Level 3 distribution boxes should use steel plates with a minimum thickness of 1.5 mm, typically ranging from 1.5 to 2.0 mm, depending on the application and environmental conditions.

Material and Thickness Standards

Level 3 distribution boxes, often used for final distribution in residential, commercial, or similar environments, are typically constructed from cold-rolled steel plates or flame-retardant insulating materials. According to national standards and construction guidelines, the minimum thickness for the steel plate of a distribution box is 1.5 mm, while switch boxes may have a minimum of 1.2 mm. The recommended thickness range for steel plates is 1.5–2.0 mm, ensuring mechanical strength, durability, and protection against environmental factors such as dust and rain .

Compliance with IEC 61439-3

IEC 61439-3:2024 specifies requirements for distribution boards intended to be operated by ordinary persons (DBO). While the standard focuses on electrical safety, rated currents, and operational suitability, it also implies that the enclosure must provide adequate mechanical protection. Verified design and material selection, including plate thickness, are essential to meet safety, IP protection, and structural integrity requirements .

Additional Considerations

• Corrosion Protection: The surface of the steel plate should be treated with anti-corrosion coatings to ensure longevity, especially for outdoor or humid environments .
• Environmental Ratings: Distribution boxes may need to meet IP ratings (e.g., IP5X or IP6X) for dust and water resistance, which can influence the required thickness and material strength .
• Installation Context: Level 3 boxes are typically installed near electrical loads, and their thickness must support secure mounting, terminal connections, and safe operation by ordinary users . In summary, for level 3 distribution boxes, use cold-rolled steel plates with a minimum thickness of 1.5 mm, apply anti-corrosion treatment, and ensure compliance with IEC 61439-3 and relevant national standards to guarantee safety, durability, and operational reliability.