Strange RCD Tripping on dead board

[jase1638]

Hi gents,

Tested a house and all faults rectified. Was asked by landlord to upgrade the fuse board to a 17th edition board and happily complied. On fitting the board I went on to carry out testing and then hit a brick wall when going live.

RCD tripped. so I isolated each circuit (only 4 and all kept on same neutral bar) - still RCD tripped I removed the live bus bar to the 4 circuits - still tripped. Removed RCD 2 and relevant cabling - still tripped. Changed the RCD (CPN model) - still tripped, Changed RCD again (CHINT model), still tripped.

T-N-CS system
Ze - 0.04 (low I know and cant see the transformer in any nearby streets)

After 3 hours of busting my brain, puffing the vape and scratching my nads, I admitted defeat and reconfigured the board. to omit the RCD (for the time being)

So now imagine the board - 25mm tails to incomer, RCD connected, no bus bar to MCB, polarity is good. As soon as I close the incomer, RCD trips. Only thing I note as unusual is the meter is missing the bottom security seal. (quite common in some tenanted properties?)

Any ideas would be most graciously appreciated.

 

[trev]

deleted

 

[Hawk81]

Did you disconnect and test each neutral to earth? Sounds like a neutral fault. Only 4 circuits should be easy to find

 

[Hawk81]

Have you tried swapping the RCD?

He says he had a cpn RCD and changed it to chint

 

[trev]

He says he had a cpn RCD and changed it to chint

Going to confess Hawk I only had a quick scan of the op. Once I read it again I saw that and deleted the idiocy

 

[Richard Burns]

This isn't the linked neutral bars scenario is it?
So there is an alternative path via the other neutral bar bypassing the RCD causing it to trip.

 

[Pete999]

N to E fault. Before you go swapping anymore RCDs disconnect ALL the outgoing circuit neutrals and carry out an IR test between earth and them individually.

 

[HandySparks]

Any chance of a photo of the board?

 

[Rockingit]

The RCD isn't in backwards, is it? As in Polarity reversed on the incoming side. I had a factory new board the other day which had me scratching my heads for a few minutes until I realised they'd put the Neutral in the wrong hole!

Other than that, it's break it down one piece at a time. I'm assuming the RCD holds with incoming connections only?

 

[Octopus]

Hi gents,

Tested a house and all faults rectified. Was asked by landlord to upgrade the fuse board to a 17th edition board and happily complied. On fitting the board I went on to carry out testing and then hit a brick wall when going live.

RCD tripped. so I isolated each circuit (only 4 and all kept on same neutral bar) - still RCD tripped I removed the live bus bar to the 4 circuits - still tripped. Removed RCD 2 and relevant cabling - still tripped. Changed the RCD (CPN model) - still tripped, Changed RCD again (CHINT model), still tripped.

T-N-CS system
Ze - 0.04 (low I know and cant see the transformer in any nearby streets)

After 3 hours of busting my brain, puffing the vape and scratching my nads, I admitted defeat and reconfigured the board. to omit the RCD (for the time being)

So now imagine the board - 25mm tails to incomer, RCD connected, no bus bar to MCB, polarity is good. As soon as I close the incomer, RCD trips. Only thing I note as unusual is the meter is missing the bottom security seal. (quite common in some tenanted properties?)

Any ideas would be most graciously appreciated.

This doesn't make sense. Surely if you've fitted a dual RCD board and only got 4 circuits? Didn't you put circuits on both RCD's.

If you are doing a 4 CU change a RCBO confirguration is far better IMHO.

Think we need a bit more info as I'm struggling with this one