Hierarchical distribution boxes on construction sites must follow a structured setup with main, sub, and switch boxes, ensuring proper placement, material, wiring, protection, and compliance with safety standards.

Hierarchical Structure

Construction site power distribution should implement a three-level hierarchical system: a main distribution box, sub-distribution boxes, and switch boxes controlling individual electrical equipment. The main distribution box is located near the power supply, sub-distribution boxes are placed where electrical loads are concentrated, and switch boxes are positioned close to the equipment they control, typically within 3 meters horizontally. The distance between distribution and switch boxes should not exceed 30 meters to maintain efficiency and safety .

Placement and Environment

• Install boxes in ventilated, dry, and normal temperature areas.
• Avoid locations exposed to gas, flue gas, steam, liquids, vibration, heat sources, or potential impact.
• Ensure sufficient space around boxes for two-person operation and maintenance, free from obstacles, debris, or vegetation .
• The installation height is generally 1.5–1.8 meters above ground for easy access .

Material and Construction

• Boxes should be made of cold-rolled steel plates or high-quality insulating materials, with steel thickness 1.2–2.0 mm (distribution boxes ≥1.5 mm, switch boxes ≥1.2 mm).
• Surfaces must be anti-corrosion treated, and boxes should be rainproof and dustproof for outdoor use .
• Electrical components inside should be mounted on metal or non-wood insulating plates, with all metal parts electrically bonded .

Wiring and Protection

• Use insulated, high-temperature resistant copper wires with cross-sectional area matching load requirements.
• Ensure secure connections, no exposed live parts, and proper labeling of all circuits.
• Grounding: Metal boxes, electrical boards, and appliance casings must be grounded; protective neutral lines should be connected via terminal blocks .
• Include protection devices: circuit breakers, fuses, surge protectors, and leakage protection. Each circuit should have one dedicated switch and one leakage protector .
• Follow the principle of “one machine, one switch; one leakage, one box” to prevent misoperation .

Compliance and Maintenance

• Adhere to national standards (e.g., JGJ46-2005) and ensure CCC certification for products .
• Perform visual inspections and multimeter tests before powering on.
• Maintain regular inspections and maintenance to ensure long-term reliability .
• Label all components clearly and consider modular designs for future upgrades . By following these requirements, hierarchical distribution boxes on construction sites can ensure safe, efficient, and compliant power distribution, minimizing risks of electrical hazards and equipment failure.