What type of cable installation is typical for buried or exterior runs and what protection is used?

• A. Armoured cable (or conduit) with appropriate cable entries; provides mechanical protection.
• B. Unarmoured twin-and-earth.
• C. Flexible cord directly buried.
• D. Metal conduit without entries.

Answer: (A)

Buried or exterior runs must have solid mechanical protection to guard the conductors from damage and moisture. Armoured cable provides a metal sheath that resists crushing and abrasion, and using it with appropriate cable entries (glands, connectors) keeps the joint sealed and the route strain-free. Alternatively, running the conductors in metal or rigid conduit offers a tough enclosure while still allowing proper terminations at each end with suitable entries to maintain weatherproofing. This combination of protection and correctly terminated entries is what makes it suitable for outdoors or underground installations.

Unarmoured twin-and-earth isn’t protected enough for underground or exterior exposure, so it’s not suitable. A flexible cord directly buried isn’t allowed for permanent installations due to safety and moisture concerns. Metal conduit without entries isn’t complete because it lacks proper sealing and strain relief at the terminations, which compromises protection and safety.