Nilan Cts400 Modbus Register 24: Exhaust fan speed

Technical Definition

The register Exhaust fan speed at address 24 is used to monitor exhaust fan speed on the Nilan Cts400.

• 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 Exhaust fan speed (Address: 24)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=24, 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: "Exhaust fan speed"
  address: 24
  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[Nilan Cts400]

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

💡 Engineer's Insight

Analysis: Current speed setting for the exhaust fan. Units are typically steps, Hz, or percentage.

Troubleshooting: Zero indicates the fan is off or in an error state. Could also be a standby mode or communication failure.