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Downstream rcd tripping

Nick Bennett
Afternoon all, I had abit of a funny one this morning. Carrying out some work at a block of flats. 

DId a Ze at the landlords board to find the main earth had been cut off! Did a Ze between the live and the stub left on the side of the ryefield. This then tripped out some of the downstream RCDs feeding tenants flats. I assume that I'd in balanced the neutral. Just wondering if anyone else had had this.

I've called in ukpn to check the earthing and to get it fixed.
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    If the RCD fires it thinks it is seeing an L-N imbalance.  If there is an NE bond  in one of the flats, perhaps deliberate  to get some sort of earthing back or perhaps a faulty water heater, then things like plumbing may be neutralled, rather than earthed.

    In that case, you may be bypassing the neutral sensing coil in the RCDs.

    Or it may just be a transient effect inducing a short duration pulse and taking an RCD already near the edge, over it - how big was your test current.

    It is possible once the main earth is fixed, that some remedial works are needed in at least one of the affected flats.

    M.
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  • 0
    If the RCD fires it thinks it is seeing an L-N imbalance.  If there is an NE bond  in one of the flats, perhaps deliberate  to get some sort of earthing back or perhaps a faulty water heater, then things like plumbing may be neutralled, rather than earthed.

    In that case, you may be bypassing the neutral sensing coil in the RCDs.

    Or it may just be a transient effect inducing a short duration pulse and taking an RCD already near the edge, over it - how big was your test current.

    It is possible once the main earth is fixed, that some remedial works are needed in at least one of the affected flats.

    M.
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