Continuity of Ring Final Circuit Conductors
The objective of this dead test is to ensure that all ring circuit conductors are continuous throughout the ring, with no breaks and no interconnections and also that all connections are electrically and mechanically sound. This test also verifies the polarity of each socket outlet.
The test is made using a continuity tester as follows…
Firstly, disconnect and separate all the conductors of both legs of the ring at the consumer unit. Then complete the following steps.
Step 1:
At the consumer unit measure the end to end resistance of the two line conductors (r1), then the two neutral conductors (rn) and the two protective conductors (r2).
Note : If there are no breaks in the ring the end to end line and neutral conductor readings should be approximately the same (i.e. within 0.05Ω) and the protective conductor reading will be 1.67 times larger if a 2.5/1.5 mm T&E cable is used.
Record the end to end results for the ring circuit on the schedule of test results as r1, rn, r2.
Step 2:
Join the opposite legs of the line and neutral conductors together and take a reading between the line and neutral at every socket outlet on the ring circuit.
The measured readings should be substantially the same at all L-N points on the ring (except on a spur) and should have a value of approximately half the line (r1) or neutral (rn) readings measured in step 1, or approximately (r1+rn)/4.
* Sockets connected as a spur will have a slightly higher value of resistance because they are fed by only one cable, while each socket on the ring is fed by two cables.
Step 3:
Disconnect the previous line and neutral connections of step 2 and this time join the opposite line and CPCs together.
A reading should then be taken between line and earth at every socket outlet on the ring.
The readings should be substantially the same at each socket outlet and this value is R1 + R2 for the ring final circuit. Record the results on the schedule of test results as the circuit’s R1+R2 value.
Again, a way of checking your readings is that the value of R1 + R2 should be equal to (r1 + r2)/4, where r1 and r2 are the end to end readings from step 1 of this test sequence.
* A failure to get a measurement at any socket outlet when completing Steps 2 or 3 is likely to be caused by a cross connection, i.e with the conductors being in the wrong terminal at back of the socket outlet.
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