15 volts on lighting circuit with circuit turned off?

[230volt]

Hi guys,

Whilst carrying out an ECR yesterday I was doing an r1r2 test on a lighting circuit (downlights) in a new extension and noticed that I was getting 15v L-N and 15v L-E with the circuit de-energised.

To cut a long story short after some investigation, I noticed that the 15v was coming from the existing main ground floor lighting circuit, which is on a completely different circuit (on a separate consumer unit). And the 15v only appears when the existing downlights s/l is energised.

The only time the 2 x separate circuits cross path to my knowledge is via the 3 x light switches via 3 cores, as the other set of downlight are on the other side of the RSJ. There are no neutrals in the switches, and even when I disconnected the main feed on the problematic circuit I'm still getting LN-LE voltage without them being connected.

Any ideas?

 

[telectrix]

might be an idea to recheck with an analogue meter to eliminate the possibility of stray ghost voltages caused by cables of different circuits being in close proximity.

 

[230volt]

I did think of it being a ghost voltage and you may be right.
But would I be getting L-N L-E readings (15v) with the neutral and earth disconnected on the suspect circuit?

 

[telectrix]

if you have the N and E dissed, they could be floating.

 

[230volt]

Ok thanks. Makes sense.

Anyone got an analogue meter I can borrow? haha

 

[Wilko]

Hi - yes, I vote for floating / induction too. If you have a 1k resistor (for example) put it across the 15v and hopefully it collapses to zero. Perhaps run insulation test between the 2 Ls? Maybe they are not so independent? Cheers, David

 

[230volt]

Thanks