Zhaga Book 18 and D4i for street lighting explained
Zhaga Book 18 and D4i are two different building blocks that together determine whether a street luminaire can be retrofitted. Zhaga Book 18 describes the mechanical and electrical interface on the luminaire that a plug-on module fits onto. D4i, based on DALI-2, describes how driver and sensor module communicate digitally and which data is made available. Only together do they give you a luminaire that can carry a node without modification and then also supply usable operating data. ENVIOTECH products are compatible with Zhaga Book 18 & D4i.
- Zhaga Book 18: interface and fit
- D4i: digital driver and sensor data
- Check both, do not assume one
- ENVIOTECH: compatible with Zhaga Book 18 & D4i
Zhaga Book 18: the interface on the luminaire head
Zhaga is an industry consortium that specifies interfaces for lighting components. Book 18 describes the interface for plug-on modules on outdoor luminaires: dimensions, connector and sealing. Its practical purpose is interchangeability, so a matching module can be fitted to a matching luminaire without opening or modifying the luminaire.
For a municipality this is above all a procurement argument. A luminaire with that interface stays extendable later without committing to one particular control product. Conversely, a missing interface does not make control impossible, but it increases the effort at the light point.
D4i: what runs digitally through the driver
D4i is a certification mark of the DALI Alliance and builds on DALI-2. Among other things it covers the driver supplying power to a plug-on module, device and operating data being stored in a standardised form, and that data being available for digital query.
The last point is the practically relevant one. Such data becomes the basis for analysis in the lighting management platform, for instance operating hours, energy values or unusual behaviour at a light point. Without a digital driver connection control is still possible, but the depth of data is lower.
How they interact, in short
- Zhaga without D4i: The module fits mechanically, but the driver provides no standardised digital data. Control works, diagnostics stay limited.
- D4i without Zhaga: The driver can be addressed digitally, but the standardised plug-on interface is missing, so a node has to be housed differently.
- Zhaga and D4i together: The straightforward retrofit case: the module fits, the power supply is defined and operating data is digitally available.
Retrofit or new luminaire: what the specifications tell you
The specifications do not decide the investment, they make the decision verifiable. Where an existing LED luminaire is in good condition and offers the right interface, that clearly favours retrofitting with a node. Where the interface is missing or the estate has reached the end of its service life anyway, a new luminaire prepared for nodes is the more durable answer.
That is why we assess the actual light point before making a recommendation, rather than relying on datasheets in general. One luminaire type may have been installed in several variants across procurement years.
A note on wording in documents
Procurement documents should clearly separate a required interface from a required certification, because the two mean different things. For our products the accurate statement is: compatible with Zhaga Book 18 & D4i. We only make wider certification claims where they are documented.
How to check retrofit suitability in your estate
- Identify luminaire type and year: The rating plate and procurement records are the starting point, often with variant-specific differences.
- Inspect the plug-on interface: Is there a prepared opening with a cover, or is the head fully closed?
- Check the driver: Datasheets or markings indicate whether digital control was designed in.
- Assess condition: Optics, gaskets and age also determine whether retrofitting is worthwhile at all.
- Verify with a sample: A visual check on a few light points per type replaces a lot of assumptions later in the project.
How ENVIOTECH handles this
Our nodes are designed to be fitted to suitably prepared luminaires and are compatible with Zhaga Book 18 & D4i. The EnvioLux system luminaire is built from the outset to accept nodes and, in our system offer, always ships with a node and a connection to EnvioTerminal.
For estates with mixed luminaire types that openness is the point: you do not have to commit to a single luminaire manufacturer in order to become controllable. Developed in Germany, data in Germany, support from Germany.
Matching products
EnvioLux Core Kit
Nodes and gateways for prepared luminaires, compatible with Zhaga Book 18 & D4i.
EnvioLux system luminaire
A new luminaire for light points that cannot be retrofitted, built to accept nodes.
EnvioTerminal (IMS)
Processes the operating data that a digital driver connection makes available.
Frequently asked questions about Zhaga and D4i
- Is Zhaga Book 18 the same as D4i?
- No. Book 18 describes the interface on the luminaire housing, D4i the digital communication and data provision through the driver. They complement each other rather than replace each other.
- Can we control lighting without that preparation?
- In many cases yes, but the effort at the light point is higher and the available data is less detailed. We check this per luminaire type.
- How should we word this in a tender?
- Separately for the interface, the digital control and the operating data you need, each referenced to the project-specific requirements. We support the drafting of technical requirements.
- Are ENVIOTECH products certified?
- We describe our products as compatible with Zhaga Book 18 & D4i. We only make wider certification claims where they are backed by documentation.
Related solutions
Checklist: retrofit street lighting
Nine checks from light-point records through to the rollout decision, to prepare your project.
Street lighting modernisation
From inventory to a documented decision for each light point.
Lighting design and tender support
Setting out requirements clearly without narrowing them to one product.
Lighting management system
What digital driver data actually delivers in day-to-day operation.
Clarify retrofit suitability in your estate
Tell us your most common luminaire types. We will indicate which light points are likely to be retrofittable and where we recommend a sample check.