Heatpump Modbus Register 208: Temperature Lower Limit Of Water Heating

Technical Definition

The register Temperature Lower Limit Of Water Heating at address 208 is used to monitor Temperature lower limit of water heating on the heatpump.

• Protocol: Modbus RTU
• Data Type: U WORD
• Unit: °C
• Access: Read Only

How to Read (Python pymodbus)

Use this code snippet to read this specific value via RS485:

from pymodbus.client.sync import ModbusSerialClient

client = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
client.connect()

# Read Temperature Lower Limit Of Water Heating (Address: 208)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=208, count=2, unit=1)

if not result.isError():
    print(f"Raw Value: {result.registers}")
else:
    print("Error reading register")

client.close()

Integration (Home Assistant)

Paste this into your configuration.yaml:

- platform: modbus_controller
  name: "Temperature Lower Limit Of Water Heating"
  address: 208
  value_type: U_WORD
  unit_of_measurement: "°C"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[heatpump]

    PLC -- "A+ (D+)" --> Device
    PLC -- "B- (D-)" --> Device
    PLC -- GND --> Device

💡 Engineer's Insight

Analysis: Sets the minimum target Temperature for domestic hot water heating in degrees Celsius or Fahrenheit. Defines the lower limit for the water Temperature.

Troubleshooting: Extremely low values suggest a configuration issue. A fault might prevent the system from reaching the setpoint, leading to '0' if it reads as an error state.