Installation of low-voltage distribution cabinets and distribution boxes

Proper installation of low-voltage electrical cabinets and distribution boxes ensures safety, reliability, and compliance with IEC and national standards.

Pre-Installation Requirements

Before installation, ensure that indoor ceiling, wall, and floor works are completed with no water leakage, and that the ground leveling layer and foundation steel are inspected and qualified. For floor-standing cabinets, verify that embedded conduits and cable trenches are properly installed. Wall-mounted distribution boxes should have completed wall finishes and inspected reserved holes and conduits for power and lighting wiring. Confirm that surge protective devices (SPD) and grounding connections meet design requirements before connecting power lines .

Cabinet Types and Mounting

Low-voltage cabinets come in fixed (GGD) and drawer-type (GCK, GCS, MNS) designs. Fixed cabinets are cost-effective but require full shutdown for maintenance, while drawer-type cabinets allow quick replacement of faulty units. Cabinets can be wall-mounted or floor-mounted with front access, and the base channel steel must be leveled to prevent skewing and poor contact . Enclosures should meet IP54 or higher for protection and may be made of cold-rolled steel, stainless steel, or corrosion-resistant materials .

Wiring and Connections

• Secondary circuit wiring must comply with design requirements, using insulated copper conductors rated at least 450/750V. Current-carrying circuits should have a minimum cross-section of 2.5mm², and other circuits 1.5mm² .
• Wire bundling and labeling are essential; circuits of different voltage levels and AC/DC lines should be separated. No more than two wires should connect to a single terminal, and anti-loosening washers must be used .
• Cable lugs should be crimped with a hydraulic tool and coated with conductive paste to prevent oxidation .
• Cable holes at the top and bottom of cabinets must be sealed with fireproof putty to prevent rodent damage or short circuits .

Grounding and Safety

• The metal frame and foundation steel must be reliably connected to the protective conductor. Doors with electrical devices should use a yellow-green insulated copper flexible wire of at least 4mm² for grounding .
• Ensure PE bars inside cabinets are connected to external protective grounding conductors. Draw-out and drawer-type cabinets must operate smoothly, with aligned moving and stationary contacts .
• Always follow the principle: disconnect the load switch first, then the isolation switch when working on live equipment .

Surge Protection

• SPD installation must follow design specifications, with short, straight connection wires not exceeding 0.5m. Grounding wires should not be near outlets .

Maintenance Considerations

• Label all wires clearly and limit two wires per terminal to simplify future maintenance .
• Inspect for overheating, loose screws, or unusual sounds during routine checks. Use temperature-indicating strips, smell for burnt odors, and listen for buzzing sounds to detect early faults .

Summary

Successful installation of low-voltage cabinets and distribution boxes requires careful attention to preparation, mounting, wiring, grounding, surge protection, and maintenance. Following IEC standards and manufacturer guidelines ensures safety, operational reliability, and ease of future maintenance .