Jsy Mk 354 Modbus Register 296: Total Reactive Energy

Technical Definition

The register Total Reactive Energy at address 296 is used to monitor total reactive energy on the Jsy Mk 354.

• Protocol: Modbus RTU
• Data Type: U DWORD
• Unit: kVARh
• 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 Total Reactive Energy (Address: 296)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=296, 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: "Total Reactive Energy"
  address: 296
  value_type: U_DWORD
  unit_of_measurement: "kVARh"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Jsy Mk 354]

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

💡 Engineer's Insight

Analysis: Total cumulative reactive energy (VARh) across all phases. Indicates overall system reactive power imbalance.

Troubleshooting: Zero value suggests no reactive power is being consumed/produced or a system-wide metering issue. Check individual phases.