--- title: "Vallox Ventilation" description: "Vallox MV series heat recovery ventilation units connected to TapHome via Modbus RTU (with RTU-to-TCP gateway)." url: "https://taphome.com/en/compatibility/vallox-ventilation/" language: en lastmod: 2026-10-08 generator: hugo ai: topics: ["modbus-tcp","modbus-rtu","air-recovery","heat-recovery-ventilation","rs485","rtu-to-tcp-gateway"] questions: ["How to integrate Vallox ventilation with TapHome?","What does the Vallox Ventilation TapHome template measure and control?","How to connect Vallox MV via Modbus RTU to TapHome?","Why does Vallox require a Modbus RTU-to-TCP gateway for TapHome?","How to activate Boost mode on Vallox via TapHome?","How to configure Modbus settings on MyVallox Control panel?"] --- # Vallox Ventilation Communication: Modbus TCP - [Vallox Official Website](https://www.vallox.com) The Vallox MV series (51, 96, 99, 101, 110, 125, 139, 145, 245 MV and ValloPlus variants) are mechanical ventilation heat recovery (MVHR) units. TapHome connects via Modbus TCP, but the MyVallox Control **does not have a native Modbus TCP option** — an RS-485 Modbus RTU-to-TCP gateway (such as Elfin EW11 or USR-W610) is required between the ventilation unit and TapHome Core. The template provides comprehensive control: Home/Away mode switching, Boost mode with timer, fan speed settings per mode, five temperature sensors, humidity and CO2 monitoring, weekly timer, and per-mode temperature targets with thermostat control. ## Hardware connection The Vallox unit exposes a Modbus RTU interface on the X102 connector board. Up to 32 units can be daisy-chained on a single RS-485 bus. A 120 Ohm termination resistor is required at the last unit on the bus. - **Protocol:** Modbus RTU (RS-485) - **Connector:** X102 terminal block (A and B terminals) - **Max units per bus:** 32 - **Termination:** 120 Ohm resistor at the end of the bus > [!WARNING] > The MyVallox Control does **not** support Modbus TCP natively. A Modbus RTU-to-TCP gateway must be placed between the Vallox unit's RS-485 bus and TapHome Core's Ethernet network. Configure the gateway with matching serial parameters (default: 19200 baud, even parity, 1 stop bit). ### Wiring diagram ![Vallox Modbus RTU wiring diagram — RS-485 bus with X102 connector, A/B terminals and 120 Ohm termination](https://taphome.com/images/compatibility/vallox-ventilation/wiring-diagram-p012_hu_a560f04e62f3696b.jpg) The wiring diagram shows the RS-485 bus connection using the X102 connector on each Vallox unit. Connect wire A to terminal A and wire B to terminal B. The Modbus master (RTU-to-TCP gateway) connects at the beginning of the bus. ## Enabling Modbus communication Modbus settings must be configured on the ventilation unit before TapHome can communicate. The following parameters are required: | Setting | Options | Default | |---------|---------|---------| | Modbus address | 1–247 | 1 | | Baud rate | 9600, 19200, 38400, 57600, 115200 | 19200 | | Parity | no, even, odd | even | | Stop bit | 1 or 2 | 1 | ### Via MyVallox Control panel ![MyVallox Control panel — Modbus settings configuration screens (address, baud rate, parity, stop bit)](https://taphome.com/images/compatibility/vallox-ventilation/modbus-settings-panel-p004_hu_b942ab1613451136.jpg) 1. Select **Settings** and navigate to **Expert settings** 2. Select **Modbus settings** and press OK 3. **Screen 1/4:** Set Modbus address (1–247) using +/- buttons 4. **Screen 2/4:** Set baud rate (default 19200) 5. **Screen 3/4:** Set parity (no/even/odd) 6. **Screen 4/4:** Set stop bit (1 or 2) 7. Press OK to save ### Via web interface The same Modbus settings (address, baud rate, parity, stop bit) can also be configured through the MyVallox web interface — navigate to **Expert settings → Modbus settings** via local network or MyVallox Cloud. ## Configuration When importing the template in TapHome, provide: - **IP Address** — the RTU-to-TCP gateway's IP address on the local network - **Slave ID** — Modbus address of the Vallox unit (default: 1) > [!TIP] > Assign a static IP address to the RTU-to-TCP gateway in the router's DHCP settings. The gateway's serial port must be configured with the same parameters as