04
2026
-
02
Technical Specifications for Distribution Boxes and Switch Boxes
Source:
1. The enclosure materials of distribution boxes and switch boxes are generally steel plates; insulating plates are also acceptable, while wooden materials are not recommended.
2. Distribution boxes and switch boxes shall be installed straight and firmly without inversion or tilting. For fixed distribution boxes and switch boxes, the vertical distance from the bottom to the ground shall be more than 1.3m and not more than 1.5m; for mobile distribution boxes and switch boxes, the vertical distance from the bottom to the ground shall be not less than 0.6m and not more than 1.5m.
3. It is strictly forbidden to connect the power supply lines leading to high-voltage switchgear with plug connectors.
4. The distance between electrical boxes shall not be excessively long. The distance between a distribution box and a switch box shall not exceed 30m, and the horizontal distance between a switch box and fixed electrical equipment shall not exceed 3m.
5. Each electrical equipment shall be equipped with its own dedicated switch box. On the construction site, every electrical equipment must have a dedicated switch box, complying with the requirement of one equipment, one switch, one residual current device (RCD). It is strictly forbidden to directly control two or more pieces of electrical equipment (including sockets) with a single switching device. An RCD must be installed in each switch box, with a rated residual operating current not exceeding 30mA and a residual operating time not exceeding 0.1s.
6. For safety purposes, all distribution box doors shall be fitted with locks. No temporary electrical equipment shall be hung or plugged in distribution boxes and switch boxes, and it is strictly forbidden to place sundries inside switch boxes.
7. The color of the external coating of distribution boxes (cabinets) shall be electrostatically sprayed according to the requirements of the Party A. The coating shall be firmly attached and evenly colored, without defects such as wrinkles, peeling, spots and missing spraying. No obvious color difference or reflection shall be observed at a distance of 1 meter, and the surface shall be flat and clean without damages such as pits and scratches. Other galvanized parts used in the boxes (cabinets) shall also be free from defects such as peeling, spots, missing plating and rust, and their surface quality shall meet the same above requirements. No sundries or dust shall be allowed inside the boxes (cabinets).
8. Mechanical Requirements for Distribution Boxes (Cabinets)
The steel plate used for the enclosure of distribution boxes shall have a thickness of not less than 1.5mm, and the cabinet body of power distribution cabinets shall be made of cold-rolled steel plate with a thickness of not less than 2.0mm. The steel plate doors and panels of the boxes (cabinets) shall have a thickness of not less than 2.0mm, and the back panels shall have a thickness of not less than 3.0mm. The guide rails must be sturdy, and the structure of power distribution cabinets shall be complete and firm. Meanwhile, two mounting lugs shall be welded at the bottom left and top right of the back of non-floor-standing distribution boxes. The mounting lugs shall be made of 40×4 flat steel with a length of 10cm. The wiring and assembly positions of electrical components inside the boxes (cabinets) shall be reasonable. The quantity, size, shape of reserved openings for incoming and outgoing wires, as well as the installation method of the boxes (cabinets) must comply with the specific parameter requirements of national standards, standard drawing sets and design drawings. The reserved incoming and outgoing wire openings or knockouts shall be equipped with corresponding seals, which shall meet the Class 3 sealing requirements after the assembly of incoming and outgoing wires is completed.
9. A main earthing terminal shall be welded on the structure of all boxes (cabinets), which shall be matched with the largest earthing conductor inside the earthed boxes (cabinets). A standard earthing terminal symbol shall be marked at the earthing terminal. The busbar of the protective earthing system shall be painted yellow and green with PE letter markings throughout its entire length. A dedicated earthing bolt with a diameter of not less than 6mm for connection with the metal foundation shall be installed on the boxes (cabinets). All conductive components of the boxes (cabinets), including the metal enclosure plates, frames, all movable doors, isolated secondary panels, metal plates of live conductors, and doors and cover plates with electrical appliances of 36V or above, must be reliably connected to the earthing terminal on the box (cabinet) body with tinned copper braided straps, so as to ensure the continuity between the normally non-live metal components of the box (cabinet) body and the earthing system during operation.
10. All components inside the boxes (cabinets) shall be strictly selected in accordance with the contract and the drawings provided by our party; any changes shall be separately notified by us. Auxiliary devices not specified in the drawings shall be qualified products from licensed manufacturers. All components used in the products shall meet the product performance requirements, and the manufacturer shall provide the component origin certificate, supplier qualification certificate, specifications and models, circuit breaker breaking capacity, certification documents for electromagnetic residual current devices and other relevant documents. Components shall be firmly installed inside the boxes (cabinets) without slipping or coating damage, and complete anti-loosening measures and fasteners shall be configured.
11. Nameplates and Various Markings
All provided nameplates, indication and warning markings must be in Chinese. The content of nameplates shall comply with relevant national regulations, and the material shall be corrosion and wear resistant metal, which must be firmly attached to the prominent position of the equipment.
Distribution Boxes,Power Distribution Cabinets,Switch Boxes
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