--- title: "Wolf WRS-K" description: "Wolf WRS-K air handling unit with Modbus RTU interface for ventilation control via TapHome." url: "https://taphome.com/en/compatibility/wolf-wrs-k/" language: en lastmod: 2026-10-08 generator: hugo ai: topics: ["modbus-rtu","air-recovery","rs485","ventilation","bms","heat-recovery"] questions: ["How to integrate Wolf WRS-K with TapHome?","What does the Wolf WRS-K TapHome template control?","How to connect Wolf WRS-K via RS-485 to TapHome?","How to enable BMS mode on the Wolf WRS-K?","What is the parity setting for Wolf WRS-K Modbus communication?","How to control fan speed and room temperature on Wolf WRS-K via TapHome?"] --- # Wolf WRS-K Communication: Modbus RTU - [Wolf Official Website](https://www.wolf.eu) The Wolf WRS-K is a commercial air handling unit (AHU) with heat recovery, controlled via the KLM-M or KLM-L controller. The optional Modbus RTU interface card plugs into the controller's serial card slot and exposes temperature sensors, fan speed control, room thermostat, CO2 air quality monitoring, and ventilation mode switching to TapHome over RS-485. The template requires **BMS mode** (Building Management System) — an initialization script automatically sets the operating mode to BMS (H:214 = 2) when the template is loaded. > [!WARNING] > **Parity inconsistency** — The TapHome template configures **even parity, 1 stop bit** (8E1), but the manufacturer specification states **no parity, 2 stop bits** (8N2). If communication fails, try switching to 8N2 in TapHome's Modbus connection settings. The baud rate is 19200 in both cases. ## Hardware connection ### ModBus interface card ![Wolf WRS-K Modbus interface card with connection block ① and RS-485 terminal block ②](https://taphome.com/images/compatibility/wolf-wrs-k/installation-steps-1-p005_hu_77cd18d63984a10a.jpg) The ModBus interface card has two connections: 1. **Connection block** ① — plugs into the KLM-M (part no. 2744747) or KLM-L (part no. 2744746) controller 2. **Terminal block** ② — 3-pin pluggable connector for the RS-485 bus The card is usually supplied pre-installed with the control unit. If retrofitted: 1. Isolate the KLM-M or KLM-L controller from the power supply 2. Remove the cover of the "serial card" slot using a screwdriver ![Removing the serial card slot cover on the KLM controller](https://taphome.com/images/compatibility/wolf-wrs-k/installation-steps-2-p005_hu_ec0b43eae26c7674.jpg) 3. Remove the inner part of the cover with wire cutters ![Removing the inner part of the slot cover with wire cutters](https://taphome.com/images/compatibility/wolf-wrs-k/installation-steps-3-p005_hu_eae05f0b5e82a464.jpg) 4. Insert the ModBus interface card into the free slot until the connection block clicks into place ![Wolf WRS-K Modbus interface card inserted into the KLM-M controller serial card slot](https://taphome.com/images/compatibility/wolf-wrs-k/installation-steps-4-p005_hu_68e21c3cbbbbc481.jpg) 5. Refit the slot cover 6. Reconnect the power supply ### RS-485 wiring (terminal block) ![Wolf WRS-K RS-485 terminal block pinout — GND, RX+/TX+, RX-/TX-](https://taphome.com/images/compatibility/wolf-wrs-k/rs485-wiring-pinout-p006_hu_601c5f8a33abd1e4.jpg) Connect using a **3-wire RS-485 connection** via the pluggable terminal block: | Pin | Signal | TapHome connection | |-----|--------|--------------------| | 1 | GND | GND on TapHome power supply | | 2 | RX+/TX+ | A+/D+ on TapHome RS-485 | | 3 | RX-/TX- | B-/D- on TapHome RS-485 | **Cable specification:** - Type: AWG 20/22, screened - Max length: **1000 m** ## Configuration ### Enabling Modbus communication If the ModBus interface was supplied with the control unit, it is already configured. For retrofitted interfaces, configure via the BMK programming module: 1. Press **Esc** to navigate to the main menu 2. Select **Heating contractor** and press Enter 3. Enter password **"1234"** and confirm with Enter 4. Select **Other...