Downlights Tripping Breaker

[mcummins7]

I've got a circuit tripping out the breaker (not the RCD it's on) when the lights in the bathroom are turned off only. The lights in the bathroom are six downlights on one switch.

Is this a problem with downlights? Is it common?

Oh, BTW it's not the switch as I've replaced it.

 

[eagleeye]

Faulty breaker by the sounds of it. are the light ELV or mains ?

 

[mcummins7]

The lights are 240V.

Any other ideas as I did change out the breaker but same!

 

[Had8Lives]

Dodgy bulb?

 

[Had8Lives]

My Dad just mentioned it could be something do do with a two way switch, switching the Live to neutral when you turn off the switch. That would explain the RCD not tripping, as there is no leakage, just a short circuit.

 

[malcolmsanford]

I would have thought that on a short circuit the RCD would have poped before the MCB as the RCD is providing you the fault protection. I have a feeling that RCD is faulty, of stuck, have you tried the functional test on the button?

 

[davelerave]

sound's bizarre

is it a 1-way switch?

 

[mcummins7]

It's a new one way pull switch in the bathroom that I replaced thinking it could have been the switch in the first place!

The RCD is testing fine.

 

[mcummins7]

Sorted problem. Looks like the circuit was part of a lighting ring circuit, or a line/neg taken from another circuit. I guessed this as the lights wouldn't trip if the other breaker was off. Once I ran both lighting circuits from the same breaker - no problem. There were six lighting circuits in all.