Zewotherm EU-L Series
The Zewotherm EU-L Series is an air-source heat pump designed for residential and light-commercial heating and domestic hot water production. This Modbus TCP template reads instantaneous power consumption, accumulated electrical energy, hot water storage temperature, and the active temperature limit, while also exposing a write register to feed PV surplus power setpoints directly to the heat pump's energy manager. Together, these registers let installers close the PV self-consumption loop and verify heat pump behavior from the ModbusCloud portal without additional hardware.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 5, read and write
- Brand
- Zewotherm
- Compatible models
- EU-L Series
- Last updated
Registers (5)
4 read, 1 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| setmaxpower | W | Write | |||
| power | W | Read | |||
| energy | Wh | Read | |||
| temp | °C | Read | |||
| limittemp | °C | Read |
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Use cases
- Monitor real-time power consumption of the Zewotherm EU-L Series to detect unexpected load spikes during defrost cycles.
- Track accumulated electrical energy at register 1020 to calculate weekly COP against heat output over time.
- Write PV surplus values to the setmaxpower register to maximize self-consumption during solar generation peaks.
- Alert on hot water storage temperature at register 2002 dropping below a threshold during cold periods.
- Compare the active temperature limit at register 2050 against the measured storage temperature to verify energy manager behavior.
Installation
Enable Modbus TCP and set the energy manager to 'Automatic' mode on the Zewotherm EU-L Series touch display: navigate to Home, then Energy Management, then E-Manager Configuration, and set E-Meter Communication Mode to 'Modbus Client'.
Connect the Zewotherm EU-L Series to your local network via its Ethernet port and confirm it has a static or reserved IP address; note the IP and confirm TCP port 502 is reachable from the ModbusCloud Gateway.
In your ModbusCloud portal, add a new ModbusCloud Gateway, import the Zewotherm EU-L Series template, enter the device IP address and port 502, and set the Modbus unit ID to 1.
Spot-check register 103 (power) in the portal live data view: the value should reflect the heat pump's current draw in watts; if it reads zero while the pump is running, verify the unit ID and network path.
Things to watch for
Why does the heat pump show Error 00506 after a short time?
The Zewotherm EU-L Series energy manager enforces a 5-minute watchdog on the setmaxpower register (address 102). If no write occurs within 300 seconds, the pump raises alarm Error 00506 ('E-Manager invalid value'). Write register 102 well within that 300-second window while active. ModbusCloud writes registers at most once per minute, which is fast enough for this window.
Register 103 returns a value but it seems wrong. What scaling applies?
Register 103 is a raw int16 representing watts with no additional scaling factor. If the value looks ten times too large or too small, confirm your Modbus client is reading a holding register (FC3) with int16 decoding and not applying an extra scale of 0.1, which belongs only to the temperature registers.
The energy register 1020 overflows or reads garbage. Why?
Register 1020 is an int32 value spanning two consecutive 16-bit registers (addresses 1020 and 1021). If your client reads only a single 16-bit word, the result will be truncated and incorrect. Configure your Modbus client to read two registers starting at address 1020 and decode them as a 32-bit integer.
Is it safe to write to the setmaxpower register at any time?
Use caution. Writing a large positive watt value to register 102 directly influences the heat pump's operating target. Sending extreme or unintended values can cause the energy manager to command the compressor beyond its normal operating envelope. Always validate the value before writing and use a watchdog wrapper to reset it to zero on communication loss.
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