Embedded Files
Ring final circuits, more commonly and erroneously known as ‘ring mains’, originated in the UK, and date back to 1942 and the reconstruction effort following World War Two. In the face of shortages of materials, ring final circuits were conceived, to minimize the amount of copper required. The 13 A socket-outlet with fused plug top to protect appliance flexes was also introduced at this time.
Ring final circuits require careful attention when installing or modifying them and additional testing to make sure they are safe and comply with the wiring regulations. When an electrician carries out work on a ring final circuit in your home they will carry out these tests. They may carry out the tests before any work commences, if any faults are discovered they should discuss them with you.
Below is an example of a typical healthy circuit, further down are some examples of common faults found of ring circuits.
Healthy Ring Final Circuit
Healthy Ring Final Circuit
Used to supply power to single and double socket outlets in UK homes.
32A Circuit Breaker or 30A Fuse.
2.5mm² Conductors for Live and Neutral.
1.5mm² Conductor for cpc (earth) (might be 1.0mm² on some older cable).
Single continuous ring for all 3 conductors that start at consumer unit and return to consumer unit.
Un-used spurs can only have one accessory.
Fused spurs can have multiple accessories, including lights.
Common Fault No1 – Ring not continuous
Common Fault No1 – Ring not continuous
One or more of the faults could exist on the circuit.
This could mean the ring is incomplete because section of the ring is missing, or
Line conductor (brown or red wire) for ring final circuit not continuous, or
Neutral conductor (blue or black wire) for ring final circuit not continuous, or
CPC (earth/green-yellow) conductor for ring final circuit not continuous
BS7671 Wiring Regulation Infringement
Regulation No. 526.6 and 643.2.1
These would be given a defect code of C2 – Potentially Dangerous, urgent remedial action required.
Common Fault No2 – Multiple accessories on a spur
Common Fault No2 – Multiple accessories on a spur
The overcurrent protective device (32 MCB or 30 fuse) rating exceeds the current carrying capacity of a (unfused) spur feeding multiple outlets and/or accessories.
BS7671 Wiring Regulation Infringement
Regulation No. 433.1.1 and 533.2
This would be given a defect code of C2 – Potentially Dangerous, urgent remedial action required.
Common Fault No3 – Ring within a Ring
Common Fault No3 – Ring within a Ring
Two ring circuits exist and would be impossible to complete any testing and subsequent certificates as required by wiring regulations.
BS7671 Wiring Regulation Infringement
Regulation No. 643.2.1
This would be given a defect code of FI (Further Investigation required without delay) or C2 (Potentially Dangerous, urgent remedial action required).
Common Fault No 4 – Figure of 8 Ring
Common Fault No 4 – Figure of 8 Ring
Two ring circuits exist and are joined through a single point. It would be impossible to complete any testing and subsequent certificates as required by wiring regulations. There is also potential to overload the junction box that joins the two rings
BS7671 Wiring Regulation Infringement
Regulation No. 643.2.1
This would be given a defect code of FI (Further Investigation required without delay) or C2 (Potentially Dangerous, urgent remedial action required).
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