Ctc Ecozenith I250 Modbus Register 642: Heat pump 1: Expansion valve position

Technical Definition

The register Heat pump 1: Expansion valve position at address 642 is used to monitor heat pump 1: expansion valve position on the Ctc Ecozenith I250.

• Protocol: Modbus RTU
• Data Type: S WORD
• 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 Heat pump 1: Expansion valve position (Address: 642)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=642, 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: "Heat pump 1: Expansion valve position"
  address: 642
  value_type: S_WORD
  unit_of_measurement: "%"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Ctc Ecozenith I250]

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

💡 Engineer's Insight

Analysis: Expansion valve position directly controls refrigerant flow into the evaporator. Units: Percentage (0-100%). Essential for maintaining optimal system superheat.

Troubleshooting: A stuck or unresponsive valve (0% or 100%) will lead to incorrect superheat, affecting cooling capacity and potentially causing system damage.