** and press Enter 5. Navigate to **BMS-Protocol** using the up/down arrows 6. Press Enter to highlight, then select **ModBus Slave Standard** 7. The transfer rate is automatically set to **19200** and the BMS address to **001** 8. Confirm with Enter, then press Esc to exit ![Wolf BMK programming module display — BMS-Protocol set to MODBUS Slave Standard, 19200 baud, address 001](https://taphome.com/images/compatibility/wolf-wrs-k/bmk-config-display-p006_hu_fc2cd73d20fb121b.jpg) ### Modbus communication parameters | Parameter | Value | |-----------|-------| | Baud rate | 19200 | | Parity | Even (template) / None (manufacturer spec) | | Stop bits | 1 (template) / 2 (manufacturer spec) | | Data bits | 8 | | Slave ID | 1 (default, configurable via BMK) | ### Modbus TCP gateway The template uses a `ModbusRtuCCU` connection type but requires an **IP address** parameter. This means the WRS-K connects to TapHome through a **Modbus TCP-to-RTU gateway** (e.g., USR-TCP232 or similar RS-485-to-Ethernet converter). Configure the gateway's IP address when importing the template. ### BMS mode activation The template's initialization script automatically writes `H:214 = 2` to set the WRS-K to BMS mode. In BMS mode, all setpoints are specified via the Modbus interface — the local BMK programming module cannot override them. Three operating modes are available: | Value | Mode | Description | |-------|------|-------------| | 0 | Manual mode | Set values from BMK module, adjustable via Modbus offsets | | 1 | 7-day program | Set values from weekly schedule, adjustable via Modbus offsets | | 2 | **BMS mode** | All set values specified via Modbus — **required for TapHome** | The operating mode can also be changed manually via the module's **Set Operating Mode** service action. ## Device capabilities ### Temperature monitoring The template provides four temperature sensors, all reading holding registers with ×0.1 scaling: - **Supply Air Temperature** (H:1) — supply air duct temperature after heat recovery and heating/cooling stages. Includes 5 service attributes for supply air humidity (H:9), pressure (H:210), flow rate (H:212), and current setpoints. Also has 2 service actions for setting supply air flow rate and pressure from BMS. - **Extract Air Temperature** (H:4) — extract (return) air duct temperature. Includes 5 service attributes for extract air humidity (H:8), pressure (H:211), flow rate (H:213), and current setpoints. - **Outside Temperature** (H:2) — outdoor air temperature sensor - **Icing Sensor** (H:27) — heat recovery icing-up sensor temperature, used for frost protection ### Room thermostat **Room Temperature** (H:3 read, H:15 write) functions as a ModbusThermostat — it reads the current room temperature from H:3 and the current setpoint from H:11 (both ×0.1 scaling), and writes the desired temperature to H:15 (×10 scaling). A write-debounce counter prevents readback overwriting the setpoint immediately after a change. ### Fan control - **Supply Air Fan Speed** (H:13 read, H:16 write) — dimmer control, 0–100%, ×0.1 scaling on read - **Extract Air Fan Speed** (H:14 read, H:17 write) — dimmer control, 0–100%, ×0.1 scaling on read - **Fan Mode** (H:215 read, H:222 write) — multi-value switch for fan staging: | Value | Mode | |-------|------| | 0 | Fans Off | | 1 | Fans On (single stage/variable) / Stage 1 (multi-stage) | | 2 | Stage 2 (multi-stage fans only) | | 3 | Stage 3 (multi-stage fans only) | Values 4–9 are defined in the template as placeholders but are not used. ### Ventilation control - **Fresh Air Proportion** (H:12 read, H:221 write) — dimmer control for fresh air proportion, 0–100%, factor 1 (no scaling) ### Air quality monitoring - **Air Quality (CO2)** (H:209) — CO2 concentration sensor in ppm, ×0.1 scaling. Read-only. ### Service diagnostics The module exposes **19 coil registers** (C:1–C:117) and **5 holding registers** as service attributes for monitoring system status: **Digital status indicators (coils):** - **Central Fault** (C:1) — system-wide fault indicator - **System Status** (C:5) — standby (0) or ready for operation (1) - **Operating Status** (C:117) — system not in use (0) or in use (1) - **Heat Source Demand** (C:61) — active heating demand - **Enable or Pump, Heat Recovery** (C:62) — heat recovery enabled/running - **Outside/Supply Air Damper** (C:63) and **Exhaust/Extract Air Damper** (C:64) — damper positions - **Pump, Hot Water** (C:60) and **Pump, Cold Water** (C:18) — pump status - Various adiabatic cooling valves and convector heater status indicators **Analog status indicators (holding registers):** - **Current