RCBO Problem

[maltaron]

My lighting circuit is protected by a 6 amp RCBO. I have, amongst the normal house lights, a 60 watt pendant in the porch and 2x50 watt halogen downlights switched together in the kitchen. The problem: when I switch the porch light on at around 9 p.m. for the dog, the RCBO trips. I reset and try the halogens and the RCBO trips. No other lights cause the problem. So, I decide to sort the problem the next morning. Morning comes, try porch light, all OK, try halogens, OK. Repeat the following evening, RCBO trips. So it appears that the fault is only there in the evening. I have reproduced the evening lounge lights setup in the day and the problem is not there. Any bright ideas? (excuse the pun)

TIA

 

[Adam_151]

Possibly moisture related

 

[riveralt]

As well as moisture related it could also be a build up of earth leakage at other points on the circuit culumating in the RCBO tripping when one of these lights are switched on.

Next time try turning all the lights on that circuit of and turn on the one you think is causing the problem. Just to see if it trips.

Out of general interest how do you determine whether the RCD or MCB (or both) side of the RCBO trips?