How to Select KNX Bus Power Supply? Don't Get These 3 Parameters Wrong

All devices on a single KNX bus are powered centrally by the bus power supply.

• Undersized power supply: Frequent device disconnections & failed program uploads.
• Oversized power supply: Unnecessary cost with no practical benefits.

Each KNX device draws a rated current of 4mA ~ 12mA.

Selection rule: Sum up the total current of all bus devices, and reserve a 20% current margin.

If you have more than 50 devices: Split into two independent buses with one power supply for each. Do not cut corners here.

• Non-backup power supply: The KNX bus shuts down once power fails, and all devices go offline.
• Uninterruptible power supply (with battery backup): Maintains bus operation during power outages. Ideal for hospitals, hotel corridors and other areas where continuous control is mandatory.

Backup is unnecessary for regular residences, but highly recommended for commercial projects.

• Only one power supply per bus. Never connect two standard power supplies in parallel (will cause bus conflicts).
• Mount the power supply at the physical midpoint of the bus to minimize voltage drop.
• Common models: Schneider MTN683003 (320mA), MTN683004 (640mA)