DALI-2, D4i or Zhaga-D4i? Four Questions to Ask Your LED Driver Supplier

The short version

DALI-2, D4i and Zhaga-D4i are often described as three generations of a protocol. They are not. They are one DALI control line with the scope wrapped progressively wider. DALI-2 makes drivers and control devices from different vendors interoperate. D4i moves power and data inside the luminaire and standardizes them. Zhaga-D4i then puts a pluggable socket on the luminaire housing for sensors and comms nodes. Decide which layer you actually need before chasing the newest badge.

DALI-2: does your gear from different vendors talk?

DALI-2 is the generation where DiiA runs a real certification and database programme. It brings control devices — occupancy and light sensors, push-buttons, application controllers — into the certified ecosystem alongside control gear. A DALI-2 subnet holds up to 64 control gear (drivers, ballasts) in one address space and a separate 64 control devices, plus 16 groups and 16 scenes. DiiA's own cabling guidance is a 300 m maximum between any two devices on 1.5 mm² cable with a 250 mA bus supply budget — that is a point-to-point figure, not total cable length.

The practical meaning for buyers: if you only need addressable dimming, zoning and scenes driven by another brand's panel or controller, a DALI-2 dimmable driver is enough. Our K02 (DALI-2 DT6 constant-voltage 12/24 V, 60–400 W), K03 (DALI-2 DT8 tunable white), H08 (triple DALI + Push + 0–10 V, IP50) and H19 (constant-current DALI / 0–10V / Triac / rotary-code, 10–52 W for downlights) all sit at this layer.

D4i: power and data, inside the luminaire

D4i is not a new protocol — it is DALI-2 inside the luminaire. It makes four data parts mandatory for an LED driver: Part 250 integrated bus power supply, Part 251 luminaire data, Part 252 energy data, Part 253 diagnostics and maintenance (Part 150 auxiliary power is optional). In plain terms, a D4i driver stores and reports luminaire and driver energy, run-time and fault records in a standard format that a building management system can read on plug-in.

D4i also aligns with the North American ANSI C137.4-2019 and is compatible with NEMA/ANSI C136.41 and the Zhaga Book 18 socket. For smart-streetlight and connected-luminaire makers, this is the step from it dims to it is asset-manageable.

Zhaga-D4i: a pluggable port on the outside

Zhaga-D4i certifies the combination of Zhaga Book 18 (outdoor socket) and DiiA D4i: a standard socket on the luminaire where a sensor or comms node clicks on, plug-and-play. The luminaire ships without a specific sensor pre-installed; the node is added per project later.

What changed in 2026: Book 18 Edition 4 reaches heritage lighting

This year Zhaga released Book 18 Edition 4, extending the standard from ordinary streetlights to decorative and heritage outdoor luminaires. Those fixtures rarely allow a sensor mounted on the housing, so the spec introduced bracket-ready luminaires — the sensor or comms module sits on a pole bracket via a Zhaga socket, and the DALI bus runs through longer in-pole cabling. The standard therefore mandates surge protection on the communication link (DALI Part 151). For driver makers the implication is clear: the driver must carry its own protection for the D4i bus, not leave it to the luminaire factory to bolt on a separate device.

Back to selection: four questions for your supplier

• Do you need interoperability, or luminaire-level maintainability and connectivity? Zoned dimming across brands needs only DALI-2; per-luminaire energy reporting and remote diagnostics are where D4i enters.
• Does the driver actually carry D4i Parts 250–253? DALI dimming capability is not the same as D4i certification — ask the two separately and do not let "supports DALI" cover both.
• Is there a Zhaga Book 18 socket on the luminaire? Without that port, pluggable sensor cannot land.
• For outdoor or heritage projects, is surge protection on the D4i bus done? Check it against the Book 18 Edition 4 mandate.

What our line gives you

• For standard DALI-2 zoned dimming: K02, K03, H08, H19 cover constant-voltage and constant-current, single-colour to tunable white, indoor to IP50.
• For wireless connected luminaires: K05 (Mijia/Tuya Bluetooth·ZigBee, 24 V 200–400 W) works as an in-luminaire wireless node that bridges to a DALI+ network.
• Where strict D4i certification or a Zhaga-D4i socket is required, we confirm the specific model's certification status before quoting — we do not blend supports DALI dimming with D4i-certified.