A distribution box should be installed on a stable, level base within the trench, above the cable bedding, with proper clearance, protection, and earthing according to IEC and utility standards.

Trench Preparation and Bedding

The trench must be excavated to the correct depth and width to accommodate the cable and distribution box. A sand bedding layer of approximately 75 mm is recommended beneath the cables to protect them from sharp stones and rough soil, and the distribution box should rest on a firm, level base above this bedding layer to prevent settlement or mechanical stress on the cables .

Positioning and Clearance

• The distribution box should be centrally located relative to the cables it serves, ensuring easy access for maintenance and inspection.
• Maintain adequate clearance between the box and the cables to avoid mechanical damage during installation or backfilling.
• If multiple services run in parallel, power ducts should be above telecommunications ducts, and a minimum separation of 12 inches of soil or concrete is recommended .

Protection and Backfilling

• Place concrete tiles or warning tapes above the cables and distribution box to prevent accidental damage during future excavation .
• Backfill with selected soil free of stones and organic material, compacted to avoid settlement that could stress the box or cables.
• Ensure the trench design allows proper drainage to prevent water accumulation around the box .

Earthing and Bonding

• The distribution box must be properly earthed, with earth conductors sized according to IEC 60364 standards to safely carry fault currents .
• If instrument or control cables are present, maintain instrument earthing standards to preserve signal integrity .

Access and Safety

• The box should be readily accessible from the surface, with covers that allow inspection and maintenance.
• Follow all local utility specifications for spacing, installation, and inspection to ensure compliance and safety . By following these guidelines, the distribution box will be mechanically protected, electrically safe, and accessible, ensuring long-term reliability of the underground cable system.