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Geo9 Modbus Register 201: Fresh air intake T1 Temperature

Technical documentation for Modbus register 201 on Geo9. Data type: S WORD. Includes Python and YAML configuration examples.

January 16, 2026 3 read

Technical Definition

The register Fresh air intake T1 Temperature at address 201 is used to monitor fresh air intake t1 Temperature on the Geo9.

  • Protocol: Modbus RTU
  • Data Type: S 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 Fresh air intake T1 temperature (Address: 201)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=201, 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: "Fresh air intake T1 temperature"
  address: 201
  value_type: S_WORD
  unit_of_measurement: "°C"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Geo9]

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


💡 Engineer's Insight

Analysis: Temperature of fresh air entering the system. Unit: Degrees Celsius. Crucial for ventilation control.

Troubleshooting: 0 may indicate a sensor fault, communication issue, or extremely cold ambient conditions. Verify sensor integrity and environment.