Distribution Box Labeling And Wiring

The labeling and wiring of distribution boxes are core aspects of electrical safety and standardized construction. Strict adherence to these standards is essential to ensure electrical safety and ease of subsequent maintenance.

I. Distribution Box Labeling Standards
Labels must be clear, accurate, and durable, and mainly include the following:

1. External Labeling
Safety Warning Sign: Must be affixed with "Caution: Electric Shock," a yellow background with a black triangle lightning bolt symbol, in a prominent position.

Distribution Box Nameplate: Name, model, serial number, protection level, rated voltage/current.

Responsibility Sign: Indicates the person responsible for maintenance and their contact number, affixed to a commonly used location in the upper left corner of the box.

Circuit Purpose Labeling: Indicates the power supply area or equipment name on the outside of the box door, such as "Building A Lighting" or "Air Compressor No. 1."

2. Internal Labeling
System Diagram: Affixed to the inside of the door, including the main switch, branch switches, wire specifications, circuit number, Pe/Kx/Ijs, etc.

Each Switch/Circuit Labeling: Indicates the purpose below or on the side of each branch switch, such as "Lighting Circuit" or "Socket Circuit." Label printing is recommended for clear and durable lettering.

N-line terminal blocks and PE-line terminal blocks: These must be labeled "N" and "PE" or "Neutral" and "Protective Grounding" respectively.

Cable tags: Tag both ends of the incoming and outgoing cables, indicating the cable number, specifications, and start/end point.

II. Distribution Box Wiring Standards

1. Wire Colors

L1 (Phase A): Yellow, no other colors allowed.

L2 (Phase B): Green, no other colors allowed.

L3 (Phase C): Red, no other colors allowed.

N (Neutral): Light blue, must not be mixed with PE.

PE (Protective Earth): Yellow/green, must not be used as a phase or neutral wire under any circumstances.

2. Terminal Blocks and Wiring

N Block: Insulated installation, all neutral wires are concentrated here. Only one wire is allowed to be crimped into each terminal block unless the manufacturer explicitly allows two.

PE Block: Directly connected to the box and grounding mains. One wire per terminal block.

Multi-strand flexible wire: Cold-pressed terminals must be used; do not insert the wire directly into the terminal screw after tightening.

3. Special Scenarios

Socket Circuit: Must be connected to a residual current device (RCD). N and PE must not be short-circuited behind the socket. Lighting circuit: If using LED drivers, ensure the neutral line is not shared, as this can easily cause flickering or false tripping due to leakage.

Three-phase motor circuit: The phase sequence must be correct; forward and reverse rotation can be achieved by swapping any two phases.