mcb on lights intermittent tripping

[johnnymacc]

Merry xmas to all,
i have a problem at an old ladys house,her lights keep tripping out so went to have a look today.The mcb's are old mem push button ones bs3871, but they are very intermittent to trip lights can be on for 20 mins,10,5 etc then they trip for no apparent reason, had all lights on,trip, tried individual sequences of turning off etc they stay on then trip out of the blue.Pulled the breaker and the red button stayed in then i got it out after pushing the white button in loads of times,then it stuck in again after i tripped it etc.
I think cos its so random that possibly the breaker is faulty does anyone have any experience of this type of fault and can you give us your thoughts.
Cheers,
John.

 

[wallyanker]

Changed a MEM RCBO for a friend just before Christmas, same kind of thing, tripping for now apparent reason. This was on a ring circuit, and even tripped when nothing was plugged in. Everything working fine now :smile5:

 

[Specialist]

Used to hate those damn things, they seem to just go all of a sudden & that's the end of them.

 

[Guest123]

Have you done any testing at all, to eliminate any of the usual suspects.....

 

[johnnymacc]

No lenny reason being they stay on for so long then trip i'd been there for 20 odd minutes before they first then varying times after,i would have thought if a fault on the circuit or accessories they would pop a lot quicker,also thought i would quiz you lot before i start stripping the board and testing

 

[telectrix]

i'd replace the breaker with a plug-in 60898. 9/10 , that's the problem.

 

[goldie]

What about high resistance fault? Ive seen many faults that take time to trip eg (squashed cable, perished vulcanised rubber cables and my favourite was the mouse with a burnt mouth laying next to a cable. Not overload then? or a loose connection which can demand more current. Id do a visual on the connections and do a insulation resistance test first.