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Ring final testing: rings onlyShould a lighting circuit ever be a ring?
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This test is only done where there is a ring final — and rings are for socket-outlet circuits. Lighting and cookers are radials. If you meet a lighting circuit wired as a ring, it’s not a standard circuit, and it’s worth asking why.
The ring came in after the war, when a great many homes were being built and copper was short: one 2.5 mm² circuit, out and back, on a 30 or 32 A device. It’s still installed every day, and there are millions of them in service, so you will test them.
It’s a dead test, so the circuit is isolated, and it uses the low-resistance ohmmeter. Disconnect all six conductors of the ring at the board: both lines, both neutrals, both CPCs. (On an RCBO, the neutrals come out of the RCBO.)
Guidance Note 3 · 2.6.6 · continuity of ring final circuit conductors · from p.63 On-Site Guide · Appendix H · Table H2.1 · standard socket circuits
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