Circuit Fault Finding

[AdamCH]

I have a Wylex CU with RCBOs + 2 RCDs with three circuits on each RCD.

One of the circuits on one of the RCDs is an external socket - just a double socket on the end of a radial with a DP switch in the kitchen to switch it one/off.

Fault I have is that any load on the ext socket causes both RCDs to trip - but not the RCBOs.

So far I've tried:
- Rigging up a temp socket to see it it's the socket itself.
- Trying a multimeter on every combination on everything I can think of.
- Replacing the DP switch with a socket so that it's just a wire from the CU to a socket.

The RCDs trip as soon as the two RCDs are closed even if the Ext Socket circuit is the only MCB closed.

If just the one RCD is closed then no trip. As soon as the other one is closed both trip even if all the MCBs on the second ore off.

Nothing trips on any circuit until there is a draw on the ext socket circuit but both RCDs trip immediately if there is a draw.

Am I missing something obvious?

 

[Jackrae]

Could be that the neutral of the external socket is on one RCD circuit whilst the line is on the other RCD. Any current drawn causes an imbalance on both RCDs.

 

[Robin0577]

Sounds as if you have a misplaced neutral, i.e. the live supply to the socket comes from one RCD and the neutral from the other. Any load on the socket and both RCDs will detect an imbalance and trip.

damn! too late.

 

[AdamCH]

Cheers gents. I think you may be right. Looks like I've used the neutral bar from the other RCD.

 

[Taylortwocities]

So, it has never worked then?

And a new circuit. Notifiable to your local authority.

 

[Chri5]

Cheers gents. I think you may be right. Looks like I've used the neutral bar from the other RCD.

So why make the first post sound like its a circuit that worked and had gone faulty?

It's not an in service fault, and could never have worked. Next time please just say "I've added a new circuit and ..."

Easy fault to make if you don't know what your doing.

 

[AdamCH]

So why make the first post sound like its a circuit that worked and had gone faulty?

It's not an in service fault, and could never have worked. Next time please just say "I've added a new circuit and ..."

Easy fault to make if you don't know what your doing.

You standing in for BAS this evening?

 

[ban-all-sheds]

So why make the first post sound like its a circuit that worked and had gone faulty?

It's not an in service fault, and could never have worked. Next time please just say "I've added a new circuit and ..."

Easy fault to make if you don't know what your doing.