the Vallox unit (default: 19200 baud, even parity, 1 stop bit). ## Device capabilities The template exposes 34 devices organized into operating mode control, fan speed management, temperature monitoring, air quality sensors, timer controls, and per-mode configuration profiles. ### Operating mode control Vallox uses two **basic modes** (Home and Away) — one is always active. Three **timed modes** (Boost, Fireplace, Programmable) can temporarily override the basic mode. - **State (Home/Away)** — toggle switch for the active basic mode via register H:4609. Write 0 for Home, 1 for Away. - **Mode (Override State)** — multi-value switch on register H:4610. Write 0 for Normal operation, 5 to switch the unit off. Mode priority when multiple modes are active simultaneously: 1. Programmable mode (highest) 2. Fireplace mode 3. Boost mode 4. Home/Away basic mode (lowest) ### Fan speed control Fan speed is configured separately for each operating mode as a percentage (0–100%): - **Fan Speed (Home)** — Home mode fan speed setting (H:20507) - **Fan Speed (Away)** — Away mode fan speed setting (H:20501) - **Fan Speed (Boost)** — Boost mode fan speed setting (H:20513) - **Current Fan Speed** — read-only sensor showing the actual fan speed (H:4353) - **Current Fan Speed (Dimmer)** — dimmer representation of the current fan speed (same register H:4353) The Programmable mode has separate supply and extract fan controls: - **Programmable Mode Supply Fan Speed** — supply fan speed for Programmable mode (H:20495) - **Programmable Mode Extract Fan Speed** — extract fan speed for Programmable mode (H:20494) ### Temperature monitoring The template includes five temperature sensors. All temperatures are stored in centKelvins and converted automatically: `Celsius = register_value / 100 - 273.15`. | Device | Register | Description | |--------|----------|-------------| | Outdoor Air Temperature | H:4356 | Outside air before entering the unit | | Extract Air Temperature | H:4354 | Air extracted from rooms before heat recovery | | Exhaust Air Temperature | H:4355 | Air exhausted outdoors after heat recovery | | Supply Cell Air Temperature | H:4357 | Air inside the heat recovery cell (supply side) | | Supply Air Temperature | H:4358 | Fresh air supplied to rooms after heat recovery | ### Air quality monitoring - **Humidity** — relative humidity percentage (H:4363, requires RH sensor accessory) - **CO2 Level** — CO2 concentration in ppm (H:4364, requires CO2 sensor accessory) ### Timer and mode controls - **Boost Remaining Time** — write desired minutes to activate Boost mode, 0 to deactivate, 65535 for indefinite (H:4612) - **Boost Timer Enabled** — enable/disable Boost timer countdown (H:21766) - **Weekly Timer Enabled** — enable/disable weekly schedule program (H:4615) - **Defrosting** — defrost cycle status indicator (H:4611) ### Per-mode temperature targets Each mode has a thermostat device that reads the current extract air temperature (H:4354) and allows setting a supply air temperature target: - **Home Mode Temperature Target** — target register H:20508 - **Away Mode Temperature Target** — target register H:20502 - **Boost Mode Temperature Target** — target register H:20514 - **Programmable Mode Temperature Target** — target register H:20493 ### Per-mode air quality control Humidity and CO2-based automatic fan speed adjustment can be enabled per mode: - **Home Mode RH Control / CO2 Control** — H:20505 / H:20506 - **Away Mode RH Control / CO2 Control** — H:20499 / H:20500 - **Boost Mode RH Control / CO2 Control** — H:20511 / H:20512 ### Diagnostics - **Cell State** — heat recovery cell operating state (H:4616) - **Remaining Time for Filter** — days until filter replacement (H:4620) - **Command Variable** — special command register for maintenance operations (H:4627) - **Programmable Mode Duration** — default duration for Programmable mode in minutes (H:20496) ### Additional capabilities The Vallox units also expose Modbus registers for fireplace mode timer control (H:4613), programmable mode timer (H:4614), fault condition reporting (H:4621), individual supply/extract fan speed monitoring, fireplace mode fan speed configuration, filter change interval settings, and