Twin and earth

It is not intended to be used where it is subject to regular movement or sunlight, because the sheathing is affected by ultraviolet radiation.

Twin and Earth cable is normally made with PVC sheathing and insulation, which has an almost indefinite life in the right conditions.

National standards for electrical wiring prohibit PVC cables in locations where this is a particular risk, such as fire escape routes.

An insidious risk can occur when PVC cable it comes into contact with expanded polystyrene insulation, either in rigid panels or as loose beads.

[1] In the UK the CPC is uninsulated (bare) and of reduced diameter compared to the main cores.

Green and yellow sleeving, which is sold separately, is required to be used to cover the exposed ends.

From 2013, Irish wiring rules require a CPC with a cross-section equal to that of the main conductors and insulated in green and yellow inside the full length of the cable, from the new standard IS 201-4:2013.

[3] [4] The older bare and reduced diameter CPC cables are no longer permitted for new wiring in the Republic of Ireland.

In Australia and New Zealand flat 'TPS' (Thermo-plastic sheathed) "Twin and Earth" cables manufactured prior to 1966 were permitted the use of an uninsulated CPC stranded core, requiring that the exposed ends of this conductor be sleeved with Green insulating tubing.