Hoval PV-Heater
Controls Hoval PV-Heater power stages and temperature limits via Modbus TCP or RTU.
Template for the Hoval PV-Heater, a photovoltaic heating element with integrated electricity meter. This template lets you control power steps, load setpoints, feed-in power, and temperature limits via Modbus TCP or RTU, and read back temperature, actual load, and emergency mode status.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 8, read and write
- Brand
- Hoval
- Key readings
- Temperature · Emergency Mode · Actual Load · Actual Temperature Limit
- Available commands
- Power Step · Load Setpoint · Load Feed-in · Temperature Limit
- Compatible models
- EP-3.5-1½″-PV · EP-4.4-1½″-PV · EP-5.2-1½″-PV · EFHK-E/C-3.5-180-PV · EFHK-E/C-4.4-180-PV · EFHK-E/C-5.8-180-PV · EP-7.5-1 1/2"-PV · EP-9.0-1 1/2"-PV · EFHK-E/C-7.5-180-PV · EFHK-E/C-9.0-180-PV
- Last updated
Registers (8)
4 read, 4 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Temperatur | °C | Read | |||
| Emergency Mode | Read | ||||
| Actual Load | kW | Read | |||
| Actual Temperatur Limit | °C | Read | |||
| Power Step | Write | ||||
| Load Setpoint | W | Write | |||
| Load Feedin | W | Write | |||
| Temp Limit | °C | Write |
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Use cases
- Monitor water temperature and actual heater load on a live cloud dashboard for each customer site.
- Set the power step remotely to match real-time PV surplus and avoid grid feed-in.
- Create an alert when emergency mode activates, indicating a potential overtemperature or communication fault.
- Log total energy consumed by the PV-Heater over time to generate monthly self-consumption reports.
- Adjust the temperature limit remotely to match seasonal heating demand without an on-site visit.
- Track actual load versus load setpoint to verify the heater responds correctly to control commands.
Installation
Wire the Modbus gateway to the Hoval PV-Heater using Modbus RTU (RS-485 two-wire) or connect via Modbus TCP over Ethernet to the same network segment.
Open the PV-Heater web interface and activate Modbus TCP or Modbus RTU, depending on your wiring choice.
Set the rotary temperature controller on the PV-Heater housing to maximum (85°C) so that Modbus-based temperature limits take effect.
Configure the Modbus slave address on the PV-Heater to match the address set in the ModbusCloud gateway.
Import the Hoval PV-Heater template in the ModbusCloud platform and assign it to the connected gateway.
Set the repetition interval to 7 seconds in the gateway configuration to ensure continuous communication with the heater.
Things to watch for
The PV-Heater keeps rebooting when connected via Modbus TCP. What is wrong?
There is a known issue when using Modbus TCP with AVM or Fritz Box routers. The heater times out and reboots repeatedly. Use Modbus RTU or 0-10V control as a workaround until a network-command-based template is released.
Why do all actual values drop to zero after a short time?
If the PV-Heater does not receive new Modbus values within 60 seconds, it resets actual values to zero as a safety fallback. Ensure the repetition interval is set to 7 seconds and that the gateway maintains a stable connection.
How is the temperature register encoded?
The temperature register at address 325 uses float32 encoding. The template handles this automatically, so no manual byte-order conversion is needed.
Do I need to adjust the physical thermostat on the heater?
Yes. Set the rotary temperature controller on the housing to maximum (85°C). This allows the Modbus temperature limit to govern operation. If the dial is set lower, the physical thermostat may cut off the heater before the Modbus setpoint is reached.
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