Requirements for the distance between secondary distribution boxes and the ground

Fixed distribution boxes should be installed 1.3–1.5 meters above the ground, while mobile boxes should be 0.6–1.5 meters above the ground.Fixed Distribution Boxes

For fixed distribution boxes, the vertical distance from the bottom of the box to the ground should be greater than 1.3 meters and less than 1.5 meters. This height ensures that operators can perform routine maintenance, switch operations, circuit inspections, and instrument readings comfortably and safely . When mounted on walls, the bottom opening is typically between 1.2 meters and 1.5 meters, with an allowable deviation of ±10 millimeters to maintain uniformity and facilitate systematic management .

Mobile Distribution Boxes

For mobile or portable distribution boxes, the bottom should be installed no less than 0.6 meters and no more than 1.5 meters above the ground. This range accommodates ergonomic handling and safe operation while allowing mobility on construction sites or temporary installations .

Additional Considerations

• Accessibility and Safety: Boxes should be installed in dry, well-ventilated, and easily accessible locations, avoiding areas with corrosive gases, liquids, or other hazards .
• Spacing: The distance between a distribution box and its associated switch box should not exceed 30 meters, and the horizontal distance between a switch box and the controlled equipment should not exceed 3 meters to reduce line losses and improve efficiency .
• Ergonomics: The recommended height ensures that maintenance personnel can work comfortably without bending or stretching excessively, which is critical for safety and efficiency .
• Compliance with Codes: In addition to local standards like GB50303-2002, installations should also consider NEC requirements for panelboards, which recommend a dedicated electrical space from the floor up to 1.8 meters and a maximum mounting height of 2 meters for accessibility . By following these height standards, secondary distribution boxes can be installed safely, ergonomically, and in compliance with both local and international electrical codes.