Published: 21 March 2011
Category: Technical articles
Cable clips must be used in the manner intended. Securing two cables, edge-on, under one clip would not be considered good workmanship:
If two flat twin and earth cables are secured using a signle cable clip, laid edge-on as shown, mechanical damage is likely.
Compression can occur due to the clip being hammered in too far.
The sheath may be split by a hammer blow, or the un-insulated protective conductor may be forced through the insulation of the lower conductor, causing either a line to earth or neutral to earth fault.
A line to earth fault is likely to be detected by the overcurrent protective device, whereas, in the absence of RCD protection, the neutral to earth fault may persist indefinitely, resulting in a risk of fire.
Furthermore, the cables are no longer clipped direct and thermal considerations may be different from those intended by the designer.
The clips are designed to hold and not unduly compress the intended cable when hammered home. They should be used in the manner intended. Good workmanship and proper materials must be used (Regulation 134.1.1 refers). Different sizes of clips are available to accommodate various cross-sectional areas (csa) and shapes (ie: circular or flat twin and earth).
Wiring systems must be erected so as to minimize mechanical damage e.g. damage due to compression or impact during installation. (Regulation 522.6.1 refers).
Where two cables are to be run next to each other, they should be individually clipped as shown.
Compression can occur due to the clip being hammered in too far.
The sheath may be split by a hammer blow, or the un-insulated protective conductor may be forced through the insulation of the lower conductor, causing either a line to earth or neutral to earth fault.
A line to earth fault is likely to be detected by the overcurrent protective device, whereas, in the absence of RCD protection, the neutral to earth fault may persist indefinitely, resulting in a risk of fire.
Furthermore, the cables are no longer clipped direct and thermal considerations may be different from those intended by the designer.
Solution
The clips are designed to hold and not unduly compress the intended cable when hammered home. They should be used in the manner intended. Good workmanship and proper materials must be used (Regulation 134.1.1 refers). Different sizes of clips are available to accommodate various cross-sectional areas (csa) and shapes (ie: circular or flat twin and earth).
Wiring systems must be erected so as to minimize mechanical damage e.g. damage due to compression or impact during installation. (Regulation 522.6.1 refers).
Where two cables are to be run next to each other, they should be individually clipped as shown.