Ithoamber Modbus Register 521: High pressure

Technical Definition

The register High pressure at address 521 is used to monitor high pressure on the Ithoamber.

• Protocol: Modbus RTU
• Data Type: S WORD
• Unit: bar
• 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 High pressure (Address: 521)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=521, 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: "High pressure"
  address: 521
  value_type: S_WORD
  unit_of_measurement: "bar"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

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

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

💡 Engineer's Insight

Analysis: Measures the pressure in the high-pressure side (discharge) of the refrigeration system, typically in bar or psi.

Troubleshooting: Unusual readings (0, very high/low) may indicate a blocked line, compressor fault, sensor error, or refrigerant overcharge/undercharge.