BS/IEC/NFPA codes and requirements to support the use of Aluminum cables as alternative to copper cables

The use of aluminum cables as an alternative to copper cables in electrical installations is recognized under various standards, including BS (British Standards), IEC (International Electrotechnical Commission), and NFPA (National Fire Protection Association). However, their acceptance requires specific considerations to ensure safety, performance, and longevity. Below are key requirements from these standards:

1. BS (British Standards) Requirements

BS 7671: Requirements for Electrical Installations (IET Wiring Regulations):

Conductor Sizing: Aluminum cables must be sized appropriately to account for their lower conductivity compared to copper. Typically, aluminum cables require larger cross-sectional areas to handle equivalent current levels.

Connections: Terminals and connections must be specifically designed for aluminum conductors to prevent oxidation and ensure reliable contact. Use bi-metallic lugs or connectors where aluminum interfaces with copper.

Temperature Rating: Aluminum has a higher coefficient of thermal expansion, so care must be taken to use suitable fittings to avoid loosening over time due to thermal cycling.

Mechanical Strength: Ensure the aluminum cables are protected from mechanical stress as they are less durable than copper cables.

2. IEC (International Electrotechnical Commission) Requirements

IEC 60228: Conductors of Insulated Cables:

Defines requirements for the design and testing of aluminum conductors.

Specifies that aluminum conductors should meet the same electrical and mechanical performance standards as copper conductors within their larger sizes.

IEC 60364: Electrical Installations of Buildings:

Requires careful attention to jointing and termination of aluminum conductors to prevent oxidation and overheating.

Stipulates that only verified accessories (e.g., lugs, clamps, and terminals) compatible with aluminum should be used.

Provides derating factors for aluminum cables based on their electrical conductivity and heat dissipation characteristics.

IEC 60947 (Switchgear and Controlgear):

Switchgear and breakers must accommodate larger cable sizes and provide proper contact pressure for aluminum connections.

3. NFPA (National Fire Protection Association) Requirements

NFPA 70: National Electrical Code (NEC):

Article 310: Covers aluminum conductors for general wiring purposes.

Aluminum cables are allowed but must comply with ampacity tables that consider aluminum's lower conductivity compared to copper.

Terminations and Connectors: Only terminals listed and identified for aluminum use (AL7CU or AL9CU-rated) should be used. This ensures compatibility and avoids overheating at connection points.

Oxidation Prevention: Aluminum conductors must be treated with antioxidant compounds at termination points to prevent corrosion and maintain conductivity.

Fire Safety:

Aluminum wiring installations must comply with fire safety guidelines to ensure the insulation and conductor performance under fault or overload conditions are equivalent to copper wiring.

Additional Design and Installation Considerations

1. Joints and Terminations:

Use compression fittings or specialized terminals to ensure tight connections.

Avoid direct contact between copper and aluminum to prevent galvanic corrosion. Use bi-metallic connectors where mixed materials are necessary.

2. Expansion and Contraction:

Aluminum expands more than copper when heated. Installers must ensure connections can withstand thermal cycling without loosening.

3. Inspection and Maintenance:

Periodic inspections of aluminum cable terminations are recommended to check for signs of overheating or loosening.

4. Cost-Effectiveness:

Aluminum cables are more cost-effective than copper, especially for larger cross-sectional areas, but installation costs may rise due to the need for specialized connectors and accessories.

5. Applications:

Aluminum cables are commonly used in large installations like utility services, underground cables, and industrial power distribution where weight reduction and cost savings are prioritized.

Conclusion

Aluminum cables can be used as alternatives to copper under BS, IEC, and NFPA standards, provided appropriate design, installation, and maintenance practices are followed. These standards highlight the need for proper conductor sizing, terminations, and accessories to ensure safety and efficiency. Always consult the latest editions of these standards and local regulations for project-specific requirements.

ODUSINA, Adewale F (Engr.) Hiworks Services Ltd.