32volts present at light fitting when it's switched off!

[Tim Brennan]

i have a light fitting that 32volts across it when it is switched off. I have changed the switch, the rose, I've done insulation resistance on the cable to the switch, which is fine.
Not sure where the voltage is coming from and why only 32volts. I assuming that it must be cable insulation fault even though it metered at >299mohms.
I decided to run new cable in to that section of the circuit.
Any ideas?

 

[SparkyChick]

32v across what? L-N, L-E, N-E?

 

[Tim Brennan]

Oh sorry, across the L-N of the pendent, so when it's off it still glows.

 

[SparkyChick]

What kind of switch? What kind of lamp?

 

[Wilko]

Well if the light is still glowing when you've switched it off it's still got supply. Did this just start? Does it go off when you safe isolated that circuit at the CU?

 

[Tim Brennan]

Single way light switch, standard rose and pendent, both brand new MK fittings

 

[SparkyChick]

I'm asking that because I've seen that before with a touch activated dimmer and an LED lamp. The touch dimmer requires a small current to operate the electronics, so it leaks through and there is enough juice to make an LED lamp glow.

 

[Tim Brennan]

No it's been a issue for a while, finally got round to sorting it out as part of a partial rewire, it does go off with safe isolation at the CU

 

[SparkyChick]

Ok, I'd safely isolate, disconnect the switch cable and check IR on that cable with the switch off. Could be a high resistance fault on the switch cable itself. I'd rule that out first. Or have you replace the switch cable?

 

[Wilko]

No it's been a issue for a while, finally got round to sorting it out as part of a partial rewire, it does go off with safe isolation at the CU

Ok, then my thought is the 30V is coming via the switch somehow (as per SC suggestion in #7) or you've got an additional connection to the lamp's switched live thats bypassing the switch. I've seen allsorts with home brewed two way switching and the next light in the circuit etc. If its simple enough perhaps try removing all other lamps on this circuit and see if the 30V disappears ?

 

[Tim Brennan]

Well, before I replaced the cables I did IR test on them, they all came up ok. Replaced them anyway. Now everything is back as it should be. But intriguing as to what was causing it, I inspected the insulation on the old cable, looked fine to me. Maybe I missed something.

 

[SparkyChick]

Any chance of a picture of the inside of the rose and switch? I'm not doubting what you're saying, I just want to see them.

 

[Octopus]

Induced voltage.

Turn off the other circuits and it will disappear

 

[Wilko]

Induced voltage.

Turn off the other circuits and it will disappear

Yes - Tim what kind of lamp is it that is glowing please (from your post #3)

 

[Octopus]

^^ my money is on an led lamp

 

[Tim Brennan]

not led, standard 60w bulb

 

[westward10]

Does it do this with all the other circuits isolated.

 

[Midwest]

Could be live & neutral cross connected between pendants loop in's/out's. When one light is turned on, presents voltage at dimmed light's neutral, if you get my drift.

 

[Tim Brennan]

To be honest, I never tried that, but I have found a number of scary things, the guy that was here before me must have been a diy enthusiast. I've found a single socket part screwed to a back box under the floorboards in one bedroom acting as a junction box! A borrowed neutral on the landing two way lights, and where they had moved the CU on the previous kitchen change, they had extended all the cables using chocblocks wrapped in tape, stuffed them into a hole in the wall, filled it with plaster and tiled over it. I found that little beauty when I took the tiles of to refit the kitchen, and noticed a line cable just showing where I pulled the tile off.

 

[Octopus]

^^nothing surprises me when doing kitchen refits any more...... I won't give a firm price until the old units are out....

Earlier this week I was working on a bathroom refurb...

Taking a light off the wall - 2 cables - 1 x 2 core and 1 T&E.. the 2 core supplied the live off circuit 2, the T&E supplied the neutral from circuit 3, and neither run in a safe zone.

And the icing on the cake - neither circuit had an earth.... just shows the importance of safe isolation