Odd lighting fault - all cables live at switch....

19 Jan 2005
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United Kingdom

Went to job at end of day today. Client reported lighting mcb tripping. 1 fitting had been leaked on, and 2 others she said had been flickering on and off. Just one lighting circuit. Tested to find dead short between p and cpc. Will need to go back and investigate further.

HOWEVER, the 2 flickery lights were on 2 gang switch and when testing I got 230 on all cables (lives and switched lives). This was confirmed at the lights, which were 'on' even if the switch was operated. The client tells me that the lights have worked before OK. The 2 gang switch appeared to have a live link and one of the gangs is two way. Neutrals looped at lights. Switch operating OK

Any ideas what could be making the switch lives live? All other lights operated OK. Could it be linked to the p-cpc fault? Cables run in a mixture of steel conduit and plastic trunking.

Ideas/thought's gratefully received

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If the supply is loop in, probably something bridging from loop to switched live, such as carbon tracking following a leak ;)
Hi guys

Thanks for suggestions. Ban - 2 way switching is singles not t and e, sorry should have said.

Hmm, I get the idea RF, but for both lights to have perm live s/l's seems a bit too much of a co-incidence?

Back this avo to do more investigation..

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Just an update - in case anyone is sad enough to be following this post...

Did full testing today, managed to isolate the cables with p-cpc dead short and when I re-energised the non faulty part of the circuit, it was the two 'flickery' lights that were knocked out. Not sure what was going on at the switch, but frankly life's too short so will rewire the sections that are faulty.

IR readings p-cpc around 25MOhms on rest of circuit, and noticed some rust in the conduit, so might be back in the future....

Thanks again

noticed some rust in the conduit, so might be back in the future

I hope theres a separate CPC, and not just relying on the conduit?
Yes adam there is, although conduit earthed as well, which I think was causing the p-cpc fault


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