remeha_modbus

Python library for accessing Remeha heating systems via Modbus TCP (GTW-08 gateway).

Designed to be used standalone or as the backend for a Home Assistant custom integration.

Features

• Async Modbus TCP client based on pymodbus
• Full register definitions from the GTW-08 parameter list
• Automatic value scaling (gain) and signed integer handling
• Invalid value detection (returns None for disconnected sensors)
• Support for all 12 heating zones
• Read/Write access for configurable parameters

Supported Registers

Installation

pip install remeha-modbus

Or for development:

git clone https://github.com/klacol/remeha-modbus.git
cd remeha-modbus
pip install -e ".[dev]"

Usage

import asyncio
from remeha_modbus import RemehaModbusClient

async def main():
    client = RemehaModbusClient(host="192.168.1.100", port=502, slave_id=1)
    await client.connect()

    # Read all appliance sensors
    data = await client.read_appliance()
    print(f"Vorlauftemperatur: {data['flow_temperature']} °C")
    print(f"Wasserdruck: {data['water_pressure']} bar")

    # Read a specific zone
    zone1 = await client.read_zone(1)
    print(f"Zone 1 Modus: {zone1['zone1_zone_mode']}")

    await client.disconnect()

asyncio.run(main())

Testing

pytest tests/ -v

Tests use mocked Modbus responses so no hardware is needed.

Hardware Setup

Requires a Remeha GTW-08 Modbus gateway connected to the heating system's L-Bus. The gateway provides Modbus TCP access over Ethernet.

• Set the Modbus address via the GTW-08 rotary switch
• Default port: 502
• Supported baud rates: 9600, 19200, 38400, 57600

Reference

• Modbus Parameter Documentation (Markdown)
• Original PDF
• GTW-08 Installation Guide (Home Assistant Community)