ECL 120/220 Modbus for Home Assistant

A custom Home Assistant integration for reading data from Danfoss ECL 120 and ECL 220 heating controllers using Modbus RTU or Modbus TCP.

This integration is created by an enthusiast (not a professional developer) and is actively evolving. It is tested on ECL 120, but ECL 220 uses the same register map, so it should work identically — feedback is welcome!

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🔧 Features

Current supported features:

The list of supported registers is continuously expanding.

The authoritative source for supported registers is:

• custom_components/ecl_modbus/registers.py

Each register definition includes:

• Modbus address
• Read / Write support
• Data type
• Unit
• Scaling
• Min / Max / Step (where applicable)

Fully configurable

• Enable/disable each sensor individually
• Supports USB (Modbus RTU) and IP (Modbus TCP)
• Automatic reconnect if connection is lost
• Friendly naming and unified device info in Home Assistant

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🚀 Installation

Install via HACS

The easiest way to install this integration is through HACS.

Click the button below:

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Manual installation

1. Download the latest release ZIP
2. Extract it into: /config/custom_components/ecl_modbus/
3. Restart Home Assistant
4. Add integration via:
   Settings → Devices & Services → Add Integration → ECL Modbus

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⚙️ Configuration

During setup you choose how the controller is connected:

🔌 Connection type

Serial (USB / Modbus RTU)

• Direct USB-to-RS485 adapter
• Typical port: /dev/ttyUSB0 or /dev/serial/by-id/...
• Baudrate: 38400
• Parity: Even
• Stop bits: 1
• Slave ID: 5 (default)

🌐 TCP (Modbus TCP via gateway)

• Uses a Modbus TCP ⇄ Modbus RTU gateway
• Typical port: 502
• Unit ID = ECL Modbus slave address (default: 5)

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Options

• Enable/disable individual registers
• Configure global polling interval

No YAML required.

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🧩 How it works

• Uses pymodbus for Modbus communication
• Supports both Modbus RTU and Modbus TCP
• One shared coordinator polls enabled registers
• Automatic reconnect on communication errors
• Groups all sensors under a single device in Home Assistant

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🧪 Compatibility

Controller	Status
ECL 120	✔ Tested
ECL 220	⚠ Untested, but register-compatible

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🧰 Tested hardware

This integration has been built and tested with the following hardware setups:

USB → RS485 (Modbus RTU)

• Industrial USB to RS485 Bidirectional Converter
  Vendor: raspberrypi.dk
  Link: https://raspberrypi.dk/en/product/industrial-usb-to-rs485-bidirectional-converter/

Used for direct Modbus RTU communication via USB (e.g. /dev/ttyUSB0 or /dev/serial/by-id/...).

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Ethernet / WiFi → RS485 (Modbus TCP via gateway)

• WaveShare Industrial Grade Serial Server RS232/485 to WiFi/Ethernet
  Vendor: raspberrypi.dk
  Link: https://raspberrypi.dk/en/product/waveshare-industrial-grade-serial-server-rs232-485-to-wifi-ethernet/

Used as a Modbus TCP ⇄ Modbus RTU gateway.
Configured in Modbus TCP ↔ Modbus RTU mode and connected to the ECL controller via RS485.

When using a gateway, ensure that the RS485 parameters (baudrate, parity, stop bits) match the ECL controller configuration.

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🛠️ Planned Features

This integration is actively evolving. Planned and possible future improvements include:

• Additional ECL registers and writable parameters
• Improved multi-controller support
• More advanced connection diagnostics

Suggestions, missing registers, and pull requests are very welcome!

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❤️ Contributions

This project is community-driven — PRs, testing, and feedback are highly appreciated.

GitHub:
👉 https://github.com/nichlasrohde/ha-ecl-modbus

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☕ Support the project

This project is developed and maintained in my spare time as a hobby.

If you find it useful and would like to support continued development,
you’re very welcome to do so — completely optional.

🇩🇰 MobilePay (Denmark): 9316PV Support via MobilePay

Thank you for the support ❤️

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📘 Official Danfoss Modbus Documentation

This integration is based on the official Modbus register list from Danfoss.

📄 Download PDF:
👉 ECL120 & ECL220 Modbus Specification (Rev 023)

The document is shared with permission from Danfoss.

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📄 License

MIT License

⚠️ Disclaimer

This integration is provided as-is, without any guarantees or warranties of any kind.

• The author is not affiliated with Danfoss.
• The author is not a professional developer.
• This integration may contain bugs, incorrect register mappings, or incomplete implementations.
• Writing values to the controller may affect system behavior and could potentially cause malfunction or damage if used incorrectly.

You are fully responsible for:

• Verifying register addresses and values
• Testing changes in a safe environment
• Ensuring that critical heating functions remain safe and operational

The author takes no responsibility or liability for:

• Damaged equipment
• Incorrect heating behavior
• Increased energy consumption
• Loss of comfort or system downtime

If you are unsure about a parameter or register — do not write to it.

Use this integration at your own risk.