ring main woes



Like my house which once only had 3 circuits, lights, ring and cooker. It now has 3 ring mains, North, South and kitchen and 2 lighting circuits, downstairs and upstairs. As it happens the lighting circuits were harder to separate, wired in part with double insulated singles but via some very odd routes.
One of the other things I have done is to try and eliminate all the diagonal wires that offend current regulations.
--
Roger Chapman

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If it's rubber, should have been done ~30 years ago. If it's PVC, then even the earliest PVC installations should still have sound cable unless it's got hot, and should remain good for decades yet. IEE estimates 1000 year live of the PVC in ideal conditions, dropping to 21 years for a cable operating continuously at max rated temperature of 70C. Some wiring schemes such as conduit can suffer high earth impedance after a long time.
Wiring accessories (switches, sockets, fuse box, etc) will not generally last as long as the wiring and should be checked periodically -- life will depend on usage and original quality. Fortunately, they are much easier to replace than the wiring. Also check for terminal screw tightness, as poor contacts there can lead to heating and damage to accessories and cable (and worse).
Standards and expectations change over the years. A 50 year old PVC installation could still be in perfect order, but would be lacking the number of sockets expected today, and below current earthing standards. That doesn't necessarily mean a rewire is required, but poorly done piecemeal expansion of an original installation is a common cuase of an installation having become an unrepairable mess.
My parents installation was one for earliest PVC ones in the 1950s. The original accessories are all MK, except the fusebox which was Wylex. I found the fusebox was in need of replacing 10 years ago during an inspection -- the contacts on the ring circuit fuse holder were getting too hot and caused insulation to go brittle. I replaced the fusebox as part of rewiring/refitting the kitchen and bringing service bonding up to spec. I can only think of one of the MK accessories which has failed -- a light switch. About half of them have been replaced during room redecorations over the 50 years, but none had anything wrong with them. A few of the terminal screws have been retightened.
--
Andrew Gabriel
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