rcd tripping

[dp1000]

Hi everyone.
I'll be ringing tech support in the morning but i cant wait for an explanation.
I've just fitted a split load CU where there was once an old rewireable wylex fuseboard. Circuits to be fitted on the RCD side of the new board all tested fine. Insulation Res good, r1r2 good, polarity good. However, RCD trips whenever any load is introduced on any of the circuits on the RCD side. As soon as the shower is switched on - trips. Anything pluged in and switched on - trips. Cooker switched on (on RCD side cos of the socket) - trips.
I thought it may be a dufff RCD. Ramp tested it and it tripped at 17mA (30mA RCD). That is a little low i thought so changed it for another. Again the same problem - constant tripping.
What could be the possible cause of this. Could I have 2 duff RCD's?
Thanks

 

[Steve]

Dont mean to insult one's intelligence, but did you connect the neutrals correctly?

 

[reggie perrin]

RCD trips whenever any load is introduced on any of the circuits on the RCD side.

Neutral/Earth fault?

 

[Spark123]

Neutrals on the wrong side of the board or some interconnection between an RCD protected circuit and a non RCD circuit.

 

[securespark]

Insulation Res good

How good?

 

[dp1000]

Thanks for replies. I thought I must have connected the neutrals wrong but double/triple checked and they're ok.
IR is >299M on all circuits on the RCD side. The ring main was showing a short circuit between neutral/earth which I assumed to be connected equipment I hadn't found. I moved the ring main over to the main switch side (including the neutrals!) but I'm still getting the tripping problem.
I'm suppose as Spark123 says there must be some interconnection between the circuits on both side of the CU. Major pain.

 

[Adam_151]

You haven't forgotten to remove a link in the CU have you?

 

[securespark]

Yup.

My next thought (treat it gently!!)

Is there a brass link between the two neutral busbars in the CU?

Is your supply type TN-C-S Or PME?

Sometimes, you can get faults on the other side of the board that trip the RCD.

 

[dp1000]

good morning.
Supply is TN-C-S.
I'm pretty sure there was no brass link as the board was set up as a split load when i got it but i'll double check when i go back at the weekend. I suppose the next question is how much time can you reasonably spend searching for the problem at the customers expense? I've already had every socket face in the house off because there is no earth sleeving inside any of the fittings in the whole house but until the problem is sorted I cant certify the new CU.

 

[Steve3948]

Check your circuits again, sounds very Neural to Earth to me.
Also check continutity of rings, the times I have found the Imm Circuit in with one leg of the ring and the other leg of the ring on it's own connected as the Imm, where the original installer did no testing.

 

[reggie perrin]

Also look for pictures hanging above sockets...