RCD trip out on all circuits

[vardymr2]

Hi all,

Yesterday i was asked by a landload to put a rcd within a ground floor flat, The CU already have bs60898 mcb's but no Rcd protection. So i got a 2way sub board with 80amp 30ma rcd and wired it into the meter tails before the CU. io have tested the flat and only problem i found was a NtoE fault on lights. Well even if i disconnect that circuit completely and turn the power on everything stays up until i put load onto the circuit the rcd trips it does not matter which circuit it is it will trip.

Also within the flat it has a 2 way off peak board for two heaters. The neutral for this board is wired into the earth block on a tnc-s supply fuse and not into a neutral terminal within the meter its self.

Do you think it could be this neutral on the off peak meter or any other idea's?

 

[telectrix]

try dissing the off peak completely, then try it

 

[Guest123]

Can you describe the arrangement there i.e.....cut-out, meter, RCD, CU.....or is it a submain arrangement???

How are the supplies divided to the CU's??? i.e does the neutral for the E7 CU come before the RCD or is it a seperate sub-main???

 

[vardymr2]

It is one meter with normal rate and E7 built in, The meter has p-n coming in and p-n going out and another Phase going out which supplies the E7 Cu, the neutral for E7 is connected to the earth block on the main fuse block,

So normal p-n leaves meter and goes to my rcd then main CU to flat,

E7 p-n just goes straight to E7 sub board

 

[sparkswillfly]

faulty rcd maybe

 

[Deleted member 9648]

Carry out an IR test between the off peak final circuits and the on peak final circuits.......if the RCD stays in when the circuits are energised but trips as soon as a load is switched on it sounds like an imbalance in the L/N going through the RCD.
If there was a link somewhere between an off peak final circuit (which doesnt go through the RCD) and on peak final circuit some of the N current in an on peak circuit could return via the off peak N causing an imbalance....a mis-connection at an off/on peak immersion heater setup for instance could result in a link.