Config Modbus Register 28: Reactive Power (Phase C)

Technical Definition

The register Reactive Power (Phase C) at address 28 is used to monitor reactive power (phase c) on the Config.

• Protocol: Modbus RTU
• Data Type: FP32
• Unit: VAr
• 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 Reactive Power (Phase C) (Address: 28)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=28, 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: "Reactive Power (Phase C)"
  address: 28
  value_type: FP32
  unit_of_measurement: "VAr"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

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

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

💡 Engineer's Insight

Analysis: Reactive power (VAR) for Phase C. Power exchanged between source and reactive components.

Troubleshooting: Zero value could indicate a purely resistive load or a sensor/wiring problem on Phase C.