own individual circumstances correctly and safely. If in doubt, stop and seek competent advice.
To go directly to our LearnElectrics Channel on KZhead Click on the link below … kzhead.info/tools/YaJQnpO4XAp0yCgqzMkmfA.html
I already know this being an electrician, but it always pays to stay up to date and to make sure I haven’t missed any changes. Superb presentation and there is no better channel for teaching electrics than this one.
Thanks John. We never stop learning, I think most sparkies are always watching or reading something about the trade. Thanks for the compliments too, appreciated. Dave.
Dave. All of your presentations are clear, concise, and extremely well put together. It must take you a considerable amount of time. Very informative, from someone who obviously has considerable knowledge and expertise. It is greatly appreciated. It’s the best electrical go to on you tube. Well done Dave. Keep them flowing.
Thanks Paul, I very much appreciate the comments. Spread the word, it all helps to make the time and effort worthwhile. Dave.
Lots more to come.
👍
Another very good video Dave with good graphics. Love watching your work, great teaching skills Amigo. 👍
Thank you Gary, thanks for your support. Dave.
Bi, yes I am putting some playlists together. Thanks for watching. Dave.
Excellent videos! Thanks.
Thank you Steve, thanks for supporting the channel, appreciated. Dave.
Very good video dave thank you
Thanks for your feedback Azizur, much appreciated, and thanks for watching. Dave.
Absolutely brilliant video and watching Learn Electrics you definitely learn from thier tutorials. Excellent channel and good learning materials. 👍👍👍
Thanks for watching, glad you are enjoying them.
Thanks again - definitely adding to my "mental toolbox"
That's it, keep learning. When you look back after a year you will realise just how much you have learnt.
Brilliant vid. Such a common job but never covered and explained as well as this
Thank you. Great comments. Dave.
Brilliantly explained
Super feedback, appreciated.
Great useful video once again, 👏
Thanks Royston, really appreciated. Dave.
excelent. Many thanks
You are very welcome Pedro. Thanks for watching. Dave.
Wow, Excellent video this is what i was searching to learn and understand this from scratch. Love to see more videos like that and any video how to learn electric as a extra hoppy or skill or other professionals how to learn and what path should need to be taken.
Great that you found the channel. There are nearly 200 videos on the LearnElectrics channel on youtube and lots more info on the LearnElectrics.com website. Thanks.
Nice one dave another well detailed video 👌👌
Thanks buddy, thanks for the support
Dave what is the scenario if the maximum Zs is exceeded, say a ring was extended for a socket and the length of cable exceeds the maximum Zs,would it be a matter of a new circuit on its own MCB/RCBO radial circuit 🤔 cheers
Quality video
Thanks Paul, much appreciated.
Thanks Dave
Thank you David, thanks for watching.
Top Video
Thank you, glad you liked it. More to come. Dave.
Thanks very helpful
Thank you Ram. Thanks for watching. Dave.
@@learnelectrics4402 I never miss your videos. keep bringing more videos
Thank Dave once more for this wonderful video well presented, illustrated, and very enriching in knowledge. Looking forward to the next topic. Dave, question: How do you do R1 + R2 on an extended radial circuit? and which chart are you talking about in this presentation?
Omar, I have made a chart or table showing how much extra resistance to add to a circuit if you know the extra distance involved. The chart is not from any books, just made to help with the video. R1+R2 for radial is fairly easy. Take a look at this video - What is R1+R2 on this link kzhead.info/sun/e9p9pbqEe6qsm6s/bejne.html Thanks for watching Dave
As a recently retired industrial electrician of 50 years I can't remember the last decade when I wired a ringmain circuit in 2.5mm twin and earth or 6491x it's nearly always 4mm and sometimes 6mm,
Lots of sparkies are installing 4mm radials now instead of 2.5 rings, especially as the boards can have more ways in them. Thanks for the input. Dave.
Thanks for your time. Good explanation
Glad that you are finding the videos helpful. Thanks for watching. Dave.
nice
Thanks for watching, appreciated.
Great videos. Helps me massively. Just a quick question if you don't mind. When spurring of the ring with a FCU, do you use the 2 legs of the ring into the supply side or just one cable? Hope this makes sense.
Just one piece of cable into the FCU, make sure it is 2.5mm. Hope this helps. Dave.
In the UK you need to be Part P registered to do any work in domestic installation.
