Rcd tripping

[matt12321]

Quick question to all

ive got and Rcd that trips out randomly through the day. Split board and the Rcd covers shower and sockets. With the shower breaker off an the other 4 socket breakers on, the Rcd will trip when u plug a tester in. However when u turn them all off a test each circuit individually the Rcd doesn't trip. Found the circuit it trips on but it only trips with all breakers on. Megger want even test as it trips before a reading is given


any ideas thanks

 

[telectrix]

dead testing procedures to start with. then leakage tests.

 

[matt12321]

Yeh cheers. Just found it weird why it only trips when all circuits are on but not individually

 

[Marvo]

As Tel says, do the tests. I wouldn't worry about which combination of MCB's being on causes the tripping, it will just sidetrack you. RCD's need a load going through them to allow then to trip, it may be some of the circuits have little or no load. Also tripping an MCB doesn't clear an insulation/earth leakage fault because only the live leg is switched so the RCD still has the circuit neutral connected to it.

 

[amlu]

small earth leakage on couple of circuits, it adds up when powered.

 

[matt12321]

Thanks marvo. Should have also mentioned the Mcb's don't trip just Rcd

 

[Deleted member 9648]

Quick question to all

ive got and Rcd that trips out randomly through the day. Split board and the Rcd covers shower and sockets. With the shower breaker off an the other 4 socket breakers on, the Rcd will trip when u plug a tester in. However when u turn them all off a test each circuit individually the Rcd doesn't trip. Found the circuit it trips on but it only trips with all breakers on. Megger want even test as it trips before a reading is given


any ideas thanks

Run that one by me again will you?

 

[matt12321]

When u do X1 or x5 Rcd test at socket the Rcd trips before any normal reading or Rcd fail shows

 

[amlu]

When u do X1 or x5 Rcd test at socket the Rcd trips before any normal reading or Rcd fail shows

test it directly in the consumer unit, with circuits disconnected.
it may be over sensitive but more likely theres earth leakage and RCD is just doing its job , leakage clamp meter comes handy for this situations.

 

[Octopus]

How long ago was the CU installed and / or the fault occur?

What are the IR readings for the individual circuits covered by said RCD?

Are the other circuits on the other "side" of the CU OK?

 

[Deleted member 9648]

Beyond my comprehension that once again an IR test seems to be the last thing in the fault finding process......

 

[Dave OCD]

I bet it's TNCS and there's a N-E fault present.