Standard Height of Secondary Distribution Box on Construction Site

The bottom of a fixed secondary distribution box on a construction site should be installed between 1.3 meters and 1.5 meters above the ground.

Installation Height Guidelines

For fixed secondary distribution boxes, the vertical distance from the ground to the bottom of the box should be greater than 1.3 meters but less than 1.5 meters. For mobile distribution boxes, the bottom should be between 0.6 meters and 1.5 meters above the ground. These heights ensure the boxes are easily accessible for operation and maintenance while remaining safe from water, dust, and accidental impact .

Placement Considerations

• Location: Install the box in a ventilated, dry area away from harmful media such as gas, steam, liquids, or heat sources .
• Spacing: Ensure there is enough space for two people to work simultaneously around the box, and avoid stacking items or placing obstacles nearby .
• Distance from switch boxes: The horizontal distance between the secondary distribution box and the switch box should not exceed 30 meters, and the switch box should be within 3 meters of the equipment it controls .
• Protection: All boxes must be rainproof and dustproof, and made of iron plate or high-quality insulating material with a minimum thickness of 1.5 mm .

Wiring and Safety

• Wire inlets and outlets should be at the bottom of the box, with waterproof bends and insulated cables .
• Electrical connections must be secure, with protective neutral and working zero lines properly separated .
• Leakage protection should be implemented at both the secondary distribution box and the final switch box to ensure two-level protection .

Summary

Installing the secondary distribution box at the recommended height of 1.3–1.5 meters for fixed units ensures safe, convenient, and code-compliant operation. Proper placement, spacing, and protective measures are essential to maintain safety and reliability on construction sites .