Cable Management Guide
Best practices for cable containment, supports, bends, and segregation per BS 7671 and BS 6701
Minimum Bend Radii
BS 7671 Chapter 52 requires that cables are not bent tighter than their minimum radius to prevent insulation damage and conductor stress.
Minimum internal bend radius by cable type
BS 7671 Table 4A, manufacturer data| Cable Type | Min. Bend Radius | Example (6mm²) |
|---|---|---|
| Flat T&E (up to 10mm²) | 3 x overall diameter | 3 x 11.6mm = 35mm |
| Flat T&E (16mm²+) | 4 x overall diameter | 4 x 15.2mm = 61mm |
| SWA (PVC) | 6 x overall diameter | Varies by size |
| MICC | 6 x overall diameter | 6 x OD |
| Singles in conduit | 2.5 x conduit OD | 2.5 x 25mm = 63mm |
| Flexible cord | 3 x overall diameter | Varies |
Cable Fixing Distances
Maximum clip/cleat spacing for common cables
IET On-Site Guide and BS 7671| Cable Type | Horizontal (mm) | Vertical (mm) |
|---|---|---|
| Flat T&E 1.0-1.5mm² | 250 | 400 |
| Flat T&E 2.5mm² | 250 | 400 |
| Flat T&E 4-6mm² | 300 | 400 |
| Flat T&E 10-16mm² | 350 | 450 |
| SWA up to 25mm² | 350 | 450 |
| SWA 35mm²+ | 450 | 600 |
Place a clip within 150mm of each bend, accessory, or enclosure entry.
Cable Segregation Requirements
BS 7671 Section 528 classifies circuits into Band I (ELV: data, fire alarm, telecoms) and Band II (LV: 230V/400V mains). These bands must be physically separated in containment systems.
Fire Alarm Segregation
Cable Tray vs Trunking vs Basket
Cable Weight on Tray
Total Load = Sum(weight/m x number of cables) x span- weight/m
- = Cable mass per metre from manufacturer data (kg/m)
- span
- = Distance between tray supports (m)
Manufacturer loading tables
Always verify that the total cable weight per metre does not exceed the tray's rated safe working load. Add a 25% safety margin for dynamic loads during cable pulling.