Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • Replies 15 replies
  • Subscribers 44 subscribers
  • Views 257 views
  • Users 0 members are here
Options
You may also be interested in

Why are we still using ring final circuits?

David Berry

Hi all, I wanted to discuss the use of ring final circuits in electrical installations in the UK. 

I am an electrical contractor based in Surrey, England and, though I have predominantly spent my 20 year electrical career in the industrial sector, I have recently found myself in the domestic installation world - which has really opened my eyes to, what I believe to be, certain dangers of this installation practice here in the UK. I'd like to share two recent scenarios I have encountered domestically.

Scenario 1

I was called to a customers house to investigate a fault which was preventing the customer from switching on her 32A MCB without it immediately tripping. Upon beginning my investigation, I immediately discovered that the ring circuit in question had no continuity on both the Line and Neutral conductors. I also noticed that various sockets on the ring circuit had a black, sticky residue seeping from all 3 terminals of each outlet. After locating the fault causing operation of the MCB, I returned to the case of the broken ring continuity. I discovered that the Line and Neutral conductors had broken behind a countertop socket in the customers kitchen. It then became apparent that all sockets with the residue were sockets on the leg of the ring leading up to the broken point. Along this route were sockets feeding every appliance and piece of equipment in the kitchen, so my assumption is that the load, and subsequent heat, on this leg of the ring must have caused the insulation to deteriorate so and seep out from the terminals. 

Scenario 2

I was asked to install a few extra sockets onto an existing ring final circuit in a customers house to provide a newly built entertainment unit with several socket outlets. Immediately, I isolated the power and tested for ring continuity of the existing circuit only to discover, again, that the Line and Neutral conductors were not continuous. After a short investigation I discovered, much to my own and my customers horror, electrical cables protruding from a box with insulation stripped and copper conductors free to the touch. Whoever had removed an electrical accessory must have completely forgotten to return and re-connect it before turning the power back on. The scary thing about this one is that it was tucked away in a cupboard that my customers 8- and 10-year old sons kept their bike helmets - which the used every day to get to and from school. 

Both of these scenarios frighten me a little in the sense that these faults lay completely hidden and undetectable from untrained eyes. Because of the configuration of the wiring, nobody could tell that anything was wrong with the circuits, or that possible danger lay in wait. Does this not pose a huge, yet unnecessary, risk? To me there's absolutely no reason that we still need to be installing these circuits in 2026.

I personally feel that the industry as a whole might have gotten a little lazy. Showing up and installing numerous rings seems, to me, to be lazy design. Though I don't feel we're being taught any different. My apprentice informs me that they're still learning about them in college at the moment. Isn't it time we started designing our installations more efficiently: dedicated circuits for fridge/freezers, washing machines & tumble driers, induction hobs etc, 20A radials for ordinary sockets? Or, am I wrong? 

At the very least, if this kind of fault occurs on a radial circuit then some points - at the very least one - will cease to work and give the user of the system an indication that something is wrong. 

Does anyone agree?

Parents

  • A good question!

    My preference is radial, but I do not think that there is anything wrong with a well-installed ring final, even though they can be problematic.

    At home, I have found a cpc (thankfully not a live conductor) flapping around in the box, one with a loose cpc (which gave a slightly elevated r2), and a N-E fault (caused by the backbox nipping the N conductor by the fixing screw). It does not say much for the initial verification.

    The route taken by my rings at home, even upstairs is not clear - it certainly is not the shortest one. However, that is poor design and not because a ring has been installed.

    David Berry said:
    My apprentice informs me that they're still learning about them in college at the moment.

    They certainly need to know about them - how else could they do periodic I&T?

    BS 1363 seems to be designed for rings because of the specified minimum terminal size:

    12.5 Line and neutral terminals in fixed socket-outlets shall permit the connection, without special preparation, of one, two or three 2.5 mm2 solid or stranded or of one or two 4 mm2 stranded conductors as given in BS 6004:2012+A1:2020, Table 4.

    Although 8 mm2 is the minimum terminal size, some of the better quality products will accept 12 mm2. If they did not, it would not be possible to have any branches in a radial circuit.

  • in reply to Chris Pearson

    Yes, Chris, I think you are correct: apprentices most definitely do require knowledge about RFC's as they will require to work on them and maintain them, but I feel that more should be done to encourage radial circuit use with dedicated circuits for different electrical items. The fridge/freezer is the best example I can think of - who wants their fridge/freezer to be knocked off due to a fault somewhere else on the circuit, especially if you're not home for a day or two?

Reply
  • in reply to Chris Pearson

    Yes, Chris, I think you are correct: apprentices most definitely do require knowledge about RFC's as they will require to work on them and maintain them, but I feel that more should be done to encourage radial circuit use with dedicated circuits for different electrical items. The fridge/freezer is the best example I can think of - who wants their fridge/freezer to be knocked off due to a fault somewhere else on the circuit, especially if you're not home for a day or two?

Children
  • in reply to David Berry
    David Berry said:
    but I feel that more should be done to encourage radial circuit use with dedicated circuits for different electrical items. The fridge/freezer is the best example I can think of - who wants their fridge/freezer to be knocked off due to a fault somewhere else on the circuit

    Been there, done that. In fact it was a matter of the pre-payment meter going off whilst I was (unavoidably and unexpectedly) absent. What a stench!

    However, there are swings and roundabouts.

    Do you put your smoke detectors/alarms on their own circuit, or for example, downstairs lights? In the former case, nothing extraneous will disturb them, but what if the circuit fails? Will you notice?

    By contrast, if the circuit includes the downstairs lights, you are bound to notice.

Community Rules & Guidelines