RCBO testing

[lister]

Heres a good one for you,
17th ed CU with rcbo's one of wich intermittantly trips, on inspection shows no fault and works fine how do we tell what kind of fault caused it to trip (to give us a clue where to start looking) , ie; was it a short and the mcb/ current rating side of it tripped or was it a earth fault and the rcd side of it caused tripping ( does this make sence so far),
I feel this is going to become more of a common problem ( or am i missing something obvious)

Your thoughts please chaps. (and chapesses)

 

[hughesy]

i woluld change it for a nomal mcb and see if that trips if not then we are looking at live to earth fault, if does live to neutral , or just get the megger out andtest the circuit if it test ok test what ever is used on the circuit , could be a faulty appliance.

 

[WarrenG]

Heres a good one for you,
17th ed CU with rcbo's one of wich intermittantly trips, on inspection shows no fault and works fine how do we tell what kind of fault caused it to trip (to give us a clue where to start looking) , ie; was it a short and the mcb/ current rating side of it tripped or was it a earth fault and the rcd side of it caused tripping ( does this make sence so far),
I feel this is going to become more of a common problem ( or am i missing something obvious)

Your thoughts please chaps. (and chapesses)

You haven't said what circuit it is or RCBO rating?
Checked connections?
Have you checked for a short circuit?
Checked the loading of the circuit?
Unplugged equipment still trips?
Any fridges ,washing machines on the circuit?

If all worked on initial inspection then it would appear if you have covered all other angles that it is something being plugged in or kicking in to cause the trip?

 

[lister]

FOUND IT!
cable caught by screw tip - just, (i love joiners)
good tip though, if you turn rcbo on with a live fault it turns off with a pop, with an earth leakage fault there is slight delay and it turns off with only a small click.

as an afterthought i suppose you could try and measure for any imbalance with a clamp ammeter???