Metal enclousres such as accessory boxes, distribution boards and consumer units can have sharp edges at cable entry points which can cut into the sheath and insulation of an unprotected cable.
Where an unprotected cable such as a twin and earth pvc-insulated and sheathed cable enters a metal enclousure, the installation designer or installer must ensure the cable is protected from damage from sharp edges.
Damage to a cable may result in the risk of electric shock or fire.
SOLUTION
Wiring systems must be selected and erected to avoid during installation, use and maintenance, damage to the sheath and insulation cables. Regulation 522.8.1 refers. Cable sheaths must be protected from any sharp edges along the whole of their length as well as at the entry point into the item of switchgear or accessory. The cable may be protected from damage by one or more of the methods of:
- deburring,
- providing suitable physical protection, or
- providing an appropriate grommet.
Failure to provide a grommet whare a cable, such as a twin and cpc flat cable, enters a metal black box is not, in its own right, a deficiency, providing the cable sheath is adequately protected against damage from any sharp edges.
Regulation 522.8.1
A wiring system shall be selected and erected to avoid installation, use and maintenance, damage to the sheath or insulation of cables and their terminations.
This Snag and its Solution were extracted from Snags and Solutions Part 2 - a practical guide to everday electrical problems, published by NICEIC.
