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Induced voltage or dodgy wiring?

A domestic Flat has 1 * 6A lighting cct, 1 * 32 RFC, and 1 * Ckr cct. Supply is TN-S.

A 2G plate switch in the kitchen (which has a flat roof / attic space above other rooms) is fed by a twin and earth - one core feeds the commons of the two switches, while on one switch the other core supplies two downlights. A sheathed single core from the second switch feeds two wall lights. Each downlight is fed by a single T&E. One wall light has a T&E loop in / loop on, the other light just a T&E in. All wiring is concealed in walls.

At the downlights, 244V (L-N) appears with the switch turned on (using a MFT). However, with the switch off, approx. 23V still shows. With the switch off and a lamp installed in either fitting, while testing at the other, V=0. The 23V does not appear at the wall lights.

With the CB’s turned off on the other ccts at the CU, the 23V remained, as when the N’s were disconnected also. V=0 with the lighting CB off.

L/N – E IR test with all switches on is > 300MOhms.

Before hunting about for things like dodgy connections in JB’s in a grotty/dirty loft space, any ideas what may be going on please?


Thanks


F
Parents
  • I agree with Andy.


    I first noticed this when testing a 2-way lighting circuit. As expected, I got 230 V for the Zs test, but when I went to change over both switches, I noticed that the voltage did not drop to nil. IIRC, it was about 20 - 30 V.


    That had me puzzled, so I tried it at home. Similar result. Then I put a multimeter in the circuit and with the switch off, I got about 1 mA.


    So off does not mean 100% off. ?
Reply
  • I agree with Andy.


    I first noticed this when testing a 2-way lighting circuit. As expected, I got 230 V for the Zs test, but when I went to change over both switches, I noticed that the voltage did not drop to nil. IIRC, it was about 20 - 30 V.


    That had me puzzled, so I tried it at home. Similar result. Then I put a multimeter in the circuit and with the switch off, I got about 1 mA.


    So off does not mean 100% off. ?
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