Proper acceptance of foundation steel and installation of distribution boxes ensures safety, compliance, and reliable electrical operation.

Foundation Steel Acceptance

Before installing a distribution box, the foundation steel and embedded conduits must be inspected and accepted as qualified. This includes verifying that the ground leveling layer is complete, the steel is correctly positioned according to design drawings, and all embedded conduits are properly aligned and secured . Any deviations in steel placement or leveling should be corrected before proceeding. For floor-standing cabinets, the foundation steel must be capable of supporting the cabinet weight and maintaining stability during operation .

Distribution Box Installation

Placement and Alignment

• Cabinet positioning: Place each distribution cabinet or panel on the foundation steel according to the construction layout. Adjust perpendicularity and levelness using sizing blocks if necessary, but no more than three blocks per cabinet, and ensure they are firmly welded .
• Wall-mounted boxes: Secure with expansion bolts or embedded dovetail/split bolts for hollow walls. Flush-mounted boxes should align with the wall surface .
• Height and accessibility: Install boxes at a height that allows safe operation and maintenance, typically around 1.5 meters for indoor setups .

Grounding and Safety

• Each cabinet or box must be individually grounded to the foundation steel using copper wire, with spring washers to prevent loosening. Doors should also be connected to the PE bus with braided copper wire .
• Ensure SPD (Surge Protective Device) wiring is short, straight, and properly grounded, with the model and layout meeting design requirements .

Wiring and Connections

• Use copper core insulated wires with appropriate cross-sectional areas (≥2.5mm² for current circuits, ≥1.5mm² for other circuits). Bundle circuits by voltage and type, avoiding interference with draw-out units .
• Ensure tight, neat connections without damaging wire cores. No more than two wires should connect to a single terminal, and anti-loosening washers must be used .
• Separate neutral (N) and protective grounding (PE) conductors to prevent cross-connections .

Final Checks

• Verify that all components, including breakers, busbars, and terminal blocks, meet design specifications and are correctly installed .
• Perform visual inspections and multimeter tests before energizing the system .
• Record installation details for future inspections and maintenance .

Summary

Acceptance of foundation steel and proper installation of distribution boxes are critical for structural stability, electrical safety, and compliance with design standards. Key steps include verifying foundation steel, precise cabinet placement, secure grounding, correct wiring, and thorough pre-energization checks. Following these procedures ensures long-term reliability and safety of the electrical distribution system .