Set Absolute Humidity** (H:24) — absolute humidity setpoint in g/kg - **Cooling Source Demand, Stage 1/2** (H:220) — cooling demand stage - **Electric Heater Bank Stage** (H:232) and **Direct Evaporator Stage** (H:233) — current stages - **Heat Pump Operating Mode** (H:255) — not enabled / heating / cooling (requires WRS-K software v3.0+) **Module service actions:** - **Set Absolute Humidity Setpoint** — writes H:26 for BMS humidity control - **Set Operating Mode** — switches between Manual (0), 7-day program (1), and BMS mode (2) ### Additional capabilities The WRS-K also exposes registers for room air humidity, supply air temperature setpoint, heating/cooling/heat recovery actuating signals, and humidifier control. Additional offset registers allow fine-tuning setpoints in Manual and 7-day program modes. The alarm system covers over 60 fault conditions including fan inverter faults, filter contamination, fire damper status, frost protection, and sensor failures. These can be added in a future template update. ## Troubleshooting ### No Modbus communication 1. **Check RS-485 cables** — verify pin 2 (RX+/TX+) connects to A+/D+ and pin 3 (RX-/TX-) connects to B-/D- on TapHome 2. **Check GND** — pin 1 must be connected to the TapHome power supply ground 3. **Verify parity settings** — the template defaults to even parity, but the manufacturer specification states no parity. Try both configurations 4. **Confirm baud rate** — must be 19200 on both sides 5. **Check the Modbus TCP gateway** — verify the gateway IP address and that it forwards RTU frames correctly ### Fan speed or temperature not responding 1. **Verify BMS mode** is active — the initialization script sets H:214 = 2 automatically, but verify via the BMK module display (should show BMS mode) 2. If in Manual or 7-day mode, TapHome can only adjust values via offsets — full control requires BMS mode 3. **Check the write-debounce** — after changing the room temperature setpoint, the thermostat ignores readback for approximately 55 polling cycles to prevent immediate overwrite ### Fan Mode values 4–9 Values 4–9 in the Fan Mode device are **placeholder entries** in the template and should not be used. Only values 0–3 are valid for the WRS-K. Setting values above 3 may produce undefined behavior. ## Available devices Wolf WRS-K Module Service Attributes | | | |---------------------------------------------|----------------------------------------------------------------------------------------------| | Central Fault | | | External System Enable | | | Hygrostat Humidity | | | Humidifier Enable | | | System Status | | | Operating Status | | | Pump, Hot Water | | | Pump, Cold Water | | | Heat Source Demand | | | Enable or Pump, Heat Recovery | reads C:62 (Bool); 0=off, 1=enabled/running | | Outside/Supply Air Damper | | | Exhaust/Extract Air Damper | | | Enable Gas Valve | | | Enable or Pump, Adiabatic Cooling | reads C:87 (Bool); 0=off, 1=enabled/running | | Enable Convector Heater (WO) | reads C:89 (Bool); 0=disabled, 1=enabled | | Thermostat, Convector Heater (WO) | reads C:90 (Bool); 0=inactive, 1=active | | Water Supply Drain Valve, Adiabatic Cooling | reads C:91 (Bool); 0=closed, 1=open | | Pan Drain Valve, Adiabatic Cooling | reads C:92 (Bool); 0=closed, 1=open | | Inlet Valve, Adiabatic Cooling | reads C:94 (Bool); 0=closed, 1=open | | Current Set Absolute Humidity | | | Cooling Source Demand, Stage 1/2 | reads H:220 (Int16); cooling source demand stage indicator | | Electric Heater Bank Stage | | | Direct Evaporator Stage | | | Heat Pump Operating Mode | Heat pump mode — Not enabled, Enable heating, Enable cooling (requires WRS-K software v3.0+) | Service Actions | | |--------------------------------| | Set Absolute Humidity Setpoint | | Set Operating Mode | Fresh Air Proportion Dimmer Fresh air proportion control — adjustable 0–100% Register: H:12 → H:221 Int16 Unit: % numeric Air Quality (CO2) Variable Read-only CO2 concentration sensor in ppm for indoor air quality monitoring Register: H:209 Int16 Unit: ppm numeric Extract Air Temperature Temperature Sensor Read-only Extract air duct temperature with humidity, pressure and flow rate service attributes Register: H:4 Int16 Unit: °C numeric Service Attributes | | |------------------------------------| | Extract