3-gang switch, non-RCD circuit tripping RCD, etc.

[xAlex]

Untitled

• xAlex
• 26 Nov 2008
• 1

Morning all,

I tried to fit 3 wall lights last night to existing cables. Lights have not been connected since I moved in.
A 3-gang switch controls 2 ceiling light and 3 wall lights. The ceiling lights each have their own switch so I assume the 3rd controls the 3 wall-lights. 2 lights are joined in parallel and 1 direct to the switch (so 2 cables into the switch for these 2 lights).
The lights are on a non-RCD circuit but...
When the L/N ends of a wall light touched (when dead), the RCD tripped. I could not re-set the RCD until I separated all of the cable-ends at the 3-gang switch.
The 2nd issue is that I am reading 3 volts between the galv capping of one of the lights and the Neutral.
I append a pic of the switch. I only had a short while to examine the cables last night but it only appears that there is 1 live feed. 3 Neutrals were joined in a block. 1 Neutral snipped off. Earths twisted together. A real mess. Do RCD's have a time delay when tripped, before resetting?

Any ideas re 3V capping-Neutral?
Any ideas why lights would trip RCD
How to rectify?

Thanks,

Alex

 

[Spark123]

One guess is there is an a twin and earth in there from the socket circuit - hopefully from a fused spur unit (but wouldn't be the first time I have seen it without which is wrong!)
What are the chances the cables run all over the place too (not in safe zones)? Could be a damaged cable with a nail or or could be you are joining two separate circuits together i.e. linking the lighting circuit across to the wall lights in the back of the switch.
Need grommets in there and some sleeve on the earths too.

RCDs don't have a time delay before resetting - if they won't reset it means the fault is still there (or the RCD is goosed which yours isn't by the sounds of it.)
You also seem to be confused by the black wires in there - some of them may be neutrals (probably the ones in the block joined together) however the other one is more likely a switched live and if so should have a red sleeve but often left off.

 

[xAlex]

...Thanks Spark. There is a separate MCB for the lights (not on the RCD way). You are right though, the runs are all over the place.