home-assistant-systemair-modbus

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home-assistant-systemair-modbus

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Home Assistant integration for Systemair SAVE ventilation units via Modbus TCP (NO/EN).

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# Home Assistant -- Systemair Modbus (SAVE + CD4)

**English** · [Les på norsk](README.no.md)

[![HACS](https://img.shields.io/badge/HACS-Default-green.svg)](https://hacs.xyz/)

This is a Home Assistant integration for Systemair ventilation units
with support for both **SAVE** and **legacy CD4 (experimental)**
systems. with support for **Modbus TCP**.

The integration provides structured monitoring and control of the
ventilation system in Home Assistant, with a focus on **correct airflow,
energy-efficient operation, and stable entity handling**.

⚠️ **Notice:**\
This is an **unofficial community project** and is **not developed,
supported, or maintained by Systemair**.

⚠️ **Disclaimer:**\
This integration is provided **as-is**, without any warranty of any
kind.\
You use it **at your own risk**. The author is not responsible for any
damage, data loss, or malfunction of your ventilation system, equipment,
or property.

Always verify changes directly on the unit and ensure your system is
correctly configured.\
If in doubt, consult a qualified technician.

------------------------------------------------------------------------

## ✨ Features

### Ventilation and operation

-   Display of actual operation based on the unit's configuration
-   Temperatures (outdoor, supply air, extract air, reheater, etc.)
-   Fan speeds and operating status
-   Heat recovery
-   Filter status, remaining time and alarms
-   Proper filter reset (writes timestamp to the unit)
-   Configurable filter replacement period

### Energy efficiency

-   **Eco mode**
-   Demand-controlled ventilation (where supported by the unit)
-   Away and Holiday modes
-   Energy-efficient operation based on load and unit configuration

### Comfort

-   **Free cooling** when conditions are met
-   Party and Boost modes
-   Manual fan speed control (Low / Normal / High)
-   Writable supply air temperature setpoint
-   Calculated exhaust air temperature (derived from system values)

### User experience

-   Norwegian and English language support (follows Home Assistant
    language)
-   Consistent and stable entities
-   Built-in **buttons** for common actions
-   Robust handling of temporary Modbus connection loss

------------------------------------------------------------------------

## 🚀 Recent improvements

Recent versions include:

-   Writable supply air setpoint directly from Home Assistant
-   Proper filter reset using native timestamp registers
-   Configurable filter replacement period
-   Calculated exhaust air temperature sensor
-   Profile-based Modbus handling for improved stability on SAVE Connect
    and similar gateways

## The integration is under active development with a strong focus on correctness, stability and transparent entity behavior.

## 📋 Systemair SAVE -- supported models

**Airflow estimation (m³/h)** is only available for models that are
explicitly defined in the code and share the expected Modbus register
layout.

**Legend:** - ✅ = Yes / available\
- ⚙️ = Supported, but not tested\
- ❌ = Not available

------------------------------------------------------------------------

### 🧪 CD4 (legacy) -- experimental support

Support for older Systemair units using the **CD4 controller** is
included in the integration and has been significantly expanded in
v1.3.0-beta.2.

⚠️ **Important:**

-   CD4 uses a different Modbus register map than SAVE
-   Support remains **experimental** while testing on real units
    continues
-   Available features may vary between legacy unit models and
    configurations

### What currently works

-   Native Home Assistant **Fan entity** for fan control
    -   Off / Low / Medium / High
    -   Off is only available when manual stop is supported by the unit
-   Native Home Assistant **Climate entity**
    -   Five documented supply-air temperature steps
    -   Current supply-air temperature
    -   Fan mode control directly from the Climate entity
    -   Heating state based on actual reheater status
-   Supply, extract, exhaust, outdoor and overheat/frost-protection
    temperatures
-   Actual SF / EF RPM values
-   Rotor, reheater, defrost and alarm status
-   Filter status and basic system values
-   Technical and raw CD4 values are available as diagnostic entities
    where appropriate

### Testing and feedback

If you have a CD4-based unit, your feedback is extremely valuable.

Feedback is especially useful for:

-   Fan control: Off / Low / Medium / High
-   Supply-air temperature control across all five steps
-   Current and target temperature in the Climate entity
-   Heating state indication
-   Temperature sensor mapping
-   Rotor, reheater, defrost and alarm states
-   General stability and Modbus communication

Please report your experience and any issues via GitHub Issues.