Not correct at all. Sorry Tony, but you've been given the wrong information by somebody. Take a look at this video and hopefully it will help. kzhead.info/sun/otqTp9ihkF-ghK8/bejne.html
Brilliant videos guys ,just quick question can you spur from a radial circuit which is protected with a 16amp mcb ? Thank you
Thanks for the question David. If the cable is 2.5mm (T/E for example) and the breaker is 16A or 20A you can have as many spurs or spurs on spurs as you sensibly wish, subject to the Zs being within limits. If its the number of sockets you need, more power usage then 20A is a good bet but it has a lower Zs than 16A. If you need the distance, longer length of circuit, then 16A breakers have a higher Zs which may be better. Hope this helps, Dave.
@@learnelectrics4402 thank you very much just what I wanted to know
Happy to help.
Great video, thank you. Could you please clarify in the situation where a 13a fused spur is taken from the ring, if the first "downstream" accessory can be a junction box. In my case the JB splits the supply cable into 2, each leg feeding one socket. Everything is protected by the 13a fuse, which I will probably downrate to 10a. All is cabled in 2.5mm t&e. I have no plans to add further sockets. I appreciate that it would probably be usual to wire the spur as a "mini radial" as per your graphics, but I had to put a fix in after stupidly nicking my new (still dead) cable with a drill, having spent 3 hours drilling walls and clipping it...Thank you
Once you put a 13A fused spur in, everything after it can be whatever shape you want. Split into two and two again, it doesn't matter. And your cables can all be 1.5mm if you wish. You can't ever exceed 13A. Nicked spur? We've all done it. Good luck, Dave.
@@learnelectrics4402 Brilliant, thank you for your clear explanation. Keep up the great work 👍👍
Can you clear something upnplease Dave. In one of the slides you have two separate radials running from a single 20A mcb. Regulation 314.4 says that each final circuit should be connected to its on way at the DB. How are we able to have two radial finals on a single way?
That always raises a question. Think of the second one as a spur, we are allowed to spur from the MCB. What is the difference between spurring at the first socket or at the MCB. And yes, for many years I thought it couldn't be done as well. Dave.
I need to break into a ring... Can you buy backboxes with all the relevant fittings pre-made for this job like the illustration at 6:10 ? If so what do I search for because it always just brings up junction boxes like the Wago boxes. Or is it simply a case of use the existing backbox with blanking plate and then use Wago connectors inside?
You can use another back box, 25mm or even 40mm and then waygos or a decent terminal connector block. 40mm depends on if its in brick or hollow wall.
hello, would it be possible for you to add your videos helping with the 18th in a playlist?
Yes, absolutely. I will do this for you. Dave.
@@learnelectrics4402 much love Dave.
@@Vaguereli many thanks. Dave.
Hi there, thanks for the videos; I am struggling to understand the situation at 8:50. To me that set-up looks like a ring circuit on the top section and a 3 socket spur to the bottom. I don't understand why that is allowed? surely the section of wire below the red socket is liable to overheat due to the potential loading on the bottom seciton? Sorry, but I am also not clear on what you have converted that from?
The previous slide starting at about 8.27 tells you that we are converting a ring circuit into radial over the folowing two slides. The slide you are asking about is showing that the circuit is using a 20A breaker and 2.5mm cable, so we can add as many sockets as we wish and still not cause problems. 2.5mm cable is rated at 27A for clipped direct and the breaker is limiting the current to 20 amps. hope this helps, Dave
could you explain about Prospective Fault current. Please
Absolutely we can Pedro and I do believe that single phase PFC and PSCC is planned in a week or two. Meanwhile take a look at today's video that we have just published. It covers single phase a little bit. 3 PHASE PFC is on this link … kzhead.info/sun/n6qwY8iGo2N7fZE/bejne.html
At 15.30 you have put a blank cover on and lost the socket, could you run a spur from this so that the socket is not lost?
No reason why not as long as it follows the rules on cable size etc. Good question. Bux.
Hi Sir, I want to make a radial circuit for 4 socket outlets using cable 4sqmm, what is the size of MCB that I should use? 20A or 32A? Thank you.
4mm will be ok with both those mcb sizes for a radial circuit. take a look at this video, it will help. kzhead.info/sun/ZsN9ZpllamSuo3A/bejne.html
How come ring resistance is different to radial? My guess would be it’s technically a 5mm at any one point as cable has two legs but that would make it half the resistance of single 2.5mm cable but the chart shows a quarter? Can you explain how you got these figures?
Have a look at this video on our channel Jon. It will explain all, and more. Thanks for watching. kzhead.info/sun/iZSYZsOPpJ2jppE/bejne.html
@6:15 you show the ring main being extended in an existing backbox. Should the earths be fully common'd together and connected to an earthing point rather than simply split and extended? Especially if the box is a metal backbox where there would be an obvious risk of it being live under a fault condition?
