How to design a low voltage distribution board?

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Designing a low voltage distribution board (LVDB) involves careful planning to ensure safety, reliability, and compliance with electrical standards.

You can find here a step-by-step guide to help you through the process.

Step 1: Define the requirements

• Determine the voltage level (e.g., 230V single-phase or 400V three-phase).
• Identify the types of loads (lighting, sockets, HVAC, motors, etc.).
• Calculate the total power demand (in kW or kVA).
• Decide on the number of circuits needed.

Step 2: Choose the enclosure

• Select the material (metal or plastic).
• Choose the IP rating based on the environment (e.g., IP65 for outdoor).
• Ensure the size allows for all components and future expansion.

Step 3: Select the components

• Main Incomer: MCCB or MCB with suitable rating.
• Busbars: rated for total current.
• Outgoing MCBs: one for each circuit, sized to the load.
• RCDs/RCBOs: for earth leakage protection.
• Surge Protection Device (SPD): optional but recommended.
• Neutral and Earth Bars: for proper termination.

Step 4: Perform load calculations

• Apply diversity factors to avoid oversizing.
• Ensure the sum of outgoing breakers does not exceed the main breaker rating.

Step 5: Design the wiring and layout

• Create a Single-Line Diagram (SLD) showing all connections.
• Size the cables based on current, voltage drop, and installation conditions.
• Clearly label all breakers and terminals.

Step 6: Ensure compliance with standards

• Follow local regulations (e.g., IEC 61439, NF C 15-100 in France).
• Ensure proper earthing and bonding.
• Prepare documentation for inspection and maintenance.

Step 7: Testing and commissioning

• Perform:
  • Insulation resistance test
  • Continuity of protective conductors
  • Polarity check
  • Functional testing of RCDs and breakers

In conclusion, a well-designed LV distribution board ensures safe, efficient, and compliant power distribution. Follow each step carefully to meet both technical and regulatory requirements.