RCCB tripping but no MCBs have tripped.

[RDB85]

I’ve a Square D Split load RCCB board that has a strange issue. The RCCB trips and none of the MCBs seem to trip.

The only thing that has recently been done is replacing the sockets and switches. I’ve tested each socket with a socket tester and it was showing as correct on all sockets. I only had to extend two which I brought up in a a previous thread and used some 5 way Wago connectors.

Any ideas what it could be? As none of the MCBs have tripped. It only seems to happen of a night.

 

[Dustydazzler]

N-E touching somewhere ?

 

[DPG]

If it's an earth fault then the RCD will trip. The MCBs will only trip on overload/short.

 

[snowhead]

It'll be a Neutral trapped behind a socket faceplate, maybe the screw trapping it and touching earth or a Neutral as it comes through into the box touching.

Is one of the replaced sockets only used at night?

 

[RDB85]

It'll be a Neutral trapped behind a socket faceplate, maybe the screw trapping it and touching earth or a Neutral as it comes through into the box touching.

Is one of the replaced sockets only used at night?

No all the sockets have peripherals plugging into it them. I will check each socket to make sure that nothing is touching.

 

[HappyHippyDad]

As the others have said, it is a Neutral to earth fault. This will trip an RCCB but not an MCB.
You now need to start splitting the faulty circuit and IR testing to track down the fault.
I guess there is a small chance it could also be lots of natural earth leakage from lots of electronic equipment plugged in and left on over night (updating).

 

[DPG]

As the others have said, it is a Neutral to earth fault. This will trip an RCCB but not an MCB.
You now need to start splitting the faulty circuit and IR testing to track down the fault.
I guess there is a chance it could also be lots of natural earth leakage from lots of electronic equipment plugged in and left on over night (updating).

I don't think the OP has an MFT yet.

 

[HappyHippyDad]

I don't think the OP has an MFT yet.

Oh yes. I remember the other thread now ?

 

[Intoelectrics]

If the problem has only started to happen since the circuit has been altered then its most likely something like a trapped cable as Snowhead suggested (this is very common), or something existing has been disturbed. I'd start by visually checking all the items that have been replaced (remove sockets and check the conductors for damage). The tester you have used will not identify the fault that's tripping the rccb.

 

[RDB85]

Thanks for the help and advice. I will check the sockets when I get home from work. If I did borrow a MFT could I test each of the sockets?

 

[Dustydazzler]

First things is unplug everything and I mean everything then drop every socket off and look for anything obvious like a pinched N

If you are happy that everything looks sound then put the socket fronts back on then turn the power back on leaving everything unplugged

Nothing should trip , If it does trip out then you have a wiring issue which will require IR testing

If it stays on okay then one by one plug things back in and if nothing trips then all good if you plug a certain item in and it suddenly trips you know what it is

 

[DPG]

First things is unplug everything and I mean everything then drop every socket off and look for anything obvious like a pinched N

If you are happy that everything looks sound then put the socket fronts back on then turn the power back on leaving everything unplugged

Nothing should trip , If it does trip out then you have a wiring issue which will require IR testing

If it stays on okay then one by one plug things back in and if nothing trips then all good if you plug a certain item in and it suddenly trips you know what it is

Might be worth him checking N-E resistance before he disturbs anything. Be nice to see the fault on the meter.

 

[Dustydazzler]

Might be worth him checking N-E resistance before he disturbs anything. Be nice to see the fault on the meter.

Agree you could unplug everything and IR test N-E at the consumer unit

 

[RDB85]

I need to see if I can get hold of a MFT, as it would come in handy, especially for this. I will check what @Dustydazzler said to do first.

 

[Dustydazzler]

You will need a decent MFT as you progress and more importantly know how to use it effectively to find potential wiring faults

Fault finding can be a pain but with experience you can usually break it down quickly to one cable or one room etc