BASEC News

Return Unstrippable Cable

01/08/10
Dr Jeremy Hodge, chief executive of the British Approvals Service for Cable (BASEC) advises about the importance of checking your cable has sufficient levels of chalk for stripping before first fix.

Electricians should check their cable can be easily stripped before first fix installation. It is a simple and worthwhile check that can save time and cost later. If cable has been laid and plastering or decoration has been completed, when the installer comes to fit accessories at second fix and the cable cannot be stripped easily, there can be serious difficulties which will cost the electrician both time and money. In the cable production process, a sprinkling of fine chalk or a silicone spray is applied in between the cores of a multi core cable, which enables the sheath to be easily stripped from the cores. If the chalk runs out during production, or an insufficient amount of chalk is used, the sheath will stick to the cores and make the cable difficult or impossible to strip. Having reviewed this problem with installer organisations and cable manufacturers, BASEC is treating this problem as a serious production failure and is advising manufacturers to be more vigilant in their production. Any cable batches found to have insufficient chalk should not be sold and should be returned to the supplier. Strippability can be readily checked by the electrician by feeling the free end of each reel of cable with a fingernail to see if the sheath can be lifted away from the cores. If it will not come away from the cores easily, then normal stripping of the cable should be attempted. If it is difficult to strip without damaging the insulation material, affected cable should be returned to the supplier. If cable has been installed and then found to be unstrippable at second fix, the electrician should advise the supplier of the particular cable batches purchased and the problem they have encountered. This should then be investigated by the supplier. With regard to the installation, ideally the problem cable should be replaced. However, if it is necessary to work around the problem, it is possible for the electrician to leave the outer sheathing in place and separate the cores by cutting down the centre line of the cable, being careful not to damage the insulation. All necessary electrical installation verification tests must then be performed. Electrician’s priority must be to ensure quality and safety. To help safeguard against the risk of installing cable which is substandard, electricians should ensure that the cable supplied is the correctly specified cable and always check the markings on the cable sheath - not just the packaging. For peace of mind, you should also insist on an independent third-party approved cable with a BASEC or HAR mark. It is also important to specify on your order the British Standard (BS) number the cable should comply with. It is important to note that the problem of unstrippable cable can happen with low smoke halogen free cables as well as PVC.

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