Ask a tradesman


Live light connection still detected with a voltage detector


Ground floor lights on circuit 1.
First floor lights on circuit 2.
Second floor and cellar lights on circuit 3.

I wanted to change a light switch on second floor landing so I switched off circuit 3 at the consumer unit. I then detected a live connection on the cables for the light switch to be changed when tested with a voltage detector. Once I switched off circuit 2, the live connection was no longer detected from the cables for the light switch to be changed when tested with a voltage detector again.

Is it not the case no live connection should be detected on the cables part of a circuit that was switched off at the consumer unit? What could be wrong here?


5 Answers from MyBuilder Electricians

Best Answer

If your talking about using a volt-stick (pen like tester) then these will pick up on the capacitive coupling effect of induced voltage from adjacent live cables! so even if the circuit was switched off for the light switch you were working on, an adjacent live cable could have induced a small voltage into the dead/isolated cable. This is the very reason that these voltage detectors (voltsticks) are considered dangerous and are not an approved electrical test device for proving live or dead. To test if a circuit is live or dead a voltage indicator as detailed in the HSE leaflet HSG38 must be used.


Answered 28th May 2015

Is it a voltage detector pen thingy that glows? Should be banned those things. I suspect the switching is 2way/intermediate. Why not save yourself the hassle get a sparky in who knows safe isolation etc to do it.


Answered 28th May 2015

Does the light switch on that landing operate the light on the first floor landing i.e. 2 way switching. This would be normal and is why safe isolation procedures should always be carried out and all electrical work carried out by a competent person. i.e with the training and or knowledge to carry out the work to the correct standard without danger to self or others.


Answered 28th May 2015

If in doubt get a qualified sparky out. Enough said


Answered 29th May 2015

this is normal in a suituaton with 2 way switching that the light fitting be fed for supply circuit for a differant floor

our best advice is to employ a registers competent contractor it will only cost you between £20-£50

be safe your life is worth more than a couple of £20 notes


Answered 1st Jun 2015

Post your job to find high quality tradesmen and get free quotes

Can’t find an answer? Ask a new question

Question Categories