----------------------------------------------------------------------
 ## ✅ Tested units / Compatibility

| Series | Model / Type | Modbus support | Airflow estimation (m³/h) | Tested |
|---|---|:---:|:---:|:---:|
| VSR | VSR 150/B | ✅ | ✅ | ❌ |
| VSR | VSR 200/B | ✅ | ✅ | ❌ |
| VSR | VSR 300 | ✅ | ✅ | ✅ |
| VSR | VSR 400 | ✅ | ✅ | ❌ |
| VSR | VSR 500 | ✅ | ✅ | ✅ |
| VSR | VSR 700 | ✅ | ✅ | ❌ |
| VTR | VTR 100/B | ✅ | ✅ | ❌ |
| VTR | VTR 150/B | ✅ | ✅ | ❌ |
| VTR | VTR 250/B | ✅ | ✅ | ✅ |
| VTR | VTR 275/B | ✅ | ✅ | ❌ |
| VTR | VTR 300 | ✅ | ✅ | ✅ |
| VTR | VTR 350/B | ✅ | ✅ | ⚙️ |
| VTR | VTR 500 | ✅ | ✅ | ✅ |
| VTR | VTR 700 | ✅ | ✅ | ❌ |
| VTC | VTC 200-1 | ✅ | ❌ | ❌ |
| VTC | VTC 300 | ✅ | ❌ | ❌ |
| VTC | VTC 500 | ✅ | ❌ | ❌ |
| VTC | VTC 700 | ✅ | ❌ | ❌ |
| VSC | VSC 100 | ✅ | ❌ | ❌ |
| VSC | VSC 200 | ✅ | ❌ | ❌ |
| VSC | VSC 300 | ✅ | ❌ | ❌ |

> ✅ **VTR 300:** Confirmed working by a community user (SAVE Touch, original Systemair Modbus gateway, Modbus TCP).  
> ✅ **VTR 500:** Confirmed working by a community user (tested with Elfin EW11 Modbus TCP gateway).  
> ✅ **VTR 250:** Confirmed working by a community user (tested with Elfin EW11 Modbus TCP gateway).  
> ⚙️ **VTR 350/B:** Reported working, but not yet fully verified across all features.  
> ✅ **VSR 300:** Confirmed working by a community user (tested with Elfin EW11 Modbus TCP gateway).  
> ✅ **VSR 500 (CD4 / legacy):** Confirmed working by a community user – fan control, temperature control and sensor values tested.

------------------------------------------------------------------------

## 🏗️ Prerequisites -- unit selection and airflow

This integration assumes that the ventilation system is **properly
designed and correctly dimensioned**.

-   The air handling unit must be selected based on actual airflow
    requirements (m³/h)
-   Airflows per zone must be correctly balanced and commissioned
-   Home Assistant does **not** replace professional ventilation design

The integration builds on the unit's existing configuration and
provides: - monitoring - control - automation

Incorrect unit selection or airflow configuration cannot be compensated
for by software.

------------------------------------------------------------------------

## 🖥️ Example Lovelace card

The image below shows an example Lovelace card built manually in Home
Assistant using entities provided by this integration.

> The card itself is **not included** and can be freely customized to
> suit your setup.

![Ventilation Card](https://raw.githubusercontent.com/Howard0000/home-assistant-systemair-modbus/main/image/Ventilasjon%20kort.png)

------------------------------------------------------------------------

## 📦 Installation (HACS)

### Requirements

-   Home Assistant **2024.6** or newer
-   Systemair SAVE unit with Modbus access
-   Modbus TCP
    -   Built-in to the unit **or**
    -   Via an external gateway (e.g. Elfin EW11)
-   HACS (Home Assistant Community Store)

------------------------------------------------------------------------

### Method 1: Install via HACS (recommended)

1.  Open **HACS**
2.  Go to **Integrations**
3.  Search for **Systemair Modbus**
4.  Click **Download**
5.  Restart Home Assistant
6.  Go to **Settings → Devices & Services → Add integration**
7.  Select **Systemair Modbus** and enter:
    -   IP address
    -   Port (usually `502`)
    -   Modbus slave ID

------------------------------------------------------------------------

### Method 2: Install as a custom repository (manual)

> This method is mainly intended for development, testing, or early
> access to changes.

1.  Open **HACS**
2.  Go to **Integrations**
3.  Open the menu (three dots) → **Custom repositories**
4.  Add this repository as an **Integration**
5.  Install **Systemair Modbus**
6.  Restart Home Assistant
7.  Go to **Settings → Devices & Services → Add integration**
8.  Select **Systemair Modbus** and enter:
    -   IP address
    -   Port (usually `502`)
    -   Modbus slave ID

------------------------------------------------------------------------

## ℹ️ Limitations and technical notes

-   **Pressure Guard** is an internal safety function of the unit\
    → exposed as status only (read-only)
-   Not all SAVE models support full stop via Modbus\
    → where full stop is unavailable, the lowest possible fan speed is
    used
-   Available features depend on unit model and configuration

## 🔧 Modbus gateways and performance profiles

Different Modbus TCP gateways behave very differently in practice.

Some gateways (such as **Systemair SAVE Connect**) are relatively
underpowered and may: - struggle with large Modbus read requests -
reject certain function codes (FC04 for input registers) - become
unstable if polled too aggressively

Other gateways (e.g. **Elfin EW11** and similar) can usually handle: -
larger batch reads - more aggressive polling - normal Modbus function
code usage

To handle this, the integration provides a **Gateway profile** setting:

-   **Generic gateway** (default)\
    Optimized for external gateways like EW11. Uses larger batches and
    faster polling.