optional external temperature sensor input. These can be added to the TapHome template in a future update. ## Troubleshooting ### No Modbus communication 1. Verify the RS-485 wiring on the X102 connector — check A/B terminal polarity 2. Confirm the RTU-to-TCP gateway serial parameters match the Vallox unit (default: 19200 baud, even parity, 1 stop bit) 3. Ensure the gateway IP address is correct and reachable from TapHome Core 4. Check that the Modbus slave address matches between the Vallox unit and TapHome configuration ### Temperature readings show incorrect values All temperature registers use centKelvin encoding. The TapHome template handles the conversion automatically (`value / 100 - 273.15`). If raw values appear instead of Celsius, verify the template was imported correctly. ### Mode changes not applied During active **defrost** cycles, the unit may ignore mode write commands. The Defrosting switch (H:4611) indicates when defrost is active. Wait for the cycle to complete before changing modes. Additionally, check mode priority — a higher-priority timed mode overrides lower-priority modes. ### Boost mode does not deactivate Write 0 to register H:4612 (Boost Remaining Time) to stop Boost mode. If the Boost Timer Enabled switch (H:21766) was set to 0 (disabled), the timer countdown was disabled and Boost runs indefinitely until manually stopped. ## Available devices Vallox Ventilation Module Remaining Time for Filter Variable Read-only Days remaining until the next filter replacement Register: H:4620 UInt16 Unit: days numeric Current Fan Speed Variable Read-only Real-time fan speed as percentage (0–100%) Register: H:4353 UInt16 Unit: % numeric Fan Speed (Home) Dimmer Fan speed setting for Home basic mode (0–100%) Register: H:20507 UInt16 Unit: % numeric Fan Speed (Away) Dimmer Fan speed setting for Away basic mode (0–100%) Register: H:20501 UInt16 Unit: % numeric State (Home/Away) Switch Basic mode selector — 0=Home, 1=Away Register: H:4609 Bool boolean Values / States: ON · OFF Mode (Override State) Multi-value Switch Unit override — Normal (0) for regular operation, Off (5) to shut down the unit Register: H:4610 UInt16 numeric Values / States: Normal · Off Outdoor Air Temperature Temperature Sensor Read-only Register: H:4356 UInt16 Unit: °C centKelvin (value/100 - 273.15) Extract Air Temperature Temperature Sensor Read-only Air temperature extracted from rooms before heat recovery Register: H:4354 UInt16 Unit: °C centKelvin (value/100 - 273.15) Exhaust Air Temperature Temperature Sensor Read-only Air temperature exhausted outdoors after heat recovery Register: H:4355 UInt16 Unit: °C centKelvin (value/100 - 273.15) Supply Cell Air Temperature Temperature Sensor Read-only Temperature inside the heat recovery cell on the supply side Register: H:4357 UInt16 Unit: °C centKelvin (value/100 - 273.15) Supply Air Temperature Temperature Sensor Read-only Fresh air temperature supplied to rooms after heat recovery Register: H:4358 UInt16 Unit: °C centKelvin (value/100 - 273.15) Humidity Variable Read-only Relative humidity — requires optional RH sensor accessory Register: H:4363 UInt16 Unit: % numeric CO2 Level Variable Read-only CO2 concentration in ppm — requires optional CO2 sensor accessory Register: H:4364 UInt16 Unit: ppm numeric Defrosting Switch Defrost cycle active indicator — mode changes may be ignored during defrost Register: H:4611 Bool boolean Values / States: ON · OFF Boost Timer Enabled Switch Boost timer countdown switch — disable to keep Boost mode on indefinitely Register: H:21766 Bool boolean Values / States: ON · OFF Weekly Timer Enabled Switch Weekly schedule program on/off Register: H:4615 Bool boolean Values / States: ON · OFF Cell State Variable Read-only Heat recovery cell operating state — heat recovery, cool recovery, bypass, defrosting Register: H:4616 UInt16 numeric Command Variable Variable Special command register for maintenance and diagnostic operations Register: H:4627 UInt16 numeric Programmable Mode Temperature Target Thermostat Supply air temperature setpoint for Programmable (Extra) mode Register: H:4354 (current), H:20493 (target) → H:20493 UInt16 Unit: °C centKelvin (value/100 - 