National Standard Dimensions and Thickness of Distribution Boxes

Distribution boxes must comply with specific dimensions, material thickness, and installation requirements to meet national safety and mechanical standards.Material and Thickness RequirementsSteel enc...

National Standard Dimensions and Thickness of Distribution Boxes

Distribution boxes must comply with specific dimensions, material thickness, and installation requirements to meet national safety and mechanical standards.

Material and Thickness Requirements

  • Steel enclosures: Minimum thickness of 1.5mm for general distribution boxes; power distribution cabinet bodies must use cold-rolled steel of at least 2.0mm thickness .
  • Doors and panels: Steel plate doors and panels must be at least 2.0mm thick, while back panels require a minimum of 3.0mm .
  • Mounting lugs: Non-floor-standing boxes must have two welded mounting lugs made of 40×4mm flat steel, 10cm in length .
  • Earth clamps: For larger KVA boxes, earth clamps should be 2mm thick .

Dimensions

  • Plastic distribution boxes (ABS material, flame-resistant) vary by series:
    • HA, HK, LGD series: Length 100–415mm, Width 105–323mm, Height 75–140mm .
    • MB-ABC series: Length 200–328mm, Width 172–174mm, Height 95mm .
  • High-capacity KVA boxes: Busbar strips and feeder droppers dimensions vary by rating, e.g., 72×50×8mm for 63/100 KVA and 1120×50×15mm for 160/315 KVA boxes .

Installation and Clearance

  • Vertical mounting height: Fixed boxes 1.3–1.5m from the ground; mobile boxes 0.6–1.5m .
  • Horizontal spacing: Distribution box to switch box ≤30m; switch box to fixed equipment ≤3m .
  • Sealing: Reserved wire openings must meet Class 3 sealing requirements after assembly .
  • Locking: All doors must be lockable; temporary equipment or sundries are prohibited inside .

Compliance

  • Boxes must follow national standards, standard drawing sets, and design drawings for dimensions, mounting, and wiring layout .
  • Plastic boxes comply with BS EN60439-3 and JB/T7121-93 standards . These specifications ensure mechanical strength, electrical safety, and proper installation for both residential and industrial applications.
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