Overview

Webasto Unite 22 kW (three-phase, IP54) is Webasto's commercial EV charger with RFID, OCPP 2.0.1, and Modbus TCP for KNX building integration. Modbus TCP on port 502, unit ID 1. Firmware version 2.x or later required for Modbus — confirm in Webasto myWebasto portal under charger details.

Register Map

Holding registers (FC3): 1001 (charge current setpoint, uint16, A, write: 0=pause, 6-32A = active charging limit), 1002-1003 (session energy, uint32, Wh), 1004-1005 (active power, uint32, W), 1006 (charge state, uint16: 0=available, 1=preparing/EV connected, 3=charging, 5=finishing, 6=reserved, 9=unavailable).

MDT Modbus Gateway Configuration

Device entry for Unite at building LAN IP, port 502, unit 1. Read task 1: regs 1004-1005 (2 regs uint32, 10s) divided by 1000 mapped to KNX DPT 9.001 kW. Read task 2: reg 1006 (10s) mapped to KNX DPT 5.010 (charge state). Write object: reg 1001 (uint16) from KNX byte GA.

Dynamic Load Management

KNX reads building grid meter (Eastron SDM630 Modbus TCP via separate gateway device): active power total (regs 52-53 float32, W). Available capacity formula: 'available_A = (contract_kVA x 1000 / 230 - house_load_W / 230)'. Clamp to 6-32A or 0 (pause). KNX logic writes 'available_A' as uint16 to Unite reg 1001 every 30s.

Multi-Charger Balancing

For 3 Unite units: KNX sums 'house_load_W', identifies how many chargers are active (reg 1006=3), distributes available capacity equally ('available_A / active_count') to each charger via separate write tasks per charger IP.

Webasto Next 7.4 kW Residential (No Modbus)

Use OCPP local mode. In myWebasto app: Settings > OCPP > WebSocket 'ws://192.168.1.50:9000/webasto'. Home Assistant OCPP integration (HACS: evse_ocpp) acts as central system, reads MeterValues (power W, session energy Wh), reports to KNX via HA KNX integration. HA automation: when KNX GA 6/0/2 (grid power) reports import > 3 kW: trigger OCPP 'SetChargingProfile' to reduce Webasto Next to minimum 6A.

Commissioning Verification

With vehicle connected but not charging (state=1): write reg 1001=6 and verify state changes to 3 (charging) and power reg 1004 shows approximately 4140W (6A x 230V x 3 phases). Write reg 1001=0 to pause, verify state returns to 1. This confirms Modbus write path is working.