860 m², 148 KNX devices, 2 020 group addresses — still readable four years after handover

At 2 000 group addresses an installation stops being a wiring job and becomes a documentation problem. Whoever opens the project in five years — us or somebody else — has to find one address among two thousand without reading the whole file.

Five vendors share the bus: Ekinex pushbuttons, Jung actuators and DALI gateways, Zennio inputs and heating boxes, HDL touch panels, and a CoolAutomation gateway for the VRF system. Each brings its own parameter model, and the VRF side speaks a proprietary protocol that has to be translated exactly once, in one place.

Underfloor heating adds a safety constraint the bus has to carry: every circuit needs its floor sensor, an over-temperature signal and a valve-flush status, not just a setpoint.

Group addresses are organised by function and floor, not by room or by device. Fifteen main groups: general, lighting per floor plus facade, shutters, ventilation, presence detectors, HVAC, underfloor heating per floor, climate sensors, pushbuttons.

Inside every lighting group the middle groups repeat in the same order — /0 switch, /1 switch status, /2 dimming, /3 brightness value, /4 brightness status, /5 detector block. Knowing the command address, an engineer derives the status address without opening the project.

Statuses live in their own middle groups rather than on neighbouring addresses. That keeps a bus trace of one function readable and lets a whole status group be filtered out at once during diagnostics.

Three bus lines with couplers, one per level, keep telegram traffic local: pushbutton traffic on a floor does not cross into the other lines.

The visualisation was not bought, it was written — Node.js and React on the front end, Python for the integration services. The owner runs and configures the whole installation from a web app on iOS and Android and sees the state of every system; a Telegram bot carries alarms and basic control; a local file server belongs to the same infrastructure. A bought visualisation ties the client to one vendor and to that vendor's release cycle. This one does not.

The bus does not only switch loads. The server rack, the electrical intake, leak protection, the pool plant and the whole climate side — air handling units, humidifiers, air conditioners, underfloor heating circuits, temperature and humidity sensors — all report their state into the same system.

Over four years that produced three interventions that would not have happened otherwise. Five water leaks were found and localised before any damage occurred. A humidifier developed a fault that showed up in its telemetry, and the unit was taken off power the same day. A damaged facade lighting cable was identified by the current leaking through it.

Monitoring in a private house is usually treated as an indulgence. Over four years here it has paid for itself three times over — and one of those times it took equipment off power before an overheating fault could go any further.