OK, to confirm it was a problem with the bathroom lighting and not the stairs/landing or bedroom 2, I bypassed the bathroom lighting junction box and connected up junction boxes 3 and 4. Both stairs/landing, and bedroom 2 were fine, not tripping, and lights came on. Therefore, I can now look into the connections from junction box 2 (bathroom lights and switch)...
RCD tripping because of lighting circuit
- Thread starter Thomasdh
- Start date
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And the answer is:
It turned out to be the mains halogen recessed downlights in the bathroom. After disconnecting the first downlight and splaying the live, neutral, and redundant earth (no earth connection in the downlight) apart from each other so they couldn't touch, then reconnecting the circuit in the CU the RCD didn't trip.
On closer inspection of the wiring, there was insulation damage to the neutral: a small scuff taking it nearly down to the copper. What with this, the redundant earth cable with nothing to terminate it, and perhaps the moisture from the bathroom, it's probable that the earth was coming into contact with the scuff and caused an earth/neutral fault as suspected by others.
I've cut away the earth now right back so there's nothing coming out of the cable, and refinished the neutral and live wires carefully. This seems to have sorted the problem, touch wood. It just goes to show how the smallest of damage can render a whole side of the CU out of action.
Apologies for turning this into a sort of problem solving journal, but writing this all down step by step, logically paring things down, has helped me fix the problem (touch wood again) which would appear to have been caused by a tiny scuff and a roaming earth wire.
Thanks Londonboy for suggesting to split up the circuit to find the source of the problem. Thanks Flameport for suggesting a damaged cable somewhere, even if it didn't turn out to one crushed by moving boxes.
It turned out to be the mains halogen recessed downlights in the bathroom. After disconnecting the first downlight and splaying the live, neutral, and redundant earth (no earth connection in the downlight) apart from each other so they couldn't touch, then reconnecting the circuit in the CU the RCD didn't trip.
On closer inspection of the wiring, there was insulation damage to the neutral: a small scuff taking it nearly down to the copper. What with this, the redundant earth cable with nothing to terminate it, and perhaps the moisture from the bathroom, it's probable that the earth was coming into contact with the scuff and caused an earth/neutral fault as suspected by others.
I've cut away the earth now right back so there's nothing coming out of the cable, and refinished the neutral and live wires carefully. This seems to have sorted the problem, touch wood. It just goes to show how the smallest of damage can render a whole side of the CU out of action.
Apologies for turning this into a sort of problem solving journal, but writing this all down step by step, logically paring things down, has helped me fix the problem (touch wood again) which would appear to have been caused by a tiny scuff and a roaming earth wire.
Thanks Londonboy for suggesting to split up the circuit to find the source of the problem. Thanks Flameport for suggesting a damaged cable somewhere, even if it didn't turn out to one crushed by moving boxes.
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