1. Distribution Box and Switch Box Installation
(1) The electrical distribution system should be designed with a main distribution box and sub-distribution boxes to ensure proper hierarchical power distribution. This helps in managing the flow of electricity efficiently and safely.
(2) The switch box must be installed at the final stage of the distribution system, directly connected to the equipment it controls. This ensures that each device is powered from the nearest source, reducing voltage drop and improving safety.
(3) The horizontal distance between the switch box and the fixed electrical equipment it serves should not exceed 3 meters. This minimizes the risk of electrical hazards and makes maintenance more accessible.
(4) There must be enough space around the distribution and switch boxes for two people to work comfortably. No items should be stored nearby that could interfere with operations or maintenance.
(5) Distribution and switch boxes must be securely mounted on solid structures. The height of fixed boxes should be between 1.3m and 1.5m above the ground to ensure easy access and safe operation.
(6) All switches and sockets within the boxes should be firmly secured and properly aligned. Loose connections can lead to dangerous situations and should be avoided.
(7) It is crucial that the working neutral wire and protective earth wire are never mixed. Mixing them can cause serious safety issues and compromise the entire system.
(8) All wiring inside the boxes must be insulated, with no exposed live parts. Connections should be tight and secure to prevent electrical faults and accidents.
(9) All metal enclosures and non-current-carrying parts must be properly grounded. This includes the box itself, internal components, and any exposed metal surfaces. Grounding is essential for electrical safety.
(10) Distribution and switch boxes must be protected from rain, dust, and physical damage. Covering them or placing them in sheltered areas can significantly increase their lifespan and reliability.
2. Selection of Electrical Equipment
(1) All electrical components within the boxes must be reliable and in good condition. Damaged or substandard devices should never be used as they pose serious risks.
(2) The main distribution box must have a total automatic circuit breaker, a shunt automatic circuit breaker, a main fuse, and a shunt fuse. The rated values and settings must be compatible with the downstream circuits.
(3) The main distribution box should also include a voltmeter, ammeter, and energy meter to monitor the electrical system effectively.
(4) Sub-distribution boxes must have a main circuit breaker, shunt circuit breaker, main fuse, and shunt fuse. These components must match the specifications of the downstream circuits.
(5) Each piece of electrical equipment must have its own dedicated switch box. This "one machine, one switch" principle prevents overloading and improves control. Never use a single switch for multiple devices.
(6) The switches in the switch box must be capable of cutting off power under all conditions. This ensures that the equipment can be safely isolated when necessary.
(7) A residual current device (RCD) must be installed in the switch box. It should be placed on the load side of the main power isolator and the switch box’s power isolator.
(8) RCDs must meet the requirements of GB6829-86. The rated leakage current should not exceed 30mA, and the operating time should be less than 0.1 seconds.
(9) Two-stage RCDs in the main distribution box and switch box must be correctly matched to provide effective hierarchical protection. This ensures that faults are quickly isolated without affecting the whole system.
(10) RCDs must be installed and operated according to the manufacturer's instructions. If an RCD has been unused for a long time or has been in continuous use for a month, it should be tested and repaired or replaced if necessary.
(11) Manual switches may only be used to control lighting circuits or motors with a capacity of up to 5.5 kW. Motors larger than this must be controlled using automatic switching devices or soft starters.
(12) The rating of all switches must match the rating of the equipment they control. Using mismatched switches can lead to overheating, damage, or even fire.
(13) The incoming and outgoing wires of the distribution and switch boxes must be located on the bottom of the box, not on the top, sides, back, or door. They should be bundled and formed into waterproof bends to prevent water ingress. The wires should not come into direct contact with the edges of the box. For mobile boxes, rubber cables must be used for the inlet and outlet.
(14) Power cords entering the switch box must not be connected via a socket. Direct connection to the power source is required to ensure a stable and safe supply.
3. Use and Maintenance
(1) Every distribution box should be clearly labeled with its name, purpose, and the circuits it serves. This helps in quick identification during emergencies or routine checks.
(2) All distribution and switch boxes must have locks on their doors, and a responsible person should be assigned to manage them. This prevents unauthorized access and ensures proper control.
(3) Distribution and switch boxes should be inspected and maintained at least once a month. Only qualified electricians should perform these tasks. During inspections, insulating shoes and gloves must be worn, and proper tools must be used to avoid electrical shocks.
(4) When inspecting or repairing the distribution or switch boxes, the corresponding power switch at the previous stage must be turned off, and a warning sign must be hung to indicate that maintenance is in progress.
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