Heat Pump.Mar.Bas Modbus Register 42: On/Off State

Technical Definition

The register On/Off State at address 42 is used to monitor on/off state on the Heat Pump.Mar.Bas.

• Protocol: Modbus RTU
• Data Type: INT16
• Unit:
• 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 On/Off State (Address: 42)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=42, 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: "On/Off State"
  address: 42
  value_type: INT16
  unit_of_measurement: ""

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Heat Pump.Mar.Bas]

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

💡 Engineer's Insight

Analysis: On/Off State (Boolean/Integer). 0 for OFF, 1 for ON, indicating the operational status of the heat pump.

Troubleshooting: An 'Off' state (0) means the unit is not running, possibly due to a demand, fault, or safety condition.