Confused: RCB off, radio off, tracer detects power?!

Gautama

I’m intending to replace a double socket in the spare bedroom. As a cautious type, I go through the same routine I always do. I check the socket with my B&Q pen-type power tracer.  It bleeps like crazy, as expected. I plug a radio into the socket in question, turn it up loud, switch off the RCB, and listen to the music die. All good, I’ve definitely got the correct RCB. 

Then, I double check with my B&Q pen-type power tracer.  Tobesuretobesuretobesure! But it’s bleeping like it did before I switched the RCB off. 

I check everything again. The RCB is off. The radio is not powered, and the power drill I’ve plugged into the other side of the socket is equally dead. 

But the I brush the power tracer along the socket and the radio/drill cables, it’s bleeping away. 

What’s going on?  Is there a live wire coming from elsewhere, bypassing the RCB?

2011

The above “tracer” would not be considered a proper test instrument.

They are untrustworthy and will pick up noise

Gautama

https://www.boards.ie/discussion/comment/119622337#Comment_119622337

What would you recommend instead, a multimeter? Thanks.

kirk.

The pens can be reliable if you're used to them but as 2011 says they're not an approved method of proving dead

2011

https://www.boards.ie/discussion/comment/119622460#Comment_119622460

A good quality test meter such as a Robin, Megger or Fluke would be ideal.

kirk.

Think the method is an 'approved' voltage tester and a proving unit combination

Can't remember how you define approved here but probably something without batteries anyhow , batteries could possibly be confusing I'd say for proving dead if you're getting continuity on the supply

No harm in having the detector pen as a backup as the voltage tester requires a "reference" ,the pen doesn't

2011

https://www.boards.ie/discussion/comment/119637819#Comment_119637819

Not really sure what you mean by "approved", personally I would be confident if the tester is made by one of the manufacturers that I mentioned. No doubt these are high quality and comply with relevent standards.

There is always a reference available, sometimes this may have to be a wander lead. A "backup" is no use unless you can have 100% confidence in it.

2011

Then I saw this:

https://safeelectric.ie/safety-notice/fluke-t110-t130-and-t150-two-pole-voltage-testers-recall/

😀😄😀

kirk.

There wouldn't be many using a wander lead for proving dead if any

I'm happy enough with a 2-wire voltage tester and a live source and a voltstick for good measure

Works for me but not everybody is confident with voltsticks you have to be used to working with them

2011

https://www.boards.ie/discussion/comment/119648287#Comment_119648287

Agreed there won’t be many times a wander lead is required, but sometimes it is needed for example broken neutral and no suitable earth available.

kirk.

https://www.boards.ie/discussion/comment/119644708#Comment_119644708

I thought there was such a thing as an "approved" voltage tester for proving dead( in combination with the proving unit )

Sounds more like an advertising slogan actually 😁

Anyhow I'd always use the voltstick after checking for voltage but they'd never be recommended for obvious reasons

Padre_Pio

Any cheap multimeter rated for the voltage will work.

You just need to check there's nothing there, not measure anything with accuracy.

Could be a lighting wire, or a separate ring for an adjacent room behind that socket.

kirk.

https://news.demesne.ie/safe-isolation-procedures-proper-equipment-save-lives

- A Dedicated voltage indicator to be used

-Proving unit checks all LEDs as against power source which doesnt

-,Multimeter requires a battery and has ranges so may not be reliable