Procedures and Standards for LED Display and Low-Voltage Electrical Installation

I. Construction Procedures:

1. Site Survey:

   • A. Material Storage: Coordinate with the client to use a nearby, spacious area for storing materials.

   • B. Water and Power: Ensure the site is equipped with necessary utilities.

   • C. Power Load: Check if the site’s power supply meets the load requirements of the project.

   • D. Equipment Layout: Determine the placement of racks, terminal devices, and cabling routes.

   • E. Sample Specifications: Confirm model and design preferences with the client, documented and signed for confirmation.

   • F. Safety: Ensure material safety and implement fire and theft prevention measures at the site.

2. Draw the Network Topology and Layout Plans for client confirmation.

3. Develop a Project Timeline, listing all tasks and their sequence with detailed timeframes. Share with the client for monitoring and coordination.

4. Assign a Project Manager and Site Supervisor, responsible for material planning, manpower, and coordination. Provide a timetable for cross-departmental cooperation and manage on-site execution.

5. Execute On-site Construction, track daily progress, adjust the schedule as needed to ensure timely delivery.

6. On-site Certification Testing, generate test reports, and print IP address tables, routing tables, and configuration tables.

7. Project Acceptance: All established documentation throughout the project will be submitted to the client and also archived internally for after-sales service.

II. Layout Specifications:

Layout planning is the foundation of all work. Any rework due to layout errors can be costly.

• Computer Desk Height: ~70 cm for primary schools, ~75 cm for secondary schools.

• Seat Dimensions: Width 60–80 cm, depth ~60 cm.

• Aisle Width Between Rows/Columns: 60–100 cm.

• Layout Drawings: Must be proportionally drawn to scale, marked with precise dimensions, and signed off by the client. If needed, layout outlines can be marked on-site for visualization.

III. Cabling Standards (Network & Power):

1. Cable Markings: Manufacturer name/code, cable model/specs, production year, and length, marked every 1m.

2. Plastic Cable Trays: Must meet design specs, suitable for -15°C and above, flame retardant (oxygen index ≥ 27%), smooth surface, free of sharp edges and deformation, with product certification.

3. Cable Slack:

   • Network cabinet: 3–6m;

   • Terminals: 0.3–0.6m;

   • Optical cables: 5–10m unless otherwise specified.

4. Raised Floor Installation: Panels must be tight and level (≤2mm deviation), properly grounded to meet anti-static design requirements.

5. Twisted Pair Length: Untwisted length ≤13mm.

6. Sheath Removal: Use proper tools; do not damage insulation.

7. No Mid-Cable Joints Allowed.

8. Twisted Pair Max Length: 100m. Use repeaters if exceeding, with no more than 3 repeaters per link.

9. Fiber Optic Transmission Distance:

   • 1Gbps, 850nm:

     • Standard 50μm MMF: 550m

     • 62.5μm MMF: 275m

     • New 50μm MMF: 1100m

10. Cable Bending Radius:

    • Unshielded twisted pair: ≥4x cable diameter (≥8x during installation)

    • Shielded twisted pair: 6–10x cable diameter

    • Backbone cable: ≥10x cable diameter

    • Fiber optic: ≥1.5x (≥20x during installation)

11. RJ45 Connections: Must follow color code standards T568A or T568B.

12. Crimping Crystal Heads: The outer sheath must be clamped inside the plug, not outside, to protect from tension.

13. Patch Panel Termination: Follow manufacturer and design requirements.

14. Shielding: Shield layer must have 360° contact with plug shell; contact length ≥100mm.

15. Labeling: Each twisted pair must have adhesive labels with unique numbers at both ends.

16. Provide Reliable Power & Grounding for server and wiring rooms.

17. Temporary Power Setup: Must include complete plugs, switches, sockets, and leakage protectors. Use cables with standardized wire colors:

    • Live wire: Red

    • Neutral: Blue

    • Ground: Yellow

    All sockets should follow wiring standards: “Left Neutral, Right Live, Center Ground” or “Top Live, Bottom Neutral”.

18. Power Conduits Underground: Use tight-fitting sleeves, with no joints underground. Protect PVC conduits during floor work to prevent damage.

19. Power Line Routing: Must be horizontal/vertical (no diagonal), to prevent damage.

20. Limit Socket Interfaces: All sockets/switches should be at least 300mm above ground and free from obstruction by furniture or doors.

21. Low-voltage and High-voltage Lines: Must not share conduits, and spacing must be ≥0.5m.

22. Three-phase Five-wire System:

    • A, B, C, N, and PE lines

    • Standard colors: A (yellow), B (blue), C (red), N (brown), PE (yellow-green)

23. Power Distribution: Segmented control between different units, ideally independent power supplies with no interference.

IV. Equipment Installation & Commissioning:

1. Rack Placement Criteria:

   • A. Safety: Concealed, ventilated, ideally in a dedicated room with restricted access.

   • B. Reliability: Stable power, good maintenance access.

   • C. Usability: Cable distances to terminals within acceptable limits.

   • D. Cost-effectiveness: Shortest overall cabling distance.

2. Network Equipment Installation:

   • A. Install on fixed shelves

   • B. Shelf height ≥500mm

   • C. Fix cables securely to prevent detachment

3. Terminal Device Installation:

   • A. Read manuals and instructions

   • B. Unbox and check against packing list

   • C. Place equipment

   • D. Power on each device individually and perform self-check

   • E. Connect to server for testing; isolate faulty devices

   • F. Install system software and conduct main system integration

   • G. Install workstation software; verify internet access

   • H. Resolve all remaining issues

   • I. Client may test functionality and become familiar with the system

   • J. Begin trial operation

V. Low-Voltage System Troubleshooting Standards:

1. Common Faults (50%–70% cable-related):

   • A. Physical Faults: Visible errors due to poor construction or damage (e.g., open/short circuits, miswiring).

   • B. Electrical Faults: Signal transmission does not meet standards due to factors like tight bends, excessive bundling, strain, or interference.

2. Most Faults Occur in Horizontal Cabling:

   • A. Product quality

   • B. Design issues

   • C. Construction techniques

3. Common Wiring Mistakes:

   • A. Open/short circuits, reverse connections (e.g., wires 1 and 2 swapped)

   • B. Crossed pairs (e.g., 1,2 to 3,6), often from mixing T568A and T568B standards or intentional crossover cables

   • C. “Split Pairs” (e.g., wiring 3,4 as a pair instead of 3,6), which may pass continuity tests but cause major crosstalk and unstable networks (soft faults)