DALI PSU Sizing and Bus Limits
A DALI line is bounded by hard numbers — 64 addressable devices, 16 groups, 16 scenes — and by a PSU current budget that has to cover every device on the bus, not just the fittings it switches. Here is how to size a line that stays inside all three.
From device count to a signed-off line
Count and classify devices
List every control gear unit and every control device — sensors, push-buttons, DT8 modules — that will sit on the line; each one takes an address whether it switches load or not.
Check against the 64/16/16 limit
One DALI line supports up to 64 individually addressed devices, up to 16 groups and up to 16 scenes — confirm the device count before committing to a single-line design.
Sum the PSU current budget
Add the DALI-bus current draw of every connected control gear and control device from its datasheet — this is separate from the 230V mains load the driver itself switches — and select a PSU with margin above that total.
Size cable and split lines if needed
Check cable length against bus voltage-drop limits for the chosen conductor size; where device count or run length is tight, split into a second DALI line with its own PSU rather than pushing one line to its ceiling.
The numbers a spec has to respect
addressable devices per line
A single DALI line supports up to 64 individually addressed devices — every control gear unit and every control device counts toward that ceiling.
16 groups per line
Devices can be assigned to up to 16 groups, so a single push-button or sensor command can switch a whole zone without rewiring for zone control.
16 stored scenes
Up to 16 scenes can be stored per line, each recallable by a single command — the level plan for a room lives in the ballasts, not in external logic.
Individual, group or broadcast addressing
Any control device can target one device, a group, or every device on the line at once — the same physical switch behaves differently depending only on configuration.
DALI-2 certified interoperability
DALI-2 certifies control gear and control devices separately against IEC 62386, so certified products from different manufacturers can sit on the same line by design.
DT8 tunable white and colour
DT8 is the DALI-2 device type for tunable white and colour fixtures, controlling brightness and colour temperature over the same two-wire bus as standard dimming.
What we help you plan
A line design an installer can commission first time, not just a bill of materials.
- Device count and address plan against the 64-device line limit
- PSU current budget calculated from datasheet bus currents
- Group and scene table matched to the control intent
- Cable-length check and line-splitting plan for larger installations
- Gateway mapping to KNX or BMS where the line needs to integrate upstream
Frequently asked questions
How many devices can one DALI line carry?
Up to 64 individually addressed devices, grouped into up to 16 groups with up to 16 stored scenes — control gear and control devices both count toward the 64.
How do I size the DALI PSU current budget?
Sum the DALI-bus current draw of every connected control gear unit and control device from its datasheet; this bus current is separate from the 230V mains load the driver itself switches, so PSU sizing needs both figures kept apart.
When should I split an installation into two DALI lines?
Split into a second line with its own PSU once device count or cable run approaches the practical limit of a single line — it's cleaner than commissioning one line at its absolute ceiling.
What does DALI-2 certification actually guarantee?
DALI-2 certifies control gear and control devices separately against IEC 62386, which is what lets certified products from different manufacturers be mixed reliably on the same line.
What is DT8 and when do I need it?
DT8 is the DALI-2 device type for tunable white and colour control, handling brightness and colour temperature together over the same bus — specify it wherever the fitting needs colour or CCT control, not just dimming.
Sizing a DALI line?
Send us the device list and layout and we'll work through the PSU budget, group/scene table and line split with you — engineer to engineer.