-   **Systemair SAVE Connect (safe mode)**\
    Uses very small batches, avoids problematic function codes, and
    prioritizes stability over speed.

You can change the gateway profile from the integration **Options**
without reinstalling.

If you experience random read errors, slow updates, or connection drops
with SAVE Connect, select **Systemair SAVE Connect (safe mode)** and
consider using a higher scan interval (e.g. 30--60 seconds).

------------------------------------------------------------------------

### 🔍 Connection troubleshooting

During setup, the integration performs a quick TCP connectivity check
before attempting Modbus communication.

If you get **"Failed to connect"**: - Make sure the IP address is
correct and reachable from Home Assistant - Verify that port `502` (or
your configured port) is open and reachable from Home Assistant - Check
that the device you are connecting to is actually a Modbus TCP endpoint
(not just a UI/network module) - If using SAVE Connect and you
experience instability, try selecting **Systemair SAVE Connect (safe
mode)** and increase the scan interval (e.g. 30--60s)

If Modbus works from a PC but not from Home Assistant, the issue is
often related to: - Network/VLAN/firewall differences between your PC
and Home Assistant - Gateway connection limits or connection handling
quirks

------------------------------------------------------------------------

## 🔌 Physical installation -- Elfin EW11 (Modbus RTU → TCP)

This section is only relevant if the unit does **not** have built-in
Modbus TCP.

### ⚠️ WARNING

Always disconnect power to the air handling unit before opening it.\
If unsure, contact a qualified professional.

### 1. Modbus connection on Systemair SAVE

Locate the external communication terminals on the main control board: -
`A (+)` - `B (–)` - `24V` - `GND`

![Example wiring diagram (VTR-500)](https://raw.githubusercontent.com/Howard0000/home-assistant-systemair-modbus/main/image/koblingsskjemaVTR-500.png)

### 2. Connect the Elfin EW11

Wire the connections according to the diagram below:

![EW11 wiring diagram](https://raw.githubusercontent.com/Howard0000/home-assistant-systemair-modbus/main/image/koblings%20skjema%20EW11.png)

------------------------------------------------------------------------

### 3. Configure the Elfin EW11

1.  Connect to the Wi-Fi network `EW1x_...` (open network)
2.  Open the web interface: `http://10.10.100.254`
3.  Log in with:
    -   Username: `admin`
    -   Password: `admin`
4.  Go to **System Settings → WiFi Settings**
    -   Set **WiFi Mode** to `STA`
    -   Connect to your local network
5.  Restart the device and assign a **static IP**
6.  Open **Serial Port Settings** and configure as shown:

![Serial Port Settings EW11](https://raw.githubusercontent.com/Howard0000/home-assistant-systemair-modbus/main/image/serial%20port%20settings%20EW11.png)

7.  Open **Communication Settings** and add a Modbus profile:

![Communication Settings
EW11](image/communication%20settings%20EW11.png)

8.  Under **Status**, packet counters should increase:

![EW11 communication status](https://raw.githubusercontent.com/Howard0000/home-assistant-systemair-modbus/main/image/kommunikasjon%20EW11.png) ⚠️
**Important note about packet counters**

The Systemair unit uses **Modbus RTU**, which is a **request/response
protocol**.\
This means the unit **does not send any data by itself**.

Communication only starts when a **Modbus client actively polls the
unit** (for example the Home Assistant integration).

Because of this, the **packet counters on the EW11 status page may
remain at 0** until Home Assistant attempts to connect.

If you see **0 packets**:

1.  Finish the EW11 configuration
2.  Add the integration in Home Assistant
3.  Start the integration
4.  Then check the EW11 status page again

Once Home Assistant starts polling registers, the **packet counters
should begin increasing**.

If they still remain at 0, verify: - RS485 wiring (`A` / `B`) - Baud
rate - Parity and stop bits - Modbus slave ID

Once communication is confirmed, the IP address can be used directly in
Home Assistant.

------------------------------------------------------------------------

## 🙏 Acknowledgements

The Elfin EW11 (Modbus RTU → TCP) installation guide is based on work
published on [domotics.no](https://www.domotics.no/), written by **Mads
Nedrehagen**.

Special thanks to [**Ztaeyn**](https://github.com/Ztaeyn) for
contributing improvements to climate state handling (`hvac_action`)
based on the TRIAC register.

Special thanks to [**larstobi**](https://github.com/larstobi) for
contributions and testing of the CD4 support, including register
information and work on fan control that helped shape the further
development of the new CD4 implementation.

An AI assistant has been used to support troubleshooting, refactoring,
and documentation improvements during development.

This integration is **independently developed** as a modern Home
Assistant integration.

------------------------------------------------------------------------

## 📝 License

MIT -- see `LICENSE`

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