UK Upstairs light always on

[Macsamillion]

Coupling between a permanent L and a switched L, enough to tickle an LED lamp into a reasonable glow when the light is supposedly switched off. Put in an incandescent lamp and you won't have enough coupling to see any visible light.

Think this is what I done and proved what you are saying. I suppose my question is around the safety. If the light is always sitting at with voltage on it whether it's lit or not

 

[SJD]

The light won't be sitting at 190V or whatever, it will be pulled down to more or less 0V by the load of the lamp.

 

[Macsamillion]

If changing a consumer unit in an emergency situation that is what I do and in my view it's the best way to interface with very old cable. Screw terminals just destroy it. Of course it still needs replacing as soon as possible, but sometimes changing the CU is even more urgent, e.g. if there's no front cover or live parts are exposed.

LED bulbs can present challenges; induced voltage from other cables can cause interesting things to happen to LED bulbs, especially cheaper ones, including staying on, flashing, or remaining dim.
Normally I'd suggest swapping the two strapper wires over, but on this one I really wouldn't touch it again, it's not worth it!

OK thanks. Seems like good advice. Do you think there is still a chance switches are still wired wrongly that I should switch the strapper. I belled them out, marked and grouped the wires with circuit 1 and 2.

 

[timhoward]

OK thanks. Seems like good advice. Do you think there is still a chance switches are still wired wrongly that I should switch the strapper. I belled them out, marked and grouped the wires with circuit 1 and 2.

I actually wasn't suggesting they were wired wrongly, and from what you've posted I don't think it's likely you got it wrong, especially if the light behaves correctly with a normal bulb.
Swapping them over would just be a throw of the dice to change the induced voltage some of the time. But I wouldn't go back inside unless a very fat cheque was being waved in my face!

 

[brianmoooore]

with a LED lamp, it's not unusual for it to glow dimly when off, as a result of capacitive coupling between the live and switched live. With 2 way switching, there's likely to more chance for capacitive coupling, because there's likely to be more switched live and permanent live running alongside each other.
In your case, the problem is likely to be good old fashioned leakage, because the insulation of the wires is breaking down.
A 500V IR test between the wires would confirm, but as said above, there really shouldn't be VIR cable still in use.

 

[Macsamillion]

with a LED lamp, it's not unusual for it to glow dimly when off, as a result of capacitive coupling between the live and switched live. With 2 way switching, there's likely to more chance for capacitive coupling, because there's likely to be more switched live and permanent live running alongside each other.
In your case, the problem is likely to be good old fashioned leakage, because the insulation of the wires is breaking down.
A 500V IR test between the wires would confirm, but as said above, there really shouldn't be VIR cable still in use.

Thanks. It's scary to think that the voltage is induced, but this is what I have come to believe through checks. I did try to check IR between conduit wires but my tester let me down before I got going.

 

[telectrix]

but my tester let me down before I got going.

sack him. plenty mores parks out there need work.

 

[ipf]

Yes, kitchen and bathrooms have been renovated and new circuits created so I don't understand why they didn't use 6A MCB.

Seems like our old friends the 'kitchen and bathroom fitters' have been up to their usual tricks.......... ideal for adding to an ageing VIR system and making things even worse.
After multiple modifications it sounds like a total rip out, to me.
A full EICR at least.