If there are two earth studs on the back box, using either one or both is ok.
@@learnelectrics4402 Thanks for the clarification
How comes you multiply by 2 for the ring circuit? Is this a fixed number?
Its just an example of extending this circuit. If we want to double the length then the resistance will double.
Can a kitchen with 3 double sockets be included in a Ring of 9 double sockets ?
Theoretically, yes it can, because the circuit breaker will trip before you plug something into every socket. Do you really need 24 socket outlets in a kitchen. Personally, if the customer really wants that many, I would consider dividing the circuit into two or even three.
@@learnelectrics4402 There is only one Ring in this 1 bed apartment total 9 double sockets, Can the kitchen be added to that ring with 3 sockets. making a total of 12 sockets for the whole apartment. Cooker has its own circut. thanks
What is the reason for having a max resistance value in a circuit? Is it because it will reduce the current to low enough levels that appliances will not work correctly?
No is the answer, there are different things happening here but if you have a look at these two videos on these links then together they will answer your questions. Thanks for asking, great question and thanks for watching. Dave. Zs WHERE DO THE NUMBERS COME FROM kzhead.info/sun/fM6peq9pnHyCra8/bejne.html & MATCHING CABLE SIZE TO CIRCUIT BREAKER and FUSE SIZE kzhead.info/sun/idiNhc-Np4NjhZs/bejne.html
In my garage there is 1x Double socket connected directly to a 16B MCB in the consumer. This is the only socket in my garage and its connected in radial fashion. The thing that's confusing me is in 1 of the plug sockets is the tumble dryer which runs at just over 11A (I've tested this using both the Watts÷voltage equation and also physically with a clamp meter.) And the other plug is connected to an extension consisting of a fridge freezer and washing machine. This totals around 9A according to my clamp meter. But obviously 9A + 11A is 20A and its connected to a B16 MCB...how come the MCB isn't tripping when both are on at the same time? I want to spur another double socket but am I right in thinking I should replace the current 2.5mm cabling with 4mm twin earth cable and a B32 MCB due to the already high 20A load on the MCB? Please any help would be greatly appreciated I've been looking everywhere.
A 16A breaker will not trip at 16A, that is its working current. At 20A, it will take a long long time to trip and even at 30 amps it will be 5 minutes if the current is constant. Your connected devices are probably switching in and out so that the current is not 20A all the time. If the current cable is 2.5mm you can change the breaker to 20A Type B for peace of mind. Also, if it was me, I would install a new, separate radial circuit and breaker for the new sockets as changing to 4mm cable is just as time consuming. Hope this helps. Dave.
@@learnelectrics4402 thank you dave yeah I have a spare MCB I can use to make a fresh radial circuit so I'll probably just do that instead much appreciated
Great. Also consider, if the new sockets are in the same area as the existing, and you are running fresh cable, run 2.5mm and convert it to a RING circuit with a 32A breaker and include the new sockets in that ring. Lots of choices. Good luck. Dave.
@@learnelectrics4402 will I still be able to use a 32A breaker with 2.5mm cable as I thought 2.5 only covers up to 27A? P.s Thanks for the help Dave you've got a new subscriber aswell 👍
@@learnelectrics4402 ah never mind dave I just watched your video on differences between radial and ring where you explain that you are able to use 2.5mm with a 32A breaker in a ring circuit as the current is virtually halved although not exact! Love these videos dave extremely helpful! I am an electrical engineer in the army but I mostly work on armoured vehicles so house electrics are relatively new to me I have completed the 17th edition installation course through work and 8ve just booked myself onto the new up to date 18th edition course where I hope to complete both installation and design aspects so these videos are gold!
How safety is ring circuit. And how does the electricity turn off if the it's go back to fuse.
Thanks. Take a look at this video on ring and radial circuits. kzhead.info/sun/h7x9gc-ja4iKenk/bejne.html
Can you do a radial in 4mm cable and fuse at 30/32amp ?
Yes, that's permitted. Some sparkies do that for a radial kitchen circuit. Good question.
@@learnelectrics4402 I was thinking about my utility room. Currently 2.5m 16amp MCB with Washing machine , tumble dryer and a large freezer with a 3A spur for lighting. All running at once can take out the MCB. If I rerun with 4mm I could change to 32amp. Or could I get away with 20amp MCB on the existing 2.5mm cable?
Three options. If the CU will take another MCB, split the ring and make the existing MCB and the new both 20A. That will split the load into two separate circuits. Or, just change the existing 16A for a 20A, that might be just enough to stop it tripping, but might be too close for comfort And third, as you say, rewire in 4mm with a 32A breaker, but that can be messy and time consuming if the cables are chased in. Lots of options, just do it safely. Dave.
