Installation of distribution box and switch box
- The power distribution system should be equipped with a distribution cabinet or a main distribution box, a distribution box, and a switch box, and implement three-level power distribution; 220V or 380V single-phase electrical equipment should be connected to the 220/380V three-phase four-wire system; when the current of the single-phase lighting line is greater than 30A, it is advisable to use a 220/380V three-phase four-wire power supply
- Several distribution boxes can be set below the main distribution box; several switch boxes can be set below the distribution box. The main distribution box should be located in an area close to the power supply, and the distribution box should be located in an area where electrical equipment or loads are relatively concentrated. The distance between the distribution box and the switch box shall not exceed 30m, and the horizontal distance between the switch box and the fixed electrical equipment it controls should not exceed 3m
- Each electrical equipment must have its own dedicated switch box. It is strictly forbidden to use the same switch box to directly control two or more electrical equipment (including sockets). One machine must have one switch, one box, and one leakage.
- The power distribution box and the lighting distribution box should be set separately. When combined and set as the same distribution box, power and lighting should be distributed separately; the power switch box and the lighting switch box must be set separately.
- There should be enough space and passages around the distribution box and switch box for two people to work at the same time. No items that hinder operation and maintenance should be piled up, and there should be no shrubs or weeds.
- The distribution box and switch box should be made of cold-rolled steel plates or flame-retardant insulating materials. The thickness of the steel plate should be 1.2-2.0mm, of which the thickness of the switch box steel plate should not be less than 1.2mm, and the thickness of the distribution box steel plate should not be less than 1.5mm. The surface of the box should be treated with anti-corrosion.
- The distribution box and switch box should be installed upright and firmly. The vertical distance between the center point of the fixed distribution box and switch box and the ground should be 1.4-1.6m. The mobile distribution box and switch box should be installed on a solid and stable bracket, and the vertical distance between the center point and the ground should be 0.8-1.6m.
- The metal electrical installation plate in the distribution box and switch box should be electrically connected to the metal box.
- The N-line terminal board and PE-line terminal board must be separately set on the electrical installation board of the distribution box. The N-line terminal board must be insulated from the metal electrical installation board; the PE-line terminal board must be electrically connected to the metal electrical installation board. The N-line in the incoming and outgoing lines must be connected through the N-line terminal board; the PE-line must be connected through the PE-line terminal board.
- The connecting wires in the distribution box and switch box must use copper core insulated wires. The branch joints of the wires shall not be crimped with bolts, but shall be welded and insulated, and there shall be no exposed live parts.
- The metal box of the distribution box, switch box, metal electrical installation plate and the metal casing of the electrical appliance that is normally not energized must be electrically connected to the PE line through the PE line terminal board, and the metal box door and the metal box body must be electrically connected through braided soft copper wire.
- The size of the distribution box and switch box should be adapted to the number and size of the electrical appliances in the box.
- The appearance and structure of the distribution box and switch box should be rainproof and dustproof.
- The inlet and outlet of the wires in the distribution box and switch box should be located at the bottom of the box.
- The inlet and outlet of the distribution box and switch box should be equipped with fixed wire clamps. The inlet and outlet wires should be insulated and bundled and fixed to the box body, and should not be in direct contact with the box body. The inlet and outlet wires of mobile distribution boxes and switch boxes should use rubber sheathed insulated cables.
Selection of electrical devices
1. The leakage protector should be installed on the side of the main distribution box and switch box close to the load, and should not be used to start the operation of electrical equipment.
2. The rated leakage action current of the leakage protector in the switch box should not be greater than 30mA, and the rated leakage action time should not be greater than 0.1s. The leakage protector used in humid or corrosive places should be splash-proof products, and its rated leakage action current should not be greater than 15mA, and the rated leakage action time should not be greater than 0.1s.
3.The rated leakage action current of the leakage protector in the main distribution box should be greater than 30mA, and the rated leakage action time should be greater than 0.1s, but the product of the rated leakage action current and the rated leakage action time should not be greater than 30mAs.
Requirements for use and maintenance of distribution boxes
1. Distribution boxes and switch boxes should have names, uses, branch markings and system wiring diagrams.
2. Distribution boxes and switch boxes should have locks on their doors and should be managed by a dedicated person (electrician).
3. Distribution boxes and switch boxes should be inspected and maintained regularly. The inspectors and maintenance personnel must be professional electricians. During inspection and maintenance, insulating shoes and gloves must be worn as required, insulating electrician tools must be used, and records of inspection and maintenance work should be kept.
4. The distribution box and switch box must be operated in the following order:
The power supply operation order is: main distribution box → distribution box → switch box;
The power outage operation order is: switch box → distribution box → main distribution box. (But emergency situations where electrical failures occur are excluded)
5. No debris should be placed in the distribution box and switch box, and they should be kept clean.
6. No other electrical equipment should be randomly connected to the distribution box and switch box.
7. The configuration and wiring of the electrical appliances in the distribution box and switch box are strictly prohibited from being changed at will; the leakage protector should be activated and the leakage test button should be tested once before use every day. If the test is abnormal, it is strictly prohibited to continue using it.
8. The incoming and outgoing lines of the distribution box and switch box are strictly prohibited from being subjected to external forces, and are strictly prohibited from contacting with sharp metal fractures, highly corrosive media and flammable and explosive materials.
