DALI-2 large installations: the four numbers to know for 100+ circuits

Small DALI jobs forgive you. Twelve drivers, one gateway, a few scenes, and nearly any approach works. Past 100 circuits the protocol’s limits stop being trivia and start deciding the design.

This post is a teaching one. I’ll give you four numbers, then run the sums on a worked example, then show you where I’d check the manufacturer’s paperwork rather than trust my memory.

Number one: 64

A single DALI bus gives you 64 addresses for control gear. That’s the DALI Alliance’s own wording. Sensors and push-buttons (control devices) get their own 64 on the same bus.

The trap is that it’s addresses, not drivers. The Alliance notes that some control gear uses one address per logical unit, for example two addresses for a driver with two independently controlled lamp connections. So the number you count is outputs, not boxes.

Number two: 250 mA

The whole DALI system is capped at 250 mA of bus supply. A normal driver may draw up to 2 mA from the bus (Wikipedia’s figure), so 64 of them sits around 128 mA. That’s comfortable. The squeeze comes from other things on the same bus: sensors, buttons and D4i luminaires. The Alliance warns that D4i luminaires’ own bus supplies may need to be disabled before installation to stay within 250 mA.

Number three: 1200 bit/s

DALI is slow, and this is the one that surprises people. Wikipedia puts the data rate at 1200 bit/s and says sending 64 individual commands takes about 1.5 seconds, roughly 40 commands per second.

Picture a lounge with 40 fittings and a “Dinner” scene. If the gateway sends 40 separate level commands, that’s about a second of lights popping in one after another. Clients notice. The fix is to let the drivers do the remembering. Each driver stores up to 16 scenes, and each can belong to up to 16 groups. Then “Dinner” is one group or broadcast command and the whole room moves together.

Think of the gateway as the manager and the drivers as interns. A good manager says “everyone do the Dinner routine.” A bad one phones each intern with his own instructions.

Number four: 300 m

The Alliance’s quick start guide gives a maximum of 300 m between the two farthest devices, on 1.5 mm² cable at the full 250 mA. Star and daisy-chain both work, and you can mix them. What you cannot do is close a loop.

One caution. Wikipedia lists a 2 V maximum voltage drop and 4 Ω maximum per wire, and recommends 2.5 mm² for 300 m. That doesn’t match the Alliance’s 1.5 mm². Don’t pick a side. Use the cable table from your gateway and driver manufacturers.

Run the sums

Say a project has 100 circuits, and 20 of them are drivers with two independent outputs. That’s 120 addresses, not 100. One line holds 64, so two lines is the minimum.

I’d go to three lines at about 40 addresses each. Spare addresses cost very little now and a great deal later. At 40 per line the bus current is around 80 mA from drivers (40 x 2 mA, using the figure above), and an individual-command sweep of one line takes about a second. That second is the argument for scenes stored in the drivers. The “three lines, 40 each” choice is my own margin, not a standard.

Check the gateway, not just the drivers

Take Hager’s TYFS672D, a 2-line KNX Secure DALI-2 gateway. It supports up to 64 devices per line, and 16 scenes. It also lists up to 2 x 32 KNX groups, with each KNX group matching one KNX actuator channel.

Read that twice. With 64 drivers on a line and 32 KNX groups, you can’t give every driver its own KNX channel through groups alone. You’d share channels, roughly two drivers per channel. If the design needs every circuit controlled individually, find out from the manual whether the gateway can address drivers one by one. The product page doesn’t say, and I won’t guess.

The same page lists DT8 tunable white and RGB, RGBW and HSV colour control. It doesn’t mention DT6 or sensor support. If your drivers are DT6, check that too. Commissioning is through ETS 5.7.7 or later with the Device Configuration App.

What the drivers need

DALI-2 certified. The Alliance is blunt about it: a product not listed in the DALI Alliance Product Database is not DALI-2 certified. DALI-1 registration is closed for new products.

The right device type. DT6 for single-colour dimming, DT8 for tunable white and colour, and make sure the gateway supports it.

A known address footprint. Ask the supplier how many addresses each driver takes.

Known bus draw. Ask what each driver pulls, especially D4i.

Commissioning is where large jobs are won

Addresses are assigned over the bus once the hardware is installed. On 100+ circuits the real work is paperwork: the address, the circuit, the room, the drawing reference. Write it down as you go. I’d put emergency lighting and feature or strip lighting on their own lines too, so a fault or re-address on one line doesn’t touch the others. That one is my opinion, not a rule.

What to take away

Count outputs, not drivers. Keep headroom on every line. Store scenes in the drivers. Read the gateway’s group limits before you promise anything. Then check each figure above against the manufacturer’s current documentation, because I’ve told you where the sources disagree.

If you’ve got a large lighting project and want a second opinion on the DALI layout, I’m happy to look at it. Just a conversation about what the project needs.

Wayne, KNX Logic

wayne@knxlogic.co.za | 082 564 3982 | www.knxlogic.co.za

Sources

DALI Alliance, DALI Quick Start Guide (v1.1, April 2023): dali-alliance.org/data/downloadables/3/4/8/dali-quick-start-guide_public-v1_1_april-2023.pdf

DALI Alliance, DALI-2 certification status: dali-alliance.org/dali2/status.html

Wikipedia, Digital Addressable Lighting Interface: en.wikipedia.org/wiki/Digital_Addressable_Lighting_Interface

Hager TYFS672D KNX DALI-2 gateway secure 2-fold: hager.com/de/katalog/produkt/tyfs672d-knx-dali-2-gateway-secure-2-fach