Editing Ring circuit (section)

==Criticism==
The ring final circuit concept has been criticized in a number of ways compared to radials, and some of these concerns could explain the lack of widespread adoption outside the United Kingdom.

===Fault conditions are not apparent when in use===
Ring circuits may continue to operate without the user being aware of any problem if there are certain types of fault condition or installation errors. This gives both robustness against failure and a potential for danger.<ref name="emc">Roger Lovegrove: EMC, April 2006</ref><ref name="lovegrove">Roger Lovegrove: Ring circuits – the disadvantages. [http://www.theiet.org/resources/wiring-regulations/ringcir.cfm?type=zip Presentation papers from a public meeting to discuss the issue of ring circuits], [[The Institution of Engineering and Technology|IET]], London, October 2007 (PDF in ZIP)</ref>
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! Fault condition !! Observations
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*Part of the ring missing or disconnected can result in 2.5&nbsp;mm<sup>2</sup> cables running above rated current without this being obvious to the user.<ref>P Knowles: Ring main lining. EMC, February 2007</ref>
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* Radials with a broken connection will not function (if L or N broken), or will function with no safety earth connection (if just E broken).
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*Inadvertent cross connection between two 32&nbsp;A rings means that the fault current protection reaches 64&nbsp;A and the required fault disconnection times are violated grossly.
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* Testing at installation can prevent this, and a similar problem applies to cross-connected radial circuits although would trip residual current protection devices if fitted to either or both radials as would be to current standards in most jurisdictions.
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*Spur circuits attached to the ring can overheat if not fused at the spur-point (i.e., if a BS 5733 or similar fused spur is not used)
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* This is almost certainly a breach of the appropriate electrical standards (e.g. BS 7671 in the UK): the maximum load on any unfused spur is a single fitting.
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===Safety tests are complex===
At least one author claims that testing ring circuits may take 5–6 times longer than testing radial circuits.<ref name="lovegrove"/> The installation tests required for the safe operation of a ring circuit are  more time-consuming than those for a radial circuit, and DIY installers or electricians qualified in other countries may not be familiar with them.

===Load balance required===
Regulation 433-02-04 of [[BS 7671]] requires that the installed load must be distributed around the ring such that no part of the cable exceeds its rated capacity. In some cases this requirement is difficult to guarantee, and may be largely ignored in practice, as loads are often co-located (e.g., washing machine, tumble dryer, dish washer all next to kitchen sink) at a point not necessarily near the centre of the ring.<ref name="lovegrove"/> However, the fact that the cable rating is 67% that of the circuit breaker, not 50%, means that a ring has to be significantly out of balance to cause a problem.

In a ring circuit, if any poor joint causes a high resistance on one branch of the ring, current will be unevenly distributed, possibly overloading the remaining conductor of the ring.