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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?

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  • David Berry said:
    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.

    Worth reading into this. The following provide some insight.

    https://electrical.theiet.org/wiring-matters/years/2020/80-may-2020/back-to-the-forum/

    https://electrical.theiet.org/wiring-matters/years/2022/89-march-2022/resistance-readings-for-step-3-of-the-ring-final-circuit-test/ 

    I have been involved with JPEL./64, helping maintain and update BS 7671, for around 20 years, and the subject has been debated a few times in that time period.

    Across experts in the industry, there are basically two 'camps':

    • Ring final circuits should be banned because we see safety issues.
    • There's nothing wrong with ring final circuits ... the faults we see are down to human influence and lack of testing, both of which are contrary to the principles in BS 7671.

    There are other side arguments, such as the amount of power wasted by fuses in BS 1363-1 plugs; however, those aren't going to disappear overnight, and that would also require a change in legislation, namely the Plugs and Sockets etc. (Safety) Regulations 1994.

  • in reply to gkenyon

    Getting rid of fused plugs would force a phase out of ring circuits and have the advantage of allowing  harmonisation with 16A European Schucko 1.5mm radial combined power and lights designs, but there would  need to be would be a long transition period or a supply of fused Schucko sockets for ring use.
    The 'crab-claw' ring is a moderately common fault but then is are all the other dodgy non-standard configurations, like lassoo/ lollipop, and then radials that are cross -linked or even re-entrant.
    The saving grace of all this, as others have noted, is that most rings are lightly loaded, 2,5mm2 cable is good for 27A clipped direct or plastered in, and in reality is fairly happy-ish at 32A for quite a long time before getting dangerously hot as well, so the wilder unbalanced configurations are not as problematic as they might at first appear.
    It's likely that if we did not already have it, the UK would not be rolling out ring finals and fused plugs now, but equally we have dodged the bullet of inadequate single phase wiring - lookup Dutch kookgroep circuits for a look at how not to make cooker circuits easy.

    I'd argue that installed well, they are fine, and if there are scheme member electricians out there who really can't manage that, then perhaps they ought to give way to the more capable unregistered who can....

    Note gunge from old cable can also be plasticiser leakage. Its unpleasant but rarely dangerous.

    Mike

  • in reply to gkenyon
    gkenyon said:

    Worth reading into this. The following provide some insight.

    https://electrical.theiet.org/wiring-matters/years/2020/80-may-2020/back-to-the-forum/

    Graham, thank you for linking to an interesting article.

    1000 sq ft is quite a big space - roughly four 16 ft square rooms. You can get a perfectly comfortable 3 bed house into 1000 sq ft.

    The shape of the circuit is important. Running around the periphery of a fairly square room (or number of rooms) is economical, but where, IMHO, the concept of a ring fails is a long thin area, such as a corridor (with or without rooms at the end).

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