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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
Yes there is a subtle difference for changing consumer units in owner occupied and rented premises. If you email me I will send you my flow chart that provides guidance for changing consumer units.
Sorry I thought that your first post on the subject was a cryptic request for information rather than a test for me, how did I do?
Andy
Yes different requirements for owner occupied and rented. I thoight you may have seen my flow chart for changing consumer units on installations without a CPC? I can send you a copy by email if you want a copy? Or alternatively you could ask the BOD as he may be able to help you!
i am guessing you are unsure otherwise you would have posted an explanation?
Really? It was a pointer for the OP to follow up if he were interested, not a reflection of any gaps in my understanding of the history of the changes to the Regs.........................................
Good evening, thanks for all the replies, much appreciated. Good to know readings are ok and safe. The lighting circuit was upgraded before we moved in and has proper earth and plastic fittings. Switches plastic on metal backboxes. The new CU has all circuits separated by RCBO's at my request. Metal case for CU and all relevant labels on front. Property not rented out. 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.
So if you have all plastic light switches and Class 2 light fittings and the circuit is 30mA RCD and there is a warning label on the consumer unit and the premises are not rented out the installation is not unsafe but remains none compliant with the current edition of the Wiring Regulations.
Different requirements for owner occupied homes to those which are tenanted?
i am guessing you are unsure otherwise you would have posted an explanation?
Up until 1966 the Wiring Regulations did not require lighting circuits to have an earth connection present at each point of termination on lighting circuits. Metallic Class 1 light fittings and switches require earthing for safety. Also if a circuit protective conductor (an earth wire or metallic conduit) is in close association with the live conductors ( line and neutral) and the circuit is RCD protected it provides a measure of fire protection although this is not recognised in the Wiring Regulations at this time. So if you have all plastic light switches and Class 2 light fittings and the circuit is 30mA RCD and there is a warning label on the consumer unit and the premises are not rented out the installation is not unsafe but remains none compliant with the current edition of the Wiring Regulations.
