lights tripping

[Innominata]

Hi guys,
I have been called out to a fault on a 10 year old flat.The lighting MCB has tripped and will not reset.The flat has 2 pendants in the bedrooms then the hall,bathrom and lounge /diner have about 30 low voltage downlights.I have tried disconnecting the majority of these and then reseting the MCB but there is a short somewhere as it will not reset.Any ideas?do the 12v transformers give faults of this type.Thanks

 

[Benny_Boy]

Any metallic faceplates or fittings?

 

[rwb]

have you made sure the MCB isn't knackered?

 

[Innominata]

Hi Guys,
Thanks for your replies.The light switches are the metal type but they have all been removed and checked.I have only assumed at this stage that the MCB is not faulty because there is a large flash when trying to reset it,indicating a short.I have not disconnected every transformer as yet - need more time on the job.I am hoping that it is not a wiring fault as the ceiling void is only about a foot high and contains air-con pipework.

 

[ukpablo]

ask them if they have done any diy lately? what has changed in the house since the fault occured?
might be missing something obvious?