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Do I need to rewire my ring final?
Former Community Member
Good afternoon, I'm looking for some advice as to whether I need to get someone in to have my ring final rewired. I have recently had a new consumer unit installed and circuits tested. All circuits tested fine according to regulations, but the ring final registered lower insulation resistance readings. live/live 119mohm and live/earth 105mohm tested at 500v. Max Z's 0.52ohm according to the certificate. I'm not sure how old the wiring is but we've been here 20 years and the wire has grey pvc outer sheath, red live pvc, black neutral pvc and 3 stranded earth, which looks like plated copper. Some of the sockets are probably the same age. Strangely, some other circuits with same type of cable registered 999mohm when tested. FYI we live in a 1960's bungalow. Just wondered if you had any thoughts. Many thanks in advance. Simon
The insulation resistance test results do not indicate that there may be a problem.
The circuit is almost certainly wired in imperial sized cables with a circuit protective conductor (earth wire) which is smaller than would installed to the current standard, however it is now presumably protected by a MCB and a 30 mA RCD, so don’t start worrying too much about it.
If the lighting circuit doesn’t have a CPC (earth wire) this should be flagged up on the certificate and have been discussed with you by the electrician, so you should already know about any issues regarding earthing on the lighting circuits.
The insulation resistance test results do not indicate that there may be a problem.
The circuit is almost certainly wired in imperial sized cables with a circuit protective conductor (earth wire) which is smaller than would installed to the current standard, however it is now presumably protected by a MCB and a 30 mA RCD, so don’t start worrying too much about it.
If the lighting circuit doesn’t have a CPC (earth wire) this should be flagged up on the certificate and have been discussed with you by the electrician, so you should already know about any issues regarding earthing on the lighting circuits.