273.15) Programmable Mode Extract Fan Speed Dimmer Extract fan speed for Programmable mode (0–100%) Register: H:20494 UInt16 Unit: % numeric Programmable Mode Supply Fan Speed Dimmer Supply fan speed for Programmable mode (0–100%) Register: H:20495 UInt16 Unit: % numeric Programmable Mode Duration Variable Default duration for Programmable mode in minutes Register: H:20496 UInt16 Unit: min numeric Away Mode RH Control Switch Automatic fan speed adjustment based on humidity in Away mode Register: H:20499 Bool boolean Values / States: ON · OFF Away Mode CO2 Control Switch Automatic fan speed adjustment based on CO2 in Away mode Register: H:20500 Bool boolean Values / States: ON · OFF Away Mode Temperature Target Thermostat Supply air temperature setpoint for Away mode Register: H:4354 (current), H:20502 (target) → H:20502 UInt16 Unit: °C centKelvin (value/100 - 273.15) Home Mode RH Control Switch Automatic fan speed adjustment based on humidity in Home mode Register: H:20505 Bool boolean Values / States: ON · OFF Home Mode CO2 Control Switch Automatic fan speed adjustment based on CO2 in Home mode Register: H:20506 Bool boolean Values / States: ON · OFF Home Mode Temperature Target Thermostat Supply air temperature setpoint for Home mode Register: H:4354 (current), H:20508 (target) → H:20508 UInt16 Unit: °C centKelvin (value/100 - 273.15) Boost Mode RH Control Switch Automatic fan speed adjustment based on humidity in Boost mode Register: H:20511 Bool boolean Values / States: ON · OFF Boost Mode CO2 Control Switch Automatic fan speed adjustment based on CO2 in Boost mode Register: H:20512 Bool boolean Values / States: ON · OFF Fan Speed (Boost) Dimmer Fan speed setting for Boost timed mode (0–100%) Register: H:20513 UInt16 Unit: % numeric Boost Mode Temperature Target Thermostat Supply air temperature setpoint for Boost mode Register: H:4354 (current), H:20514 (target) → H:20514 UInt16 Unit: °C centKelvin (value/100 - 273.15) Current Fan Speed (Dimmer) Dimmer Read-only Dimmer representation of current fan speed — read-only duplicate of Current Fan Speed Register: H:4353 UInt16 Unit: % numeric Boost Remaining Time Variable Boost mode countdown in minutes — write desired time to activate, 0 to stop, 65535 for indefinite Register: H:4612 Int16 Unit: min numeric **Connection:** Modbus TCP • Slave ID: $\[SlaveId] Possible improvements (17) - H:4613 Fireplace Timer — Int16 R/W, minutes remaining. Write desired time to activate fireplace mode - H:4614 Programmable Timer — Int16 R/W, minutes remaining. Write desired time to activate programmable mode - H:21767 Fireplace Timer Enabled — Bool R/W, 0=timer off, 1=timer on - H:21772 Programmable Timer Enabled — Bool R/W, 0=timer off, 1=timer on - H:4621 Fault Condition — UInt16 R, 0=normal, 1=fault - H:4361 Extract Fan Actual Speed — UInt16 R, extract fan RPM/speed - H:4362 Supply Fan Actual Speed — UInt16 R, supply fan RPM/speed - H:4359 RH Level — UInt16 R, 0=no sensor, 1=low, 2=med, 3=high - H:4360 CO2 Level (Threshold) — UInt16 R, 0=no sensor, 1=low, 2=med, 3=high - H:4365 Fireplace Switch State — UInt16 R, physical fireplace switch state - H:4389 Optional Temperature Sensor — UInt16 R, centKelvin, optional external temperature sensor - H:4617 Total Uptime Years — UInt16 R, total operating time in years - H:4618 Total Uptime Hours — UInt16 R, total operating time in hours - H:20537 Filter Change Interval — UInt16 R/W, filter change interval in days - H:20487 Fireplace Extract Fan Speed — UInt16 R/W, fireplace mode extract fan speed % - H:20488 Fireplace Supply Fan Speed — UInt16 R/W, fireplace mode supply fan speed % - H:20497 Fireplace Air Temp Target — UInt16 R/W, centKelvin, fireplace mode temperature setpoint ## Sources - MyVallox Modbus Configuration — Technical Instructions [res.cloudinary.com](https://res.cloudinary.com/vallox/image/upload/v1683801768/FileStock/AllManuals/Manual_Modbus_ENG_Colour_20150925.pdf) 2026-03-20 [PDF](https://taphome.com/compatibility/devices/vallox-ventilation/manufacturer/modbus-manual.pdf) - Vallox WebSocket API — Complete Register Map [github.com](https://github.com/yozik04/vallox_websocket_api) 2026-03-20 ## 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/)