@@learnelectrics4402 replacing 16amp MCB with 20amp will be easy and safe as the 2.5mm is good for 20amp+ as it is direct clipped and dose not run under plaster at any point. It only trips when 2 motors start at once. 4 Amps extra 'head room' should be enough.
@@learnelectrics4402 done the 20amp MCB on the existing 2.5mm cable and has not tripped since, thanks.
Hi.i dont zs for 32A TYPE B is 1.09.i checked page 68 table 41.3 amedment 2 showing 1.37.correct me if i am wrong.thanks
Saman, In the Wiring Regs book Zs for a 32A type B breaker is 1.37 ohms. In the on-site guide they quote measured values using the 80% value which is 1.09 ohms. To convert the wiring regs numbers to measured values, multiply by 0.8 Thanks for watching. Dave.
ring some of cable 4mm line and neutral some 2.5 mm line and neutral how to add r1 +R2
Azizur, thanks for watching, great question. If its a 32A RING then 4mm cable is ok. It must never be less than 2.5mm. Just do your normal r1, rn, r2 continuity and then cross link to measure the R1+R2 See the video below on Ring Circuit Testing. kzhead.info/sun/YLR6otmrnIecY2w/bejne.html Good luck, Dave
If accessories MUST be rated at minimum 20a, how comes we can use 13a sockets rated at max 13a?
The socket fuse is rated at 13 amps but the actual component that make up the plug will not be damaged by 20 amps, except the fuse, which should blow.
@@learnelectrics4402 I've never seen a socket with a fuse in it? I still don't get it - if the socket itself is rated for 13a how come it 'must' be rated at minimum 20a? This one needs clearing up i feel.
Cables and components must be capable of taking 20 amps even if that part of the circuit is fused at 13A.
@@learnelectrics4402 But there is no fuse in sockets? And you said 'accessories' which is sockets and light fixtures and fittings? So if something is 'rated' for 13a it means it can only safely take 13a without risk of damage or malfunction so either sockets are 13a or they can take 20a and so are actually 20a rated? Still confused sorry.
@@electricalstuff259 - you're forgetting the fuse in the plug top. The 'socket' rating of '20A' just like like any rating of accessories or circuit breakers or connectors must have an operating limit before being fried or blown to bits. If you have a fuse or circuit breaker with a rating on it in Amps, it just means that it will sit and allow that MAXIMUM current to pass through it without any issue. A fuse rated at 13A will therefore protect a cable if the fault current exceeds the fuse rating rather than the cable heating up and melting so generally, the cable should have a higher rating than the fuse (Ib In Iz)
So if one wire is disconnected or breaks in a ring the whole then radial will still work, no fault will be detected, but the draw could be well over the cable is rated up to but the fuse won’t blow. ! Why haven’t these been banned?
That about sums it up, which is why many sparkies prefer radial socket circuits. they should be installed correctly, protected from damage, and inspected regularly. Thanks for watching.
8:45 - how is that a radial? That's just a ring with a spur surely?
We are reducing the size of the breaker to bring it under the same rules as a Radial circuit because the cable is now rated higher than the breaker. With a 20A breaker and all in 2.5mm we can have any arrangement.
@@learnelectrics4402 So you can essentially change a ring to a radial just by changing the MCB size to 20a?
That's why I suggest in the video to reducing the breaker size and removing a link to make it into a pure radial. The rules for radial circuits now apply as per p506 in the Regs. If it is all in 2.5mm with a 20A or 16A then any arrangement is possible subject to Zs max of course. Hope this helps. Thanks for watching. Dave.
@@electricalstuff259 -Yes if you split the ring. 2.5mm is rated at approx 27A. The original 32A breaker would now not protect the cable so you need to protect it with a 16 or 20A breaker. The breaker has to be less or equal to the actual design current which both have to be less than the current carrying capacity of the cable. (Ib In Iz)
Thanks EF. Great additional info. Appreciated. Dave.
Why are ring circuits still used? Weren't ring circuits invented to save copper during the war effort? Could we just use radials now so you don't have a pull an extra leg back to the consumer unit?
Absolutely, but ring circuits do still save copper. Fortunately, with modern CUs there are more free ways in the board and we can run 20A radials in 2.5mm. Great question. Dave.
If radial circuit is safe too. Why do we return the line to breaker and make it a ring? it seems so much easier to add socket in radial circuit.
About 80 plus years ago it was way of saving copper as there was a world wide copper shortage. And since then its just stuck. Hope this helps. Dave.