Porch light trips rcd

[mbradbrook]

Hi there,

We have recently had an extension built and ever since then, when we turn on our porch light, the RCD in the consumer unit trips. I've removed the light fitting (thinking this was at fault) and installed another fitting and yet it still trips. If the bulb is removed then the RCD does not trip. Is this pointing to an earth fault on the neutral? The wiring for the light is right next to the consumer unit and the electrician has done some rewiring in the consumer unit - is it likely that he may have disturbed something?

Any help would be much appreciated!

Thanks

Matt

 

[PrenticeBoyofDerry]

The best route to take is to get an insulation resistance test done on this circuit.
It could be a few things, even moisture in the cables.

 

[westie101]

Or the more basic check where the neutral is connected, perhaps?

 

[EFLImpudence]

We have recently had an extension built and ever since then, when we turn on our porch light, the RCD in the consumer unit trips. I've removed the light fitting (thinking this was at fault) and installed another fitting and yet it still trips. If the bulb is removed then the RCD does not trip

If it were an actual fault the RCD would trip whether the lamp was in or not when switched on (unless, of course the lamp was faulty).
Because it does not I suspect the Neutral is connected to the wrong Neutral bar in the CU.

 

[sparkwright]

There could be instances where the RCD could only trip if the light is on, depending on the fault.

 

[EFLImpudence]

There could be instances where the RCD could only trip if the light is on, depending on the fault.

How obscure are you thinking?

It doesn't trip when switched on if lamp removed.

 

[RF Lighting]

If it's a borrowed neutral for example. Not that obscure.

 

[EFLImpudence]

Yes, fair enough

The wiring for the light is right next to the consumer unit

I took this to mean the cable ran from CU to light.

 

[RF Lighting]

Ok neutral in the wrong neutral bar then

 

[AdrianUK]

Or even the lamp wired between live & earth instead of live & neutral......

 

[RF Lighting]

Yep good call!