Hello there,
Update 19 April 2026: v1.1.0 is now in test. See the post below for
the install link and what’s changed. The description below covers
the current stable version (v1.0.2).
I’ve developed a Homey App that connects your Remeha heat pump directly to Homey over your local network using Modbus TCP. It polls the heat pump’s registers in real-time via the GTW-08 service gateway, giving you full monitoring and control from Homey dashboards and Flows.
Note: NO cloud, direct local Modbus TCP communication.
Remeha Modbus
This Homey app connects to a Remeha heat pump through the local network using Modbus TCP and retrieves real-time operating data. It allows you to monitor temperatures, pressures, energy consumption and COP directly from your Homey smart home system. Using Flows you can send commands to the heat pump to change thermostat mode, DHW comfort setpoint, silent mode, hybrid mode and tariffs.
FEATURES
When a device is added and communication is working, the device will display various statistics such as:
- Room, flow, return, outdoor and heat pump temperatures
- Water pressure and flow rate
- System status (standby, heating, heat pump, hybrid, defrost, error)
- Tap water (DHW) active indicator
- COP (Coefficient of Performance)
- Pump speed
- Compressor starts and operating hours
- Total energy consumption (kWh)
- DHW energy consumption (kWh)
- CH energy delivery (kWh)
- DHW energy delivery (kWh)
- Boiler energy consumption and delivery (kWh)
You can also send commands to the heat pump through Homey Flows (‘Then…’):
- Thermostat mode (auto / heat / off)
- Room temperature setpoint
- DHW comfort setpoint and on/off
- Silent mode with schedule
- Hybrid mode (auto / heat pump only / boiler only)
- Electricity and gas tariffs
- Push live power (W) and energy (kWh) readings from any external meter
REQUIREMENTS
This app requires Homey Pro or Homey Pro Mini (firmware 13.0.0 or newer) and a Remeha heat pump with the following hardware setup:
- Remeha GTW-08 gateway connected to the service connector on your heat pump
- RS485 to Ethernet converter (e.g. Waveshare RS485 TO ETH (B)) to bridge the GTW-08’s Modbus RTU (RS485) to Modbus TCP on your local network
Supported models:
- Elga Ace Hybride Split (indoor unit)
- Elga Ace Monoblock (outdoor unit)
- Elga All-in-One Hybrid (indoor combined unit)
HARDWARE SETUP
Remeha Heat Pump → GTW-08 (service connector) → RS485 → Waveshare RS485 TO ETH → Ethernet → Your local network → Homey
The GTW-08 module exposes the heat pump’s Modbus registers via RS485. Since Homey communicates over your local network (TCP/IP), you need an RS485 to Ethernet converter to bridge the two protocols.
Configure the Waveshare converter with:
- Protocol: Modbus TCP to RTU
- Port: 502 (default Modbus TCP port)
- Static IP address on your local network (so Homey can always reach it)
DEVICE PAIRING
Choose the Remeha Heat Pump device during pairing, select your heat pump model, and enter:
- IP address of your GTW-08 / RS485-to-ETH converter
- Port (default: 502)
- Modbus slave ID (default: 100)
The app will test the connection before adding the device. You can optionally enable external energy meter capabilities during pairing or later in device settings.
STEP BY STEP INSTRUCTIONS
- Install the Remeha Modbus app from the Homey App Store.
- Set up the GTW-08 + RS485 to Ethernet converter on your local network (see HARDWARE SETUP).
- In Homey: Add new device → Remeha → Remeha Heat Pump.
- Select your heat pump model (Elga Ace Hybride Split, Monoblock or All-in-One Hybrid).
- Enter IP address, port and Modbus slave ID, then confirm.
- Watch the magic happen as the heat pump data is retrieved and displayed on the device card.
EXTERNAL ENERGY METER (OPTIONAL)
Want to see live power (W) and cumulative energy (kWh) from an external meter (P1, Shelly, HomeWizard, etc.) on your heat pump device?
Step 1 — In the device settings, enable:
- Show power (W) from external meter — adds
measure_power - Show energy (kWh) from external meter — adds
meter_power
Step 2 — Create a single Flow:
| When | Your energy meter → Power has changed |
| Then | Action 1: Set heat pump power (W) on your Remeha device → use the Power tag |
Action 2: Set heat pump energy (kWh) on your Remeha device → use the Energy tag |
After the Flow runs, your Remeha device shows live W + cumulative kWh and appears in Homey’s Energy dashboard (Grootverbruikers). Works with any energy meter in Homey — regardless of brand or protocol.
FLOW ACTION CARDS
| Action | Description |
|---|---|
| Set heat pump power (W) | Push live power reading from an external meter |
| Set heat pump energy (kWh) | Push cumulative energy reading from an external meter |
| Set electricity tariff peak | Update peak electricity tariff (ct/kWh) |
| Set electricity tariff off-peak | Update off-peak electricity tariff (ct/kWh) |
| Set gas tariff | Update gas tariff (ct/m3) |
VERSION HISTORY
- 1.0.2 — [current LIVE release] Documentation updates, minor stability fixes.
- 1.0.1 — Updated documentation with hardware setup instructions (GTW-08 + RS485 to Ethernet converter). Step-by-step guide for external energy meter Flow integration.
- 1.0.0 — Initial release. Support for Elga Ace Hybride Split, Monoblock and All-in-One models. Real-time monitoring of 45+ registers via Modbus TCP. Thermostat, DHW, silent mode and hybrid mode control. Built-in Remeha energy counters. Optional external energy meter integration via Flow actions. Bilingual support (English and Dutch).
NOTES
- This app uses the Modbus TCP protocol directly against the Remeha GTW-08 gateway — no cloud service involved.
- Runs on both Homey Pro and Homey Pro Mini.
- The register map is based on the official Remeha GTW-08 parameter documentation.
- Developed and tested on Elga Ace Hybride Split. Let me know if other Elga variants work as well!
- Modbus slave ID defaults to 100; adjust if your GTW-08 is configured differently.
- You can update the GTW-08 connection settings (IP, port, slave ID) at any time via the device settings page — the app will automatically reconnect.
- Remeha, Elga Ace and GTW-08 are trademarks of BDR Thermea Group.
KNOWN ISSUES
- Some register readings may temporarily return 0 during heat pump start-up cycles.
- COP reading is only meaningful when the heat pump is actively running.
- When the RS485-to-ETH converter is power cycled, it may take up to 30 seconds before the app reconnects automatically.
TROUBLESHOOTING
If the device shows no data after pairing:
- Confirm the GTW-08 is correctly wired to the heat pump’s service connector.
- Confirm the RS485-to-ETH converter is set to Modbus TCP to RTU, port 502, and has a static IP on the same subnet as Homey.
- Verify the Modbus slave ID in the device settings matches the GTW-08 configuration (default: 100).
- Try power-cycling the RS485-to-ETH converter and wait ~30 seconds.
- If you use the Waveshare converter’s web UI, verify the RS485 baud rate matches the GTW-08 (typically 9600 8N1).
RELEASE version: Latest Version
Feedback, questions and model-compatibility reports are very welcome!
