RCCB works for a few days, then begins tripping

[photodiarist]

I have a 63A RCCB, 30mA trip rating (LS Industrial Systems), "protecting" all circuits in our house; it was installed 5 months ago by an electrician. Until last week, there was no nuisance tripping. One morning the RCCB tripped. We reset it, and a few minutes later it tripped again. And again. No changes were made to our setup in the five months since it was installed.

To try and find a short, we switched off all circuit breakers, switched the RCCB back on, then switched the circuit breakers back on, one at a time. No matter which circuit breaker we turned on, the RCCB immediately tripped.

I was advised that the RCCB itself might have become faulty, or that it was overloaded and eventually damaged as a result. We tried replacing with another one, same model, and after one week without problems, we're now facing the exact same issue.

As a first step, should I be focusing on determining the total load, or is it more likely that there is indeed a short somewhere in the system? Are there other common faults I should check for?


Thanks in advance!

 

[bernardgreen]

If it trips no matter which single MCB is turned on then the fault is most probably a fault that has connected the NEUTRAL to earth somewhere.

Water in outside lights or sockets is a very common fault.

To find this will need a insulation resistance test on all circuits. This will involve disconnecting wires inside the consumer unit and requires the correct test equipment.

It is not really a task for an in-experienced DIYer. Even some electricians have a problem understanding the reason a circuit can trip an RCD when the MCB for that circuit is switched off.

Neutral_Earth_trip

• bernardgreen
• 16 Jan 2011
• 48

 

[photodiarist]

Excellent, thanks for such a speedy reply! I'll do my best to find a qualified electrician who can carry out the insulation test here.

If the RCCB was not tripping for a week or so, but now is tripping due to a neutral-earth fault, would that imply the possibility that the neutral and earth are connected for a while, then no longer connected for a while? Perhaps because of presence/lack of water or other conductive matter on different days?

Thanks again!
Chris

 

[bernardgreen]

Neutral earth faults due to water do come and go as the water dries out.

Whether the RCD trips depends on how conductive the fault is and how much current is being used on the non faulty circuits.

 

[17thman]

warer ingress into fittings can be the source of an intermittant neutral to earth fault. Ie conductivity can vary. Is the much rain in iraq at the moment?

 

[photodiarist]

Thanks a million! I'll try to remember to post an update here once we figure it out.

 

[photodiarist]

17thman, we did have a LOT of rain the past two months. Most recently was last week. We also have a lot of dust around, and it gets into everything; it could also be possible that ionized dust particles increase the conductivity of any water present.

Thanks!