Standard for Three-Level Electrical Distribution Boxes in Factory Construction

A standard three-level electrical distribution box system provides tiered power distribution with main, sub, and switch-level boxes, ensuring safe and organized temporary electricity supply on construction sites.Structure and LevelsFirst-Level Distribution Box (Main Distribution Box): This is the primary hub installed near the power source. It receives electrical energy from the incoming line and distributes it to second-level boxes. It typically contains the main circuit breaker, main leakage protector, voltmeter, and ammeter for centralized monitoring and control of the entire site's power supply. The main switch rating is determined by the number of downstream boxes and total load capacity, usually between 50–150 kW per box . Second-Level Distribution Box (Sub-Distribution Box): Installed near high-power equipment or in specific construction areas, the second-level box receives power from the main box and redistributes it to third-level boxes. It includes branch circuit breakers and branch leakage protectors to safeguard individual circuits. The box often features an inner and outer door design, spray-painted exterior, and a rainproof top for outdoor use . Third-Level Distribution Box (Switch Box): This is the final junction box directly connected to electrical equipment, such as lighting, power tools, or machinery. Each switch box typically controls one appliance or a group of similar devices. It contains isolation switches, circuit breakers, and leakage protectors for direct control and protection of the connected equipment .Materials and DesignConstruction site distribution boxes are commonly made from cold-rolled steel plates or fiberglass/polyester enclosures for durability and weather resistance. Rainproof designs often include sloped roofs and reinforced triangular brackets to prevent water accumulation and enhance stability. Internal wiring is organized for safety, and pre-wired options are available for quick installation .Safety and Protection FeaturesLeakage protection: Installed at both main and branch levels to prevent electric shock.Circuit breakers: Multiple air circuit breakers accommodate varying power requirements (e.g., 2P/32A, 3P/63A, 3P/10A, 100A).Load management: Ensures no single switch controls multiple devices, following the principle of “one machine, one switch, one protection, one box, one lock” .Outdoor suitability: Rainproof tops and reinforced brackets allow safe use in outdoor construction environments .ApplicationsThese three-level distribution boxes are suitable for temporary power supply in:Steelwork and rebar processing areasWoodworking and carpentry shedsConstruction elevators and tower cranesLighting, power tools, and small machinery By implementing a three-level distribution system, construction sites achieve organized, safe, and efficient power management, minimizing risks of overload, short circuits, and electrical hazards.