Flexible Cables in Fixed Installations
The use of flexible cables in fixed installations has often been shrouded in confusion, with many believing that they are prohibited. However, this is a misconception. While there are specific requirements to be met, flexible cables can be used in various applications, as outlined in BS 7671.
Key Considerations:
Mechanical Robustness: The flexible cable should have appropriate mechanical strength for the intended application, as described in BS EN 50565-1.
Temperature Rating: The cable's temperature rating must be suitable for the connected wiring accessories.
Wiring Terminations: Appropriate wiring accessory terminals must be used, as specified in Regulation Group 526.9 and IET Guidance Note 3.
Current-Carrying Capacity and Voltage Drop: Refer to Appendix 4 of BS 7671 for appropriate tables and calculations, considering the type of cable and its stranding.
Required Applications:
Suspended Current-Using Equipment: Regulation 522.7.2 mandates the use of flexible cables for this purpose.
Installations in Flexible Structures or Moving Structures: Regulation 522.15.2 requires flexible cables in these scenarios.
Equipment Connections: Flexible cables are necessary for connecting equipment that may be regularly or occasionally moved (Regulations 521.9.2 and 521.9.3).
High Protective Conductor Current: Regulation 543.7.1.202 specifies the use of flexible cables in this case.
Special Locations: Certain Part 7 special locations require flexible cables, as outlined in Regulation 522.15.2 and other relevant regulations.
General Requirements:
Compliance with BS 7671: Flexible cables must comply with all relevant provisions of BS 7671, including general rules and specific requirements for their use.
Cross-Sectional Area: Ensure that the cable's cross-sectional area is appropriate for the application, as specified in Regulation 132.6.
Wiring and Installation Methods: Follow the guidelines in Regulation 132.7 for selecting appropriate wiring and installation methods.
Equipment Selection: Refer to Regulation Group 133 for guidance on selecting suitable equipment.
Conclusion:
Contrary to popular belief, flexible cables are not prohibited in fixed installations. By understanding the specific requirements and guidelines outlined in BS 7671, you can confidently use flexible cables in appropriate applications, ensuring a safe and compliant electrical installation.