Confused by this one, and any explanations & advice gratefully received. NB Although I'm a DIYer, I will be getting a professional to do the part P and a PIR when I am done.
I have an old house that was last rewired more than 30 years ago (no earthed lighting circuits, etc).
I have replaced the CU and am going through the circuits replacing them, one by one.
I do have one lighting circuit that is about 5 years old, is earthed, and because of the decorative work involved in replacing the circuit, I would like to try and reuse it.
When I disconnected it from the old CU, it was in a 6a MCB. I have inserted the cables into a 6a MCB in the new CU.
When I flick the MCB on, the RCD protecting the socket circuits in the CU blows (but not the MCB for this lighting circuit), and the negative bar in the CU lights up a neon screwdriver suggesting it is live. If all the switches on the circuit are off, this doesn't happen.
If I wire the circuit into a 32a MCB covered by the RCD, I get no fault, and the lights work and switch fine.
The circuit has 2 sets of 4 GU10s (single-way switching) and 2 60w bulbs on 2way switching.
I don't think I've done anything to the circuit in between disconnecting from one CU and connecting to the other. I originally suspected a short, but that wouldn't explain it working on a 32a MCB would it?
Advise gratefully received, or suggestions of what to stick my multimeter in (polite ones only please!)
Thanks for your help.
Robin
I have an old house that was last rewired more than 30 years ago (no earthed lighting circuits, etc).
I have replaced the CU and am going through the circuits replacing them, one by one.
I do have one lighting circuit that is about 5 years old, is earthed, and because of the decorative work involved in replacing the circuit, I would like to try and reuse it.
When I disconnected it from the old CU, it was in a 6a MCB. I have inserted the cables into a 6a MCB in the new CU.
When I flick the MCB on, the RCD protecting the socket circuits in the CU blows (but not the MCB for this lighting circuit), and the negative bar in the CU lights up a neon screwdriver suggesting it is live. If all the switches on the circuit are off, this doesn't happen.
If I wire the circuit into a 32a MCB covered by the RCD, I get no fault, and the lights work and switch fine.
The circuit has 2 sets of 4 GU10s (single-way switching) and 2 60w bulbs on 2way switching.
I don't think I've done anything to the circuit in between disconnecting from one CU and connecting to the other. I originally suspected a short, but that wouldn't explain it working on a 32a MCB would it?
Advise gratefully received, or suggestions of what to stick my multimeter in (polite ones only please!)
Thanks for your help.
Robin