faulty RCD ?

[slippyr4]

I didn't say that PVC has a 30 year life.

However, 30 years of use is plenty of time for some possible problems to show up- if the cable was installed with too tight bends, then there may be some migration of the copper causing low insulation resistance. Cables may have been subject to overload and hence suffer from the effects of overheating, there may be polystyrene in contact with the PVC which may leach the plasticiser out of the cable.

 

[Qedelec]

RCD's monitor both lives in a circuit and detect an inbalance, i.e. current in one live is less than in the other. This means the current is going somewhere else, usually to earth. to do this the output side of the RCD must be separated from the incoming supply. If a circuit is connected, live to RCD out and neutral to the incoming then there will be an inbalance and it will trip. Viola!

 

[jenki]

confused over the seperate nuetral bar for RCD side

rcd's (simplified) work by monitoring the Flow of Electricity out via the Phase and back in via the Neutral, if these are not the same - then the imbalance causes the RCD to TRIP, (if it's not returning via the neutral then it's returning via the CPC - of somebody!).

Thus in a split load CU, there are 2 neutral bars. if you look at page 3 of this link you can clearly see the 2 bars separated, you can also see 3 separate Neutrals, one from the incomer, 1 going to the RCD and one returning from the RCD.
http://www.tlc-direct.co.uk/Technical/DataSheets/MK_Sentry/SENTRY_prod1.pdf
Now if you don't separate your RCD protected circuits from the Non-RCD protected circuits by using these " Neutral bars then you will create an imbalance which will trip the RCD. Does this make sense?