RCD Tripping when light is switch off

hutch6447 · Oct 5, 2012

Hi, right been to a 3 storey house that has been turned into offices the problem is first all the circuits are protected by 1 RCD the actual fault itself is when you switch the light on in the basement its fine when you turn it off it trips the RCD then everything is off, so I have narrowed it down to the circuit that has the fault on it an isolated it so the rest of the installation is fine.

The circuit that has the problem is a 6A Lighting circuit with 3x lighting points and 2 way switch and an emergency light the occupier said that the in house contractors changed a few lights and did something else.

The bottom switch you can turn that on/off all day and its fine the switch upstairs going on is fine and sometimes it lets you turn it off but other times you turn it off and it trips the RCD, I have tried a new switch that didnt work had a look behind the lights and it seems ok and apparently it all worked fine before the contractors change the lights so to me rules out damaged cable but will do another insulation resistance test on circuit anyway.

Anyone had this problem before? Thanks

Clive P · Oct 5, 2012

Hi,

Had a similar problem some years ago with a fluorescent fitting, fine when you turned it on ; blew the fuse ( 3036 ) when you turned it off. Turned out to be the light was one of the one's you could buy back then without a capacitor ( similar to what was used on lead /lag circuits ). Worth a check anyway,

Regards.

hutch6447 · Oct 5, 2012

Yeah narrowed it down to the switch lead going into the plug & play there was a snipped part of the cable just before it entered the plug & play but was not fully broke, probably way it was sometimes ok and other times not. Isolated switch lead and going to run a new lighting circuit for the light.

- - - Updated - - -

Yeah narrowed it down to the switch lead going into the plug & play there was a snipped part of the cable just before it entered the plug & play but was not fully broke, probably way it was sometimes ok and other times not. Isolated switch lead and going to run a new lighting circuit for the light.

vjsmarwick · Oct 5, 2012

You are right - double pole is an intermediate switch or a main switch or FSU for example
2 way is a light switch.

I think that comment is wrong I would never class an intermediate switch as a double pole all the do is connect opposite connections together in either of these patterns II X please correct me if I am wrong ?

D80 · Oct 5, 2012

An intermediate switch is anything but double pole, it functions as vjsmarwick says. A 2 way switch isn't double pole either. Light switch are generally single pole.

Intermediate switch