--- title: "Systemair SAVE VTR 700" description: "Systemair SAVE VTR 700 heat recovery ventilation unit with Modbus RTU control via TapHome." url: "https://taphome.com/en/compatibility/systemair-save-vtr-700/" language: en lastmod: 2026-03-20 generator: hugo ai: topics: ["modbus-rtu","air-recovery","rs485","heat-recovery","demand-control","ventilation"] questions: ["How to integrate Systemair SAVE VTR 700 with TapHome?","What does the Systemair SAVE VTR 700 TapHome template control?","How to connect Systemair SAVE VTR 700 via RS-485 to TapHome?","How to configure Modbus communication on Systemair SAVE units?","What user modes are available for Systemair SAVE VTR 700 via TapHome?","How to monitor CO2 and humidity levels from Systemair SAVE in TapHome?"] --- # Systemair SAVE VTR 700 Communication: Modbus RTU - [Systemair Official Website](https://www.systemair.com) The Systemair SAVE VTR 700 is a residential heat recovery ventilation unit (HRV) that communicates with TapHome via Modbus RTU over a 3-wire RS-485 connection (A, B, GND). The template provides control over user modes, fan speed, ECO mode, free cooling, and monitors temperatures, CO2 levels, humidity and fan RPM. A comprehensive alarm monitoring system reports 30+ alarm conditions directly in TapHome. The SAVE VTR 700 is part of the Systemair SAVE family. Other SAVE models (VSR 300, VSR 500, VTC, VTR) using the same control platform should be compatible with this template, as they share the same Modbus register map. ## Hardware connection ### RS-485 wiring Connect using a **3-wire RS-485 connection** to the Connection Board (CB) inside the unit: - **A** → A+/D+ on TapHome RS-485 - **B** → B-/D- on TapHome RS-485 - **GND** → GND on TapHome power supply (**mandatory**) > [!WARNING] > **Important — Grounding** > > The GND wire **must** be connected between the Systemair unit and the TapHome power supply. Without proper grounding, communication errors may occur. ### Technical specifications - **Protocol:** Modbus RTU Slave, RS-485 - **Baud rate:** 9600 to 115200 (configurable) - **Default baud rate:** 115200 - **Parity:** None, Even, or Odd (configurable) - **Stop bits:** 1 - **Slave address:** 1–247 (configurable) - **All registers:** 16-bit integers ## Configuration ### Enabling Modbus communication Modbus RTU is available on the Connection Board (CB) as standard. Communication parameters can be changed through the unit's Control Panel: 1. Navigate to **Service → Communication → Modbus** 2. Set the **Slave address** (default: 1) 3. Set the **Baud rate** (template default: 115200) 4. Set **Parity** (template default: None) 5. Confirm and restart if required **For TapHome:** Configure TapHome to match the unit's settings — 115200 baud, no parity, 1 stop bit, matching Slave ID. > [!TIP] > **Modbus TCP alternative** — Systemair offers the Internet Access Module (IAM, Art. No. 211243) as an accessory, which provides Modbus TCP access over Ethernet on port 502. This can be used as an alternative to direct RS-485 wiring. ### Initialize script The template runs an initialization script that sets the fan speed regulation type to "Manual %" (H:1273=0) and enables fan stop detection (H:1352=1). These settings are applied automatically when TapHome connects to the unit. ## Device capabilities ### User mode control **Active User Mode** — a multi-value switch that reads the current mode from I:1160 and writes mode changes via H:1161. Ten operating modes are available: | Value | Mode | Description | |-------|------|-------------| | 0 | Auto | Automatic ventilation based on demand control (CO2/RH sensors) | | 1 | Manual | Fixed fan speed set by the Fan Speed device | | 2 | Crowded | Increased ventilation for occupied spaces (timed) | | 3 | Refresh | Maximum ventilation burst (timed) | | 4 | Fireplace | Reduced extract air to create positive pressure for fireplaces (timed) | | 5 | Away | Reduced ventilation during absence (timed) | | 6 | Holiday | Minimum ventilation for extended absence (timed) | | 7 | Cooker Hood | Increased extract for kitchen ventilation (timed) | | 8 | Vacuum Cleaner | Adjusted airflow for central vacuum systems (timed) | | 9 | Pressure Guard | Maintains pressure balance when external devices affect airflow | Each mode has configurable supply and extract fan speeds visible as service attributes (22 in total), showing the actual fan speed percentage for both supply air fan (SAF) and extract air fan (EAF) in each mode. ### Fan speed control **Fan Speed** — a 4-level multi-value switch (H:1130) with offset conversion (read: −1, write: +1): | Value | Level | |-------|-------| | 0 | Off | | 1 | Low | | 2 | Normal | | 3 | High | Fan speed applies when the unit is in Manual mode. In other modes, the fan speed is determined by the active user mode configuration. **Supply Fan Speed** and **Extract Fan Speed** — analog input devices that monitor the current fan operation. Each has a service attribute showing the actual fan RPM from the TACHO sensor (I:12400 for supply, I:12401 for extract). ### Temperature monitoring The template provides two temperature sensors with automatic °C × 10 conversion: - **Outdoor Air Temperature** (H:12101) — outdoor air temperature from the frost protection sensor. Service attribute: Room Air Temperature (I:12103, accessory sensor) - **Supply Air Temperature** (H:12102) — supply air temperature after the heat exchanger. Three service attributes: Extract Air Temperature (I:12104), Frost Protection Temperature (I:12100), and Overheat Temperature (I:12107) ### Air quality monitoring - **Highest CO2** (H:1001) — highest reading across all connected CO2 sensors, in ppm. Five service attributes show individual sensor values (I:12150–I:12154) - **Highest Humidity** (H:1000) — highest reading across all connected RH sensors, in % (value ÷ 100 conversion) ### ECO mode **ECO Mode** (H:2504) — a boolean switch that enables energy-saving operation. When active, ECO mode reduces heating energy by applying a configurable temperature offset to the heating setpoint. - Service attribute: **Heating Offset During ECO Mode** (H:2503, ÷10, °C) — shows the current offset - Service action: **Set Temperature Offset** — configures the heating offset (1–10°C) ### Free cooling **Free Cooling Enable** (H:4100) — a boolean switch that enables night-time free cooling. When outdoor temperatures are low enough, the unit uses cool outdoor air to pre-cool the building without running the active cooling system. - Service attribute: **Free Cooling Active** (I:4110) — indicates whether free cooling is currently being performed ### Alarm monitoring The module monitors 30+ alarm conditions through the ReadScript. When an alarm is active, it is reported as an error in TapHome. Monitored alarms include: - **Fan alarms:** SAF/EAF control, SAF/EAF RPM - **Protection alarms:** Frost protection, defrosting, overheat, fire - **Sensor alarms:** FPT, OAT, SAT, RAT, EAT, ECT, EFT, OHT, EMT temperature sensors - **System alarms:** RGS (rotating guard), BYS (bypass), secondary air, filter, external stop - **Air quality alarms:** RH, CO2, low SAT - **Other:** Manual override outputs, PDM sensors, manual fan stop A **Clear All Alarms** service action writes to all 30 alarm clear registers, resetting all alarm states at once. ### Service diagnostics The module exposes five service attributes for monitoring system status: - **System Time** (H:6001–H:6006) — current date and time formatted as HH:MM DD.MM.YYYY - **Actual Season** (H:1038) — Summer or Winter - **Indoor IAQ Level** (I:1122) — Economic, Good, or Improving - **Fan Speed Regulation Type** (H:1273) — Manual %, Manual RPM, Constant Pressure, Constant Flow, or External - **Demand Control** (I:1003) — CO2 or RH Two service actions allow setting the unit's clock: - **Set Date** — writes year (2020–2999), month (1–12), day (1–31) - **Set Time** — writes hour (0–23), minute (0–59), second (0–59) A **Set Fan Speed Regulation Type** service action allows switching between Manual %, Manual RPM, Pressure, Flow, and External regulation modes. ### Additional capabilities The SAVE VTR 700 also exposes Modbus registers for temperature setpoint control (H:2001, range 12–30°C with supply/room/extract control mode selection), a separate ECO mode enable register, ECO function active status, actual fan speed output percentages (SAF/EAF 0–100%), filter replacement period tracking with remaining time, individual extract air temperature and relative humidity sensors, and a complete 7-day week schedule with two periods per day and temperature offsets. These can be added in a future template update. > [!TIP] > The temperature setpoint register (H:2001) is not included in the current template. To control the supply air setpoint, it can be added as a custom Modbus device in TapHome using holding register 2001 with a value range of 120–300 (representing 12.0–30.0°C with ÷10 conversion). ## Troubleshooting ### No Modbus communication 1. **Check RS-485 cables:** - A correctly connected to A+/D+ on TapHome - B correctly connected to B-/D- on TapHome - **GND connected to TapHome power supply ground** — most common issue 2. Verify the Modbus Slave address matches between the unit and TapHome 3. Confirm TapHome is set to: 115200 baud, no parity, 1 stop bit (or matching the unit's configured parameters) 4. Check the Connection Board (CB) for proper RS-485 terminal connections ### User mode not changing 1. Verify the unit is not in a timed mode (Crowded, Refresh, Fireplace, Away, Holiday) — timed modes must expire or be manually cancelled before switching 2. Check that the write register (H:1161) is responding — the read register (I:1160) and write register are different addresses 3. Mode value 12 (PressureGuard) is automatically mapped to value 9 in the template ### Temperature readings incorrect 1. Temperature values use ÷10 conversion — a raw value of 215 means 21.5°C 2. Verify the correct sensor is connected: Outdoor Air uses H:12101 (frost protection sensor), Supply Air uses H:12102 3. Accessory sensors (room air, extract air) require optional sensor hardware to be installed ## Available devices Systemair SAVE VTR 700 Module Service Attributes | | |---------------------------| | System Time | | Actual Season | | Indoor IAQ Level | | Fan Speed Regulation Type | | Demand Control | Service Actions | | |-------------------------------| | Set Date | | Set Time | | Set Fan Speed Regulation Type | | Clear All Alarms | Active User Mode Multi-value Switch Ventilation operating mode — Auto, Manual, Crowded, Refresh, Fireplace, Away, Holiday, Cooker Hood, Vacuum Cleaner, Pressure Guard Register: I:1160 → H:1161 UInt16 multi-value Values / States: Auto · Manual · Crowded · Refresh · Fireplace · Away · Holiday · Cooker Hood · Vacuum Cleaner · Pressure Guard ECO Mode Switch Energy-saving mode — reduces heating by applying a configurable temperature offset Register: H:2504 Bool Values / States: ON · OFF Service Actions | | |------------------------------| | Set temperature offset \[°C] | Extract Fan Speed Analog Input Read-only Extract air fan speed with RPM monitoring from TACHO sensor UInt16 numeric Service Attributes | | |-------------------| | Extract Fan r/min | Fan Speed Multi-value Switch Manual fan speed level — Off, Low, Normal, High Register: H:1130 UInt16 multi-value Values / States: ${level\_0Of3} · ${level\_1Of3} · Normal · ${level\_3Of3} Free Cooling Enable Switch Night-time free cooling using outdoor air to pre-cool the building Register: H:4100 Bool Values / States: ON · OFF Highest CO2 Variable Read-only Highest CO2 reading across all connected sensors, with individual sensor values Register: H:1001 UInt16 Unit: ppm numeric Service Attributes | | |----------| | Sensor 1 | | Sensor 2 | | Sensor 3 | | Sensor 4 | | Sensor 5 | Highest Humidity Variable Read-only Highest relative humidity reading across all connected RH sensors Register: H:1000 UInt16 Unit: % numeric Outdoor Air Temperature Temperature Sensor Read-only Register: H:12101 Int16 Unit: °C numeric Service Attributes | | |-----------------------------| | Room Air Temperature sensor | Supply Air Temperature Temperature Sensor Read-only Register: H:12102 Int16 Unit: °C numeric Service Attributes | | |-------------------------------------| | Extract Air Temperature sensor | | Frost Protection Temperature Sensor | | Overheat Temperature sensor | Supply Fan Speed Analog Input Read-only Supply air fan speed with RPM monitoring from TACHO sensor UInt16 numeric Service Attributes | | |------------------| | Supply fan r/min | **Connection:** Modbus RTU • 115200 baud• 8N1 • Slave ID: $\[SlaveId] Possible improvements (11) - H:2001 Temperature Setpoint — REG\_TC\_SP (H:2001, 12.0–30.0°C, /10 conversion) — primary temperature setpoint for supply air temperature control - H:2031 Temperature Control Mode — REG\_TC\_CONTROL\_MODE (H:2031); 0=Supply, 1=Room, 2=Extract — selects which temperature sensor drives the control loop - H:1162 User Mode Change Request — REG\_USERMODE\_HMI\_CHANGE\_REQUEST (H:1162); direct mode switch 0–7 without multi-value switch — alternative to Active User Mode device - I:1111/1112 User Mode Remaining Time — 32-bit value (low + high word) showing remaining time for timed user modes (Holiday, Away, Fireplace, Refresh, Crowded) - H:2505 ECO Mode Enable — REG\_ECO\_MODE\_ON\_OFF (H:2505); separate from ECO offset — template uses H:2504 (offset) as the switch - I:2506 ECO Function Active — REG\_ECO\_FUNCTION\_ACTIVE (I:2506); indicates if ECO mode conditions are currently met - I:14001/14002 SAF/EAF Fan Speed Output — REG\_OUTPUT\_SAF (I:14001) and REG\_OUTPUT\_EAF (I:14002); actual fan speed output 0–100% - H:7001 Filter Replacement Period — REG\_FILTER\_PERIOD (H:7001, 3–15 months) and remaining time (I:7005/7006) — filter maintenance tracking - I:12105 Extract Air Temperature — REG\_SENSOR\_EAT (H:12105, /10 °C); extract air temperature — available as accessory sensor - I:12109 Relative Humidity Sensor — REG\_SENSOR\_RHS (H:12109, 0–100%); relative humidity — accessory sensor, useful alongside Highest Humidity device - H:5001–5114 Week Schedule — Complete 7-day, 2-period schedule with temperature offsets and fan levels — complex multi-register configuration ## Sources - Systemair SAVE Modbus Variable List Rev.36 2026-03-20 [PDF](https://taphome.com/compatibility/devices/systemair-save-vtr-700/manufacturer/SAVE_MODBUS_VARIABLE_LIST_REV36.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/)