Light Modbus Register 1103: Days since last filter change alarm

Technical Definition

The register Days since last filter change alarm at address 1103 is used to monitor days since last filter change alarm on the Light.

• Protocol: Modbus RTU
• Data Type: INT16
• Unit: days
• 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 Days since last filter change alarm (Address: 1103)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=1103, 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: "Days since last filter change alarm"
  address: 1103
  value_type: INT16
  unit_of_measurement: "days"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

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

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

💡 Engineer's Insight

Analysis: Number of days elapsed since the last filter change alarm was triggered. Units: Days.

Troubleshooting: A value of 0 typically means the filter change alarm was recently reset or triggered. Check filter status and reset procedure.