Volt stick gives "false" reading

[KeenPensioner]

I'm not an electrician but have worked as a mate and know my limitations. To fit a new light in a bedroom (loop at ceiling rose), I isolated the supply at the CU and tested supply at ceiling rose with Fluke T150, obviously no voltage detected between L and N or L and CPC (safe isolation - near enough, I was the only person in the house). Out of interest I also tested using a Kewtech Duo volt stick and got a "reading" from the Neutral. I realise that only the live conductor is isolated at the MCB so was this "back feed", if so can someone explain please?

 

[bill01803]

Throw it away they are uselessssss

 

[Andy5678]

If you rub a volt stick on your jumper it lights up.
Follow proper safe isolation procedures using the correct tools.

 

[Grant webber]

Did you have neutrals separated at the time.

 

[snowhead]

Induction from an adjacent cable somewhere possibly.

Voltsticks are usefull sometimes, but not to be relied on for safe isolation.

 

[KeenPensioner]

Thanks for your replies. I understand what safe isolation is and voltsticks are only an indication and never to be used to assume circuit is dead. As I said I used a Fluke T150 to test the circuit was actually safe to work on.

 

[telectrix]

Throw it away they are uselessssss

they do have their uses. limited as maybe.

 

[davesparks]

Duo volt stick and got a "reading" from the Neutral. I realise that only the live conductor is isolated at the MCB so was this "back feed", if so can someone explain please?

If it was a backfeed then it would have shown up when you tested it properly, and the lighting circuit wouldn't have worked properly in the first place.

This will most likely have been due to capacitive coupling, though this normally happens on disconnected cables. Did you check the polarity of the supply at any point?

 

[KeenPensioner]

If it was a backfeed then it would have shown up when you tested it properly, and the lighting circuit wouldn't have worked properly in the first place.

This will most likely have been due to capacitive coupling, though this normally happens on disconnected cables. Did you check the polarity of the supply at any point?

Thanks for taking the time to reply. I did test between L/N, L/E and N/CPC and got the expected results. I'll need to think this through.

 

[davesparks]

Thanks for taking the time to reply. I did test between L/N, L/E and N/CPC and got the expected results. I'll need to think this through.

Do you mean you tested for polarity and it was ok or that you tested for isolation?

 

[KeenPensioner]

Do you mean you tested for polarity and it was ok or that you tested for isolation?

Thanks for taking the time to reply. I isolated the MCB at the CU and tested for isolation at the ceiling rose (L/N, L/cpc, N/cpc) so no, I didn't test for polarity at the ceiling rose.