A KNX weather station is essential for automatic blind control in buildings with large glazed facades — preventing solar gain in summer (cooling energy savings), optimising daylight harvesting for DALI dimming systems, and protecting blinds from wind damage. The Elsner Compact P04/3-RS KNX is the industry standard for Central European KNX installations: three lux channels (east, south, west), wind speed, rainfall detection, and GPS-calculated sun position all integrated in one rooftop unit communicating via KNX TP.

Elsner Compact P04/3-RS hardware installation

The Compact P04/3-RS mounts on a rooftop mast (not supplied) at a minimum 2m above roof level to avoid shadowing from parapet walls and HVAC equipment. Orientation: orient the weather station so the labelled South sensor faces geographic south (use compass app on phone for orientation alignment; ±10° acceptable). Fixings: M8 bolts to mast, weatherproof. Cable routing: bring KNX YCYM 2×2×0.8 mm² cable from rooftop junction box through conduit to nearest KNX line coupler in the electrical panel — maximum 350m KNX bus cable length. Weatherproof junction box: IP54 minimum at cable exit point from weather station (below mast mounting flange). KNX connection: push KNX cable into spring-clamp terminals inside weather station housing — + (red) and - (black). GPS module: the P04/3-RS includes an internal GPS receiver for precise latitude/longitude and current time — powers up from KNX bus, acquires fix in 5-10 minutes with clear sky view. GPS position is used for astronomical sun position calculation (azimuth and elevation) every minute.

ETS6 parameter configuration

Download the Elsner P04/3-RS product database from elsner-elektronik.de or KNX online catalog. Key ETS6 parameters: Lux channel calibration: each of the 3 lux sensors (East/South/West) has a calibration factor (0.5-2.0×, default 1.0). Measure actual lux with a calibrated meter (e.g. Extech LT300) on each sensor face during commissioning on a clear midday. Adjust calibration factor so ETS6-reported lux matches meter reading. Wind speed: alarm threshold 1 (default 6 m/s = Beaufort 4, first blind retraction), alarm threshold 2 (default 11 m/s = Beaufort 6, immediate blind retraction, safety mode). Hysteresis: alarm reset at threshold - 2 m/s. Hold time after wind alarm: 15 minutes (prevents blinds lowering immediately after gust; allows wind to stabilise). Rain sensor: alarm delay 10 seconds (ignores brief splashes from HVAC equipment), cancel delay 30 minutes after last rain detection (allows facade to dry before blinds lower).

Sun position and tracking

GPS-based astronomical calculation: the Compact P04/3-RS calculates sun azimuth (0°-360° from north) and elevation (0°-90° above horizon) every minute from GPS coordinates and UTC time. KNX communication objects: Sun azimuth (DPT 5.003, 0-360°, 1-byte scaled), Sun elevation (DPT 5.001, 0-90°, 1-byte scaled). ETS6 blind controller (MDT SCN-JAL1600.02 or Gira 2013): receives sun azimuth and elevation as KNX inputs → calculates optimal blind slat angle to prevent direct solar penetration into room while maintaining diffuse daylight. Elsner Raffstore sun control (built-in to P04/3-RS): for Raffstore venetian blind applications, the weather station itself calculates optimal slat angle from sun elevation and window orientation — publishes directly as DPT 5.001 slat position (0=horizontal, 255=vertical closed) for each facade orientation. Blind controller receives slat position from weather station, overrides manual control when sun tracking is active.

Lux-based blind automation logic

ETS6 logic for facade blind control using lux channels: South facade blinds: when South lux > 40,000 lux (bright sunshine on south glass) AND wind speed alarm = 0 AND rain alarm = 0 → lower blinds to 80% position, slat angle = 45° (from P04/3-RS slat output). When South lux < 10,000 lux (overcast) AND no sun tracking override → raise blinds to 0% (fully open). East facade blinds: use East lux channel with lower threshold (20,000 lux — morning sun lower intensity than midday south). West facade: use West lux channel, active typically 13:00-19:00 local time. ETS6 logic block parameters: threshold type = absolute lux; hysteresis 5,000 lux (prevents blind hunting between open/closed at threshold boundary); minimum time in state: 3 minutes (prevents rapid cycling on intermittent cloud). Wind safety override: if wind alarm = 1 → KNX priority output on blind actuator (priority level 3, highest) → raise blinds to 0% regardless of lux or manual commands. Priority remains active until wind alarm = 0 AND hold time expired.

Combining multiple weather stations for large buildings

For buildings with complex rooflines or blocked sensor views: install multiple P04/3-RS units (one per unobstructed roof zone). Each unit outputs its own lux and wind measurements as KNX group addresses on different GAs. ETS6 Maximum logic (ABB or MDT ETS6 multi-input function block): takes wind speed from all weather stations → outputs maximum wind speed → if maximum > threshold → blind safety retraction. For lux: use facade-closest sensor (South-facing zone for south blinds). If one weather station KNX connection fails (bus fault): ETS6 watchdog timer (cyclic sending from P04/3-RS set to every 60 seconds) → if no lux telegram received in 120 seconds → ETS6 triggers "sensor fault" flag (DPT 1.001) → blinds to safe position (fully raised) until sensor restored.