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Dating existing electrical installations by type of cable

Dave Thomas
Modern pvc T&E cables 4mm and below are a  usually single solid conductor, but going back a few years ring mains were regularly installed with either 2.5mm ( or possibly older imperial  cables?) that were multi stranded conductors. Does anyone know, was there a date, or edition of the good book, when this changed, and at what point was metric mmsq specified instead of the older wire gauge?

.
  • 0
    Yes, the stranded (and tinned copper) smaller sizes of T&E will be imperial (although I think current 4mm² is stranded for the live conductors)


    Date wise, if it's of any help, page 8 of the current BS 7671 says that a Supplement on the use of metric terms was issued in 1969 and the regs themselves were reprinted in metric units in 1970.


      - Andy.
  • 0
    I believe that the old imperial sized cable used for ring circuits was 7/.029 inches. That is 7 strands of 0.029 dia. inch wires per live and neutral conductor, the earth wire being smaller. An old text book I have states that the 7/.029 conductor of rubber insulated cables had a nominal area of .0045 square inches and a resistance of 5.374 Ohms per 1,000 yards at 20 degrees C. Popular in the 50s and 60s, but the insulation was changed to P.V.C. latterly. The book I have says that a British Standard, No.7 of 1953 refers to the insulation thickness of rubber cables, it refers to the insulation as "dielectric." Tinned copper was used with rubber insulation to protect the copper from attack by sulphur I believe in the rubber insulation.


    Z.
  • 0
    A short history of old cables.....

    http://wiki.diyfaq.org.uk/index.php/Historic_Mains_Cables


    Z.

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