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Toot

Written by groff on 2024-12-05 at 16:37

There is absolutely no way this lighting circuit passed insulation testing when the fuseboard was replaced 4 years ago. There's been a screw through this cable for at least 15 years. No wonder they had random nuisance tripping. Amazingly the RCBO held most of the time.

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Descendants

Written by tautology on 2024-12-05 at 16:49

@geoffl How much of the inner wire has it clipped though? Though be careful cutting it open to see. I still have the scar from when I tried to do it haphazardly with a penknife!

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Written by groff on 2024-12-05 at 17:56

@tautology Enough that an insulation test n-pe caused the MFT to screech and the screen to flash red while showing 0.01MΩ. Being the feed to the last light on the upstairs ring help add some resistance.

I think the temperature in the loft caused just enough movement that that the RCBO held most of the time. They've been restetting it on a regular basis.

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Written by tautology on 2024-12-05 at 20:47

@geoffl I had similar weirdness when I got a smart meter fitted. When it came up the upstairs lighting RCBO just kept tripping under load, even from other circuits.

Eventually I managed to get a spark in who found out it was a neutral-earth short in the metal lamp fitting in the spare room. The hasn't been touched in the 4 years we've been in the house and has been like that since we had the CU replaced.

No idea why it decided to start tripping then, but at least it was easy to fix.

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Written by groff on 2024-12-06 at 10:41

@tautology Earth-neutral faults can sometimes exhibit in really odd ways. They said this one seemed to trip when different lights were switched on. Possibly related to total load, maybe 🤷‍♀️

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Written by Stewart Russell on 2024-12-08 at 13:55

@geoffl looks like the standard practice in $COUNTRY of securing cables along walls using tacks through the centre of the insulation

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