Wolf ISM7i Internet Service Module

The Wolf ISM7i is a plug-in connectivity module for Wolf CGB-2 condensing boilers that adds Ethernet and Modbus TCP capability. Installation: insert the ISM7i into the boiler's digital input bus slot (access via the boiler front panel, following Wolf ISM7i installation guide). Connect an Ethernet cable from the ISM7i RJ45 port to the building LAN. The ISM7i obtains an IP address via DHCP by default; assign a static IP via the Wolf system app or via the ISM7i web interface at its DHCP-assigned address.

Enable Modbus TCP in the ISM7i web interface: navigate to Connectivity → Modbus TCP, set Modbus TCP port to 502, enable Modbus TCP server, and set the holding register mapping. The ISM7i exposes Modbus Holding Registers on TCP port 502, function codes 03 (read holding registers) and 06 (write single register).

Modbus register map

Critical registers for KNX integration: Register 1 = flow temperature setpoint (read/write, unit: °C × 10; write 650 to set 65°C flow setpoint). Register 100 = operating mode (read/write: 0=standby, 1=heating, 2=DHW only, 3=combined heating + DHW). Register 200 = fault code (read-only: 0=no fault; non-zero values correspond to Wolf fault code table in ISM7i manual). Register 201 = daily gas consumption (read-only, kWh × 10; divide by 10 for kWh). Register 202 = outdoor temperature from Wolf sensor (read-only, °C × 10). Register 203 = current boiler flow temperature (read-only, °C × 10).

Additional registers: Register 5 = DHW setpoint (read/write, °C × 10), Register 300 = operating hours today (minutes), Register 301 = starts today (count).

Intesis IN701KNX gateway configuration

The Intesis IN701KNX Modbus TCP-to-KNX gateway is configured using Intesis MAPS software. Create a new project, select gateway model IN701KNX, connection type Modbus TCP master, set slave IP = ISM7i static IP, port 502, slave ID 1, polling interval 10 seconds.

Map each Modbus register to a KNX datapoint and group address: Register 1 (flow setpoint) → DPT 9.001 (divide register value by 10 for °C) → GA 8/0/0 (bidirectional, enables ETS6 to write setpoint). Register 100 (operating mode) → DPT 5.001 → GA 8/0/1 (bidirectional). Register 200 (fault code) → DPT 5.001 → GA 8/0/2 (read-only). Register 201 (gas consumption today) → DPT 13.013 (multiply by 100 for Wh) → GA 8/0/3 (read-only, sent every 15 minutes). Register 203 (current flow temp) → DPT 9.001 → GA 8/0/4 (read-only, send-on-change 1°C).

8-zone KNX underfloor heating system

The CGB-2 serves an 8-zone underfloor heating system. Each zone has a KNX room thermostat (ABB Busch-Thermostat or Theben RAMSES 811 top2) with a heating demand output (DPT 1.001, GA 3/x/0 per zone). An MDT manifold controller (MDT AKD-0800.02, 8-zone actuator block) drives zone valves based on KNX heat demand GAs.

A KNX logic function (OR gate) combines all 8 zone demand GAs: if any zone demands heat → write 1 to GA 8/0/5 (boiler heat call DPT 1.001). The Intesis gateway maps GA 8/0/5 to Register 100: value 1 from GA 8/0/5 → write Register 100 = 1 (heating mode); value 0 → write Register 100 = 0 (standby). This gives zone-aggregated heat demand control to the boiler.

Weather-compensated flow setpoint

The Wolf CGB-2 has internal weather compensation, but for KNX-controlled setpoint override, a KNX outdoor sensor on GA 0/0/0 drives a logic curve: T_outdoor 0°C → flow setpoint 60°C; T_outdoor 15°C → flow setpoint 40°C. Linear: setpoint = 60 − ((T_outdoor / 15) × 20). The result (multiplied by 10 for register units) is written to GA 8/0/0 → forwarded by Intesis to Register 1.

Wolf CWL-2 HRV companion integration

For buildings with Wolf CWL-2 heat recovery ventilation units, a separate Modbus RTU register map is available (Wolf CWL-2 Modbus manual). Fan speed: Register 209 (0–3 = off/low/medium/high). Ventilation mode: Register 235 (1=manual, 2=automatic CO2). Wire the CWL-2 Modbus RTU port to a Moxa NPort 5110 RS-485-to-TCP converter (set baud rate 9600, parity none, stop bit 1), then add a second Modbus device in the Intesis MAPS project for CWL-2 registers with separate KNX GAs (GA 8/1/0 fan speed, GA 8/1/1 mode).

Commissioning: write value 450 (45.0°C) to GA 8/0/0 in ETS6 Group Monitor → verify ISM7i web interface shows flow setpoint updated to 45°C within 15 seconds. Test fault simulation by temporarily disconnecting the outdoor sensor and verify Register 200 changes to the Wolf sensor fault code (check code against Wolf fault table in ISM7i documentation).