Air Humidity | | Extract Air Pressure | | Extract Air Flow Rate | | Current Set Pressure, Extract Air | | Current Set Flow Rate, Extract Air | Extract Air Fan Speed Dimmer Extract air fan speed control — adjustable 0–100% Register: H:14 → H:17 Int16 Unit: % numeric Supply Air Fan Speed Dimmer Supply air fan speed control — adjustable 0–100% Register: H:13 → H:16 Int16 Unit: % numeric Room Temperature Thermostat Room thermostat — reads current and desired temperature, writes setpoint to BMS register Register: H:3 → H:15 Int16 Unit: °C numeric Supply Air Temperature Temperature Sensor Read-only Supply air duct temperature with humidity, pressure and flow rate service attributes Register: H:1 Int16 Unit: °C numeric Service Attributes | | |-----------------------------------| | Supply Air Humidity | | Supply Air Pressure | | Supply Air Flow Rate | | Current Set Pressure, Supply Air | | Current Set Flow Rate, Supply Air | Service Actions | | |--------------------------| | Set Supply Air Flow Rate | | Set Supply Air Pressure | Icing Sensor Temperature Sensor Read-only Heat recovery icing-up sensor temperature for frost protection monitoring Register: H:27 Int16 Unit: °C numeric Fan Mode Multi-value Switch Fan stage selector — Off, On/Stage 1, Stage 2, Stage 3 for multi-stage fans Register: H:215 → H:222 Int16 enum Values / States: Ventilátor vypnutý · Ventilátor zapnutý · Ventilátor stupeň 2 zapnutý (viacstupňové ventilátory) · Ventilátor stupeň 3 zapnutý (viacstupňové ventilátory) Outside Temperature Temperature Sensor Read-only Register: H:2 Int16 Unit: °C numeric **Connection:** Modbus RTU • 19200 baud• 8E1 • Slave ID: $\[SlaveId] Possible improvements (18) - H:5 Air Quality (Mixed Gas) — Air quality mixed gas sensor, factor 0.1, unit V - H:6 Set Room Transducer — Set room transducer temperature, factor 0.1, unit °C - H:7 Room Air Humidity — Room air humidity, factor 0.1, unit %r.H. - H:10 Current Set Supply Air Temperature — Current set value supply air temperature, factor 0.1, unit °C - H:23 Current Set Relative Humidity — Current set value relative humidity, factor 0.1, unit %r.H. - H:28 Actuating Signal, Heating — Heating actuating signal, factor 0.1, unit % - H:29 Actuating Signal, Cooling — Cooling actuating signal, factor 0.1, unit % - H:30 Actuating Signal, Heat Recovery — Heat recovery actuating signal, factor 0.1, unit % - H:31 Actuating Signal, Humidifier — Humidifier actuating signal, factor 0.1, unit % - H:32 Extract Air Temp After Humidifier — Extract air temperature after humidifier for adiabatic cooling, factor 0.1, unit °C - H:33 Actuation Signal, Reheating — Reheating actuation signal, factor 0.1, unit % (requires WRS-K software v3.0+) - H:25 Set Relative Humidity from BMS — Write relative humidity setpoint from BMS, factor 0.1, unit %r.H. - H:221 Set Fresh Air Proportion from BMS — Write fresh air proportion from BMS, factor 1, unit % - H:224 Set Pressure, Extract Air from BMS — Write extract air pressure setpoint from BMS, factor 1, unit Pa - H:226 Set Flow Rate, Extract Air from BMS — Write extract air flow rate from BMS, factor 10, unit m³/h - H:18 Offset Set Temperature — Temperature offset for manual/7-day modes, factor 0.1, unit K - H:19 Offset Set Speed, Supply Air Fan — Supply air fan speed offset for manual/7-day modes, factor 0.1, unit % - H:20 Offset Set Speed, Extract Air Fan — Extract air fan speed offset for manual/7-day modes, factor 0.1, unit % ## Sources - Wolf WRS-K Modbus Interface — Installation and Operating Instructions [wolf.lt](https://wolf.lt/uploads/Turinys/Control%20systems/Ventilation%20Air%20handling/3062947_201211_Modbus-Schnittstelle-fuer-WRS-K.pdf) 2026-03-20 [PDF](https://taphome.com/compatibility/devices/wolf-wrs-k/manufacturer/modbus-interface-manual.pdf) ## Related Documentation - [Modbus Integration](https://taphome.com/en/compatibility/modbus-guide/) - [Modbus](https://taphome.com/en/docs/integration/modbus/) - [Simple configuration using templates](https://taphome.com/en/docs/integration/modbus/templates/) - [Modbus scripts and prefetch](https://taphome.com/en/docs/script/modbus-scripts/) - [Modbus functions](https://taphome.com/en/docs/script/modbus/) - [Modbus data types](https://taphome.com/en/docs/script/modbus-data-types/)